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Elevational patterns of plant richness and their drivers on an Asian mountain
Abstract
We examined the elevational patterns of plant species along two transects on Mt Seorak, South Korea, and calculated four richness indices from field survey data: total number of species per 100 m elevational band; mean number of species per plot in each elevational band; total estimated number of species per elevational band; and beta diversity of each elevational band. We evaluated the effects of area, mean distance between plots, climatic variables (mean annual temperature and precipitation), and productivity on the richness patterns along the two transects. In total, 235 plant species belonging to 72 families and 161 genera were recorded from 130 plots along the two transects. The analyses revealed different patterns including monotonic decline, and unimodal and multimodal shapes for richness indices of total, woody, and herbaceous plants with the change in elevation along the two transects. The proportion of suitable area (as opposed to rocky areas) was the best predictor for total number of species per elevational band, mean number of species per plot, and total estimated number of species per elevational band of total and herbaceous plants along the two transects. Mean distance between plots was the most important variable for beta diversity of all plant groups. Although regional area, climatic variables, and productivity were important variables for predicting woody plant richness patterns, the effects were not consistent between the two transects. Our study suggests that elevational species richness patterns may differ not only among different plant groups, but also between nearby elevational transects, and that these differences are explained by differences in the underlying mechanisms shaping these patterns.
... (2) Does the relative importance of landscape variables differ among plant groups? We expect that the relative roles and importance of landscape variables will vary with plant groups and that the main drivers of diversity patterns and community structure will also be different among plant groups due to the varying responses to environmental conditions by different plant groups (Lee et al. 2014;Chun and Lee 2019). ...
... Moreover, small-scale dispersal limitations affect species distribution. Restrictions on dispersal may drive aggregated distributions of populations of each species (Lee et al. 2014). Interactions between functional traits, such as seed mass and number of seeds with landscape variables, have been reported elsewhere and provide valuable contexts in understanding the differences in community structures among plant groups and along environmental gradients (Lindborg et al. 2012;Carvajal-Endara et al. 2017). ...
... However, we used Shannon-Wiener index as the heterogeneity index because most of the islands are rocky islands and have very low soil depths, so soil samples could not be collected (Lee et al. 2010;Kim et al. 2017). Therefore, our index may not fully reflect habitat heterogeneity of study islands, although some previous studies have documented that the diversity index of land cover types can indirectly reflect habitat heterogeneity and be used as a proxy of the heterogeneity (Lee et al. 2014;Aggemyr et al. 2018). ...
ContextAlthough there have been methodological advances in the analysis of biodiversity and landscape properties, most studies in landscape ecology primarily explore whether certain landscape properties, such as island area and isolation, have universal effects on species-centric measures.Objectives
We assessed how landscape variables drive species richness, phylogenetic diversity (PD), and phylogenetic community structure. Moreover, we explored the dominant processes structuring plant community assembly, including phylogenetic community structure.Methods
We used plant data from 235 uninhabited islands in the western and southern seas, South Korea. Species richness, Faith’s PD, and standardized effect size of mean pairwise phylogenetic distance (SES.MPD) were quantified for three plant groups, all, woody, and herbaceous plants for each island. Island area, distance from mainland, habitat heterogeneity, and structural connectivity were also calculated to examine the relationships between indices of plant diversity and community structure.ResultsThe relative importance of landscape variables differed among indices of diversity and community structure as well as among plant groups. Island area and distance from mainland were the main drivers of species richness and PD across plant groups, whereas distance from mainland significantly affected community structure measured by SES.MPD. We found that the community structure in islands farther from mainland showed phylogenetic clustering patterns driven by niche-based deterministic processes across the three plant groups.Conclusions
We found that community structure analysis provides more information related to ecological processes and assembly mechanisms than diversity indices alone. Therefore, we recommend that community structure analysis with plant diversity should be implemented as an additional measure of biodiversity for landscape ecology and for conservation planning in island ecosystems.
... Seorak and Mt. Baekhwa (S1 Fig), which are typical rocky mountains of South Korea with randomly distributed rocky areas in each elevational band; the areas belong to a mountain ecoregion and a temperate, deciduous forest biome [31,32]. Mt. ...
... Seorak has an area of 398.2 km 2 with the highest peak, Daechungbong, at 1708 m a.s.l., and the bedrock mainly contains dissected granite and gneiss [33]. The annual mean temperature and precipitation are 11˚C and 1228 mm, respectively [32]. Mt. ...
... sargentii; and (4) alpine forest (> 1500 m) dominated by P. pumila, Rhododendron mucronulatum var. ciliatum and B. ermanii [32]. In addition, Mt. ...
Recently, new alternative matrices of biodiversity such as phylogenetic and functional diversity as a complement to species diversity have provided new insights into the mechanisms of community assembly. In this study, we analyzed the phylogenetic signals of five functional traits and the relative contribution of environmental variables and distance matrices to the alpha and beta components of taxonomic, phylogenetic and functional diversity in woody plant assemblages along four local elevational transects on two different mountains. We observed low but significant phylogenetic signals of functional traits, which suggest that phylogenetic dispersion can provide a rough approximation of functional dispersion but not perfect correlations between phylogenetic and functional diversity. Taxonomic alpha diversity showed a monotonic decline with elevation, and climatic variables were the main drivers of this pattern along all studied transects. Furthermore, although the phylogenetic and functional alpha dispersions showed different elevational patterns including increase, decrease and no relationship, the underlying processes driving the patterns of both types of alpha dispersion could be explained by the gradients of climatic and habitat variables as well as biotic interactions such as competition. These results suggest that both alpha dispersion patterns may be significantly controlled by niche-based deterministic processes such as biotic interactions and environmental filtering in our study areas. Moreover, the beta diversity with geographical distances showed distance-decay relationships for all transects. Although the relative importance of the environmental and geographical distances for beta diversity varied across the three facets of diversity and the transects, we generally found that environmental distances were more important for the beta components of the three facets of diversity. However, we cannot discriminate the effects of both distances on the three facets of diversity. Therefore, our study suggests that niche-based deterministic processes, potentially combined with neutral processes such as dispersal limitation and demographic stochasticity, may influence patterns of woody plant assemblage turnover in our study areas.
... The distribution of plant populations is determined by seed dispersal and colonization ability [45]. That is, herbaceous plants have small seed dispersal ranges, which causes small-scale dispersal limitation, with colonies in a limited range [46]. As a result, herbaceous plants may not be affected by structural connectivity. ...
... The habitat heterogeneity hypothesis implies that an increase in the number of habitats leads to an expansion of the available niche dimensionality, which in turn can lead to an increase in species diversity [40]. Therefore, further research needs to reflect factors relevant to habitat heterogeneity such as topography, soil physical and chemical properties, and land cover diversity [9,46]. In addition, the current study compared the relative importance of environmental factors to the species richness of each island group by dividing inhabited and uninhabited islands. ...
Previous studies on island biogeography theory have limitations in that they are mostly focused on total plant species and the landscape factors of the islands. Our study was conducted to overcome these limitations by dividing the plants into five growth forms and analyzing climate and landscape factors on inhabited islands, uninhabited islands, and overall. This was achieved using plant data from 578 islands of an archipelago in South Korea. To test the relationship between the species richness of each growth form and environmental factors, we performed ordinary least squares regressions and multi-model inference tests. The results showed that the island area had the largest influence on species richness of all growth forms in overall and uninhabited islands. Moreover, climate factors, in addition to island area, significantly affected species richness of all growth forms on inhabited islands. However, the effect and of isolation-related landscape factors (i.e., distance from the mainland and structural connectivity) were different among growth forms and island categories. Our study reveals that there are differences in the effects of environmental factors on the growth forms of plants among island categories. This suggests that biodiversity management and conservation strategies should be applied separately to different growth forms and islands.
... Moreover, this study investigated whether significant phylogenetic signal was present in the functional trait data to better understand the degree to which the phylogenetic tree can estimate the functional trait similarity of species. The study of biodiversity patterns at the regional (large) scale is critical for understanding the patterns across spatial scales, whereas the study of biodiversity patterns at the local (small) scale is salient for understanding the within-domain biodiversity in biogeographic groups 18,23 . This study provides a valuable contribution by exploring elevational patterns and the underlying mechanisms using empirical data collected simultaneously at regional and local scales. ...
... Accordingly, several genera such as Lonicera, Syringa, Thuja, and Hydrangea are common at high elevations (>1100 m) along the SO transect (Table S6). These genera represent the contribution of completely novel lineages to the woody plant assemblages at higher elevations along this transect 23 , and many other genera are widely distributed across the entire elevation range along the SO transect (Table S6). These potential explanations are not mutually exclusive, and thus one or more might be involved in contributing to the phylogenetic overdispersion observed at higher elevations along the SO transect. ...
Species-centric approaches to biodiversity in ecological research are limited in their ability to reflect the evolutionary history and functional diversity of community assembly. Recently, the introduction of alternative facets of biodiversity, such as phylogenetic and functional diversity, has shed light on this problem and improved our understanding of the processes underlying biodiversity patterns. Here, we investigated the phylogenetic and functional diversity patterns of α, β and γ components in woody plant assemblages along regional and local elevational gradients in South Korea. Although the patterns of phylogenetic and functional diversity varied along regional and local elevational transects, the main drivers were partitioned into two categories: regional area or climate for phylogenetic diversity, depending on whether the transect was at a regional or local scale; and habitat heterogeneity for functional diversity, which was derived in elevational bands. Moreover, environmental distance was more important than was geographic distance for phylogenetic and functional β diversity between paired elevational bands. These results support the hypothesis that niche-based deterministic processes such as environmental filtering and competitive exclusion are fundamental in structuring woody plant assemblages along temperate elevational gradients regardless of scale (regional vs. local) in our study areas.
... La structure diamétrique des arbres, leur densité, leur surface terrière et leur hauteur sont influencées par les facteurs environnementaux, comme l'altitude, les pentes, la luminosité (Givnish, 1999 ;Lovett et al., 2006;Alves et al., 2010;Biresaw and Pavliš, 2010), par les types d'utilisation de terre ou les formations végétales (Lieberman et al., 1996;Zapfack et al., 2002;Ren et al., 2006;Bouko et al., 2007;Rahaingoson et al., 2013;Lee et al., 2014). Hormis ces facteurs clés, la structure d'un écosystème peut être, aussi influée par des facteurs naturels comme la présence ou l'absence de lianes envahissantes (Masumbuko et al., 2012), l'intensité de la perturbation de l'écosystème favorisant des trouées (Huang et al. 2003;Sahu et al., 2008;Boyemba, 2011), ou des vents violents (Masumbuko et al., 2012 ;Mangambu et al., 2015). ...
... C'est dans ce sens que la tranche d'altitude 1800-2400 m présente des particularités ; Symphonia globulifera qui a le plus gros diamètre de tous les inventaires se retrouve dans la parcelle de cette tranche qui a également un nombre important d'individus de petits diamètres (soit 80 %). Ainsi, selon qu'il s'agisse d'une formation primaire ou secondaire la structure de la végétation pourrait changer (Lieberman et al., 1996;Zapfack et al., 2002;Bouko et al., 2007;Rahaingoson et al., 2013;Lee et al., 2014). ...
This work aims to determine the change in the diametric structure, density, basal area, height and dominance of trees dbh ≥ 10 cm depending on altitude range or forest types. The study was conducted in 30 ha in Kahuzi Biega National Park and surrounding areas in DR Congo. In total, 16,797 individual trees were surveyed. The number of family, genus and species regress following the altitudinal gradient as the density increases. Mountain ecosystems in Kahuzi-Biega and its surroundings are dominated by Meliaceae, Euphorbiaceae, Moraceae, Fabaceae and Rubiaceae families. The Chi square analysis showed that the diametric structure of vegetation
... Tianshan in central Xinjiang, China [35] and Mt. Seorak in South Korea [36]. First, Sang [35] reported that the total and herbaceous plant species diversity of total, tree, shrub and herbaceous plants showed multimodal patterns along an elevational gradient. ...
... Tianshan in China. Lee et al. [36] also revealed different patterns, including monotonic decline as well as hump-shaped and multimodal patterns for the different diversity indices of total, woody and herbaceous plants with elevation on Mt. Seorak in South Korea. ...
Understanding patterns of biodiversity and their drivers along environmental gradients is one of the central topics in ecology. However, whether diversity patterns along environmental gradients differ among diversity components as well as life forms and what kind of variables control or interact to shape the diversity patterns are poorly known. This study scrutinized the distribution patterns of three plant groups with four diversity indices and evaluated the effects of regional area, topography, topographic heterogeneity, climate, primary productivity, vegetation structure diversity and vegetation type diversity along an extensive elevational gradient on the Baekdudaegan Mountains in South Korea. Different elevational patterns, including hump-shaped, reversed hump-shaped, increasing, multimodal and no relationship, were observed among both the diversity indices and the plant groups. Regional area, habitat heterogeneity and climate were included to explain most of the elevational diversity patterns. In particular, habitat heterogeneity was the most important variable for explaining the patterns of diversity. The results suggest that patterns of elevational diversity may differ not only among plant groups but also among diversity indices and that such patterns are primarily caused by habitat heterogeneity in the Baekdudaegan Mountains because more heterogeneous and diverse habitats can support more coexisting species.
... In contrast, a recent study conducted in the primary successional foreland environment of the retreating high-Arctic glacier Midtre Lovénbreen in Svalbard revealed that, within the microbial co-occurrence network, bacteria exert a more significant influence on the network structure compared to fungi . Mt. Seorak is a relatively stable ecosystem with high plant richness (Lee et al., 2014), and plant diversity may enhance the complexity and stability of the soil fungal network . ...
Fungi outperformed bacterial in maintaining the microbial co-occurrence networks.
Fungi showed different elevational network co-occurrence pattern from bacteria.
Distinct biotic/abiotic factors influenced bacterial and fungal network dynamics.
The interplay between soil micro-organisms in mountain ecosystems critically influences soil biogeochemical cycles and ecosystem processes. However, factors affecting the co-occurrence patterns of soil microbial communities remain unclear. In an attempt to understand how these patterns shift with elevation and identify the key explanatory factors underpinning these changes, we studied soil bacterial and fungal co-occurrence networks on Mt. Seorak, Republic of Korea. Amplicon sequencing was used to target the 16S rRNA gene and ITS2 region for bacteria and fungi, respectively. In contrast to bacteria, we found that fungi were predominantly situated in the core positions of the network, with significantly weakened co-occurrence with increasing elevation. The different co-occurrence patterns of fungal and bacterial communities could be resulted from their distinct responses to various environments. Both abiotic and biotic factors contributed significantly to shaping co-occurrence networks of bacterial and fungal communities. Fungal richness, bacterial community composition (indicated by PCoA1), and soil pH were the predominant factors influencing the variation in the entire microbial co-occurrence network. Biotic factors, such as the composition and diversity of bacterial communities, significantly influenced bacterial co-occurrence networks. External biotic and abiotic factors, including climatic and vegetative conditions, had a significant influence on fungal co-occurrence networks. These findings enhance our understanding of soil microbiota co-occurrences and deepen our knowledge of soil microbiota responses to climatic changes across elevational gradients in mountain ecosystems.
This study was implemented to clarify the patterns of plant species richness across forest strata and the relative importance of climatic and topographic factors on the Mt. Huiyang, South Korea. From the vegetation survey of 131 study plots, A total of 202 species belonging to 71 families and 144 genera were recorded. Of these plant species, woody and herbaceous plants were 85(42.1%) and 117(57.9%) species, respectively. In addition, 28, 69, and 173 species were observed in the overstory, midstory and understory, respectively. From the results of the structural equation modeling explaining the causal relationships among biotic and abiotic factors, topographic factor had a negative effect on the species richness of overstory and midstory, but had no effect on the understory species richness. Climate factor showed nonsignificant effect on the species richness across forest strata. Overstory species richness had a significant effect on the midstory species richness. Moreover, midstory species richness had significant effects on total and herbaceous species richness of the understory. We found midstory species richness and topographic factor had more important contributions to the understory species richness than climate factor and overstory species richness. This study suggests that plant diversity in the Mt. Huiyang are controlled by interactions between forest strata as well as abiotic factors such as topographic and climate factors.
Recently, a phylogenetic diversity and community structure analysis as complementary to species-centric approaches in biodiversity studies provides new insights into the processes of community assembly. In this study, we analyzed species and phylogenetic diversity and community structures for woody and herbaceous plants along two elevational transects on Mt. Baekhwa, South Korea. The species richness and phylogenetic diversity of woody plants showed monotonic declining patterns with increasing elevation along all transects, whereas herbaceous plants showed different patterns, such as no relationship and a reversed unimodal pattern, between the study transects. The main drivers of these patterns were climate and habitat variables for woody and herbaceous plants, respectively. In addition, the phylogenetic community structure primarily showed phylogenetic clustering regulated by deterministic processes, especially environmental filtering, such as climate or habitat factors, along the two transects, although herbaceous plants along a transect depicted phylogenetic randomness as a result of a neutral process. Our findings suggest that deterministic and neutral processes may simultaneously control the community structures along small-scale elevational gradients such as local transects, although the deterministic process may be the predominant type.
Understanding biodiversity patterns and the underlying drivers along environmental gradients is a central topic in ecology and biogeography. Despite intensive research devoted to the topic, it is poorly known how the diversity components (α-, β- and γ-) are forming the diversity patterns along gradients and whether they differ when taking individual life forms into account. In the present study, we evaluated α-, β- and γ-diversity for all, woody and herbaceous plants in relation to regional area, topographic heterogeneity, vegetation type diversity, climate and primary productivity along an extensive elevation gradient in the temperate forests of South Korea. We also examined the effect of latitude on the diversity patterns. We found differences in patterns among the diversity components as well as life forms. Habitat heterogeneity, represented by topographic heterogeneity and vegetation type diversity, was the most important driver of α- and γ-diversity, and the combined effects of habitat heterogeneity and climate were important for β-diversity of the individual life forms. Diversity patterns did not show significant relationships with latitude. Our results suggest that diversity patterns may differ among diversity components and life forms, and that habitat heterogeneity and climate along an extensive temperate elevation gradient are important biodiversity drivers in South Korea. At the same time, the effect of the elevation gradient may not be paralleled in relation to the latitudinal gradient, and this fact deserves attention in future studies.
The understory flora of successional forest in the Delaware/Pennsylvania Piedmont zone (USA) is species poor relative to old regrowth stands in the region. Impoverishment may reflect (a) limitations on dispersal of potential colonists, or (b) the unsuitability of successional stands for establishment. To examine the importance of dispersal, herb and shrub distributions were surveyed in successional stands of varying age and spatial arrangement. In successional stands contiguous with species-rich old-regrowth forest, understory species richness declined with distance into the successional stands, implying contagion across the old-regrowth ecotone. Individual species showed evidence of contagion in 67% of site x species combinations. Mean rates of migration ranged from to measurable movement (e.g., Carex laxiflora, Cimicifuga racemosa) to >2 m/yr in some species (e.g., Galium aparine, Potentilla canadensis). Significant differences in rate of migration were observed among seed dispersal modes: ingested > adhesive @? wind @> ants @> none. By contrast, there were no significant differences in rate between clonal and exclusively sexual species. In stands disjunct from old regrowth, the understory was species poor relative to old-regrowth forest due to a lack of species dispersed by ants and spores and those with no obvious dispersal vector. Understory species richness was greater in older disjunct stands and in stands closer to potential sources of propagules than in young and isolated stands, trends that were also noted in distributions of individual species. These results suggest that accessibility to colonists plays an important role in determining understory composition of successional stands. Medium- and long-range migration appears to be an issue of seed and spore dispersal rather than vegetative propagation. The extremely low migration rates of some species threaten their continued existence in the second-growth forest landscape.
Studies of elevation clines in diversity and composition of ecological communities date back to the origins of biogeography. A modern resurgence of interests in these elevational clines is likely to contribute important insights for developing a more general theory of species diversity. In order to gain a more comprehensive understanding of geographical clines in diversity, the research programme for montane biogeography should include statistically rigorous tests of apparent patterns, comparisons of patterns among regions and taxonomic or ecological groups of species, and analyses of clines in environmental variables concurrent with biogeographical surveys. The conceptual framework for this research programme should be based on the assumption that elevational gradients in species diversity result from a combination of ecological and evolutionary processes, rather than the presumed independent effects of one overriding force. Given that montane ecosystems are hot spots of biological diversity, an expanded and integrated programme for biogeographic surveys in montane regions should provide valuable insights for conservation biologists.
Higher Fungi were collected twice a month from May to September 2004 during field survey trips to Seoraksan and Odaesan National Parks. All the collected specimens were investigated for the morphological characters of carpophores and other features, and deposited in the herbarium of the Entomopathogenic Fungal Culture Collection (EFCC), Kangwon National University, Chuncheon. Among the identified specimens, three genera Rhodotus, Hotermannia and Sebacina and four species Rhodotus palmatus, Gomphus clavatus, Holtermannia corniformis and Sebacina incrustans were confirmed as new to Korea and reported here with descriptions.
Abstract Studies of elevation clines in diversity and composition of ecological communities date back to the origins of biogeography. A modern resurgence of interests in these elevational clines is likely to contribute important insights for developing a more general theory of species diversity. In order to gain a more comprehensive understanding of geographical clines in diversity, the research programme for montane biogeography should include statistically rigorous tests of apparent patterns, comparisons of patterns among regions and taxonomic or ecological groups of species, and analyses of clines in environmental variables concurrent with biogeographical surveys. The conceptual framework for this research programme should be based on the assumption that elevational gradients in species diversity result from a combination of ecological and evolutionary processes, rather than the presumed independent effects of one overriding force. Given that montane ecosystems are hot spots of biological diversity, an expanded and integrated programme for biogeographic surveys in montane regions should provide valuable insights for conservation biologists.
It is often claimed that we do not understand the forces driving the global diversity gradient. However, an extensive literature suggests that contemporary climate constrains terrestrial taxonomic richness over broad geographic extents. Here, we review the empirical literature to examine the nature and form of the relationship between climate and richness. Our goals were to document the support for the climatically based energy hypothesis, and within the constraints imposed by correlative analyses, to evaluate two versions of the hypothesis: the productivity and ambient energy hypotheses. Focusing on studies extending over 800 km, we found that measures of energy, water, or water-energy balance explain spatial variation in richness better than other climatic and non-climatic variables in 82 of 85 cases. Even when considered individually and in isolation, water/ energy variables explain on average over 60% of the variation in the richness of a wide range of plant and animal groups. Further, water variables usually represent the strongest predictors in the tropics, subtropics, and warm temperate zones, whereas energy variables (for animals) or water-energy variables (for plants) dominate in high latitudes. We conclude that the interaction between water and energy, either directly or indirectly (via plant pro- ductivity), provides a strong explanation for globally extensive plant and animal diversity gradients, but for animals there also is a latitudinal shift in the relative importance of ambient energy vs. water moving from the poles to the equator. Although contemporary climate is not the only factor influencing species richness and may not explain the diversity pattern for all taxonomic groups, it is clear that understanding water-energy dynamics is critical to future biodiversity research. Analyses that do not include water-energy variables are missing a key component for explaining broad-scale patterns of diversity.
Aim We studied pteridophyte species richness between 100 m and 3400 m along a Neotropical elevational gradient and tested competing hypotheses for patterns of species richness.
Location Elevational transects were situated at Volcán Barva in the Braulio Carrillo National Park and La Selva Biological Station (100–2800 m) and Cerro de la Muerte (2700–3400 m), both on the Atlantic slope of Costa Rica, Central America.
Method We analysed species richness on 156 plots of 20 × 20 m and measured temperature and humidity at four elevations (40, 650, 1800 and 2800 m). Species richness patterns were regressed against climatic variables (temperature, humidity, precipitation and actual evapotranspiration), regional species pool, area and predicted species number of a geometric null model (the mid‐domain effect, MDE).
Results The species richness of the 484 recorded species showed a hump‐shaped pattern with elevation with a richness peak at mid‐elevations ( c . 1700 m). The MDE was the single most powerful explanatory variable in linear regression models, but species richness was also associated strongly with climatic variables, especially humidity and temperature. Area and species pool were associated less strongly with observed richness patterns.
Main conclusions Geometric models and climatic models exclusive of geometric constraints explained comparable amounts of the elevational variation in species richness. Discrimination between these two factor complexes is not possible based on model fits. While overall fits of geometric models were high, large‐ and small‐ranged species were explained by geometric models to different extents. Species with narrow elevational ranges clustered at both ends of the gradient to a greater extent than predicted by the MDE null models used here. While geometric models explained much of the pattern in species richness, we cannot rule out the role of climatic factors (or vice versa) because the predicted peak in richness from geometric models, the empirical peak in richness and the overlap in favourable environmental conditions all coincide at middle elevations. Mid‐elevations offer highest humidity and moderate temperatures, whereas at high elevations richness is reduced due to low temperatures, and at low elevations by reduced water availability due to high temperatures.
Patterns of species richness along latitudinal, elevational and depth gradients often exhibit a mid-gradient peak. Similar patterns with a mid-domain peak in richness are produced, as a result of geometric constraints on species distributions, by models that randomize species range size and placement over a bounded gradient. Proponents of these so-called mid-domain models argue that they provide an appropriate null hypothesis for examining species richness patterns along spatial gradients. Furthermore, some claim that because these models seem to explain a large proportion of the large-scale spatial variation in richness, geometric constraints on species distribution are in fact the cause of these patterns.
A critical examination of model assumptions reveals that some are unrealistic, conceptually flawed or internally inconsistent. Additionally, tests of mid-domain models have suffered from methodological deficiencies derived from arbitrariness and circularity in the definition of domain boundaries, collapsing two-dimensional (2-D) patterns into a single dimension (1-D), and the use of interpolated ranges, all of which can bias test results in favour of the models. Tests have also been statistically naive by using fairly insensitive measures of deviation between observed and predicted patterns and ignoring the increased
probability of Type I error that can result in analyses of spatially autocorrelated data. In spite of this, a review of the empirical evidence indicates that most studies do not show a high degree of concordance between observed and predicted species richness patterns, particularly in 2-D. Additionally, spatial patterns of variation in range size and species turnover do not unequivocally support mid-domain models. Thus, the models do not adequately describe observed species richness gradients and thus fail to explain them. Although mid-domain models have served a useful purpose in drawing attention to
the need to clarify the null expectation in the study of species richness gradients, their use appears to be severely limited by difficulties associated with the treatment of ranges, boundary definitions and a lack of clarity regarding the extent to which the observed data should be used to generate the null patterns.
Aim Little is known about the elevational gradient of plant endemism. It is mostly assumed that patterns are determined by topographical factors such as area of elevational belts and degree of habitat fragmentation, but comparative studies of different plant taxa along the same elevational gradient are lacking. The aim was to compare the elevational patterns of plant endemism of the entire flora and selected families and genera in a search for commonalities.
Methods The elevational patterns of endemism for the entire Ecuadorean vascular plant flora, for twenty-seven selected families, and for twenty-four selected genera based on the Catalogue of Vascular Plants of Ecuador were analysed.
Results Elevational patterns of endemism were non-random at all taxonomic levels but there was no common elevational pattern. Rather, the study groups showed a wide variety of independent patterns at all taxonomic levels. Most groups had hump-shaped patterns with maxima at different elevations and mostly at the same or at higher elevations than the maxima of species richness. The overall flora showed highest endemism in the narrowest and most fragmented elevational belts, presumably because of the consequent fragmentation of species populations.
Main conclusions Patterns of endemism appear to be influenced both by taxon-specific ecological traits (e.g. life form, reproduction, dispersal, demography, spatial population structure, competitive ability) in their specific interaction with historical processes and by environmental factors such as topographical fragmentation. The degree to which these influences become visible along the elevational gradient are determined by which combination of species is analysed: for a given genus or family, taxon-specific traits dominate the patterns, for the entire flora taxon-specific patterns are blurred by averaging and the signal of topography emerges. Beyond the elevational gradient as such, this study shows that the frequently stated assumption that given biogeographical settings lead to similar patterns of endemism among different taxa is wrong.
Broad-scale variation in taxonomic richness is strongly correlated with climate. Many mechanisms have been hypothesized to explain these patterns; however, testable predictions that would distinguish among them have rarely been derived. Here, we examine several prominent hypotheses for climate–richness relationships, deriving and testing predictions based on their hypothesized mechanisms. The ‘energy–richness hypothesis’ (also called the ‘more individuals hypothesis’) postulates that more productive areas have more individuals and therefore more species. More productive areas do often have more species, but extant data are not consistent with the expected causal relationship from energy to numbers of individuals to numbers of species. We reject the energy–richness hypothesis in its standard form and consider some proposed modifications. The ‘physiological tolerance hypothesis’ postulates that richness varies according to the tolerances of individual species for different sets of climatic conditions. This hypothesis predicts that more combinations of physiological parameters can survive under warm and wet than cold or dry conditions. Data are qualitatively consistent with this prediction, but are inconsistent with the prediction that species should fill climatically suitable areas. Finally, the ‘speciation rate hypothesis’ postulates that speciation rates should vary with climate, due either to faster evolutionary rates or stronger biotic interactions increasing the opportunity for evolutionary diversification in some regions. The biotic interactions mechanism also has the potential to amplify shallower, underlying gradients in richness. Tests of speciation rate hypotheses are few (to date), and their results are mixed.
Recent overviews have suggested that the relationship between species richness and productivity (rate of conversion of resources to biomass per unit area per unit time) is unimodal (hump-shaped). Most agree that productivity affects species richness at large scales, but unanimity is less regarding underlying mechanisms. Recent studies have examined the possibility that variation in species richness within communities may influence productivity, leading roan exploration of the relative effect of alterations in species number per se as contrasted to the addition of productive species. Reviews of the literature concerning deserts, boreal forests, tropical forests, lakes, and wetlands lead to the conclusion that extant data are insufficient to conclusively resolve the relationship between diversity and productivity, or that patterns are variable with mechanisms equally varied and complex. A more comprehensive survey of the ecological literature uncovered approximately 200 relationships, of which 30% were unimodal, 26% were positive linear, 12% were negative linear, and 32% were not significant. Categorization of studies with respect to geographic extent, ecological extent, taxonomic hierarchy, or energetic basis of productivity similarly yielded a heterogeneous distribution of relationships. Theoretical and empirical approaches increasingly suggest scale-dependence in the relationship between species richness and productivity; consequently, synthetic understanding may be contingent on explicit considerations of scale in analytical studies of productivity and diversity.
The species-area relationship may be the strongest empirical generalisation in community ecology. We explore the effect of trophic rank upon the "strength" of the species-area relationship, as measured by z, the slope of a log(species) vs.log(area) plot. We present a simple model for communities closed to immigration, composed of "stacked specialist" foodchains (where each plant species supports a specialist herbivore, which in turn sustains a specialist carnivore, etc.), that predicts z should increase with trophic rank; the model brings out some of the spatial implications of sequential dependencies among species. We discuss empirical examples in which the z values of taxa differing in trophic rank were reported and lament the shortage of well-documented examples in the ecological literature. Several examples fit the expected pattern, but others do not. We outline several additional reasons why z values might increase with trophic rank , even for generalists. If the qualitative assumptions of the model are relaxed, the predicted effect of trophic rank on z should weaken or even be reversed . Trophic rank may not have systematic effect on the species-area relationship if :
(1) there are strong top-down interactions leading to prey extinctions
(2) communities are open, with recurrent immigration, particularly at hgher trophic levels
(3) consumers are facultative generalists, able to exist on a wide range of resource species
(4) systems are far from equilibrium
Our aim in this thought piece is to stimulate community ecologists to link theoretical and empirical studies of foodweb structure with analyses of spatial dynamics and landscape ecology , and to encourage empirical studies of the species-area relationship focused on comparisons across taxa varying in trophic rank.
We conceived the idea for this book after teaching a graduate seminar on 'Habitat Complexity' at The University of South Florida. Discussions during the seminar led us to conclude that similar goals were to be found in studies of the topic that spanned the breadth of ecological research. Yet, the exact meaning of 'habitat structure', and the way in which it was measured, seemed to differ widely among subdisciplines. Our own research, which involves several sorts of ecology, convinced us that the differences among subdisciplines were indeed real ones, and that they did inhibit communica tion. We decided that interchange of ideas among researchers working in marine ecology, plant-animal interactions, physiological ecology, and other more-or-less independent fields would be worthwhile, in that it might lead to useful generalizations about 'habitat structure'. To foster this interchange of ideas. we organized a symposium to attract researchers working with a wide variety of organisms living in many habitats, but united in their interest in the topic of 'habitat structure'. The symposium was held at The University of South Florida's Chinsegut Hill Conference Center, in May. 1988. We asked participants to think about 'habitat structure' in new ways; to synthesize important, but fragmented, information; and. perhaps. to consider ways of translating ideas across systems. The chapters contained in this book reflect the participants' attempts to do so. The book is divided into four parts, by major themes that we have found useful categorizations.
In both ancient and recent woods the number of species increased with area, probably because of a correlated increase in habitat diversity. The number of species present in part of an ancient wood was not significantly different from the number present in whole ancient woods of equivalent area. The number of species present in recently reduced ancient woods was not significantly different from the number present in ancient woods which were reduced to their present size long ago. Ancient woods were significantly richer than isolated recent woods. Recent woods which have had a physical contact with an ancient wood were significantly richer in species than isolated recent woods, and significantly poorer than ancient woods. The number of species present in recent woods did not increase with age. This was tested in woods originating between 1600 and 1947. Number of species present in recent woods was influenced by habitat diversity. Previous land use influenced which species were present, not how many. Although ancient woods comprised only 25% of all sites (43% by area), 62 of the 174 species recorded had >50% of their localities in ancient woods (= ancient woodland species) and 43 species had <33% of their localities in ancient woods (= recent woodland species). Recent woodland species tended to inhabit disturbed parts of ancient woods; ancient woodland species tended to inhabit undisturbed parts. -from Authors
At landscape and regional scales topography is recognized as one of the most important determinants of vascular plant diversity, primarily due to the influence of mountains. As temperature changes markedly over the elevation ranges in mountain areas, topography offers a wide variety of different habitats as well as buffering against climate change. However, for local vegetation, notably in lowland areas, the general importance of topography is less well recognized and the mechanisms by which it exerts influence on local vascular plant diversity are not comprehensively understood. In this review, we provide an overview of the evidence for the different mechanisms involved in topography’s control of local patterns in potential vegetation drivers, namely incident solar energy, wind exposure, hydrology, geochemistry, and biotic conditions. Furthermore, we review the processes through which these factors shape local terrestrial vascular plant diversity patterns and provide directions for future studies on this topic. We find that topography is an important factor for local vascular plant diversity patterns in a broad range of habitats throughout the world, even in relatively flat lowlands. However, the mechanisms involved are varied and complex. Local patterns in soil moisture seem to be affected by topography through more mechanisms than other topographically controlled factors and have a strong and consistent influence on local plant diversity. Hence, local hydrology is probably the main mechanistic factor through which topography influences local terrestrial vascular plant diversity patterns. Future research should focus on employing high-coverage fine-resolution topographic data to comprehensively explore the role of topography in controlling local dynamics over large areas. Moreover, we recommend including several different habitats, particularly those in which the role of topography is poorly understood. Finally, we propose to integrate relevant functional topographic variables such as topographic wetness indices instead of simple topographic measures into future investigations.
A comprehensive mapping project for agroclimatic zoning in South Korea will end by April 2010, which has required 4 years, a billion won (ca. 0.9 million US dollars) and 22 experts from 7 institutions to complete it. The map database from this project may be categorized into primary, secondary and analytical products. The primary products are called "high definition" digital climate maps (HD-DCMs) and available through the state of the art techniques in geospatial climatology. For example, daily minimum temperature surfaces were prepared by combining the climatic normals (1971-2000 and 1981-2008) of synoptic observations with the simulated thermodynamic nature of cold air by using the raster GIS and microwave temperature profiling which can quantify effects of cold air drainage on local temperature. The spatial resolution of the gridded climate data is 30m for temperature and solar irradiance, and 270m for precipitation. The secondary products are climatic indices produced by statistical analysis of the primary products and includes extremes, sums, and probabilities of climatic events relevant to farming activities at a given grid cell. The analytical products were prepared by driving agronomic models with the HD-DCMs and dates of full bloom, the risk of freezing damage, and the fruit quality are among the examples. Because the spatial resolution of local climate information for agronomic practices exceeds the current weather service scale, HD-DCMs and the value-added products are expected to supplement the insufficient spatial resolution of official climatology. In this lecture, state of the art techniques embedded in the products, how to combine the techniques with the existing geospatial information, and agroclimatic zoning for major crops and fruits in South Korea will be provided.
We compared woody plant species distributions across nested spatial scales (local scale to entire Western Himalaya) and explored landscape scale patterns in detail to obtain inferences about the elevational gradient in species richness. Distribution data were compiled for 1100 species in the Western Himalaya, and primary data, comprising 123 species and 47 000 individuals, were collected for a landscape. Correlates of diversity were examined for the five spatial scales, and for different biogeographic groups at the landscape scale. The results indicate multiple mechanisms both within and across scales. At the landscape scale, though the mechanisms explaining unimodal species richness patterns were hard to separate, the underlying correlates of biogeographic groups were more distinct; temperate species richness followed mid-domain model predictions, and showed a nonlinear relationship with temperature, whereas tropical species richness tracked temperature and area. Simulations demonstrated that models with varying assumptions, while resulting in monotonic, unimodal, or multimodal patterns at local scales, could all lead to unimodal patterns at regional scales when multiple local replicates are aggregated, with a peak in the major ecotone. The turnover or successive accumulation of marginal species in ecotones potentially explains the mid-elevational peak in this zone. Landscape scale primary data on distribution and abundance could therefore be critical to understanding key aspects of macroecological patterns.
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Draws together ideas on the meaning of habitat structure and ways in which such a feature can be measured and used in ecology. The 21 chapters are arranged into sections on: patterns; responses - colonization, succession and resource use; responses - predation, parasitism and disturbance; and applications. Apart from the final review chapter (Habitat structure: synthesis and perspectives, by E.D.McCoy, S.S.Bell and H.R.Mushinsky), each chapter is abstracted separately: 92L/02424, 02443, 02444, 02490, 02497, 02569, 02607, 02611, 02634, 02722, 02736, 02752, 02799, 02817, 02837, 03186, 03198 and 03377-03379. -P.J.Jarvis
Geographic variation of species richness is strongly correlated with environmental gradients. However, random arrangement of species distributions within a bounded domain can also theoretically produce richness gradients without underlying environmental gradients. This mid-domain effect (MDE) could serve as the null hypothesis against which to test effects of environmental variables, or as a component of a multivariate explanation of species-richness patterns. Recent reviews have concluded that there is a substantial MDE signature in observed geographical patterns of richness, based on correlations between observed patterns of richness and the predictions of mid-domain models. However, the mid-domain hypothesis makes additional powerful predictions about how richness should vary through space, and about the slope of the relationship between predicted and observed richness. Very few studies have tested these more powerful MDE predictions. Here, we reexamine the published mid-domain literature for agreement between observed patterns of richness and MDE predictions. We find that 50 of 53 published studies of MDEs showed significant deviations from the predictions of mid-domain models. When observed richness is correlated with MDE predictions, there are nearly always strongly collinear environmental gradients (e.g., in the Americas, climatic favorability and MDE-predicted richness are both maximal in the middle). Interpolation in sparsely sampled data can also give rise to spurious, apparently strong, mid-domain effects (e.g., the classic study of the Madagascan rain forest). We conclude that observed broad-scale patterns of species richness are not consistent with the mid-domain hypothesis.
Elevational gradients in species diversity have great potential for increasing our knowledge about broad-scale diversity mechanisms. In this article the authors describe the history of studies of elevational species richness patterns from Grinnell and Whittaker until today. The observed elevational trend in species varies among groups of organisms and from one area to another. The most commonly observed patterns are decreasing richness with increasing elevation and a humped pattern with a richness peak at intermediate elevations. The authors discuss some hypotheses which may be important in shaping the richness trends, including productivity/energy, mid-domain effect, source–sink dynamics, species–area relationships, heterogeneity, and history.
Geographic patterns of species richness are influenced by many factors, but the role of shared physiographical and physiological boundaries in relation to range-size
distributions has been surprisingly neglected, in spite of the fact that such geometric
constraints lead to mid-domain richness peaks even without environmental
gradients (the mid-domain effect). Relying on null models, several recent studies
have begun to quantify this problem using simulated and empirical data. This
approach promises to transform how we perceive geographic variation in diversity,
including the long unresolved latitudinal gradient in species richness. The question is
not whether geometry affects such patterns, but by how much.
Aim Data and analyses of elevational gradients in diversity have been central to the development and evaluation of a range of general theories of biodiversity. Elevational diversity patterns have, however, been severely understudied for microbes, which often represent decomposer subsystems. Consequently, generalities in the patterns of elevational diversity across different trophic levels remain poorly understood. Our aim was to examine elevational gradients in the diversity of macroinvertebrates, diatoms and bacteria along a stony stream that covered a large elevational gradient.
Location Laojun Mountain, Yunnan province, China.
Methods The sampling scheme included 26 sites spaced at elevational intervals of 89 m from 1820 to 4050 m elevation along a stony stream. Macroinvertebrate and diatom richness were determined based on the morphology of the specimens. Taxonomic richness for bacteria was quantified using a molecular fingerprinting method. Over 50 environmental variables were measured at each site to quantify environmental variables that could correlate with the patterns of diversity. We used eigenvector-based spatial filters with multiple regressions to account for spatial autocorrelation.
Results The bacterial richness followed an unexpected monotonic increase with elevation. Diatoms decreased monotonically, and macroinvertebrate richness showed a clear unimodal pattern with elevation. The unimodal richness pattern for macroinvertebrates was best explained by the mid-domain effect (r2 = 0.72). The diatom richness was best explained by the variation in nutrient supply, and the increase in bacterial richness with elevation may be related to an increased carbon supply.
Main conclusions We found contrasting patterns in elevational diversity among the three studied multi-trophic groups comprising unicellular and multicellular aquatic taxa. We also found that there may be fundamental differences in the mechanisms underlying these species diversity patterns.
The mechanisms shaping patterns of biodiversity along spatial gradients remain poorly known and controversial. Hypotheses have emphasized the importance of both environmental and spatial factors. Much of the uncertainty about the relative role of these processes can be attributed to the limited number of comparative studies that evaluate multiple potential mechanisms. This study examines the relative importance of six variables: temperature, precipitation, productivity, habitat heterogeneity, area, and the mid-domain effect on patterns of species richness for non-volant small mammals along four neighboring mountain ranges in central Utah. Along each of these elevational gradients, a hump-shaped relationship of richness with elevation is evident. This study evaluates whether the processes shaping this common pattern are also common to all gradients. Model selection indicates that no one factor or set of factors best explains patterns of species richness across all gradients, and drivers of diversity may vary seasonally. These findings suggest that commonality in the pattern of species richness, even among elevational gradients with a similar biogeographic history and fauna, cannot be attributed to a simple universal explanation.
This study analyzes the variations in the structure and composition of ant communities in burned Pinus nigra forests in central Catalonia (NE Spain). Pinus nigra forests do not recover after fire, changing to shrublands and oak coppices. For this reason, we suggest that ant communities of burned P. nigra forests will change after fire, because the post-fire scenario, in particular with the increase of open areas, is different to the unburned one, and more favourable for some species than for others. In four locations previously occupied by P. nigra forests where different fires occurred 1, 5, 13 and 19 yr before the sampling, we sampled the structure and composition of ant communities with pitfall traps, tree traps and net sweeping in unburned plots and in plots affected by canopy and understory fire. The results obtained suggest that canopy and understory fire had little effect on the structure of ant communities. Thus, many variables concerning ant communities were not modified either by fire type (understory or canopy fire) or by time since fire. However, a number of particular species were affected, either positively or negatively, by canopy fire: three species characteristic of forest habitats decreased after fire, while eight species characteristic of open habitats increased in areas affected by canopy fire, especially in the first few years after fire. These differences in ant community composition between burned and unburned plots imply that the maximum richness is achieved when there is a mixture of unburned forests and areas burned with canopy fire. Moreover, as canopy cover in P. nigra forests burned with canopy fire is not completed in the period of time studied, the presence of the species that are characteristic of burned areas remains along the chronosequence studied, while the species that disappear after fire do not recover in the period of time considered. Overall, the results obtained indicate that there is a persistent replacement of ant species in burned P. nigra forests, as is also the case with vegetation.
Aim To calculate the degree to which differences between local and regional elevational species richness patterns can be accounted for by the effects of regional area.
Location Five elevational transects in Costa Rica, Ecuador, La Réunion, Mexico and Tanzania.
Methods We sampled ferns in standardized field plots and collated regional species lists based on herbarium and literature data. We then used the Arrhenius function S = cAz to correct regional species richness (S) for the effect of area (A) using three slightly different approaches, and compared the concordance of local and regional patterns prior to and after accounting for the effect of area on regional richness using linear regression analyses.
Results We found a better concordance between local and regional elevational species richness after including the effect of area in the majority of cases. In several cases, local and regional patterns are very similar after accounting for area. In most of the cases, the maximum regional richness shifted to a higher elevation after accounting for area. Different approaches to correct for area resulted in qualitatively similar results.
Main conclusions The differences between local and regional elevational richness patterns can at least partly be accounted for by area effects, suggesting that the underlying causes of elevational richness patterns might be the same at both spatial scales. Values used to account for the effect of area differ among the different study locations, showing that there is no generally applicable elevational species–area relationship.
A global analysis of elevational diversity trends for nonvolant small mam-mals revealed a clear pattern of mid-elevational peaks in species richness. Fifty-six data sets were used to test the predictions of a null model (the mid-domain effect) and climatic hypotheses. Very few data sets fit entirely within the predictions of the null model, and the average predictive power of the null model was low. Regional (gamma) diversity fit the null model better than did local (alpha) diversity. Diversity peaked at higher elevations on taller mountains, consistent with climatic factors producing elevationally correlated habitat bands (Massenerhebung effect). This positive, linear relationship was documented for all data sets but was particularly pronounced for alpha diversity. Gamma diversity, which is generally highly influenced by area, exhibited a trend of highest diversity shifting toward lower elevations, and higher elevational peaks in species diversity at higher latitudes. The elevation of temperate diversity peaks exhibited a negative association with latitude. These results are evidence for the importance of a suite of interacting climatic, area, and geometric factors on elevational diversity patterns, apparent in spite of noise associated with different sampling techniques, localities, and historical pressures.
Recent research in aquatic systems suggests that productivity–richness re-lationships change with spatial scale and that species turnover (i.e., spatial and temporal variation in species composition) plays an important role in generating this scale depen-dence. The generality of such scale dependence and the effects of variation in temporal scale remain unknown. We examined the extent to which the richness–productivity rela-tionship in terrestrial plant communities depends on spatial or temporal scale and evaluated how spatial and temporal turnover (i.e., species turnover in space and time) generates scale dependence in these relationships using data from two Long-Term Ecological Research (LTER) sites (Jornada and Konza). We found a weak hump-shaped relationship (Jornada) and no relationship (Konza) between richness and productivity at the smallest focal scale (1 m 2 at Jornada and 50 m 2 at Konza) at each site, but strong hump-shaped relationships at the largest focal scale (49 m 2 at Jornada and 200 m 2 at Konza) for each site. Relationships between spatial turnover and productivity at each site mirrored the productivity–richness relationships that emerged at the larger spatial scale (i.e., a significant hump-shaped pattern). In contrast, temporal turnover was unrelated to productivity, and hence increasing temporal scale did not appreciably change the form of the productivity–richness relationship. Our study suggests that the way in which productivity–richness relationships change with spatial or temporal scale depends on the form and strength of the underlying relationship between species turnover and productivity. Moreover, we contend that a dominant effect of increasing productivity is the generation of dissimilarity in species composition among localities that comprise a region, rather than increasing the number of species that occur within local communities. Thus, understanding the mechanisms that cause species turnover to vary with productivity is critical to understanding scale dependence in richness–productivity rela-tionships.
Aim Latitudinal‐ and regional‐scale studies of reptile diversity suggest a predominant temperature effect, unlike many other vertebrate richness patterns which tend to be highly correlated with both temperature and water variables. Here I examine montane gradients in reptile species richness with separate analyses of snakes and lizards from mountains around the world to assess a predominant temperature effect and three additional theories of diversity, including a temperature–water effect, the species–area effect and the mid‐domain effect (MDE).
Location Twenty‐five elevational gradients of reptile diversity from temperate, tropical and desert mountains in both hemispheres, spanning 10.3° N to 46.1° N.
Methods Elevational gradients in reptile diversity are based on data from the literature. Of the 63 data sets found or compiled, only those with a high, unbiased sampling effort were used in analyses. Twelve predictions and three interactions of diversity theory were tested using nonparametric statistics, linear regressions and multiple regression with the Akaike information criterion (AIC).
Results Reptile richness and, individually, snake and lizard richness on mountains followed four distinct patterns: decreasing, low‐elevation plateaus, low‐elevation plateaus with mid‐elevation peaks, and mid‐elevation peaks. Elevational reptile richness was most strongly correlated with temperature. The temperature effect was mediated by precipitation; reptile richness was more strongly tied to temperature on wet gradients than on arid gradients. Area was a secondary factor of importance, whereas the MDE was not strongly associated with reptile diversity on mountains.
Main conclusions Reptile diversity patterns on mountains did not follow the predicted temperature–water effect, as all diversity patterns were found on both wet and dry mountains. But the influence of precipitation on the temperature effect most likely reflects reptiles' use of radiant heat sources (sunning opportunities) that are more widespread on arid mountains than wet mountains due to lower humidity, sparser vegetation and less cloud cover across low and intermediate elevations.
Despite two centuries of exploration, our understanding of factors determining the distribution of life on Earth is in many ways still in its infancy. Much of the disagreement about governing processes of variation in species richness may be the result of differences in our perception of species-richness patterns. Until recently, most studies of large-scale species-richness patterns assumed implicitly that patterns and mechanisms were scale invariant. Illustrated with examples and a quantitative analysis of published data on altitudinal gradients of species richness (n = 204), this review discusses how scale effects (extent and grain size) can influence our perception of patterns and processes. For example, a hump-shaped altitudinal species-richness pattern is the most typical (c. 50%), with a monotonic decreasing pattern (c. 25%) also frequently reported, but the relative distribution of patterns changes readily with spatial grain and extent. If we are to attribute relative impact to various factors influencing species richness and distribution and to decide at which point along a spatial and temporal continuum they act, we should not ask only how results vary as a function of scale but also search for consistent patterns in these scale effects. The review concludes with suggestions of potential routes for future analytical exploration of species-richness patterns.
Aim The objective of this study was to comprehensively document and examine the alpha and gamma patterns of species richness in non-volant, small mammals (rodents, shrews and mouse opossums) along a tropical elevational gradient. These data were used to determine the support for existing hypotheses of species richness encompassing mid-domain null models, as well as climatic, and community overlap hypotheses.
Location Field studies were conducted along a Caribbean slope of the Río Peñas Blancas watershed in the north-eastern region of Costa Rica between 750 and 1850 m at 10 sampling sites.
Methods Species richness and abundances of small mammals were surveyed for four seasons including three temporal replicates at each of five elevational sites: late wet season (2000), early wet season (2001), and dry season (2002), and one spatial replicate at five different sites within the same elevations during the late wet season (2001). Species richness at elevations below 700 m was compiled from specimen records from 23 US national and international collections. Predictions of a null model based solely on geometric constraints were examined using a Monte Carlo simulation program, Mid-Domain Null.
Results In 16,900 trap nights, 1561 individuals from 16 species were captured. Both alpha and gamma species richness peaked at mid-elevation between 1000 and 1300 m, with richness declining both at higher and lower elevations. Most of the empirical curves of species richness occur within 95% prediction curves of the mid-domain model, although deviations from the null model exist. Regression of the empirical richness on the null model predictions explained nearly half of the variation observed (r2 = 0.45, P = 0.002).
Main conclusions The geometric constraints of montane topography appear to influence the diversity pattern of small mammals, although climatic conditions including an intermediate rainfall and temperature regime, and distance from the persistent cloud cap also are correlated with the pattern of species richness. The predictions of productivity, and community overlap hypotheses are not supported with the empirical data.
Aim Elevational gradients distributed across the globe are a powerful test system for understanding biodiversity. Here I use a comprehensive set of bird elevational gradients to test the main drivers of diversity, including sampling, area, mid-domain effect, temperature, temperature and water availability, and hypotheses of evolutionary history.
Location Seventy-eight elevational gradients of bird diversity from mountains in both hemispheres spanning 24.5° S to 48.2° N, including gradients from various climates, biogeographical regions and habitat types.
Methods Data on bird elevational diversity were taken from the literature. Of the 150 datasets found or compiled, only those with a high, unbiased sampling effort were used in analyses. Datasets sampled all birds, all breeding birds or all forest birds; a few studies detailed seasonal, elevational shifts. Eighteen predictions of diversity theory were tested, including three sets of interactions.
Results Birds display four distinct diversity patterns in nearly equal frequency on mountains: decreasing diversity, low-elevation plateaus, low-elevation plateaus with mid-peaks, and unimodal mid-elevational peaks. Bird elevational diversity strongly supports current climate as the main driver of diversity, particularly combined trends in temperature and water availability. Bird diversity on humid mountains is either decreasing or shows a low-elevation plateau in diversity, while on dry mountains it is unimodal or a broad, low-elevation plateau usually with a mid-elevation maximum. The predictions of sampling, area and mid-domain effect were not consistently supported globally. The only evolutionary hypothesis with preliminary support was niche conservatism.
Main conclusions Both water and temperature variables are needed to comprehensively predict elevational diversity patterns for birds. This result is consistent for breeding and forest birds, for both hemispheres, and for local- or regional-scale montane gradients. More analyses are needed to discern whether the mechanism underlying these relationships is ecological, based on direct physiological limitations or indirect food resource limitations, or historical, based on phylogenetic niche conservation or other evolutionary trends related to climate. The species–area and mid-domain effects are not supported as primary drivers of elevational diversity in birds.
Spatial patterns of species richness follow climatic and environmental variation, but could reflect random dynamics of species ranges (the mid-domain effect, MDE). Using data on the global distribution of birds, we compared predictions based on energy availability (actual evapotranspiration, AET, the best single correlate of avian richness) with those of range dynamics models. MDE operating within the global terrestrial area provides a poor prediction of richness variation, but if it operates separately within traditional biogeographic realms, it explains more global variation in richness than AET. The best predictions, however, are given by a model of global range dynamics modulated by AET, such that the probability of a range spreading into an area is proportional to its AET. This model also accurately predicts the latitudinal variation in species richness and variation of species richness both within and between realms, thus representing a compelling mechanism for the major trends in global biodiversity.
The recovery of forest vegetation following abandonment of agriculture was followed by surveying forest herbs in central New York State at 25 sites where postagricultural forest occurred directly adjacent to old‐woods (forest that has never been ploughed).
The abundance, richness and diversity of 50 forest herbs were on average lower in postagricultural forests than in old‐woods.
Thirty of 39 forest herbs that were found in at least four stands were less frequent (number of plots present out of 60) in postagricultural forests than in old‐woods. Three species ( Aster divaricatus , Dryopteris intermedia and Polystichum acrostichoides ) had significantly higher frequency in old‐woods, while none was significantly more common in postagricultural forests.
Although differences among species in their frequency in the two forest types were not strongly related to dispersal mode, species with rapid clonal expansion were significantly more frequent in postagricultural stands.
Several species that were less frequent in postagricultural forests than in old‐woods showed decreases in density in postagricultural forests with increasing distance from the adjacent old‐woods.
The purpose of this investigation was to explore the determinants of vascular plant species richness for temporary, isolated wetland habitats which are influenced by hydrologic gradients and characterized by variation in habitat area. The dependent variables total plant species richness and the number of obligate wetland species were analyzed consecutively. In regression analyses habitat area explained between 11 and 15% of the variation in the dependent variables. Habitat area was correlated with the heterogeneity of the hydroperiods between the upper and lower parts of the hydrologic gradients. In multivariate regression analyses, habitat heterogeneity accounted for 70-77% of the variation in the dependent variables, and habitat area did not have a significant impact. The results are most consistent with the habitat heterogeneity hypothesis. I therefore concluded that area is a surrogate variable for habitat heterogeneity which directly enhances vascular plant species diversity. There was no significant impact of isolation on species richness. The data suggest that the expanses of agricultural fields are not an effective barrier to the dispersal of the studied plant species. Only 10 of,52 wetland species were negatively influenced by isolation. This group of species did not differ from the other wetland species with respect to dispersal strategies and longevity of seed banks. However, the longevity of the seed banks was generally high, and there was a dominance of species whose propagules are transported with the soil clinging to the feet of birds. The results are discussed in the context of accurate dispersal strategies and remnant populations, which may counteract the effects of isolation.
Patterns of plant diversity along the altitudinal gradient of Tianshan in central Xinjiang, China were examined. Plant and
environment characteristics were surveyed from higher, south of Bogeda peak, to lower, north of Guerbantonggute desert. There
were a total of 341 vascular plant, 295 herbage, 41 shrub, and seven tree species in the sampled plots. The plant richness
of vegetation types generally showed a unimodal pattern along altitude, with a bimodal change of plant species number at 100-m
intervals of altitudinal samples. The two belts of higher plant richness were in transient areas between vegetation types,
the first in areas from dry grass to forest, and the second from forest to sub-alpine grass and bush. The beta diversity varied
with altitudinal changes, with herbaceous species accounting for most species, and thus had similar species turnover patterns
to total species. Matching the change of richness of plant species to environmental factors along altitude and correlating
these by redundancy analysis revealed that the environmental factors controlling species richness and its pattern were the
combined effects of temperature, precipitation, soil water, and nutrition. Water was more important at low altitude, and temperature
at high altitude, and soil chemical and physical characters at middle altitudes. This study provides insights into plant diversity
conservation of Bogeda Natural Reserve Areas in Tianshan Mountain.
NOTE: This is not a book, contrary to what ResearchGate claims. This is a software application and User's Guide. The current version is Version 9. The citations here are incomplete, since each version has its own citations. EstimateS currently has more than 4000 citations in the peer-reviewed literature. For the full list, go to GoogleScholar: http://bit.ly/11YdUlg .
Only ca. 3000 individuals of Ilex khasiana Purk. are surviving today. The tree species is endemic to Khasi hills of northeast India, and is critically endangered. For improving the conservation status of the species, potential area and habitat for reintroduction were predicted using Maximum Entropy (MaxEnt) distribution modelling algorithm. The model was developed using 16 locality data in the native range of Khasi hills, and 16 environmental parameters including enhanced vegetation index (EVI) and digital elevation data. The model predicted that the suitable habitats of I. khasiana was restricted to an area of approximate to 500 km(2) in the Khasi hills of Meghalaya. The distribution of potential habitats was strongly influenced by elevation and the EVI layers for the period April-May, which corresponds to the flowering phase of the species, thus indicating the importance of flowering stage in determining the species distribution. Population status was positively correlated with higher model thresholds in the undisturbed habitats confirming the usefulness of the habitat model in population monitoring, particularly in predicting the successful establishment of the species. The study delineated the potential habitats in the higher elevations of Khasi hills within the current home range where the species can be reintroduced.
Why do larger areas have more species? What makes diversity so high near the equator? Has the number of species grown during the past 600 million years? Does habitat diversity support species diversity, or is it the other way around? What reduces diversity in ecologically productive places? At what scales of space and time do diversity patterns hold? Do the mechanisms that produce them vary with scale? This book examines these questions and many others, by employing both theory and data in the search for answers. Surprisingly, many of the questions have reasonably likely answers. By identifying these, attention can be turned toward life's many, still-unexplained diversity patterns. As evolutionary ecologists race to understand biodiversity before it is too late, this book will help set the agenda for diversity research into the next century.
Describes how organisms behave and live in relation to their environment and evolutionary history, bearing in mind the different resources that are required, and the nature of the interactions between these resources. The balance between birth rates and death rates, which indicates abundance, is shown to have profound effects on the behaviour of populations. Dispersal of organisms is linked with escape from unfavourable environments and the colonisation and exploitation of new environments. In looking at interactions between organisms, the nature and consequences of intra- and interspecific competition are explored. The nature of predation and grazing, behaviour of consumers and consumed, and implications of predation/grazing for population dynamics are also discussed. Decomposition and detritivore trophic linkages are reviewed, as are parasitism and disease. The evolution of mutualistic relationships is noted. Surveys of the range of life history strategies exhibited by living organisms, and of the range of patterns of abundance, are used to provide overviews of the organismic and the population levels in the ecological hierarchy. The final section considers interactions at the community level, looking at how community patterns change through space and time, examining the flux of energy and matter through communities, and indicating the influence of competition, predation and disturbance on community structure. Aspects of island biogeography theory are also discussed. The final chapters examine community stability and structure, and patterns of species diversity. -P.J.Jarvis