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Fire drives phylogenetic clustering in Mediterranean Basin woody plant communities
Journal of Ecology
Abstract
Summary 1. Many Mediterranean plant species persist after fire because their seeds are protected from the heat of the fire (e.g. hard-coated seeds, serotinous cones), thus permitting rapid post-fire recruitment. For simplicity, this trait will hereafter be called P and its two possible phenotypes P+ (seeder) and P- (non-seeder). 2. Because P+ appears in a narrow taxonomic spectrum and confers persistence under high fire frequencies, we test the extent to which communities with different fire histories have different phenotypic and phylogenetic structures. Specifically, we compare coastal vegetation growing in a warm and dry Mediterranean climate subject to high fire frequency (HiFi vegetation) with montane vegetation subject to a subhumid climate where fires are rare (LowFi) under the hypothesis that P+ species will be over-represented in HiFi communities, thus producing phenotypic and phylogenetic clustering. 3. Trait conservatism on P is evaluated by testing the presence of a phylogenetic signal, phenotypic clustering is tested by correlating co-occurrence and phenotypic distance matrices, and the phylogenetic structure is evaluated by testing whether the phyloge- netic distances between species in each community are different from those expected by chance. 4. The results suggest that: (a) P is a strongly conserved trait; (b) co-occurring species have similar P phenotypes (phenotypic clustering); and (c) the phylogenetic structure in HiFi vegetation is significantly clustered while LowFi vegetation tends to be overdispersed. 5. Synthesis : Fire is a strong driving force in assembling HiFi communities while other forces, such as competitive interactions, are the main assembly mechanisms in LowFi communities. This result supports the role of recurrent disturbances as filters driving phylogenetic community structure.
... In these communities, fire selects species based on their ability to cope with the subsequent changes in abiotic conditions (He et al., 2019). When the fire regime is the dominant assembly process, higher intensity of this disturbance can restructure biological communities, retaining species showing similar characteristics and niches (i.e., able to cope with the post-fire ecosystem) (Verdú and Pausas, 2007). Conversely, under conditions of low to moderate fire activity, community dynamics are likely to be predominantly molded by alternative ecological processes, including competition and facilitation (Webb, 2000). ...
... Although the protected area is dominated by savanna ecosystems that are naturally impacted by fire, most recent fires have been caused by human activities (ICMBio, 2007). Therefore, we hypothesized that frog communities in landscapes severely affected by fires (i.e., under higher fire frequency, greater burned area and more recent fires) would present: i) lower taxonomic diversity, due to the competitive exclusion between similarly fire-resistant species (Pérez-Valera et al., 2018), and ii) lower phylogenetic diversity, due to co-occurrence of closely-related species as a result of environmental filtering driven by fire (Verdú and Pausas, 2007). This research will provide key information on the effects of fire on fauna, thereby aiding in the formulation of comprehensive Integrated Fire Management (IFM) policies currently under development in Brazil (Durigan, 2020). ...
... Although it is commonly expected that environmental filters such as fire promote phylogenetic clustering in communities (Webb et al., 2002), previous studies observed the opposite scenario, in which fire promoted phylogenetic overdispersion in communities of plants (Verdú and Pausas, 2007;Pausas and Verdú, 2008;Silva and Batalha, 2010;Cianciaruso et al., 2012;Nóbrega et al., 2019) and microbiota (Rincón et al., 2014;Pérez-Valera et al., 2018). These authors demonstrate that the phylogenetic overdispersion observed in plant communities under the influence of fire activity is precisely due to the convergence of functional characteristics in different plant lineages. ...
Fire is a natural disturbance that has shaped Earth's biodiversity for millions of years. In a fire-prone ecosystems, fire acts as an important environmental filter, selecting species presenting tolerant traits to fire events and post-fire environmental conditions. It is expected that intense fire activity selects for closely-related species, thus promoting a phylogenetic and functional clustering of communities. In view of the severe changes in natural fire regimes observed in different regions of the planet, an increasing body of research has been dedicated to exploring their impact on frogs, a particularly susceptible group in the context of wildfires. However, it is notable that most of the research focuses on the traditional dimension of diversity, the taxonomic diversity, leaving a significant gap in our understanding of how fire disturbances affect the phylogenetic diversity of these communities. Here, we tested the effects of three fire regime parameters (i.e., total burned area, time since the last fire and fire count at the landscape scale) on the taxonomic and phylogenetic diversity of frog communities in 26 sites within a fire-prone Brazilian protected area. We used Hill numbers to characterize the taxonomic (Species richness, Shannon and Simpson's diversity) and phylogenetic diversity (Phylogenetic richness, Mean phyloge-netic diversity of common lineages and Mean phylogenetic diversity of dominant lineages). We found that the fire regime did not explain patterns of the taxonomic diversity. Nonetheless, there was a positive correlation between phylogenetic richness and the frequency of fire occurrences, while a slight negative correlation was observed with the percentage of burned area. In addition, moderate fire activity seems to be an important driver of phylogenetic diversity. Therefore, management practices toward a mosaic of areas with different fire histories are fundamental in this protected area. We finally emphasize that all diversity facets of anurans should be assessed and considered in management decisions to guaranteeing anuran conservation in this region.
... The vegetation of many Mediterranean species shows resilience after fire. In particular, seeder species, well exemplified by Cistus albidus, show enhanced post-fire germination from soil seed bank or neighbouring populations (Pausas 2012;Pausas et al. 2004;Verdú and Pausas 2007). Factors associated with fire that enhance seed germination include high temperatures (Corral et al. 1990;Roy and Sonié 1992;Thanos et al. 1992;Troumbis and Trabaud 1986), smoke (Keeley and Fotheringham 1997;Reyes andTrabaud 2009), ash (González-Rabanal andCasal 1995), changes in light regime (Bell 1999) and charred wood (Enright and Kintrup 2001). ...
... Species with this postfire regeneration strategy share some physiological and morphological characteristics that can be associated with water use, defence and fire response, including low leaf water content, the presence of resins, oils and volatile compounds providing high flammability (Bond and Midgley 1995;Keeley et al. 2011;Pausas and Verdú 2005;Saura-Mas et al. 2009). In summary, both fire and climate can potentially represent evolutionary pressures shaping species traits, particularly those related to regeneration, in Mediterranean-type ecosystems (Bradshaw et al. 2011a(Bradshaw et al. , 2011bKeeley et al. 2011;Moreira et al. 2012;Pausas and Verdú 2007). ...
... The protection of a hard coat confers longevity on seeds, which can remain viable for several years in the soil bank (Buhk and Hensen 2008;Roy and Sonié 1992); however, dormancy impedes germination even under conditions that would be expected to be suitable for germinating. Hard seeds are considered a common trait in Mediterraean-type vegetation and a controversial fire-adaptive trait (Bradshaw et al. 2011a(Bradshaw et al. , 2011bKeeley et al. 2011;Verdú and Pausas 2007). In nature, there are several mechanisms that help break down dormancy, such as heat (Bastida and Talavera 2002;Ferrandis et al. 2001) and smoke (Reyes and Trabaud 2009) associated with wildfires, heating of the soil by the sun, alternating dry and wet periods (Martinez-Ghersa et al. 1997;Quinlivan 1971) and chemical scarification suffered throughout the herbivore digestive tract (Malo and Suarez 1996). ...
Aims
Cistus albidus reproductive traits have been studied on typical Mediterranean shrublands along a water availability gradient in Northeastern Iberian Peninsula. Germination of this species is known to be highly favoured by fire. Moreover, Mediterranean species are particularly dependent on water availability. Therefore, we establish the hypothesis that in addition to fire disturbance, seedling recruitment in this Mediterranean seeder will be improved in drought-induced episodes resulting in generalized canopy die-off.
Methods
Individuals of several populations of C. albidus were collected and the size, weight and number of fruits and seeds were measured. Germination tests were also carried out on five pre-germination treatments: seeds’ exposure to heat shock, imbibition, two cycles of imbibition/desiccation and the combination of heat shock and imbibition and imbibition/desiccation cycles. Moreover, the number of seedlings after a drought event was surveyed in the field and correlated with canopy die-off.
Important findings
Our study shows the variability of the C. albidus reproductive traits, such as germination rate or fruit production, along the water availability gradient. This variability resulted in a decrease in fruit production but an increase in successful germination under drier conditions. Cistus albidus seeds increased germination with heat, demonstrating their ability to successfully establish after fire. However, recruitment was not exclusively fire dependent since seedling establishment was higher under C. albidus canopies that had collapsed after the extreme drought. Finally, adult density increased C. albidus die-off and mortality, as well as seedling establishment. These results suggest that this species exhibits a trade-off between different reproductive outcomes (i.e. seed production vs. viability), which in turn is determined by climate. This study also provides evidence of how intra-specific competition, climate, particularly drought events and fire disturbance, can determine the success of key early stages of the life history of a common, representative Mediterranean fire-prone seeder shrub.
... For example, in Mediterranean ecosystems, climate and geology (soils) have been traditionally considered the most fundamental forces of community assembly (Raven and Axelrod, 1978;Thompson, 2005;Ackerly, 2009). However, it has been suggested in recent years that fire can also be a factor of equal or greater importance in some cases (Verdú and Pausas, 2007;Keeley et al., 2012). In this ecosystem type, fire is a recurrent disturbance caused by hot dry summers that makes vegetation highly flammable (Keeley et al., 2012). ...
... In the Mediterranean Basin (MB), the HS trait is a phylogenetic conserved trait that is present mainly in species from the Fabaceae and Cistaceae families (Verdú and Pausas, 2007). In this region, these families have been detected to date back to the Neogene period, but their presence intensified in the Quaternary, concomitantly with the definitive onset of a dry seasonal climate (Mediterranean climate) and frequent fires (Thompson, 2005;Rundel et al., 2016). ...
... On local and regional scales, both gradients often follow the same pattern with higher fire frequencies at dry and hot sites. For example, phenotypic and phylogenetic clustering of seeder species has been observed in the MB when comparing wet areas with low fire frequency to drier areas with higher fire frequency (Lloret et al., 2005;Verdú and Pausas, 2007). Nevertheless, if we are to know the relative importance of fire or climate on HS trait selection, it is essential that we distinguish between these two environmental gradients. ...
Hardseededness is a common trait in Mediterranean plant communities, although the origin of its selection is controversial. It may be a mechanism of persistence to fire temperatures, but could also form part of a gap-detecting mechanism to provide germination cues under arid conditions. To disentangle this, we studied the phylogenetic structure of plant communities against fire frequency and aridity gradients. The phylogenetic structure in Mediterranean Basin ecosystems was analysed for the hardseededness trait as a whole and was separated by the families composing this trait (Fabaceae and Cistaceae). This study focused on woody perennial species. The phylogenetic structure was also contrasted against soil classes. Hardseededness on the whole, and for the Fabaceae family alone, showed phylogenetic clustering as aridity increased. Cistaceae displayed the opposite pattern with phylogenetic clustering in most humid areas, together with a significant soil effect. Surprisingly, fire frequency had no influence in any case. This climate-driven phylogenetic clustering indicates that the hardseededness trait could confer some fitness advantage under dry conditions. For this reason, coexisting species were more closely related in the community with increasing aridity. This effect was especially evident for the Fabaceae family. These results shed some light on the evolutionary selection of this adaptive trait under Mediterranean conditions. Our results question the role of fire in the selection of the hardseededness trait in Mediterranean Basin ecosystems and indicates that climate is the most important factor. Therefore, we should be cautious in assigning to fire a preponderant role in the selection of some plant traits.
... Consequentemente, o fogo modifica a estrutura da vegetação de cerrado, favorecendo as espécies herbáceas em detrimento das espécies arbóreas (Moreira 2000, Gottsberger & Silberbauer-Gottsberger 2006. Nas vegetações sujeitas a queimadas frequentes, como na vegetação mediterrânea, o fogo atua como um importante filtro ambiental, selecionando as espécies que podem ocorrer na comunidade (Pausas & Verdú 2005, Verdú & Pausas 2007. Nesse sentido, a frequência de fogo pode determinar a similaridade ecológica e o grau de parentesco das espécies vegetais coocorrentes (Webb et al. 2002, Slingsby & Verboom 2006. ...
... Por outro lado, a capacidade de rebrota é diferente entre as fisionomias de cerrado, e a rebrota pode não ser eficiente para manter a estrutura e composição de espécies da vegetação (Miranda & Sato 2005, Medeiros & Miranda 2008. Em formações vegetais sujeitas ao fogo, como as formações vegetais mediterrâneas, algumas adaptações específicas a altas frequências de fogo, como a germinação após o fogo, estão concentradas em algumas famílias (Cistaceae e Fabaceae, por exemplo, em Verdú & Pausas 2007). No cerrado, contudo, adaptações associadas ao fogo estão distribuídas em várias linhagens. ...
O fogo é um importante agente evolutivo que pode causar alterações florísticas, filogenéticas e funcionais nas comunidades vegetais de cerrado, alterando a composição do solo e modificando as interações interespecíficas. Aqui discutimos os efeitos do fogo sobre a vegetação de cerrado e levantamos sugestões para o seu manejo em unidades de conservação. Com especial ênfase para trabalhos realizados no Parque Nacional das Emas, na fisionomia de campo cerrado, compilamos os seguintes resultados: em maiores frequências de fogo (queimadas anuais ou bienais) ocorre agrupamento fenotípico, diminuição da competição, diminuição da biomassa vegetal e enriquecimento dos solos; em menor frequência (sem queimadas há doze anos), há maior competição entre as espécies e grande acúmulo de biomassa seca. Além disso, diferentes regimes de fogo suportam diferentes composições florísticas, com grupos de espécies exclusivos em cada regime, tanto de espécies herbáceo-subarbustivas quanto de arbustivo-arbóreas. Portanto, sugerimos que seja mantido um mosaico com diferentes regimes de fogo e que se evitem áreas de cerrado sem queimadas por muitos anos. Palavras-chave: biomassa vegetal, diversidade filogenética, diversidade funcional, manejo, solo.
... By contrast, resprouters were at risk of accumulating harmful somatic mutations over much longer lifespans and had lower recruitment rates than seeders. This paradigm has more recently been challenged by studies which found that resprouter lineages did not have lower rates of molecular evolution and diversification than seeders (Fowler et al., 2018;Lamont and Wiens, 2003;Verd u and Pausas, 2007). ...
... Neither PR nor YS are serotinous and so in this instance PR individuals would have a one-to-three-year period in which they alone would be contributing to the seedbank, while YS individuals would be contributing zero to very little seed to their own seedbank. Despite this temporary advantage, our population data show that YS outnumbers PR by § 27:1 and that PR typically occurs as isolated plants or small subpopulations, confirming prior studies that resprouters typically set fewer seeds and have lower seedling recruitment than seeders (Bond and Midgley, 2001;Bond and van Wilgen, 1996;Keeley, 1986;Lamont et al., 1985;Lamont and Witkowski, 2021;Verd u and Pausas, 2007). Regarding trade-offs in resprouting versus seeding strategies (Bond and Midgley, 2003), in YS we see allocation to reproduction, for example seed set and nectar sugar concentration, further suggesting that any possible seedbank deposition advantage period for PR, in addition to being seed-and seedbank-limited (Clarke et al., 2013), is short. ...
The Cape Floristic Region (CFR) genus Erica is hyperdiverse with approximately 800 taxa in an area roughly the size of Austria. To date no studies have systematically investigated the biotic and abiotic differences between sympatric Erica variants with a view to helping explain patently explosive speciation within the genus in the region. Erica mammosa L. has four distinct resprouting and seeding variants occurring over a wide geographic area within the south-western CFR. Here we focus upon two sympatric variants of this taxon, a resprouting pink-flowered variant and a seeding yellow-flowered variant, on the Cape Peninsula. Results show that considerable differences exist between the two variants in fine scale geographic distribution, the populations being homogeneous and not intermixed; in fire survival strategies and responses, in that the seeder variant is killed by fire and the resprouter variant requires fire when moribund and to recruit occasional seedlings; in seed set, the seeder variant having more ovules and producing more seeds than the resprouter variant; in population proportions, the seeder variant vastly outnumbering the resprouter variant; in water stress responses, the seeder variant being significantly more drought stressed; and in and in flowering phenologies, the resprouter variant flowering from November to May and the YS variant from January to March; The variants share two sunbird pollinator species although are not significantly cross-compatible in terms of seed set, suggesting that pollinators may not be primary drivers of speciation in this instance, but rather other selective pressures such as fire, edaphic habitat and soil-moisture availability.
... Forest fires constitute one of the main drivers of tree mortality and forest cover loss in Mediterranean countries [100]. The long-term impact of forest fires can explain speciation in Mediterranean trees [101] and the low genetic diversity found in thermophilic, obligatory seeding species, such as pines [23]. Also, a clear genetic signature of natural selection for serotiny, a major fire-response trait, has been demonstrated [102]. ...
... The keyword "Fire" occurred in only 10 articles and is linked to 29 other keywords; however, the strength of these connections is quite low. Figure 8 and its related table indicate a shift of research focus from selection and measurement of diversity to drought and climate change, potentially because of an increased interest in the correlation between drought and fire in a climate change context. Although weak, a link exists with the blue cluster 2 (see phylogeny in Fig. 8), indicating an interest for studying the role of fire and fire-response traits in evolutionary patterns of Mediterranean trees (e.g., [101]). ...
Purpose of Review
Recognizing that in the context of global change, tree genetic diversity represents a crucial resource for future forest adaptation, we review and highlight the major forest genetics research achievements of the past decades in biodiversity-rich countries of the Mediterranean region. For this, we conducted a bibliometric analysis of the scientific literature spanning the past thirty years (1991–2020). Putting together the representative regionwide expertise of our co-authorship, we propose research perspectives for the next decade.
Recent Findings
Forest genetics research in Mediterranean countries is organized into three different scientific domains of unequal importance. The domain “Population diversity and Differentiation” related to over 62% of all publications of the period, the domain “Environmental conditions, growth and stress response” to almost 23%, and the domain “Phylogeography” to almost 15%. Citation rate was trending the opposite way, indicating a strong and sustained interest in phylogeography and a rising interest for genetics research related to climate change and drought resistance. The share of publications from Asia and Africa to the total within the Mediterranean increased significantly during the 30-year period analyzed, reaching just below 30% during the last decade.
Summary
Describing poorly known species and populations, including marginal populations, using the full potential of genomic methods, testing adaptation in common gardens, and modeling adaptive capacity to build reliable scenarios for forest management remain strategic research priorities. Delineating areas of high and low genetic diversity, for conservation and restoration, respectively, is needed. Joining forces between forest management and forest research, sharing data, experience, and knowledge within and among countries will have to progress significantly, e.g., to assess the potential of Mediterranean genetic resources as assisted migration material worldwide.
Introductory quote
Let us collect with care the facts we can observe, let us consult experience wherever we can, and when this experience is inaccessible to us, let us assemble all the inductions which observation of facts analogous to those which escape us can furnish and let us assert nothing categorically; in this way, we shall be able little by little to discover the causes of a multitude of natural phenomena, and, perhaps, even of phenomena which seem the most incomprehensible... J.B. de Lamarck (Philosophie zoologique, 1809), cited by O. Langlet (1971).
... Certaines études ont montré que les perturbations favorisent des assemblages d'espèces apparentées (Warwick & Clarke 1998 ;Verdu & Pausas 2007 ;Helmus et al. 2010) car sélectionnant probablement des traits de tolérance aux perturbations conservés phylogénétiquement (Dinnage 2009 La résilience d'un écosystème peut être définie comme la capacité de ce dernier à faire face aux perturbations sans changer de fonctionnement ). Le concept de résilience peut être présenté à partir de deux concepts initiaux : l'Engineering Resilience et l'Ecological Resilience (Holling 1973 ;Holling 1996). ...
... Competitive species are favored by an increase in fertilization, leading to a decrease of functional diversity of the plant community because of the convergence of many functional traits . Moreover, an increase in defoliation intensity corresponds to an increase in disturbances that favor the selection of closely related species (Verdu & Pausas 2007;Helmus et al. 2010). Indeed, increased disturbances might select disturbance-tolerance traits that could be phylogenetically conserved (Dinnage 2009), thus reducing phylogenetic diversity at the community level. ...
En Europe, les prairies semi-naturelles de moyenne montagne sont principalement des écosystèmes ayant évolués au cours de plusieurs décennies d’activité humaine. Ces écosystèmes présentent une biodiversité remarquable et dépendent de régimes traditionnels de perturbations par la fauche ou le pâturage. Cependant, dans l’objectif d’augmenter leur production de fourrage, les prairies semi-naturelles sont soumises à des régimes de perturbations de plus en plus importants ainsi qu’à de nouveaux types de perturbations. Ce travail de thèse propose d’apporter de nouveaux éléments pour suivre et comprendre l’impact des perturbations sur la diversité des communautés végétales des prairies semi-naturelles.Dans un premier temps, la comparaison de relevés de végétation anciens (2005 à 2009) avec des relevés récents (2019) a été réalisée dans des prairies de fauche de moyenne montagne. Cette comparaison a permis de mettre en évidence des évolutions contrastées de la diversité végétale et des régimes de perturbations entre deux massifs. Dans le massif des Vosges, la diversité végétale ainsi que les régimes de perturbations ne semblent pas avoir évolué. A l’inverse, dans le massif du Jura, la diversité végétale a fortement diminué, probablement en association avec une augmentation de la fréquence des régimes de perturbations et de la fertilisation.Dans un second temps, l’impact de perturbations de forte intensité sur la diversité végétale a été évalué. Dans les prairies de fauche, les perturbations par les pullulations de campagnols terrestres semblent permettre une augmentation de la richesse spécifique par la réduction de la compétition pour la lumière. A l’inverse, ces perturbations semblent favoriser des espèces proches phylogénétiquement et entraîner une diminution de l’équitabilité phylogénétique. Dans les pelouses sèches, les perturbations par l’utilisation de broyeurs de pierres ne semblent pas impacter la diversité végétale. En revanche, la composition en espèces des milieux perturbés évolue vers des végétations de prairies productives suite à la perte des espèces typiques des pelouses.Dans un troisième temps, l’utilisation d’espèces diagnostiques comme indicateurs des régimes de perturbations et de la diversité végétale dans les prairies pâturées du massif du Jura a été testée. Le nombre d’espèces diagnostiques dans un relevé de végétation s’est révélé être un bon indicateur de la diversité végétale et des régimes de fertilisation. Cependant, les espèces diagnostiques ne semblent pas être de meilleurs indicateurs que des espèces généralistes des prairies pour évaluer l’intensité des régimes de perturbations.Nos résultats confirment que les changements de pratiques agricoles sont une menace majeure pour la diversité végétale des prairies semi-naturelles de moyenne montagne, en particulier dans le massif du Jura. Nos travaux mettent également en avant que l’augmentation de la fréquence des régimes de perturbations est susceptible d’avoir davantage d’effets négatifs sur la diversité végétale que des perturbations de forte intensité mais peu fréquentes. Néanmoins, certaines perturbations de forte intensité, comme l’utilisation de broyeurs de pierres, peuvent entraîner des modifications très importantes et irréversibles de la composition en espèces des milieux perturbés. Dans l’objectif de concilier enjeux sociétaux et environnementaux, il convient de maintenir des parcelles productives ou les régimes de perturbations par la fauche ou le pâturage sont fréquents, ce qui permet d’assurer une production fourragère importante. Cependant, Il est également nécessaire de limiter la fréquence et l’intensité des perturbations dans des parcelles encore peu intensifiées afin de protéger leur composition en espèces ainsi que leur diversité végétale.
... To address these predictions, we characterized the structure of root-tip ECM fungal communities of natural P. pinaster and P. halepensis forests (Hernández-Serrano et al., 2013). For both pine forests, serotinous populations growing under a warm and dry Mediterranean climate subjected to high fire recurrence and nonserotinous populations growing under a subhumid climate where fires are rare (Verdú & Pausas, 2007) were surveyed ( Figure S1). Additionally, we determined, on excised ECM root tips, potential fungal enzymatic traits related to C turnover and mobilization of nutrients. ...
... Different authors have proposed that in ecosystems subjected to frequent fires, the positive response of microorganisms would indicate a selection of the fire-tolerant ones over time (Buscardo et al., 2015;Dooley & Treseder, 2011;Rincón et al., 2014). Fire recurrence in Mediterranean forests is intimately linked to temperature and drought (Pausas, 2004) plant and microbial communities is regulated by sequentially operating assembly rules: abiotic filtering is an omnipresent structuring force, and biological interactions (e.g., competition) further finetune the community assemblages (Pérez-Valera et al., 2018;Verdú & Pausas, 2007). ...
Fire is a major disturbance linked to the evolutionary history and climate of Mediterranean ecosystems, where the vegetation has evolved fire‐adaptive traits (e.g., serotiny in pines). In Mediterranean forests, mutualistic feedbacks between trees and ectomycorrhizal (ECM) fungi, essential for ecosystem dynamics, might be shaped by recurrent fires. We tested how the structure and function of ECM fungal communities of Pinus pinaster and Pinus halepensis vary among populations subjected to high and low fire recurrence in Mediterranean ecosystems, and analyzed the relative contribution of environmental (climate, soil properties) and tree‐mediated (serotiny) factors. For both pines, local and regional ECM fungal diversity were lower in high than low fire recurrence areas, although certain fungal species were favored in the former. A general decline of ECM root‐tip enzymatic activity for Pinus pinaster was associated with high fire recurrence, but not for Pinus halepensis . Fire recurrence and fire related‐factors such as climate, soil properties or tree phenotype explained these results. In addition to the main influence of climate, the tree fire‐adaptive trait serotiny recovered a great portion of the variation in structure and function of ECM fungal communities associated with fire recurrence. Edaphic conditions (especially pH, tightly linked to bedrock type) were an important driver shaping ECM fungal communities, but mainly at the local scale and likely independently of the fire recurrence. Our results show that ECM fungal community shifts are associated with fire recurrence in fire‐prone dry Mediterranean forests, and reveal complex feedbacks among trees, mutualistic fungi and surrounding environment in these ecosystems.
... Environmental filters also impact the phylogenetic structure of communities, manifesting in patterns of phylogenetic clustering, where community members are more closely related due, for instance, to shared traits for persistence in a particular environment [41,42]. In contrast, in the absence of environmental filters, a pattern of phylogenetic overdispersion emerges, where individuals are not closely related, and interactions predominate [41,[43][44][45]. ...
In southern South America, zonal flora, defined by macroclimatic conditions, is strongly influenced by an aridity filter near 29°S. Cushion bogs, high-altitude wetlands along the Andes, display homogeneous flora with cushion species dominance, contrasting with zonal vegetation. Despite being influenced by microclimatic conditions, these ecosystems experience varied environmental effects. This study identifies environmental filters affecting bog communities along a broad-scale latitudinal gradient from 15°S to 42°S. We analyzed 420 bogs and 284 species across three macroclimatic regions with distinct summer, winter, and transitional arid rainfall regimes. Using variance partitioning and membership-based regionalization models, we examined the impacts of climatic, edaphic, and spatial variables on beta diversity. We also assessed species' niche overlap and the influence of environmental filters on the communities' phylogenetic diversity. Results show that species turnover and niche overlap vary with macroclimatic differences, delineating three distinct regions. Notably, phylogenetic clustering in the driest part of the gradient (23°S —24°S) highlights the impact of the environmental filter. Aridity and temperature variations at a broad scale serve as environmental filters shaping the composition of bog communities across southern South America.
... The key role of wildfires as a driver of the floristic composition, structure and dynamics of Mediterranean ecosystems has long been emphasized (Di Pasquale et al., 2004;Naveh, 1975;Verdú & Pausas, 2007). However, the combined effect of wildfire and climate change on current plant community dynamics is poorly understood (Buhk et al., 2007;Carrillo-García et al., 2023;Fernández-García et al., 2020;Quézel & Médail, 2003), mainly due to the scarcity of long-term vegetation monitoring studies and large-scale climate-change experiments. ...
Worldwide, large wildfires are becoming increasingly common, leading to economic damages and threatening ecosystems and human health. Under future climate change, more frequent fire disturbance may push ecosystems into non‐forested alternative stable states. Fire‐prone ecosystems such as those in the Mediterranean Basin are expected to be particularly vulnerable, but the position of tipping points is unclear.
We compare long‐term palaeoecological data from Sardinia with output from a process‐based dynamic vegetation model to investigate the mechanisms controlling the complex interactions between fire, climate, and vegetation in the past and the future.
Our results show that past vegetation changes from Erica ‐shrublands to mixed evergreen‐broadleaved Quercus ilex ‐dominated forests were driven by a climate‐induced fire regime shift. By simulating vegetation dynamics under varying fire regimes, we could reproduce Holocene vegetation trajectories and mechanistically identify tipping points.
Without an immediate reduction of greenhouse gas emissions, we simulate future expansion of fire‐prone Mediterranean maquis and increasing fire occurrence. Similarly, high anthropogenic ignition frequencies and plantations of non‐native, highly flammable trees could induce a shift to fire‐adapted Erica shrublands. However, our simulations indicate that if global warming can be kept below 2°C, Quercus ilex forests will be able to persist and effectively reduce fire occurrences and impacts, making them a valuable restoration target in Mediterranean ecosystems.
Synthesis . By combining long‐term records of ecosystem change with a dynamic vegetation model, we show that past climate‐driven fire regime shifts were the main driver of vegetation change, creating alternative stable states that persisted over centuries. Projected future climate change exceeding Holocene variability leads to pronounced vegetation changes and increased fire risks in our simulations, requiring new fire management strategies to maintain current ecosystem services.
... The region (defined as the region around the Mediterranean sea with a Mediterranean-type climate by Chergui et al. (2018)) has an annual dry and warm period (summer) when intense crown fires are frequent (Pausas 2004;Archibald et al. 2013;Bedia et al. 2015). In such ecosystems, fire controls the age and structure of the vegetation, as well as the composition of species (Verdú and Pausas 2007), that is, vegetation depends not only on climate, but also on the fire regime (Trabaud and Galtié 1996), and human activities have strongly regulated fire regimes across the Mediterranean region (Pausas and Vallejo 1999;Keeley et al. 2011). Indeed, there is evidence that fires were frequent during the late Quaternary (Carrión et al. 2004), and they were also probably frequent much earlier, as many species have acquired adaptive mechanisms to persist and regenerate after recurrent fires (Pausas 2004;Pausas and Verdú 2005). ...
Understanding and predicting forest fires have proved a highly difficult endeavour, which requires extending and adapting complex models used in different fields. Here, we apply a marked point process approach, commonly used in ecology, which uses multiple Gaussian random fields to represent dynamics of Mediterranean forest fires in a spatio-temporal distribution model. Inference is carried out using Integrated Nested Laplace Approximation (INLA) with , an accessible and computationally efficient approach for Bayesian hierarchical modelling, which is not yet widely used in species distribution models. Using the marked point process approach, intensity of forest fires and dispersion were predicted using socioeconomic factors and environmental and fire-related variables. This demonstrates the advantage of complex model components in accounting for spatio-temporal dynamics that are not explained by environmental variables. Introduction of spatio-temporal marked point process can provide a more realistic perspective of a system, which is of particular importance for a practical and impact-focused worldwide problem such as forest fires.
Supplementary materials accompanying this paper appear online.
... Thriving in the warmest and driest environments of Europe, the Mediterranean vegetation type is considered highly vulnerable to climate-change impacts, primarily due to aridity, disturbance-driven forest decline, biodiversity loss, and changes in vegetation, which also increase the frequency of wildfires [26] and references therein. In this context, heat-shock-stimulated germination is prominently observed in Mediterranean-type ecosystems of California, the Mediterranean Basin, South Africa, and southwestern Australia [16,[27][28][29][30]. Heat-shock-stimulated germination is also a phylogenetically conserved trait [31] and is therefore restricted to a few families [32]. In the Mediterranean Basin, for example, heat-shock-stimulated germination is mainly observed in the Fabaceae and Cistaceae [33] and references therein. ...
Many Astragalus species exhibit seeds with physical dormancy (PY), but little is known about the ecological context of this dormancy. We focused on A. maritimus and A. verrucosus, two threatened Sardinian endemic species inside the subgenus Trimeniaeus Bunge. Fresh seeds collected from the only two respective known populations were used to investigate the effect of mechanical scarification, heat shock, and water imbibition processes on PY release and germination. PY can be overcome through mechanical scarification of the water-impermeable seed coats, while no dormancy break was detected, nor a subsequent increase in seed germination due to fire-induced heat. This suggests that fire does not trigger dormancy release and seed germination in these species. The seeds tolerate relatively high heat shock temperatures (up to 120 and 100 °C for A. verrucosus and A. maritimus, respectively), but after 120 °C for 10 min, the number of dead seeds increases in both species. These facts suggest the capacity to develop a soil seed bank that can persist after fires and delay germination until the occurrence of optimal conditions. As regards water imbibition, both Astragalus species did not show the typical triphasic pattern, as germination started without further water uptake. This study emphasizes the significance of understanding germination processes and dormancy in threatened species. In fire-prone ecosystems, PY dormancy plays a crucial role in soil seed bank persistence, and it may be selectively influenced by post-fire conditions. Understanding such adaptations provides useful insights into conservation strategies.
... This leaves a strong fingerprint on current phylogenetic diversity and may explain the stronger effect of fire on this biodiversity component compared to other components (see variance partitioning analyses in Fig. 3; PSES.mpd). Consequently, analyzing biodiversity responses to nurse plants collectively and considering the time since the last fire offers strong potential for linking fire to the evolutionary history of post-fire vegetation and the mechanisms of nurse plants (Keeley et al. 2012;Verdu and Pausas 2007). ...
Abstract
Backgrounds Plant-plant interactions are among the most important factors affecting the natural recovery of vegetation. While the impacts of nurse plants on species composition and biodiversity are well documented, the effects
of different nurse’s growth forms on all biodiversity components including taxonomic, functional, and phylogenetic
diversity have been less studied and compared, especially for their effects on different times after fire disturbance. This
research was focused on comparing the efects of a perennial grass (Elymus hispidens), a perennial herb (Phlomis can�cellata), and a high shrub species (Lonicera nummulariifolia) on species composition and the biodiversity components,
and how these impacts change across five sites with short-term (1 and 4 years sites), long-term (10 and 20 years sites)
times since last fire and a control site where no fire was known in recorded history in semi-arid shrublands of Fereizi
Chenaran located in Northeast of Iran. The changes of species composition and taxonomic, functional, and phylogenetic diversity were calculated with respect to the presence/absence of nurse’s growth forms, fire history, and their
interactions.
Results Nurse shrubs affected species composition and all biodiversity components, whereas all indices were
reduced when considering Elymus grass as nurse plant. On the other hand, the herb Phlomis enhanced species composition and taxonomic diversity, while it had a negative effect on functional and phylogenetic diversity. Such specific
effects of nurse types were mostly observed under long timescales (i.e., 10- and 20-year sites). Interestingly, the relative importance of nurse types and time since the last fire largely explained the variation of species composition
and biodiversity components, with larger effects of nurse types on all biodiversity components. However, we found
a significant contribution of fire explaining variation of species composition and phylogenetic diversity.
Conclusions These results indicated nurse plants can affect the post-fire recovery of vegetation by providing specific
mechanisms controlling beneficiary relatedness depending on their growth forms and time scales since the last fire.
Therefore, these findings suggest perennial plants in the form of nurse species as a useful factor to develop techniques of active restoration in burned ecosystems
... The fire was recurrent much previously as many species have gained adaptive mechanisms to continue and regenerate after recurrent fires [27,28]. Even at a community level, the phylogenetic biodiversity of the Mediterranean basin plant has been sorted out as a function of the fire regime [39]. Mediterranean basin biodiversity has been composition according to the various fire regimes. ...
الغرض الرئيسي من هذه الدراسة هو تحديد وتحليل وقياس تغيرات الغطاء الأرضي من حرائق الغابات الإنتاجية في الجبل الأخضر باستخدام صور لاندسات 8 في عام 2021. تم إجراء تصنيفات خاضعة للإشراف على صور لاندسات 8. تم تحديد التغييرات من خلال حساب مركب اللون الحقيقي ، ومركب الألوان الزائفة ، وإخراج NDVI أحادي النطاق ، و NBR. أظهر تحليل الصور ذات الألوان الحقيقية والألوان الزائفة وجود الغطاء النباتي وغيابه. يمكن استخدام NDVI لتحديد كمية الغطاء النباتي الموجود وصحته النسبية. تعد صور Landsat-8 ، خاصة عند تحويلها إلى NDVI ، أداة مفيدة لمديري الأراضي الذين يبحثون عن طريقة رخيصة وفعالة لمراقبة التغيرات في مستوى المناظر الطبيعية. أظهرت النتائج أن NBR لديه قدرة أكبر على تقييم مستويات شدة الحرائق. وقد أوضحت النتائج أن إجمالي المساحة المحروقة حوالي 90 هكتاراً في منطقة الدراسة -2021. قد تكون أسباب الحريق طبيعية أو بشرية ، لكن الظروف الجوية يمكن أن يكون لها مساهمات كبيرة في انتشارها. يمكن مراقبة المنطقة المحروقة وتحليلها على مساحات واسعة بطريقة فعالة في وقت قصير وبتكلفة منخفضة باستخدام صور الأقمار الصناعية ويمكن تحديد المنطقة المتأثرة باستخدام صور الأقمار الصناعية من خلال تقنية نظم المعلومات الجغرافية.
... In contrast, the less Mediterranean species were more fragmented in the FTs of broadleaved species. The role of past land uses (e.g., harvesting for firewood, extensive livestock) (Valbuena-Carabaña et al., 2010;Elena-Rosselló et al., 2013;Iriarte-Goñi, 2013;López-Leiva et al., 2020;Vadell et al., 2022) and wildfires (Ortega et al., 2012;Martín-Martín et al., 2013), which are intrinsically associated with the Mediterranean environment (Pausas and Vallejo, 1999;Verdú and Pausas, 2007), and the influence of land ownership Mölder et al., 2021), should be considered in future works aiming to explain these findings. ...
... The Mediterranean Basin, in which Türkiye is located, has been under the influence of Mediterranean climate types characterized by summer drought for approximately 1.6 million years. The transition to the settled order in the region since 790,000 years ago, anthropogenic fires were added to the natural fires (Goren-Inbar et al., 2004) and the plants in the Mediterranean region have been under the influence of the fires that have occurred frequently since those times (Verdú ve Pausas, 2007). ...
The main purpose of the study is to examine the impact of drastic and proactive forest fire interventions, which are applied to avoid the risk of loss of life and property close to urban areas, on the continuity of plant species with fire-adapted characters and the potential to cause species loss. In this context, the basic assumption of the study is that the reduced frequency of fires caused by suppressed fires in natural areas in order to avoid the risk of forest fires that may affect residential areas, will lead to the reduction of various plant species that sustain their lives thanks to their fire-adaptive characters. As a qualitative data analysis method, the rates of urban and forest areas, the number of forest fires, the amount of burned area and plant species diversity data were used to deal with the study data with document analysis. In the selection of the 10 metropolitan cities that constitute the sample area of the study, the criteria of being in the Mediterranean ecosystem, containing plant species adapted to fire, and being metropolitan (where natural and built environment elements are intertwined) were taken as basis. The study will create an ecological perspective in fire prevention policies and strategies to be developed through the determination of plant species characteristics in large cities located in the fire-prone Mediterranean ecosystem.
... The ROAD site, which was particularly subject to disturbance through the frequent cutting and removal of vegetation, recorded the only significant phylogenetic pattern (clustering) for both pools (all species and only natives). A possible explanation for this finding relies on the assumption that a local community frequently subjected to disturbances, such as those sustained by the ROAD site, is expected to be mostly composed by phylogenetically closely related species, which have similar functional attributes that allow them to better establish in those conditions (Verdú & Pausas, 2007;Zhang et al., 2014). Further, the close phylogenetic relatedness between the alien and native species within the community may confer some resistance to invasion if intense disturbance is less frequent, since their high trait overlapping tends to enhance competition in moderate environmental conditions (Brunbjerg et al., 2012;Gerhold et al., 2011;Guerin et al., 2019;Liendo et al., 2021;Violle et al., 2011). ...
Alien species can modify ecosystem functions and ecological processes in natural communities and potentially become invasive. In the Brazilian Pampean grasslands, reports of changes in land use and invasions of alien plant species are becoming more frequent. This study aimed to investigate species composition and phylogenetic relationships between native and alien plants across four sites of Brazilian Pampean grasslands under distinct land uses (NOM: no agricultural management; GRZ: grazed pastures; AGR: agrarian crops; ROAD: roadside). The phylogenetic relationship between native and alien species was analyzed at two scales: inter-site and intra-site. We found phylogenetic diversity dissimilarity across all sites considering all species. Overall, across all sites, we found random phylogenetic relationships among alien and native species. We found significant phylogenetic clustering in the most disturbed site (ROAD) for the two sets of species: all (alien and natives) and only native species. We conclude that clustering of phylogenetic relationships among alien and native species is only evident at small (intra-site) sampling scales in environments subject to high levels of disturbance (i.e., roadsides) in the studied Pampean Grasslands, suggesting that environmental filtering plays an important role in local community assembly.
... Comparing fire syndromes across regions can be challenging, since there is no universal way of measuring R, S and F. This is because these axes (specific functions) depend on the combination of many underlying functional traits Pausas et al., 2017;Pausas & Keeley, 2014;Poulos et al., 2018), which, in turn, are differentially influenced by multiple factors, fire being a prominent, but not the only one. In addition, it is not uncommon for these traits to show a phylogenetic signal, that is a tendency to be strongly associated or confined to particular clades (Silva & Batalha, 2010;Verdú & Pausas, 2007). Bearing these limitations in mind, one can still consider widely used variables that have a similar ecological interpretation across floras. ...
Plant fire syndromes are usually defined as combinations of fire response traits, the most common being resprouting (R) and seeding (S). Plant flammability (F), on the other hand, refers to a plant's effects on communities and ecosystems. Despite its important ecological and evolutionary implications, F has rarely been considered to define plant fire syndromes and, if so, usually separated from response syndromes.
We propose a three‐dimensional model that combines R, S and F, encapsulating both plant response to fire regimes and the capacity to promote them. Each axis is divided into three possible standardized categories, reflecting low, medium and high values of each variable, with a total of 27 possible combinations of R, S and F.
We hypothesized that different fire histories should be reflected in the position of species within the three‐dimensional space, and that this should help assess the importance of fire as an evolutionary force in determining R‐S‐F syndromes.
To illustrate our approach, we compiled information on the fire syndromes of 24 dominant species of different growth forms from the Chaco seasonally dry forest of central Argentina, and we compared them to 33 species from different Mediterranean‐type climate ecosystems (MTCEs) of the world.
Chaco and MTCEs species differed in the range (7 syndromes vs. 13 syndromes, respectively) and proportion of extreme syndromes (i.e. species with extreme values of R, S and/or F) representing 29% of species in the Chaco vs. 45% in the MTCEs.
In addition, we explored the patterns of R, S and F of 4032 species from seven regions with contrasting fire histories, and found significantly higher frequencies of extreme values (predominantly high) of all three variables in MTCEs compared to the other regions, where intermediate and low values predominated, broadly supporting our general hypothesis.
The proposed three‐dimensional approach should help standardize comparisons of fire syndromes across taxa, growth forms and regions with different fire histories. This will contribute to the understanding of the role of fire in the evolution of plant traits and assist vegetation modelling in the face of changes in fire regimes.
Read the free Plain Language Summary for this article on the Journal blog.
... The fire was recurrent much previously as many species have gained adaptive mechanisms to continue and regenerate after recurrent fires [27,28]. Even at a community level, the phylogenetic biodiversity of the Mediterranean basin plant has been sorted out as a function of the fire regime [39]. Mediterranean basin biodiversity has been composition according to the various fire regimes. ...
The main purpose of this study is to determine, analyze and quantify land cover changes from production forest fires in the Al-Jabal Al-Akhdar using Landsat8 imagery in 2021. Supervised classifications were performed on the Landsat 8 images. Changes were identified by calculating a true-color composite, false-color composite, a single-band NDVI output, and NBR. The analysis of true-color and false-color images showed the presence and absence of vegetation. The NDVI can be used to quantify the amount and relative health of the vegetation present. Landsat-8 imagery, especially when converted to NDVI, is a useful tool for land managers looking for a cheap, and efficient way to monitor landscape level changes. Results have shown the NBR has a greater capacity to assess fire severity levels. The results have found the total burned area about 90 hectares in study area-2021. The causes of fire may be natural or anthropogenic, but weather conditions can have significant contributions to their propagation. The burned area can be monitored and analyzed over large areas in an efficient manner in a short time and at low cost by using satellite images and the affected area can be defined using satellite imagery through geographic information systems technology.
... In this study, the two pine species P. halepensis, and P. sylvestris were chosen because they are obligate seeders that are not able to resprout after a fire; the post-fire recruitment is therefore only based on seeds [43]. This type of recruitment facilitates faster generation turnover and makes the species more sensitive to changes in fire frequency [67]. Furthermore, these two species have different adaptive strategies to fire (fire-embracer vs. fire-resistant, respectively). ...
Flammability is a major factor involved in Mediterranean plant evolution that has led to the diversity of fire-related traits according to fire regimes and fire-adaptive strategies. With on-going climate change, new fire regimes are threatening plant species if they do not adapt or acclimate. Studying flammability and terpene content variation according to the different fire frequencies in the recent fire history represents a great challenge to anticipating the flammability of ecosystems in the near future. The flammability of shoots and litter as well as the needle terpene contents of two pine species with different fire adaptive strategies (Pinus halepensis and Pinus sylvestris) were measured according to two fire modalities (0 vs. 1–2 fire events over the last 60 years). Results showed that, regardless of the species and the fuel type, flammability was higher in populations having undergone at least one past fire event even when factors influencing flammability (e.g., structural traits and hydric content) were considered. The terpene content did not vary in P. sylvestris’ needles according to the fire modality, but that of sesqui- and diterpenes was higher in P. halepensis’ needles sampled in the “Fire” modality. In addition, associations made between flammability and terpene content using random forest analyses indicated that the terpene molecules differed between fire modalities for both species and fuel types. The same results were obtained with significant terpenes driving flammability as were highlighted in the PLS analyses, especially for P. halepensis for which enhanced shoot flammability in the “Fire” modality agreed with the adaptive strategy of this species to fire.
... However, rare, large scale disturbances can have major impacts in the short and long term (Flynn et al. 2010, Yee et al. 2019. Large scale alterations in plant communities can occur for various reasons including, fire, pest outbreak, anthropogenic pressures, and hurricanes (Walker 1991, Verd u and Pausas 2007, Hooper 2008, Hogan et al. 2016, Hu and Smith 2018. These types of disturbances are known to have long-lasting effects on the dynamics, structure, and function of plant communities (Brokaw and Grear 1991, Zimmerman et al. 1994, Shiels et al. 2010, Comita et al. 2018. ...
Large scale disturbances are known to impact the alpha and beta diversity of communities. However, whether these disturbances increase or decrease diversity is often debated. The goal of this study was to quantify how the diversity of the seedling community was impacted within and across elevation in the El Yunque forest of Puerto Rico following a major hurricane. We tested two alternative hypotheses, that hurricanes are relatively more homogenizing or non‐homogenizing forces, by quantifying changes in alpha and beta diversity of the seedling community post‐hurricane. This approach highlights whether ecological mechanisms associated with community homogenization (species‐specific survival, successional processes, and reduced environmental heterogeneity) or non‐homogenization (resource release, increased environmental heterogeneity, and stochastic processes) structure the seedling community post‐hurricane. We compared species richness, Fisher’s α, Simpson’s evenness, and multiple aspects of beta diversity within and among 25 seedling plots at 300, 400, and 500 m in elevation pre‐ and post‐hurricane. We found that species richness, diversity, and evenness were higher post‐hurricane, but abundance decreased 19%. Increases in alpha diversity suggest that hurricanes are non‐homogenizing forces potentially linked with increases in light levels promoting colonization of early‐successional species and resource release for other light‐demanding species. The beta diversity results varied in their support for hurricanes as homogenizing depending upon the spatial scale of the analysis, potentially due to a combination of mechanisms including species‐specific survival and site‐specific differences. To fully grasp how the seedling community responds and recovers from disturbance, additional long‐term monitoring will be needed to allow insight into the future of species richness, abundance, and spatial and temporal changes in community composition.
... In addition to complexities that can obscure links between processes and patterns using PCS, studies typically assume that PCS-climate relationships are stable through time, and although community assembly is a dynamic process [8], most studies have analyzed PCS using static community data [27][28][29]. When studies have examined PCS through time, most have either used (1) a proxy for time rather than a time series of observations (e.g., chronosequences; [30][31][32][33] or (2) relatively short time sequences [34][35][36]. ...
Disentangling the influence of environmental drivers on community assembly is important to understand how multiple processes influence biodiversity patterns and can inform understanding of ecological responses to climate change. Phylogenetic Community Structure (PCS) is increasingly used in community assembly studies to incorporate evolutionary perspectives and as a proxy for trait (dis)similarity within communities. Studies often assume a stationary relationship between PCS and climate, though few studies have tested this assumption over long time periods with concurrent community data. We estimated two PCS metrics—Nearest Taxon Index (NTI) and Net Relatedness index (NRI)—of fossil pollen assemblages of Angiosperms in eastern North America over the last 21 ka BP at 1 ka intervals. We analyzed spatiotemporal relationships between PCS and seven climate variables, evaluated the potential impact of deglaciation on PCS, and tested for the stability of climate-PCS relationships through time. The broad scale geographic patterns of PCS remained largely stable across time, with overdispersion tending to be most prominent in the central and southern portion of the study area and clustering dominating at the longitudinal extremes. Most importantly, we found that significant relationships between climate variables and PCS (slope) were not constant as climate changed during the last deglaciation and new ice-free regions were colonized. We also found weak, but significant relationships between both PCS metrics (i.e., NTI and NRI) and climate and time-since-deglaciation that also varied through time. Overall, our results suggest that (1) PCS of fossil Angiosperm assemblages during the last 21ka BP have had largely constant spatial patterns, but (2) temporal variability in the relationships between PCS and climate brings into question their usefulness in predictive modeling of community assembly.
... Some studies have shown that disturbed ecosystems present more functionally related species than undisturbed ones (Verdú and Pausas, 2007;Tabarelli et al., 2008). Nevertheless, despite the low functional beta diversity and higher functional redundancy in OGF, probably different shade-tolerant species have different functions in comparison to SGF that are re-growing after SC. ...
Predicting how multiple drivers shape beta diversity across tropical forest is one of the most important issues in ecology. However, the relative importance of drivers to the spatial and temporal dissimilarities in woody species composition (beta diversity) along Amazon forest succession remains poorly studied. In this study, we assessed how stand age (factor related to habitat filtering and succession), soil properties (factors related to resource availability and environmental filtering) and forest patches distance (spatial factor related to dispersal limitation) affect the taxonomic and functional beta diversity along an Amazon forest succession. Taxonomic and functional beta diversity indices were quantified based on abundance-based metrics and trait-based approach using functional traits related to plant dispersion and growth. Overall, taxonomic and functional beta diversity was consistently higher in initial successional stage among plots and sites; however, old-growth forest presented the lowest functional beta diversity. We observed differences in beta diversity components among successional stages and old-growth forest. The beta diversity components showed a clear higher pattern in the different second-growth forests than in the old-growth forest. Soil fertility and stand age explained most of the variation in taxonomic and functional turnover and beta diversity. This pattern probably is an outcome of the patches within a continuous old-growth forest as main seed sources for the colonization and establishment of tree species. We observed that functional beta diversity was lower than taxonomic beta diversity; therefore we presumed that there is higher functional redundancy in old-growth forests, compared to taxonomic beta diversity. However, despite the lower functional beta diversity and higher functional redundancy in old-growth forest, probably shade-tolerant species have different functions than second-growth forests that re-growing after shifting cultivation. We argue that an old-growth forest has lower functional diversity than second-growth forests but, it is probably induced by a high turnover of second-growth forests.
... halepensis; PS, P. sylvestris; F, "Fire" populations; NF, "No-Fire" populations) In the present study, we focused on obligate seeders with post-fire recruitment that is solely based on seeds (Nuñez et al., 2003). This facilitates faster generation turnover and makes the species more sensitive to changes in fire frequency (Verdú & Pausas 2007). We sampled populations of two species commonly found in the study area (Pinus halepensis and Pinus sylvestris) and that present two different adaptive strategies to fire. ...
Key message
Climate change will induce a change in fire frequency in Mediterranean region and that could impact fire-adapted plant species. We showed that fire-related traits of some pine species are strongly related to other factors than fire but the recent fire history has nonetheless an impact on the variation of key traits for different fire adaptive strategies.
ContextIn fire-prone Mediterranean areas, climate change is expected to exacerbate the fire pressure on ecosystems, altering the current fire regime and threatening species if they cannot acclimate.AimsStudying intraspecific variations of some fire-related traits in relation to variation in recent fire activity is thus an important step to better understand if this acclimation is possible.Methods
We measured structural (bark thickness, shoot bulk density, self-pruning, leaf surface to volume ratio) and functional (serotiny level for Pinus halepensis only) traits in two pines species (Pinus halepensis and Pinus sylvestris) commonly found in southeastern France and that present different fire-adaptive strategies (resilience vs resistance, respectively). Populations were sampled according to different fire frequency modalities (0 vs 1 to 2 fires) along a geographical gradient, measuring numerous environmental and plant characteristics to be used cofactors in the analyses.ResultsAs expected, trait variation was strongly linked to environmental and tree characteristics as well as to ontogeny overriding the effect of fire modalities, even though using integrative models with random effect. However, fire modalities had an impact on the variance of some key fire-related traits of Pinus halepensis.Conclusion
This study will help to anticipate the future response of these Mediterranean pine species and further underlines the importance of investigating chemical traits, flammability, and genetic variation of highly heritable traits, such as serotiny.
... In addition to complexities that can obscure links between processes and patterns using PCS, studies typically assume that PCS-climate relationships are stable through time, and although community assembly is a dynamic process [8], most studies have analyzed PCS using static community data [27][28][29]. When studies have examined PCS through time, . ...
Disentangling the influence of environmental drivers on community assembly is important to understand how multiple processes influence biodiversity patterns and can inform understanding of ecological responses to climate change. Phylogenetic Community Structure (PCS) is increasingly used in community assembly studies to incorporate evolutionary perspectives and as a proxy for trait (dis)similarity within communities. Studies often assume a stationary relationship between PCS and climate, though few if any studies have tested this assumption over long time periods with concurrent community data. We estimated Nearest Taxon Index (NTI) and Net Relatedness index (NRI), two PCS metrics, of fossil pollen assemblages of angiosperms in eastern North America data over the last 21 ka BP at 1ka intervals. We analyzed spatiotemporal relationships between PCS and seven climate variables, evaluated the potential impact of deglaciation on PCS, and tested for the stability of climate-PCS relationships. The broad scale patterns of PCS, with overdispersion increasing towards the southern and eastern parts of the study area, remained largely stable across time. Most importantly, we found that significant relationships between climate variables and PCS (slope) were unstable as climate changed during the last deglaciation and new ice-free regions were colonized. We also found weak, but significant, relationships between both PCS metrics (i.e., NTI and NRI) and climate and time-since-deglaciation, which were stable even though the baselines (intercepts) changed through time. Overall, our results suggest that (1) PCS of fossil Angiosperm assemblages during the last 21ka BP have had predictable spatial patterns, but (2) the instability in the relationships between PCS and climate brings into question their usefulness in predictive modeling of community assembly.
... The benefits of facilitation in stressful habitats are magnified as phylogenetic relatedness is reduced because the plants not only compete less but also can cooperate more (Montesinos-Navarro et al. 2017. Competition is lower between phylogenetically distant species because they tend to have different physiological and life history traits and therefore to segregate their niches (Webb et al. 2002, Cavender-Bares et al. 2004, Verdú and Pausas 2007. Also, recent evidence indicates that the cooperation between distantly related species may explain plant facilitation due to nutrient transfer through common mycorrhizal networks (Montesinos-Navarro et al. 2019b). ...
Environmental conditions can modify the intensity and sign of ecological interactions. The stress gradient hypothesis (SGH) predicts that facilitation becomes more important than competition under stressful conditions. To properly test this hypothesis, it is necessary to account for all (not a subset of) interactions occurring in the communities and consider that species do not interact at random but following a specific pattern. We aim to assess elevational changes in facilitation, in terms of species richness, frequency and intensity of the interaction as a function of the evolutionary relatedness between nurses and their associated species. We sampled nurse and their facilitated plant species in two 1000–2000 m. elevation gradients in Mediterranean Chile where low temperature imposes a mortality filter on seedlings. We first estimated the relative importance of facilitation as a mechanism adding new species to communities distributed along these gradients. We then tested whether the frequency and intensity of facilitation increases with elevation, taking into account the evolutionary relatedness of the nurse species and the facilitated species.
We found that nurses increase the species richness of the community by up to 35%. Facilitative interactions are more frequent than competitive interactions (56% versus 44%) and facilitation intensity increased with elevation for interactions involving distantly related lineages.
Our results highlight the importance of including an evolutionary dimension in the study of facilitation to have a clearer picture of the mechanisms enabling species to coexist and survive under stressful conditions. This knowledge is especially relevant to conserve vulnerable and threatened communities facing new climate scenarios, such as those located in Mediterranean‐type ecosystems.
... However, there was no evidence about clustering or divergence of traits in both studies. Verdú et al. showed high fire frequency leads to phylogenetic clustering (Verdú & Pausas, 2007), caused by environmental filtering similarly. Moreover, the similar pattern was even showed in avian studies that a hasher habitat results in phylogenetic clustering (Gianuca, Dias, Debastiani, & Leandro, 2014;González-Caro, Parra, Graham, Mcguire, & Cadena, 2012). ...
Community assembly processes is the primary focus of community ecology. Using phylogenetic-based and functional trait-based methods jointly to explore these processes along environmental gradients are useful ways to explain the change of assembly mechanisms under changing world. Our study combined these methods to test assembly processes in wide range gradients of elevation and other habitat environmental factors. We collected our data at 40 plots in Taibai Mountain, China, with more than 2,300 m altitude difference in study area and then measured traits and environmental factors. Variance partitioning was used to distinguish the main environment factors leading to phylogeny and traits change among 40 plots. Principal component analysis (PCA) was applied to colligate other environment factors. Community assembly patterns along environmental gradients based on phylogenetic and functional methods were studied for exploring assembly mechanisms. Phylogenetic signal was calculated for each community along environmental gradients in order to detect the variation of trait performance on phylogeny. Elevation showed a better explanatory power than other environment factors for phylogenetic and most traits' variance. Phylogenetic and several functional structure clustered at high elevation while some conserved traits overdispersed. Convergent tendency which might be caused by filtering or competition along elevation was detected based on functional traits. Leaf dry matter content (LDMC) and leaf nitrogen content along PCA 1 axis showed conflicting patterns comparing to patterns showed on elevation. LDMC exhibited the strongest phylogenetic signal. Only the phylogenetic signal of maximum plant height showed explicable change along environmental gradients. Synthesis. Elevation is the best environment factors for predicting phylogeny and traits change. Plant's phylogenetic and some functional structures show environmental filtering in alpine region while it shows different assembly processes in middle-and low-altitude region by different trait/phy-logeny. The results highlight deterministic processes dominate community assembly in large-scale environmental gradients. Performance of phylogeny and traits along gradients may be independent with each other. The novel method for calculating functional
... Thus, when abiotic filters select individuals based on their tolerance to resource availability, this leads to a restriction in the range of the amplitude of functional trait values with different functions and a convergent distribution with low dispersion around the functional trait mean (Kunstler et al., 2012;Kraft and Ackerly, 2015). Therefore, when this filter is connected to the disturbance, it may lead to an increase in dispersion or divergence of functional trait values, mainly those related to regeneration (Verdú and Pausas, 2007;Ding et al., 2012). In contrast, density-dependent biotic filters may have contrasting effects with respect to functional trait distributions during succession, such as the relative importance of limiting similarity and competitive exclusion (Webb et al., 2002;Schwilk and Ackerly, 2005;Violle et al., 2011). ...
Two competing ecological hypotheses, i.e., the niche complementarity (NCH) and the mass ratio (MRH) hypotheses , have been proposed to explain how stand structural complexity, functional trait diversity and composition simultaneously determine aboveground biomass in natural forests. Here, we hypothesized that the effects of stand structural attributes and functional trait composition overrule the effects of functional diversity on aboveground biomass during tropical forest succession. We tested different linear mixed-effects models to determine the effects of abiotic (i.e. nutrients and soil texture), taxonomic (i.e. woody species richness and composition), stand structural (i.e. stem count and maximum tree diameter), and functional attributes (func-tional divergence and composition). The functional attributes were based on functional divergence (FDvar) and community-weighted mean (CWM) trait values of wood density (WD). We collected data using 45 sample plots (20 m × 50 m) established in four old-growth and second-growth forests with varied stand stages from three sites in the northern region of Amazonas State, Venezuela. The MRH model showed that CWM-WD had a strong direct positive effect on aboveground biomass, followed by a positive effect of maximum tree diameter, but had a weak positive relationship with soil fertility and FDvar-WD. Our study suggests that low trait diversity and high CWM-WD and maximum tree diameter determine high levels of aboveground biomass, which could be concentrated in species with larger diameters and high wood density. We conclude that stand structural attributes and functional dominance override the effects of FDvar of WD on aboveground biomass, and hence, it is important to test the mutual effects of functional diversity and composition when exploring the effects of functional traits on forest functioning.
... Similarly, in the western Mediterranean Basin, the proportion of species with fire-stimulated germination was higher in Mediterranean heathland (acid, nutrient-poor soils) than in garrigue-like shrublands (more fertile soils; [24]). Since the investigation of the role of fire in the evolution of Mediterranean species in the Mediterranean region has traditionally focused on garrigue vegetation (e.g., [27][28][29][30]), comparative studies have shown that fire-recruiting species are less frequent in the Mediterranean Basin than in other Mediterranean-type regions, thus concluding that fire-selective pressures would not have been so strong in the Mediterranean region [1,31]. However, the highly fire-dependent Mediterranean heathland habitat [24], although less abundant than the garrigue, has a non-negligible, wide range in the western Mediterranean Basin [32]. ...
Some fire ecology studies that have focused on garrigue-like vegetation suggest a weak selective pressure of fire in the Mediterranean Basin compared to other Mediterranean-type regions. However, fire-prone Mediterranean heathland from the western end of the Mediterranean Basin has been frequently ignored in the fire ecology literature despite its high proportion of pyrogenic species. Here, we explore the evolutionary ecology of seed traits in the generalist rockrose Cistus salviifolius L. (Cistaceae) aiming to ascertain the role of the Mediterranean heathland for fire adaptations in the Mediterranean Region. We performed a germination experiment to compare the relationship of seed size to (i) heat-stimulated germination, (ii) dormancy strength, and (iii) heat survival in plants from ‘high-fire’ heathland vs. ‘low-fire’ coastal shrubland. Germination after heat-shock treatment was higher in large seeds of both ‘high-fire’ and ‘low-fire’ habitats. However, dormancy was weaker in small seeds from ‘low-fire’ habitats. Finally, seed survival to heat shock was positively related to seed size. Our results support that seed size is an adaptive trait to fire in C. salviifolius, since larger seeds had stronger dormancy, higher heat-stimulated germination and were more resistant to heat shock. This seed size–fire relationship was tighter in ‘high-fire’ Mediterranean heathland than ‘low-fire’ coastal shrubland, indicating the existence of differential fire pressures and evolutionary trends at the landscape scale. These findings highlight the Mediterranean heathland as a relevant habitat for fire-driven evolution, thus contributing to better understand the role of fire in plant evolution within the Mediterranean region.
... Especially, FD based on water, light availability, pH and soil nutriments properties, was considerably lower than expected, indicating that species environmental properties are more similar among trees assemblages than what one would expect given the regional species pool. Competing mechanisms may act on trees assemblages' composition, with climate and fire potentially driving convergence in traits and resulting to functional and phylogenetic clustering in plants (Verdú & Pausas, 2007;Nóbrega et al., 2019), while biotic factors, like competitive exclusion through species niche overlap, may force species to select different adaptations in order to remain competitive and thus cause traits divergence (Webb et al., 2010;Cadotte et al., 2011). In which direction and what extent these abiotic or biotic filters drive the observed mismatches in FD and PD should be further analyzed. ...
Adopting a multifaceted approach of biodiversity is believed to capture different aspects of the ecosystem functioning and it is thus advised for conservation prioritisation, especially for anthropogenic ecosystems but this key topic has never been conducted for the Mediterranean tree assemblages, despite their ecological importance. We explored how the multi-faceted diversity of woody plant assemblages, as measured by taxonomic (TD), functional (FD) and phylogenetic (PD) diversities, are distributed over space in the French part of the Mediterranean biome, and to which extend they are spatially correlated to each other, in order to understand whether one facet can be used as a proxy for another, especially for conservation management purposes.
We analysed data from 5885 plots over the study area. We estimated several FD types by considering separately (i) regeneration, (ii) morphology traits (iii) modalities on species ecological properties, and finally (iv) considering all traits together. We used the Rao quadratic entropy to estimate the TD, FD and PD diversity facets. We tested for the links and spatial correlation (congruence) levels among these facets, using simultaneous autoregressive (SAR) models and partial Mantel tests.
Spatial structure varied among diversity facets and spatial autocorrelation patterns were identified for all diversity indices from 30 to 50 km distances. We observed a functional convergence and a phylogenetic divergence within tree assemblages comparing to the ones expected given the regional species pool, indicating that even in tree communities with functional similarities, phylogenetic diversity may be high. PD was zero to slightly congruent to FD, regardless the type of functional traits considered. The highest SAR slope (=0.3) and partial Mantel test (=0.2) were revealed between the PD and the FD based on species morphological traits, but still remained considerably low.
Each one of the diversity indicators reflected a different tree community spatial pattern. Functional diversity patterns varied according to the type of traits considered. Using only taxonomic indices may be misleading for responding to Mediterranean tree assemblages conservation needs and additional information about the species phylogeny and functional responses to disturbance pressures should be considered in large scale analyses.
... These processes depend on physiological tolerances in relation to environmental gradients and intensity of competition as a consequence of shared resource requirements (Webb 2000a(Webb , 2002. The underlying conceptual framework was formalized in terms of functional traits in individual case studies (Cavender- Verdu and Pausas 2007). The tendency to oversimplify the interpretation of phylogenetic patterns in communities, whereby phylogenetic overdispersion was equated with the outcome of competitive exclusion and phylogenetic clustering was interpreted as evidence for environmental sorting, led to a series of studies investigating the importance of scale (Cavender-Bares et al. 2006;Swenson et al. 2006) and the role of Janzen-Connell-type mechanisms, i.e., densitydependent mortality due to pathogens and predators (Gilbert and Webb 2007;Parker et al. 2015). ...
Biodiversity is organized hierarchically from individuals to populations to major lineages in the tree of life. This hierarchical structure has consequences for remote sensing of plant phenotypes and leads to the expectation that more distantly related plants will be more spectrally distinct. Applying remote sensing to understand ecological processes from biodiversity patterns builds on prior efforts that integrate functional and phylogenetic information of organisms with their environmental distributions to discern assembly processes and the rules that govern species distributions. Spectral diversity metrics critical to detecting biodiversity patterns expand on the many metrics for quantifying multiple dimensions of biodiversity—taxonomic, phylogenetic, and functional—and can be applied at local (alpha diversity) to regional (gamma diversity) scales to examine variation among communities (beta diversity). Remote-sensing technologies stand to illuminate the nature of biodiversity-ecosystem function relationships and ecosystem service trade-offs over large spatial extents and to estimate their uncertainties. Such advances will improve our capacity to manage natural resources in the Anthropocene.
... At the opposite, phylogenetic evenness was lower in plant communities highly disturbed by montane water voles, suggesting that disturbances might select for disturbance tolerance traits which could be phylogenetically conserved (Dinnage, 2009). Indeed, some studies have shown that disturbance increases average relatedness among species (Warwick and Clarke, 1998;Verdu and Pausas, 2007). Because of reduced competition, disturbed plant communities might be more strongly influenced by environmental filtering of niche traits (Dinnage, 2009), allowing only closely related species to become dominant. ...
It is recognized that disturbances by fossorial small mammals are important factors determining plant community diversity, especially in grasslands. However, although information about the effects of disturbances by fossorial small mammals on species richness are starting to accumulate, we know little about the impact of these disturbances on the functional and phylogenetic facets of plant community diversity in grasslands.
In a study site located in the French Jura Mountains, we compared taxonomic, functional and phylogenetic diversity of plant communities in areas highly disturbed by montane water vole (Arvicola terrestris) with areas lowly disturbed by this small mammal. In accordance with previous studies, we found that species richness was higher in highly disturbed communities. Indeed, competitive species unable to withstand disturbances were less abundant in disturbed communities, allowing species less adapted to competition for light to survive. Because these species have different trait values in comparison to strong competitors, functional richness was also higher in highly disturbed communities. Results were similar for phylogenetic richness, maybe due to the fact that the used metric was not independent from species richness. Although species composition differed between highly and lowly disturbed communities, functional composition was very similar. Thereby, the studied disturbances were probably not strong enough to affect plant community functioning. Rao functional diversity and functional evenness were not different between both community types. Interestingly, phylogenetic evenness was lower in highly disturbed areas, supporting the idea that disturbances might select for disturbance tolerance traits that are phylogenetically conserved.
Though correlational, our results suggest that water vole disturbances may modify multiple facets of plant community diversity, while ecosystem functioning is maintained across disturbance levels. Further research is needed to understand causal mechanisms in this system and the ecological repercussions of small mammal disturbances more broadly.
Understanding the phylogenetic diversity and structure of woody communities can explain how deterministic or stochastic processes drive a forest community assembly. This study assessed the tree community's phylogenetic diversity and structure during secondary succession after shifting cultivation (SC) in the Northern Amazon Forest. We hypothesized that soil-mediated filtering, rather than habitat filtering based on stand age and neutrality-based stochastic processes, determines phylogenetic diversity and structure of woody community along Amazon Forest succession after SC. We used forest inventory data from 45 plots across three sites representing second-growth forests (SG) having stand ages after shifting cultivation (e.g., 5, 10, 15, and 20 years old) and an old-growth reference forest (> 100 years old, OG). We tested different linear mixed-effects models to determine the main effects of soil-mediated filtering (i.e., nutrients and soil texture) and stand age on phylo-genetic metrics. Phylogenetic diversity (PD) showed a significant difference between SG and OG: the highest PD was found in OG, whereas the lowest PD was found during the initial successional stage. We found a trend of phylogenetic structure promoted by soil attributes; the variability of soil texture mainly explained most of the variation of phylogenetic diversity and structure. Stand age did not demonstrate a significant influence on phylogenetic metrics across any of the tested models. Higher soil fertility may favor the growth of species from multiple distant clades, increasing phylogenetic diversity and reducing phylogenetic clustering. However, SC may affect the fertility content in silt soils of OG and generate soils with a high proportion of sand and low fertility in SG. Thus, our study demonstrates that soil-mediated abiotic filtering shapes the phylogenetic structure and diversity of tree communities along Amazon forest succession due to deterministic processes rather than stand age and neutrality-based stochastic processes.
En Andalucía se realizan diversas actuaciones para la catalogación y conservación de la biodiversidad por parte del gobierno autonómico. Con respecto a las plantas, es notable la creación de una red de Jardines Botánicos asociados a espacios naturales protegidos. Estos jardines y áreas protegidas contienen una buena representación de la flora y de las especies amenazadas andaluzas, lo que supone un gran potencial para la investigación en biodiversidad. En este artículo se exploran posibilidades que ofrecen estos jardines, dirigidas hacia la investigación y se muestran algunos resultados obtenidos. Estas investigaciones se dirigen por un lado hacia el pasado histórico que ha generado la actual diversidad evolutiva (filogenética) de la flora leñosa usando marcadores genéticos y genómicos. Por otro lado, la representación de flora amenazada en los jardines ha permitido conocer también su nivel de singularidad filogenética y compararla con su rareza basada en aspectos biogeográficos y ecológicos. Los Jardines Botánicos han proporcionado gran parte de las muestras de tejido vegetal para la extracción de ADN necesario para resolver las filogenias. Finalmente, se exponen posibilidades futuras de investigación para prevenir los efectos del cambio climático en los sistemas naturales de Andalucía, usando los jardines como estaciones de observación fenológica. La información sobre el pasado evolutivo es muy relevante para determinar su influencia en la respuesta de las plantas a los cambios que ya están aconteciendo
Wildfires are a natural disturbance in many ecosystems. Consequently, plant species have acquired traits that allow them to resist and regenerate in an environment with recurrent fires. A key trait in fire‐prone ecosystems is the age at first reproduction (maturity age); populations of non‐resprouting species cannot persist when the fire interval is shorter than this age. Maturity age is variable among individuals, so we hypothesized that short fire intervals select for early seed production (precocity). We selected 13 plots with different fire regimes in eastern Spain, all dominated by Pinus halepensis (a non‐resprouting serotinous pine species). Then, we evaluated the age at first reproduction and the size of the canopy seed bank of each individual tree. Our results show a significant effect of fire regime on the onset of reproduction in this species, suggesting a selection towards higher precocity in populations subject to shorter fire intervals. Due to this higher precocity, pines stored more cones and therefore, increased their potential for reproduction post‐fire. We provide the first field evidence that fire can act as a driver of precocity. Being precocious in fire‐prone environments is adaptive because it increases the probability of having a significant seed bank when the next fire arrives.
Forests hold a significant proportion of global biodiversity and terrestrial carbon stocks and are at the forefront of human-induced global change. The dynamics and distribution of forest vegetation determines the habitat for other organisms, and regulates the delivery of ecosystem services, including carbon storage. Presenting recent research across temperate and tropical ecosystems, this volume synthesises the numerous ways that forests are responding to global change and includes perspectives on: • the role of forests in the global carbon and energy budgets • historical patterns of forest change and diversification • contemporary mechanisms of community assembly and implications of underlying drivers of global change • the ways in which forests supply ecosystem services that support human lives. The chapters represent case studies drawn from the authors' expertise, highlighting exciting new research and providing information that will be valuable to academics, students, researchers and practitioners with an interest in this field.
Forests hold a significant proportion of global biodiversity and terrestrial carbon stocks and are at the forefront of human-induced global change. The dynamics and distribution of forest vegetation determines the habitat for other organisms, and regulates the delivery of ecosystem services, including carbon storage. Presenting recent research across temperate and tropical ecosystems, this volume synthesises the numerous ways that forests are responding to global change and includes perspectives on: • the role of forests in the global carbon and energy budgets • historical patterns of forest change and diversification • contemporary mechanisms of community assembly and implications of underlying drivers of global change • the ways in which forests supply ecosystem services that support human lives. The chapters represent case studies drawn from the authors' expertise, highlighting exciting new research and providing information that will be valuable to academics, students, researchers and practitioners with an interest in this field.
Forests hold a significant proportion of global biodiversity and terrestrial carbon stocks and are at the forefront of human-induced global change. The dynamics and distribution of forest vegetation determines the habitat for other organisms, and regulates the delivery of ecosystem services, including carbon storage. Presenting recent research across temperate and tropical ecosystems, this volume synthesises the numerous ways that forests are responding to global change and includes perspectives on: • the role of forests in the global carbon and energy budgets • historical patterns of forest change and diversification • contemporary mechanisms of community assembly and implications of underlying drivers of global change • the ways in which forests supply ecosystem services that support human lives. The chapters represent case studies drawn from the authors' expertise, highlighting exciting new research and providing information that will be valuable to academics, students, researchers and practitioners with an interest in this field.
Forests hold a significant proportion of global biodiversity and terrestrial carbon stocks and are at the forefront of human-induced global change. The dynamics and distribution of forest vegetation determines the habitat for other organisms, and regulates the delivery of ecosystem services, including carbon storage. Presenting recent research across temperate and tropical ecosystems, this volume synthesises the numerous ways that forests are responding to global change and includes perspectives on: • the role of forests in the global carbon and energy budgets • historical patterns of forest change and diversification • contemporary mechanisms of community assembly and implications of underlying drivers of global change • the ways in which forests supply ecosystem services that support human lives. The chapters represent case studies drawn from the authors' expertise, highlighting exciting new research and providing information that will be valuable to academics, students, researchers and practitioners with an interest in this field.
Forests hold a significant proportion of global biodiversity and terrestrial carbon stocks and are at the forefront of human-induced global change. The dynamics and distribution of forest vegetation determines the habitat for other organisms, and regulates the delivery of ecosystem services, including carbon storage. Presenting recent research across temperate and tropical ecosystems, this volume synthesises the numerous ways that forests are responding to global change and includes perspectives on: • the role of forests in the global carbon and energy budgets • historical patterns of forest change and diversification • contemporary mechanisms of community assembly and implications of underlying drivers of global change • the ways in which forests supply ecosystem services that support human lives. The chapters represent case studies drawn from the authors' expertise, highlighting exciting new research and providing information that will be valuable to academics, students, researchers and practitioners with an interest in this field.
Forests hold a significant proportion of global biodiversity and terrestrial carbon stocks and are at the forefront of human-induced global change. The dynamics and distribution of forest vegetation determines the habitat for other organisms, and regulates the delivery of ecosystem services, including carbon storage. Presenting recent research across temperate and tropical ecosystems, this volume synthesises the numerous ways that forests are responding to global change and includes perspectives on: • the role of forests in the global carbon and energy budgets • historical patterns of forest change and diversification • contemporary mechanisms of community assembly and implications of underlying drivers of global change • the ways in which forests supply ecosystem services that support human lives. The chapters represent case studies drawn from the authors' expertise, highlighting exciting new research and providing information that will be valuable to academics, students, researchers and practitioners with an interest in this field.
Forests hold a significant proportion of global biodiversity and terrestrial carbon stocks and are at the forefront of human-induced global change. The dynamics and distribution of forest vegetation determines the habitat for other organisms, and regulates the delivery of ecosystem services, including carbon storage. Presenting recent research across temperate and tropical ecosystems, this volume synthesises the numerous ways that forests are responding to global change and includes perspectives on: • the role of forests in the global carbon and energy budgets • historical patterns of forest change and diversification • contemporary mechanisms of community assembly and implications of underlying drivers of global change • the ways in which forests supply ecosystem services that support human lives. The chapters represent case studies drawn from the authors' expertise, highlighting exciting new research and providing information that will be valuable to academics, students, researchers and practitioners with an interest in this field.
Forests hold a significant proportion of global biodiversity and terrestrial carbon stocks and are at the forefront of human-induced global change. The dynamics and distribution of forest vegetation determines the habitat for other organisms, and regulates the delivery of ecosystem services, including carbon storage. Presenting recent research across temperate and tropical ecosystems, this volume synthesises the numerous ways that forests are responding to global change and includes perspectives on: • the role of forests in the global carbon and energy budgets • historical patterns of forest change and diversification • contemporary mechanisms of community assembly and implications of underlying drivers of global change • the ways in which forests supply ecosystem services that support human lives. The chapters represent case studies drawn from the authors' expertise, highlighting exciting new research and providing information that will be valuable to academics, students, researchers and practitioners with an interest in this field.
Alien species can modify ecosystem functions and ecological processes in natural
communities, and potentially become invasive. In the Brazilian Pampean grasslands, reports
of changes in land use and invasions of alien plant species are becoming more frequent. This
study aimed to investigate species composition and phylogenetic relationships between native
and alien plants across four sites of Brazilian Pampean grasslands under distinct land uses
(NOM: no agricultural management; GRZ: grazed pastures; AGR: agrarian crops; ROAD:
roadside). The phylogenetic relationship between native and alien species was analyzed at two
scales: inter-site (large scale) and intra-site (small scale). We found inter-site differences in
phylogenetic diversity. Overall, across all sites we found random phylogenetic relationships
among alien and native species. In the most disturbed site (ROAD) we found significant
phylogenetic clustering among all species (alien and natives), while at the small scale,
clustering was only found among natives. We conclude that clustering of phylogenetic
relationships among alien and native species is only evident at small sampling scales in
environments subject to high levels of disturbance (i.e., road sides) in the studied Pampean
Grasslands, suggesting that environmental filtering plays an important role in local
community assembly.
Keywords : disturbance, land use, phylogenetic pattern, plant invasion, native communities
Alien species can modify ecosystem functions and ecological processes in natural communities, and potentially become invasive. In the Brazilian Pampean grasslands, reports of changes in land use and invasions of alien plant species are becoming more frequent. This study aimed to investigate species composition and phylogenetic relationships between native and alien plants across four sites of Brazilian Pampean grasslands under distinct land uses (NOM: no agricultural management; GRZ: grazed pastures; AGR: agrarian crops; ROAD: roadside). The phylogenetic relationship between native and alien species was analyzed at two scales: inter-site (large scale) and intra-site (small scale). We found inter-site differences in phylogenetic diversity. Overall, across all sites we found random phylogenetic relationships among alien and native species. In the most disturbed site (ROAD) we found significant phylogenetic clustering among all species (alien and natives), while at the small scale, clustering was only found among natives. We conclude that clustering of phylogenetic relationships among alien and native species is only evident at small sampling scales in environments subject to high levels of disturbance (i.e., road sides) in the studied Pampean Grasslands, suggesting that environmental filtering plays an important role in local community assembly
Aim
The aim was to characterize fire regimes and estimate fire regime parameters (area burnt, size, intensity, season, patchiness and pyrodiversity) at broad spatial scales using remotely sensed individual‐fire data.
Location
Western part of the Palaearctic realm (i.e., Europe, North Africa and the Near East).
Time period
2001–2021.
Methods
Initially, I divided the study area into eight large ecoregions based on their environment and vegetation: Mediterranean, Arid, Atlantic, Mountains, Boreal, Steppes, Continental and Tundra. Next, I intersected each predefined ecoregion with individual‐fire data obtained from remote sensing hotspots to estimate fire regime parameters for each environment. This allowed me to compute annual area burnt, fire size, fire intensity, fire season, fire patchiness, fire recurrence and pyrodiversity for each ecoregion. I related those fire parameters to the climate of the ecoregions and analysed the temporal trends in fire size.
Results
Fire regime parameters varied across different environments (ecoregions). The Mediterranean had the largest, most intense and most recurrent fires, but the Steppes had the largest burnt area. Arid ecosystems had the most extended fire season, Tundra had the patchiest fires, and Boreal forests had the earliest fires of the year. The spatial variability in fire regimes was largely explained by the variability of climate and vegetation, with a tendency for greater fire activity in the warmer ecoregions. There was also a temporal tendency for large fires to become larger during the last two decades, especially in Arid and Continental environments.
Main conclusion
The fire regime characteristics of each ecoregion are unique, with a tendency for greater fire activity in warmer environments. In addition, fires have been increasing in size during recent decades.
Wildfires are ecological disturbances that shift soil microbes and the ecosystem functions they drive in forests. The temporal dynamics and assembly processes of the bacterial community following fire are essential but remain unknown. This study aimed to investigate how the assembly processes and their associated factors mediate the abundant and rare bacterial communities across temporal trajectories (21 months from 2019 to 2020) in severely burned and contiguous unburned forest soils. Results revealed that the temporal turnover rate of abundant sub-community in unburned soils was lower than that of rare sub-community, and abundant taxa exhibited a wider niche breadth than rare taxa; null model analyses indicated that variable selection made a paramount contribution to bacterial community assembly, with stronger phylogenetic clustering of the rare taxa; soil ammonium nitrogen and pH were the most decisive factor for community assembly of abundant and rare taxa, as evidenced by how divergences in them decreased the proportion of stochasticity. Compared with the unburned soils, the temporal turnover of the soil bacterial community was accelerated in burned soils; moreover, determinism had more important roles in rare taxa, whereas the abundant taxa were primarily dominated by dispersal limitation; soil dissolved organic carbon and bulk density regulated the balance between deterministic and stochastic assembly of the abundant and rare bacteria, respectively. Overall, these findings suggested distinct community assembly of abundant taxa in burned and unburned forest soils, which is of great significance to understand the establishment and maintenance mechanism of the soil bacterial community in forests following wildfire.
Environmental stress response in plants has been studied using a wide range of approaches, from lab‐based investigation of biochemistry and genetics, to glasshouse studies of physiology and growth rates, to field‐based trials and ecological surveys. It is also possible to investigate evolution of environmental stress responses using macroevolutionary and macroecological analyses, analysing data from many different species, providing a new perspective on the way that environmental stress shapes the evolution and distribution of biodiversity. ‘Macroevoeco’ approaches can produce intriguing results and new ways of looking at old problems. In this review, we focus on studies using phylogenetic analysis to illuminate macroevolutionary patterns in the evolution of environmental stress tolerance in plants. We follow a particular thread from our own research – evolution of salt tolerance – as a case study that illustrates a macroevolutionary way of thinking which opens up a range of broader questions on the evolution of environmental stress tolerances. We consider some potential future applications of macroevolutionary and macroecological analyses to understanding how diverse groups of plants evolve in response to environmental stress, which may allow better prediction of current stress tolerance and a way of predicting the capacity of species to adapt to changing environmental stresses over time.
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Because wildfires alter plant communities, we describe the effects of a single fire event on the composition and diversity of Amazonian ferruginous savannas, locally known as cangas. We installed 20 observation plots in burned and unburned parts of a homogeneous canga site from the Carajás Massif. The single fire event shifted community composition slightly, increased functional richness and the abundance of anemochoric and subshrub species, but did not influence the number of phanerophyte species, highlighting the importance of both seeding and resprouting strategies in the post-fire scenario. In contrast, neither taxonomic nor phylogenetic diversity was affected by the fire event. The absence of differences in the phylogenetic community structure indicated that specific adaptations to fires are widespread within the canga phylogeny, although fires are not an eminent part of these ecosystems, as in other neotropical savannas. As diversity metrics were not negatively affected by a single fire event and only small shifts in species composition were observed, our data indicate maintenance of important ecosystem properties despite an occasional wildfire event in the analysed canga shrubland. Further research should outline how different physiognomies are affected and how different fire regimes influence communities to assist in the design of effective management plans for this ecosystem.
An examination of 203 seed lots from 42 Old World species (or 54 taxa), with representatives from all five genera (Cistus, Fumana, Halimium, Helianthemum, and Tuberaria) and an additional seed lot of the New World Lechea maritima shows that the phenomenon of hardseededness is a prominent characteristic of the entire Cistaceae family. Promotion of seed germination in the laboratory can be obtained by mechanical scarification and thermal pretreatment, while light seems to be totally ineffective. A seed ecology syndrome for Cistaceae is postulated, featuring small seed size, hardcoatedness (primary dormancy), short-distance dispersal, long-term persistence in soil seed banks, fire- or heat- induced seed “softening”, an opportunistic strategy of germination (germination at a wide range of temperature and light conditions), and a slow germination rate of “softened” seeds. This syndrome is suggested to endow Cistaceae, a principally Mediterranean family, with a considerable ecological advantage in the summer-dry and fire-prone Mediterranean climatic conditions.
The genusEricaL., with more than 600 species, and a high number of endemics, represents the most remarkable example of floristic diversity in the Cape Floristic Region (CFR). It is largely confined to nutrient-poor, acidic, sandy soils, being one of the most characteristic element of fynbos. The ability to survive fires, resprouting from a lignotuber, is a common trait among Euro-mediterraneanEricaspecies. In contrast, resprouting is fairly uncommon among ericas in the CFR (less than 10%). Most of them are killed by fire, regenerating only but readily by seed germination. An extensive survey on the resprouting ability of South AfricanEricaspecies was carried out and the pattern of geographical distribution of resprouters and seeders in the CFR was determined. The geographical distribution of these two regeneration classes was related to a climatic gradient of seasonality along the CFR. A pattern of higher proportions of resprouter species towards the mediterranean, strongly seasonal northwestern CFR and the non-seasonal eastern CFR and summer rainfall area outside the CFR was identified. The number of resprouter species reaches a maximum in the eastern CFR and is lower in the southwestern CFR despite the overall higher concentration of species in this subregion. Summer drought strongly influences the effectiveness of post-fire regeneration and growth (i.e. new recruits plus survivors) ofEricaspecies, and is the major selective force accounting for the pattern of distribution of seeders and resprouters in the CFR. A mild mediterranean climate with reliable autumn-winter rains and a short summer drought, typical of the mountain areas of the southwestern CFR, favours recruitment of seeders but hampers recruitment of resprouters. Resprouter species persist and become dominant under harsh conditions for recruitment (severe summer drought) and would coexist with seeders under situations of no summer stress. Diversification is associated with seeder lineages. Hence, number of seeder species will be higher than number of resprouters, especially in the southwestern CFR, where favourable conditions for recruitment allow a massive concentration of seeder species, many of them narrow endemics.
This is the second edition of a multi-author book first published in 1992. It deals with all aspects of plant regeneration by seeds, including reproductive allocation, seed dispersal and predation, longevity, dormancy and germination. All chapters have been updated, and four new chapters added on seed size, seedling establishment, the role of gaps, and regeneration from seed after fire.
We present ADE-4, a multivariate analysis and graphical display software. Multivariate analysis methods available in ADE-4 include usual one-table methods like principal component analysis and correspondence analysis, spatial data analysis methods (using a total variance decomposition into local and global components, analogous to Moran and Geary indices), discriminant analysis and within/between groups analyses, many linear regression methods including lowess and polynomial regression, multiple and PLS (partial least squares) regression and orthogonal regression (principal component regression), projection methods like principal component analysis on instrumental variables, canonical correspondence analysis and many other variants, coinertia analysis and the RLQ method, and several three-way table (k-table) analysis methods. Graphical display techniques include an automatic collection of elementary graphics corresponding to groups of rows or to columns in the data table, thus providing a very efficient way for automatic k-table graphics and geographical mapping options. A dynamic graphic module allows interactive operations like searching, zooming, selection of points, and display of data values on factor maps. The user interface is simple and homogeneous among all the programs; this contributes to making the use of ADE-4 very easy for nonspecialists in statistics, data analysis or computer science.
Mediterranean climate ecosystems of the Mediterranean rim are rich in legumes, both as woody shrubs of the late successional stages and as short-lived, pioneer herbaceous plants. In a survey of the floras of numerous geographic regions of Greece, legumes in Mediterranean parts are found to contribute considerably more (11-16% of the total number of species) than in non-Mediterranean regions (6-8%). Legume presence is also notable in other Mediterranean-type ecosystems of the world; nevertheless most leguminous taxa of the Mediterranean basin are herbs in contrast to a significant contribution of shrubs in California and Chile. Due to their long-lived soil banks of hard coated seeds herbaceous legumes are usually among the early post-fire colonizers in the Mediterranean and may play a significant role in the succession of fire-prone communities.
Species abundances are important properties of ecological communities. Theoretical debate has arisen over whether communities are governed by assembly rules. Some ecologists have suggested that community organization depends on the phylogenetic relatedness of its interacting members. This postulate has not been adequately tested primarily because molecular phylogenies for entire communities are rare. We use the molecular phylogeny and species abundances from the well‐studied yeasts that live in decaying cactus tissue (i.e., cactus yeast community) to demonstrate that community structure is indeed linked to genetic relatedness but that the relationship is different for the same yeasts found in hosts of two subfamilies of the Cactaceae. In the Opuntia cacti, the genetically related and unrelated yeasts have equivalent probability of being similar in abundance. Conversely, in the columnar cacti, the abundant yeast species tend to be genetically distant from one another, whereas the rare species tend to be closely related. The distinctive biochemical differences between the Opuntia and columnar cacti habitats suggest that conditions imposed by the environment modify the relationship between phylogenetic relatedness and species abundances in the cactus yeast community.
The influence of high temperatures on germination of four Cistus and five Halimium taxa is analysed. Seeds were heated to a range of temperatures (from 50ºC to 150ºC) and a range of exposure times (from 1 to 60 min), simulating those heat conditions registered on the soil surface during wildfires. After the thermal pretreatments, seeds were sown in plastic Petri dishes and monitored for germination over 60 days. For all the species, germination was increased signifi- cantly over the control set (untreated seeds) by at least one of the thermal pretreatments. Temperatures of 120 and 150ºC were the most efficient temperatures promoting seed germi- nation, although germination was interrupted at 150ºC if exposure times were equal to or longer than 5 minutes for the majority of species. The preheating at 50ºC was effective on;y for C. populifolius, but only at long exposure times (60 min). H. atriplicifolium had the highest heat requirements for stimulating germination, requiring at least 120ºC for 5 min. H. halimifolium subsp. halimifolium seeds showed the highest heat resistance: the final germination level reached at 150ºC for 7.5 minutes ranged between 52.5 and 55.5%. The germination rates after preheating were much lower than in mechanically scarified seeds, and closely resembled those of the untreated seeds. In general, species sharing the same habitat showed different heat requirements in promoting ger- mination. For C. crispus and H. halimifolium subsp. halimi- folium, the experiment was carried out on seeds collected from two different localities. For both species the germina- tion patterns were similar between populations, although some high temperature pretreatments showed different ger- mination percentages.
The genus Erica L., with more than 600 species, and a high number of endemics, represents the most remarkable example of floristic diversity in the Cape Floristic Region (CFR). It is largely confined to nutrient-poor, acidic, sandy soils, being one of the most characteristic element of fynbos. The ability to survive fires, resprouting from a lignotuber, is a common trait among Euro-mediterranean Erica species. In contrast, resprouting is fairly uncommon among ericas in the CFR (less than 10%). Most of them are killed by fire, regenerating only but readily by seed germination. An extensive survey on the resprouting ability of South African Erica species was carried out and the pattern of geographical distribution of resprouters and seeders in the CFR was determined. The geographical distribution of these two regeneration classes was related to a climatic gradient of seasonality along the CFR. A pattern of higher proportions of resprouter species towards the mediterranean, strongly seasonal northwestern CFR and the non-seasonal eastern CFR and summer rainfall area outside the CFR was identified. The number of resprouter species reaches a maximum in the eastern CFR and is lower in the southwestern CFR despite the overall higher concentration of species in this subregion. Summer drought strongly influences the effectiveness of post-fire regeneration and growth (i.e. new recruits plus survivors) of Erica species, and is the major selective force accounting for the pattern of distribution of seeders and resprouters in the CFR. A mild mediterranean climate with reliable autumn-winter rains and a short summer drought, typical of the mountain areas of the southwestern CFR, favours recruitment of seeders but hampers recruitment of resprouters. Resprouter species persist and become dominant under harsh conditions for recruitment (severe summer drought) and would coexist with seeders under situations of no summer stress. Diversification is associated with seeder lineages. Hence, number of seeder species will be higher than number of resprouters, especially in the southwestern CFR, where favourable conditions for recruitment allow a massive concentration of seeder species, many of them narrow endemics.
The seedbanks of four arid trees from Australia were examined using periodicrecovery of seeds buried in nylon mesh bags in the field. Casuarina pauper did not maintain a soil seedbank. Seeds were not dormant at release and available rainfall will govem the timing of germination events. Three Acacia species have seedbanks of varying longevities. In A. oswaldii, the seedbank was very shortlived with most seeds from any one annual seed-crop having germinated in the first 1–2 years after release. In A. ligulata the seedbank was persistent, although it did vary between different populations. A. loderi had a relatively short-lived seedbank, with only 5% of seeds from an annual seed-crop surviving in the soil for between 3–5 years. Both C. pauper and A. oswaldii must rely on the production of annual seed-crops to maintain a seedbank through time and hence, take advantage of infrequent and irregular rains promoting germination and establishment. For A. ligulata and A. loderi, occasional seed production is all that is required to ensure the presence of a soil seedbank.
The retention of seeds in the plant canopy for one to 30 years or more is termed serotiny. It is well represented floristically and physiognomically in fire-prone, nutrient-poor and seasonally-dry sclerophyll vegetation in Australia, and to a lesser extent, South Africa followed by North America. While the seed-storing structures vary greatly, all will release their propagules following exposure to the heat of a fire (pyriscence). This phenomenon can be contrasted with seed release at maturity (non-storage) and soil storage of seeds. Although the evolutionary requirements for serotiny are clear, its adaptive advantages over other seed storage syndromes are largely the subject of conjecture in the absence of comparative experiments. Nine hypotheses were assessed here. Canopy storage maximises the quantity of seeds available for the next post-fire generation (unlike non-storage). Synchronized post-fire release satiates post-dispersal granivores (unlike non-storage and soil storage) and ensures arrival on a seed bed conducive to seedling recruitment (unlike non-storage). Canopy stored seeds are better insulated from the heat of a fire than non-stored, and probably soil-stored, seeds. Fluctuating annual seed crops, the opportunity for post-fire wind-dispersal, the possible advantages of dense stands of adults, short lifespan of the dispersed seeds and their optimal location in the soil for germination have only a limited role in explaining the advantages of serotiny. It is concluded that canopy seed storage is favoured in regions where seed production is restricted and inter-fire establishment and maturation are unlikely. In addition, these regions have a reliable seasonal rainfall and are subjected to intense fires at intervals occurring within the reproductive lifespan of the species.
A climatic series (1941 to 1994) from a Mediterranean locality of NE Spain was used to calculate two wildfire hazard indices based on daily meteorological data. Both fire hazard indices increased over this period, as a consequence of increasing mean daily maximum temperature and decreasing minimum daily relative humidity. These trends were observed in both mean values of the indices and in the number of very high risk days. Annual data on the number of wildfires and burned area also show an increase from 1968 to 1994, and are significantly correlated with both fire hazard indices. Although other non-meteorological causes (e.g., human activities, fuel accumulation) have likely contributed to the observed increase of wildfires, an effect of climatic warming on wildfire occurrence is supported by this relationship.
The influence of high temperatures (dry heat and hot water) on germination of seven Mediterranean Leguminosae species typical of fire-prone ecosystems in southern Spain is analyzed, in order to know the response of seeds to wildfires and the possible implications in their regeneration after this disturbance. Seeds were heated to a range of temperatures (50 –150 C) and exposure times (1–60 min) similar to those registered in the upper soil layers during wildfires. Germination tests were carried out in plastic Petri dishes over 60 days. In general, the degree of seed germination promotion by dry heat treatments showed a wide interspecific variation, although the final germination level was increased in all the studied species except for Scorpiurus muricatus. The thermal pretreatment of 50 C, however, was not effective for germination in any species, and rising the temperature to 70 C only slightly enhanced the germination in Cytisus patens. The preheatings of 90 C (5 and 10 min), 120 C (5 and 10 min), and 150 C (1 min) were the most effective in promoting seed germination. Hot water (100 C) scarification also increased the final germination level in all cases, with the exception of C. patens. The germination rates after preheating were much lower than in mechanically scarified seeds and closely resembled those of the untreated seeds, except for C. reverchonii, whose seed germination rate decreased with heat. The response of species to heat shock had no clear relationship with life trait or with the specific post-fire regeneration strategy (obligate seeder or facultative resprouter). Those species coexisting in the same habitats had different heat optimal requirements for seed germination, an strategy suggested by some authors as minimizing interspecific competition in the secondary succession started after fire.
In the California chaparral there are two syndromes contrasted by the timing of seedling recruitment relative to wildfires. The fire-recruiter or refractor seed syndrome includes species (both resprouting and non-resprouting) which share the feature that the timing of seedling establishment is specialized to the first rainy season after fire. Included are woody, suffrutescent and annual life forms but no geophytes have this syndrome. These species are linked by the characteristic that their seeds have a dormancy which is readily broken by environmental stimuli such as intense heat shock or chemicals leached from charred wood. Such seeds are referred to as "refractory' and dormancy, in some cases, is due to seed coat impermeability. The fire-resister or non-refractory seed syndrome includes species that are resilient to frequent fires (mostly by vegetative resprouting), but require fire-free periods for recruiting new seedlings. Included are shrubs, sub-shrubs, suffrutescents, lianas, geophytes and annuals. All are linked by the characteristic that their seeds germinate in the absence of cues related to wildifes. In many cases no form of seed dormancy is present and the seeds germinate soon after dispersal; these species do not accumulate a persistent seed bank. -from Author
The primary rationale for the use of phylogenetically based statistical methods is that phylogenetic signal, the tendency for related species to resemble each other, is ubiquitous. Whether this assertion is true for a given trait in a given lineage is an empirical question, but general tools for detecting and quantifying phylogenetic signal are inadequately developed. We present new methods for continuous-valued characters that can be implemented with either phylogenetically independent contrasts or generalized least-squares models. First, a simple randomization procedure allows one to test the null hypothesis of no pattern of similarity among relatives. The test demonstrates correct Type I error rate at a nominal alpha = 0.05 and good power (0.8) for simulated datasets with 20 or more species. Second, we derive a descriptive statistic, K, which allows valid comparisons of the amount of phylogenetic signal across traits and trees. Third, we provide two biologically motivated branch-length transformations, one based on the Ornstein-Uhlenbeck (OU) model of stabilizing selection, the other based on a new model in which character evolution can accelerate or decelerate (ACDC) in rate (e.g., as may occur during or after an adaptive radiation). Maximum likelihood estimation of the OU (d) and ACDC (g) parameters can serve as tests for phylogenetic signal because an estimate of d or g near zero implies that a phylogeny with little hierarchical structure (a star) offers a good fit to the data. Transformations that improve the fit of a tree to comparative data will increase power to detect phylogenetic signal and may also be preferable for further comparative analyses, such as of correlated character evolution. Application of the methods to data from the literature revealed that, for trees with 20 or more species, 92% of traits exhibited significant phylogenetic signal (randomization test), including behavioral and ecological ones that are thought to be relatively evolutionarily malleable (e.g., highly adaptive) and/or subject to relatively strong environmental (nongenetic) effects or high levels of measurement error. Irrespective of sample size, most traits (but not body size, on average) showed less signal than expected given the topology, branch lengths, and a Brownian motion model of evolution (i.e., K was less than one), which may be attributed to adaptation and/or measurement error in the broad sense (including errors in estimates of phenotypes, branch lengths, and topology). Analysis of variance of log K for all 121 traits (from 35 trees) indicated that behavioral traits exhibit lower signal than body size, morphological, life-history, or physiological traits. In addition, physiological traits (corrected for body size) showed less signal than did body size itself. For trees with 20 or more species, the estimated OU (25% of traits) and/or ACDC (40%) transformation parameter differed significantly from both zero and unity, indicating that a hierarchical tree with less (or occasionally more) structure than the original better fit the data and so could be preferred for comparative analyses.
Closely related species that occur together in communities and experience similar environmental conditions are likely to share phenotypic traits because of the process of environmental filtering. At the same time, species that are too similar are unlikely to co-occur because of competitive exclusion. In an effort to explain the coexistence of 17 oak species within forest communities in North Central Florida, we examined correlations between the phylogenetic relatedness of oak species, their degree of co-occurrence within communities and niche overlap across environmental gradients, and their similarity in ecophysiological and life-history traits. We show that the oaks are phylogenetically overdispersed because co-occurring species are more distantly related than expected by chance, and oaks within the same clade show less niche overlap than expected. Hence, communities are more likely to include members of both the red oak and the white + live oak clades than only members of one clade. This pattern of phylogenetic overdispersion arises because traits important for habitat specialization show evolutionary convergence. We hypothesize further that certain conserved traits permit coexistence of distantly related congeners. These results provide an explanation for how oak diversity is maintained at the community level in North Central Florida.
Community resilience after fire is determined by species' ability to regenerate through two main mechanisms growth of new sprouts (resprouter species) and germination from surviving seed banks or from seeds arriving from neighbouring populations (seeder species). Both the mechanisms are present in Mediterranean communities. The occurrence of both the types in a community depends on fire history and the bio-geographical history determining the available species pool. Regenerative traits also covary with other functional attributes associated with resource acquisition and stress tolerance. As post-fire regenerative responses can be related to various ecological factors other than fire, we tested the hypothesis of a different proportional representation of post-fire regenerative syndromes in forest woody species along a climatic gradient in Catalonia (NE Spain) ranging from Mediterranean to temperate-boreal climates. Specifically, we expected seeder species to become less common with colder and moister conditions while resprouters would not be so influenced by the climatic gradient. We also tested the hypothesis of change in the relative abundance of regenerative syndromes in relation to recent fire history. We analysed a large database obtained from extensive forestry surveys and remote sensing fire records. After correction for spatial autocorrelation, we found an increase in the proportion of seeder species under more Mediterranean conditions and a decrease in fire-sensitive species (with no efficient mechanisms of post-fire recovery) in moister conditions. Resprouter species were similarly present across the whole gradient. A similar pattern was observed after excluding recently burnt plots. Therefore, post-fire regenerative syndromes segregate along the climatic gradient. Recent fires reduced the occurrence of fire-sensitive species and increased the proportion of seeder species. No significant effect was observed on resprouter species. Fire has a sorting effect, shaping the occurrence of species with different regenerative traits. Overall, fire seems to explain better the variability of the proportion of fire-sensitive species and climate the variability of seeder species. In addition, other factors (forestry practices and the covariation between regenerative and functional attributes) are likely to contribute to the regional pattern of regenerative syndromes.
This paper has two complementary purposes: first, to present a method to perform multiple regression on distance matrices, with permutation testing appropriate for path-length matrices representing evolutionary trees, and then, to apply this method to study the joint evolution of brain, behavior and other characteristics in marsupials. To understand the computation method, consider that the dependent matrix is unfolded as a vector y; similarly, consider X to be a table containing the independent matrices, also unfolded as vectors. A multiple regression is computed to express y as a function of X. The parameters of this regression (R(2) and partial regression coefficients) are tested by permutations, as follows. When the dependent matrix variable y represents a simple distance or similarity matrix, permutations are performed in the same manner as the Mantel permutational test. When it is an ultrametric matrix representing a dendrogram, we use the double-permutation method (Lapointe and Legendre 1990, 1991). When it is a path-length matrix representing an additive tree (cladogram), we use the triple-permutation method (Lapointe and Legendre 1992). The independent matrix variables in X are kept fixed with respect to one another during the permutations. Selection of predictors can be accomplished by forward selection, backward elimination, or a stepwise procedure. A phylogenetic tree, derived from marsupial brain morphology data (28 species), is compared to trees depicting the evolution of diet, sociability, locomotion, and habitat in these animals, as well as their taxonomy and geographical relationships. A model is derived in which brain evolution can be predicted from taxonomy, diet, sociability and locomotion (R(2) = 0.75). A new tree, derived from the "predicted" data, shows a lot of similarity to the brain evolution tree. The meaning of the taxonomy, diet, sociability, and locomotion predictors are discussed and conclusions are drawn about the evolution of brain and behavior in marsupials.
Random trees and random characters can be used in null models for testing phylogenetic hypothesis. We consider three interpretations of random trees: first, that trees are selected from the set of all possible trees with equal probability; second, that trees are formed by random speciation or coalescence (equivalent); and third, that trees are formed by a series of random partitions of the taxa. We consider two interpretations of random characters: first, that the number of taxa with each state is held constant, but the states are randomly reshuffled among the taxa; and second, that the probability each taxon is assigned a particular state is constant from one taxon to the next. Under null models representing various combinations of randomizations of trees and characters, exact recursion equations are given to calculate the probability distribution of the number of character state changes required by a phylogenetic tree. Possible applications of these probability distributions are discussed. They can be used, for example, to test for a panmictic population structure within a species or to test phylogenetic inertia in a character's evolution. Whether and how a null model incorporates tree randomness makes little difference to the probability distribution in many but not all circumstances. The null model's sense of character randomness appears more critical. The difficult issue of choosing a null model is discussed.
Species abundances are important properties of ecological communities. Theoretical debate has arisen over whether communities are governed by assembly rules. Some ecologists have suggested that community organization depends on the phylogenetic relatedness of its interacting members. This postulate has not been adequately tested primarily because molecular phylogenies for entire communities are rare. We use the molecular phylogeny and species abundances from the well‐studied yeasts that live in decaying cactus tissue (i.e., cactus yeast community) to demonstrate that community structure is indeed linked to genetic relatedness but that the relationship is different for the same yeasts found in hosts of two subfamilies of the Cactaceae. In the Opuntia cacti, the genetically related and unrelated yeasts have equivalent probability of being similar in abundance. Conversely, in the columnar cacti, the abundant yeast species tend to be genetically distant from one another, whereas the rare species tend to be closely related. The distinctive biochemical differences between the Opuntia and columnar cacti habitats suggest that conditions imposed by the environment modify the relationship between phylogenetic relatedness and species abundances in the cactus yeast community.
Historically, since fire is a recurrent catastrophic disturbance, mediterranean-climate shrubs have been classified by their mode of postfire regeneration, i.e., obligate seeders, facultative seeders or obligate resprouters. While these terms are useful, they are too restrictive in that they only refer to a species’ response to fire and do not adequately describe modes of reproduction for all taxa.
Oldfield succession in Mediterranean ecosystems has been studied extensively in mesic conditions. However, this phenomenon is still poorly understood in semi-arid Mediterranean areas, where reduced plant cover, the importance of facilitation processes and the role of abiotic factors make these environments distinct. We first test whether the carob tree (Ceratonia siliqua) generates nucleation patterns in semi-arid oldfields, and to what extent such patterns change with abandonment age. Then we test to what extent nucleation can be explained by the perch effect. And finally, we test whether the nucleated pattern around carob trees is a source of diversity in the oldfields studied. To answer these questions we located oldfields abandoned 25 and 50 years ago (20 in each case) in the Alacant Province (SE Spain, Iberian Peninsula) on the basis of aerial photographs and personal interviews with local landowners and managers. In each oldfield woody plant density and richness were sampled on two microsites: under the carob tree and in the open field. Analysis was performed on all woody plants and by separating the species in two functional groups: fleshy-fruited (with fleshy mesocarp) and non-fleshy-fruited species. The results suggest that woody vegetation colonising abandoned C. siliqua fields in SE Spain is not randomly distributed but follows a nucleation pattern with higher plant density under the trees. However, the nucleation pattern is only significant for fleshy-fruited species, suggesting that facilitative interactions alone cannot explain the nucleation pattern and that the perch effect plays an important role. The results also show that the nucleation pattern (total plant density and density of non-fleshy-fruited plants) did not increase with abandonment age, while the perch effect (density of fleshy-fruited plants) did increase significantly. Furthermore, the results also show that the nucleation pattern is not only a loci of high plant density but also a loci of high species richness. Thus we can conclude that the nucleation pattern found in oldfield succession is best explained by the perch effect, while facilitation has a secondary importance. This emphasises the key role that dispersal mode has on the dynamics of vegetation recovery in formerly cropped areas.
Random trees and random characters can be used in null models for testing phylogenetic hypothesis. We consider three interpretations of random trees: first, that trees are selected from the set of all possible trees with equal probability; second, that trees are formed by random speciation or coalescence (equivalent); and third, that trees are formed by a series of random partitions of the taxa. We consider two interpretations of random characters: first, that the number of taxa with each state is held constant, but the states are randomly reshuffled among the taxa; and second, that the probability each taxon is assigned a particular state is constant from one taxon to the next. Under null models representing various combinations of randomizations of trees and characters, exact recursion equations are given to calculate the probability distribution of the number of character state changes required by a phylogenetic tree. Possible applications of these probability distributions are discussed. They can be used, for example, to test for a panmictic population structure within a species or to test phylogenetic inertia in a character's evolution. Whether and how a null model incorporates tree randomness makes little difference to the probability distribution in many but not all circumstances. The null model's sense of character randomness appears more critical. The difficult issue of choosing a null model is discussed.
Disturbance is a dominant factor in many ecosystems, and the disturbance regime is likely to change over the next decades in response to land-use changes and global warming. We assume that predictions of vegetation dynamics can be made on the basis of a set of life-history traits that characterize the response of a species to disturbance. For crown-fire ecosystems, the main plant traits related to postfire persistence are the ability to resprout (persistence of individuals) and the ability to retain a persistent seed bank (persistence of populations). In this context, we asked (1) to what extent do different life- history traits co-occur with the ability to resprout and/or the ability to retain a persistent seed bank among differing ecosystems and (2) to what extent do combinations of fire- related traits (fire syndromes) change in a fire regime gradient? We explored these questions by reviewing the literature and analyzing databases compiled from different crown-fire ecosystems (mainly eastern Australia, California, and the Mediterranean basin). The review suggests that the pattern of correlation between the two basic postfire persistent traits and other plant traits varies between continents and ecosystems. From these results we predict, for instance, that not all resprouters respond in a similar way everywhere because the associated plant traits of resprouter species vary in different places. Thus, attempts to generalize predictions on the basis of the resprouting capacity may have limited power at a global scale. An example is presented for Australian heathlands. Considering the com- bination of persistence at individual (resprouting) and at population (seed bank) level, the predictive power at local scale was significantly increased.
The two main fire response traits found in the Mediterranean basin are the resprouting capacity (R) and the propagule-persistence capacity (P). Previous studies suggested that these two traits might be correlated. In this paper we first test whether R and P have evolved independently. Then, we ask if the correlation occurs because (a) one trait is not the target of selection but it is genetically linked to the other trait which is the one under selection pressure (indirect selection), or (b) because different evolutionary responses to the same selective pressure are acting in parallel on populations at different genetic starting points (parallel selection). Finally, we test to what extent resprouting is associated with some vegetative and reproductive traits.
To answer these questions we used a traits database for the eastern Iberian Peninsula and we assembled the phylogenetic tree on the basis of published information. The results indicate that the two traits are negatively associated and support the parallel selection scenario in which changes in R precedes changes in P. The phylogenetic–informed associations of resprouting with other traits (plant height, age at maturity) support the existence of allocation tradeoffs.
The results are consistent with the biogeographical history of the Mediterranean basin flora where most of lineages already resprouted to persist after a disturbance during the Tertiary, thus making it improbable that an additional costly persistence strategy would evolve under the Quaternary climatic conditions.
Differences in allocation patterns between seeders and resprouters in several Mediterranean plant communities (Australia, California and South Africa) have led to the prediction that seedlings of seeders grow faster than those of resprouters. In the Mediterranean Basin, it has also been hypothesized that regeneration strategy of plants after fire is associated with several other life history traits. This paper tests both hypotheses for the dominant plants in the Mediterranean Basin from literature data. Results show that seeders from the Mediterranean Basin grow significantly faster and allocate more biomass to leaf plus paracotyledons than resprouters. Seeders are mainly non‐sclerophyllous, anemochorous, dry‐fruited, small‐seeded species that evolved in the Quaternary (post‐Pliocene) and are associated with earlier successional stages. Resprouters are mainly sclero‐phyllous, vertebrate‐dispersed, fleshy‐fruited, large‐seeded species that evolved in the Tertiary (pre‐Pliocene) and are associated with late successional stages.
Ecological patterns are not only a consequence of adaptive processes, but also influenced by phylogenetic constraints, historical effects, and sorting processes. In contrast to the attention paid to the influence of phylogeny on interspecific ecological patterns, historical effects and sorting processes have been considered less frequently. This article shows that, for the woody flora of western Andalusia, southwestern Spain, these factors may be of substantial importance for explaining covariation among life-history traits (and associated "character syndromes") in plant communities. Multivariate analysis of the covariation across genera of 10 qualitative characters (related to general habit and reproductive biology) revealed a dominant life history-reproductive gradient (called "dimension 1") defining two distinct groups of genera and associated syndromes. Syndromes may largely be explained by reference to historical effects and species sorting processes, without recourse to adaptive explanations. Lineage age (as estimated from paleontological and biogeographical data) explained a significant proportion of intergeneric variation in position along dimension 1. Many character associations contributing to the syndromes vanished after the sample was split into groups based on lineage age, and those remaining occurred exclusively within the group of "old" (pre-Mediterranean) genera. No supporting evidence was found for the contribution of differential extinction of pre-Mediterranean genera to observed syndromes. Differential diversification of lineages as a function of life-history and reproductive characteristics did contribute significantly.
The floras of mediterranean SW Australian shrublands (kwongan) and SW Cape fynbos have evolved under conditions of low soil nutrients and recurrent fire. The vegetation of both regions (Gondwanan shrublands) is broadly convergent in structure and functioning. In particular these shrublands have high species diversity at all levels. Populations respond differentially to varying components of the fire regime and post-fire population extinction is not uncommon. Since each fire is a unique event, high alpha richness could be maintained by the creation of fire-induced transient niches resulting in differential establishment. Under this form of 'lottery' recruitment, competitive effects are weakened and many species of the same guild can coexist. Recurrent fire is probably a major driving force in the massive speciation of the Gondwanan shrubland floras. Small demes would be isolated in peculiar habitats after fire-induced population fragmentation. Strong disruptive selection would result in the rapid evolution of isolated populations into distinct and specialized species. -from Author
This paper has two complementary purposes: first, to present a method to perform multiple regression on distance matrices, with permutation testing appropriate for path-length matrices representing evolutionary trees, and then, to apply this method to study the joint evolution of brain, behavior and other characteristics in marsupials. To understand the computation method, consider that the dependent matrix is unfolded as a vector y; similarly, consider X to be a table containing the independent matrices, also unfolded as vectors. A multiple regression is computed to express y as a function of X. The parameters of this regression (R(2) and partial regression coefficients) are tested by permutations, as follows. When the dependent matrix variable y represents a simple distance or similarity matrix, permutations are performed in the same manner as the Mantel permutational test. When it is an ultrametric matrix representing a dendrogram, we use the double-permutation method (Lapointe and legendre 1990, 1991). When it is a path-length matrix representing an additive tree (cladogram), we use the triple-permutation method (Lapointe and Legendre 1992). The independent matrix variables in X are kept fixed with respect to one another during the permutations. Selection of predictors can be accomplished by forward selection, backward elimination, or a stepwise procedure. A phylogenetic tree, derived from marsupial brain morphology data (28 species), is compared to trees depicting the evolution of diet, sociability, locomotion, and habitat in these animals, as well as their taxonomy and geographical relationships. A model is derived in which brain evolution can be predicted from taxonomy, diet, sociability and locomotion (R(2) = 0.75). A new tree, derived from the ''predicted'' data, shows a lot of similarity to the brain evolution tree. The meaning of the taxonomy, diet, sociability, and locomotion predictors are discussed and conclusions are drawn about the evolution of brain and behavior in marsupials.
Abstract The herbivorous arthropod fauna of bracken fern (Pteridium aquilinum (L.) Khun), at a site near Sydney, Australia, is described and compared with previously reported bracken faunas in other geographic regions. Monthly sampling over 18 months found 17 species of herbivorous arthropods (15 insect and two mite species) from five orders. At the ordinal level, the mixture differed substantially from the bracken faunas of sites in Britain and Papua New Guinea. Notable was the presence of Thysanoptera and Acari, and the absence of Coleoptera and Hymenoptera. The mixtures of orders/families represented in the site bracken faunas in Britain, and less so in Australia, resembled those in the pool of herbivorous arthropods in those regions. Further, the mixture of orders on bracken was more similar to the mixture of orders on other ferns than to the mixture of orders among herbivorous insects on all plants; such similarity was not evident at family level. Compared with sites in other regions, the Sydney site had an abundance of pinna-sucking species and a dearth of mining species. Differences between regions in feeding niches most occupied tended to correspond with the differences in orders represented. Not all features of the fauna of bracken near Sydney reflected differences in the general herbivorous arthropod fauna of Australia compared with other regions, or differences between the herbivore faunas of ferns and seed plants. Its composition must be attributed in part to stochastic aspects of the speciation of herbivorous arthropods onto host plants.
Aim To understand changes in fire persistence traits of plants along a latitudinal gradient, considering the interactions between productivity, community (fuel) structure and fire regime.
Location A gradient in the south of Australia (latitude 33–37° S; longitude 140–143° E), including: Little Desert National Park (VIC), Big Desert Wilderness Park (VIC), Murray-Sunset National Park (VIC), Danggali Conservation Park (SA) and Tarawi Nature Reserve (NSW).
Methods We selected four areas along a latitudinal gradient for which information on fire history and vegetation was available. Then, we tested to what extent the four selected areas have different climate and different fire regimes. Plant cover values of different life forms provided an indication of the plant community structure and flammability, and the proportion of species with different fire persistence traits (resprouting, seedbank persistence) informed us on the trait selection.
Results Precipitation decreases and temperature increases from south to north. Thus the selected sites represent a gradient from high productivity (low aridity) in the south to low productivity (high aridity) in the north. Fire statistics suggest that fire frequency parallels productivity. There is a tendency for life form dominance and community structure to shift in such a way that fuel connectivity is reduced towards the north. Resprouting species increase and obligate seeders decrease along the fire–productivity gradient.
Main conclusions Changes in plant traits are difficult to understand without simultaneous consideration of both the disturbance and the productivity gradients. In our study area, fire regime and productivity interact in such a way that decreases in productivity imply changes in fuel structure that produce a reduction in fire frequency. Resprouting species are better represented at the high fire–productivity part of the gradient, while obligate seeders are better represented at the opposite end of the gradient. The results also emphasize the importance of considering not only climate changes but also changes in fuel structure to predict future fire regimes.
Key Words community assembly and organization, phylogenetic conservatism, biogeography, species diversity, niche differentiation s Abstract As better phylogenetic hypotheses become available for many groups of organisms, studies in community ecology can be informed by knowledge of the evo-lutionary relationships among coexisting species. We note three primary approaches to integrating phylogenetic information into studies of community organization: 1. examining the phylogenetic structure of community assemblages, 2. exploring the phylogenetic basis of community niche structure, and 3. adding a community context to studies of trait evolution and biogeography. We recognize a common pattern of phy-logenetic conservatism in ecological character and highlight the challenges of using phylogenies of partial lineages. We also review phylogenetic approaches to three emer-gent properties of communities: species diversity, relative abundance distributions, and range sizes. Methodological advances in phylogenetic supertree construction, charac-ter reconstruction, null models for community assembly and character evolution, and metrics of community phylogenetic structure underlie the recent progress in these ar-eas. We highlight the potential for community ecologists to benefit from phylogenetic knowledge and suggest several avenues for future research.
Woody plant responses to crown removal in fire‐prone vegetation are of two types: resprouting (resprouters) or killed (obligate seeders). Obligate seeders maximize their fitness by ensuring they are reproductively mature before the next fire; resprouters invest in structures that increase their chance of surviving the next fire.
We tested whether seven congeneric pairs of resprouter and obligate seeder shrubs differ in plant size, leaf traits, water relations, biomass allocation and root starch formation in response to resource availability. This was tested by examining the interactive effects of water and nutrient availability in a factorial experiment.
Plant size (dry mass and shoot length), leaf area and stomatal conductance did not differ consistently among resprouters and obligate seeders, but were affected by water and nutrient availability. Leaf‐area ratio and specific leaf area were not affected consistently by nutrient or water availability, and did not differ among obligate seeders and resprouters.
Biomass allocation responded to resource availability and differed between resprouter and obligate seeder pairs. Nutrient addition reduced allocation to root mass, and resprouters consistently allocated more than obligate seeders to root mass. Leaf mass ratios were higher in obligate seeders, and were maintained at the expense of stem mass when nutrients limited growth.
Starch concentrations in the roots of resprouters were higher than in obligate seeders. Resprouters increased the concentration of starch in their roots when growth was limited by nutrients, but obligate seeders did not. Resprouters appear to develop a starch‐storage capacity through both reserve formation and accumulation mediated by nutrient availability.
Allocation, rather than growth differences, provide some insight into why resprouters are often more common than obligate seeders, especially on fertile sites. Seedlings of resprouters may be advantaged at fertile sites because allocation to roots and starch reserve formation enable them to be better competitors after fire. We predict that the interplay of biomass allocation, reproduction, starch storage and disturbance frequency provide a framework for patterns of coexistence in shrubs in fire‐prone ecosystems.
Resprouting capacity (R) and propagule‐persistence (P) are traits that are often considered to have evolved where there are predictable crown fires. Because several indicators suggest a stronger selective pressure for such traits in California than in the Mediterranean Basin, we hypothesize that plant species should have evolved to become R+ and P+ more frequently in California than in the Mediterranean Basin.
To test this hypothesis we studied the phylogenetic association between R and P states in both California and the Mediterranean Basin using published molecular phylogenies.
The results suggest that R and P evolved differently in the two regions. The occurrence of the states differs significantly between regions for trait P, but not for trait R. The different patterns (towards R+ and P+ in California and towards R+ and P– in the Mediterranean Basin) are reflected in the higher abundance and the wider taxonomic distribution of species with both persistence traits (R+P+ species) in California.
The differential acquisition of fire persistence mechanisms at the propagule level (P+) supports the idea that fire selective pressures has been higher in California than in the Mediterranean Basin.
Our comparative phylogenetic‐informed analysis contributes to an understanding of the differential role of the Quaternary climate in determining fire persistence traits in different Mediterranean‐type ecosystems and, thus, to the debate on the evolutionary convergence of traits.
Abstract Risk spreading of germination may be particularly common in environments with unpredictable climates. Germinability, propensity to germinate at different temperatures and germination speed were classified for seeds of 105 species from the central Australian arid zone, and related to plant growth form, perenniality, seed size and seed dispersal mode. Almost all species had at least some seeds which were dormant, consistent with the idea that risk spreading is important in arid zones. Dispersal mode and plant perenniality were not found to be associated with germinability. Seeds of most species germinated rapidly relative to what has been recorded from higher-rainfall environments, as might be expected in an environment where wet soils are usually temporary. Faster germination tended to be associated with low germinability, suggesting a spectrum of strategies from species that risk a small number of their seeds in many rainfall events, to those that germinate only in large rainfall events but then risk large numbers of seeds.
Fire is a dominant ecological factor in Mediterranean ecosystems, and changes in the fire regime can have important consequences for the stability of our landscapes. In this framework I asked firstly, what is the trend in fire number and area burned in the eastern Iberian Peninsula, and then, to what extent is the inter-annual variability of fires determined by climatic factors. To answer these questions I analysed the meteorological data (temperature and precipitation) from 350 stations covering the eastern Iberian Peninsula (1950–2000), and the fire records for the same area (historical data, 1874–1968, and data from recent decades, 1968–2000). The results suggested a slight tendency towards decreasing summer rainfall and a clear pattern of increasing annual and summer temperatures (on average, annual temperatures increased 0.35 C per decade from 1950 to 2000). The analysis of fire records suggested a clear increase in the annual number of fires and area burned during the last century; however, in the last three decades the number of fires also increased but the area burned did not show a clear trend. For this period the inter-annual variability in area burned was significantly related to the summer rainfall, that is, in wet summers the area burned was lower that in dry summers. Furthermore, summer rainfall was significantly cross-correlated with summer area burned for a time-lag of 2 years, suggesting that high rainfall may increase fuel loads that burn 2 years later.
Gap models have been applied to a wide range of ecosystems, mainly temperate and boreal forests, but rarely have such models been applied to Mediterranean ecosystems. In the present review we address some problems of gap models for predicting the long-term dynamics of Mediterranean ecosystems, and we suggest plant functional types suitable for modelling based on responses to disturbance. Most gap models do not take into account different life forms, interactions with fire (e.g., resprouting and stimulation of the germination), and underground structures. Long term human impact on Mediterranean ecosystems has made a significant impact on the current landscapes. That intense land use, involving long-lived slow-growing species, has had long-term consequences. It is not possible to understand Mediterranean vegetation and to validate any model without considering these factors. The lack of data for Mediterranean species may be overcome by taking into account correlations of traits and trade-offs between different functional types. A simple disturbance-based functional group system is discussed.
Fire has played a decisive role in Post-Glacial biological and cultural evolution in the Mediterranean Region. Its evolutionary impact on plants has been manifested by feedback responses, in which the fire and its after-effects selected plants for physiological and other mechanisms that enable direct fire tolerance or permit avoidance followed by vegetative and reproductive regeneration.
The dominant, sclerophyll, drought-tolerant phanerophytes of the maqui are obligatory rootsprouters, whereas the subordinate, drought-evading chamaephytes, as well as herbaceous perennials, are both vegetative and reproductive regenerators and are well adapted to new, fire-denuded habitats. Annual and perennial grass fire-followers are also able to escape high surface fire temperatures with the aid of torsion devices on seeds. Evolutionary strategies to overcome fire are closely interwoven with those against other environmental stresses such as drought and grazing. These combinations of stresses have brought about convergence in plant form and function in mediterranean climates.
Fire has thus been important in the evolution of more xeric grasslands and woodlands and more mesic maqui and shrubland communities. Contrary to the present view of fire as simply destructive, both fire and grazing have favored genetical as well as ecological diversity. They should be studied as integral components of Mediterranean ecosystems and their evolution.
Because of the correlation expected between the phylogenetic relatedness of two taxa and their net ecological similarity, a measure of the overall phylogenetic relatedness of a community of interacting organisms can be used to investigate the contemporary ecological processes that structure community composition. I describe two indices that use the number of nodes that separate taxa on a phylogeny as a measure of their phylogenetic relatedness. As an example of the use of these indices in community analysis, I compared the mean observed net relatedness of trees (>/=10 cm diameter at breast height) in each of 28 plots (each 0.16 ha) in a Bornean rain forest with the net relatedness expected if species were drawn randomly from the species pool (of the 324 species in the 28 plots), using a supertree that I assembled from published sources. I found that the species in plots were more phylogenetically related than expected by chance, a result that was insensitive to various modifications to the basic methodology. I tentatively infer that variation in habitat among plots causes ecologically more similar species to co-occur within plots. Finally, I suggest a range of applications for phylogenetic relatedness measures in community analysis.
Growing evidence of morphological diversity in angiosperm flowers, seeds and pollen from the mid Cretaceous and the presence of derived lineages from increasingly older geological deposits both imply that the timing of early angiosperm cladogenesis is older than fossil-based estimates have indicated. An alternative to fossils for calibrating the phylogeny comes from divergence in DNA sequence data. Here, angiosperm divergence times are estimated using non-parametric rate smoothing and a three-gene dataset covering ca. 75% of all angiosperm families recognized in recent classifications. The results provide an initial hypothesis of angiosperm diversification times. Using an internal calibration point, an independent evaluation of angiosperm and eudicot origins is performed. The origin of the crown group of extant angiosperms is indicated to be Early to Middle Jurassic (179-158 Myr), and the origin of eudicots is resolved as Late Jurassic to mid Cretaceous (147-131 Myr). Both estimates, despite a conservative calibration point, are older than current fossil-based estimates.
One of the most important floristic sorting periods to affect modern plant communities occurred during the shift from the wet Tertiary period to the unusually dry Quaternary, when most global deserts developed. During this time, a wave of new plant species emerged, presumably in response to the new climate. Interestingly, most Tertiary species that have been tracked through the fossil record did not disappear but remained relatively abundant despite the development of a much more unfavorable climate for species adapted to moist conditions. Here we find, by integrating paleobotanical, ecological, and phylogenetic analyses, that a large number of ancient Tertiary species in Mediterranean-climate ecosystems appear to have been preserved by the facilitative or “nurse” effects of modern Quaternary species. Our results indicate that these interdependent relationships among plants have played a central role in the preservation of the global biodiversity and provided a mechanism for stabilizing selection and the conservation of ecological traits over evolutionary time scales.
• Mediterranean-type ecosystems
• Mexical shrubland
• phylogenetic niche conservatism
• plant facilitation
• stabilizing selection
With the advent of molecular phylogenies the assessment of community assembly processes has become a central topic in community ecology. These processes have focused almost exclusively on habitat filtering and competitive exclusion. Recent evidence, however, indicates that facilitation has been important in preserving biodiversity over evolutionary time, with recent lineages conserving the regeneration niches of older, distant lineages. Here we test whether, if facilitation among distant-related species has preserved the regeneration niche of plant lineages, this has increased the phylogenetic diversity of communities. By analyzing a large worldwide database of species, we showed that the regeneration niches were strongly conserved across evolutionary history. Likewise, a phylogenetic supertree of all species of three communities driven by facilitation showed that nurse species facilitated distantly related species and increased phylogenetic diversity.