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R-Selection and K-Selection
... distinguish generalized life history strategies employed by multiple taxa (Pianka, 1970), including fishes (Winemiller & Rose, 1992), and links between traits and climate change sensitivity may depend upon trade-offs and interactions among traits. Evidence suggests that considerations of individual traits may be useful for understanding mechanisms that drive species responses to global changes (Williams et al., 2010). ...
... Using a comparable sample size, Mims et al. (2018) found no relationship between traits (including body size, longevity, maturity, fecundity, and parental investment) and geographically derived intrinsic sensitivity for 54 freshwater fishes of the U.S. Pacific Northwest, an area that falls entirely within our West region. While traits associated with generalized life history strategies (Pianka, 1970;Winemiller & Rose, 1992) were correlated with geographically derived sensitivity at the national scale, this pattern did not hold true in the West and suggests that individual traits may complement geographic assessments of intrinsic climate risk at regional scales (Williams et al., 2010). Taken together, these results demonstrate the potential for relationships between geographic-derived and traits-based assessments of intrinsic sensitivity to vary across spatial extents and regions. ...
Assessing the sensitivity of freshwater species to climate change is an essential component of prioritizing conservation efforts for threatened freshwater ecosystems and organisms. Sensitivity to climate change can be systematically evaluated for multiple species using geographic attributes such as range size and climate niche breadth, and using species traits associated with climate change sensitivity. These systematic evaluations produce relative rankings of species sensitivity to aid conservation prioritization and to identify relatively sensitive species that may otherwise be understudied or overlooked. Due in part to biogeographic constraints, species assemblages change across regions and spatial extents; yet, the degree to which spatial factors influence relative rankings of species sensitivity is unclear. The spatial extent of multispecies analyses may alter relative rankings of species climate sensitivity; alternatively, relative climate sensitivity may be conserved among spatial scales, resulting in consistent identification of sensitive species among regions and spatial extents. We investigated how spatial extent influences our understanding of relative climate sensitivity for 137 native freshwater fishes of the United States that were representative of taxonomic, trait, and geographic diversity. Using publicly available occurrence data from the Global Biodiversity Information Facility, we calculated a systematic, geographically derived index of climate change sensitivity for study species at national and regional extents, including within four major hydrologic subregions of the United States. We examined the effects of spatial extent on the relative ranking of climate sensitivity among species, and we explored relationships among climate sensitivity, species traits, and conservation status at regional and national extents. We found that climate sensitivity rankings of species were influenced by spatial extent in some specific instances, but that relative rankings were largely conserved across spatial scales. However, correlations among geographically derived climate sensitivity rankings and species traits associated with climate sensitivity were variable across scales and regions, suggesting that links between geographic rarity and species traits may be scale‐dependent in some cases. Finally, we found few associations between climate sensitivity and current conservation status among species. Systematic approaches to quantifying climate sensitivity may offer an opportunity to identify sensitive but overlooked species for pre‐listing actions such as monitoring or conservation agreements.
... Reproduction-with its myriad forms-has been studied extensively in the context of trade-offs. One of its central theories is r/K selection (Pianka 1970), which posits trade-offs between number of offspring and parental investment, sometimes shorthanded as quality of offspring. The balance of where a species lands in this trade-off will depend on their specific biology and which strategies confer the highest fitness: for example, organisms in unpredictable environments will often decrease offspring number but increase parental investment (Husby 1986;Badyaev and Ghalambor 2001), while organisms from ephemeral environments or those frequently disturbed tend to produce many offspring with relatively lower investment per offspring (Eckerström-Liedholm et al. 2017;Morrongiello et al. 2012). ...
Biological trade-offs present a central issue for evolutionary biology: it has been a fundamental understanding within the field that limits exist on the phenotypic traits a species is able to exhibit in part due to trade-offs. Reproduction-with its myriad forms-has been studied extensively in the context of these dynamics. And while considerable literature has explored trade-offs between seed size and number and their associated environmental conditions, none has looked at spore size trade-offs in ferns. We can hypothesise potential trade-offs in spore size: smaller spores should be able to disperse farther, but may not have sufficient provisions to survive in environments that require them to remain at the gametophyte stage for longer periods if their germination cues are mismatched. Reproductive mode (sexual vs. asexual) and ploidy may also be playing a role. In order to study trade-offs related to spore size, I focus on the Australasian fern species Cheilanthes distans (Pteridaceae), which is most often found in xeric environments, growing in crevices or on top of rocks which are haphazardly scattered across their range. Apomictic diplospores in this species are formed through first division restitution, a meiotic pathway particularly prone to mistakes in chromosome pairing and cell division (as compared to premeiotic endomitosis). Rather than being problematic, these mistakes ultimately lead to considerable additional variation in spore size, spore products (through a range of aneuploid spores), and spore ploidy. In this study, I explore trade-offs between spore size, dispersal, and germination, taking into account effects from reproductive mode and ploidy. I carried out an extensive survey of C. distans specimens to establish the prevalence of sexual vs. apomictic (asexual) specimens, and to describe in greater depth the variation in ploidy across the species. I also collected data on spore size and sporogenesis forms. With these data I then asked: is spore size correlated with range area or with germination? And does spore form correlate with either spore size or germination? Ultimately, I find that variations in sporogenesis may be leading to large variation in spore sizes-especially since spores traditionally considered abortive are in fact viable-and that this variation may provide abundant fodder for evolution to act through trade-offs between dispersal into large ranges and germination leading to establishment. Especially in light of the fact that many spores that were historically considered abortive are fully viable and likely shaping evolution in important ways, it is worth remarking on what these results illustrate more broadly: the way in which we have constructed 'disability' ultimately affects how we perceive so-called 'genetic errors'-both in humans and in other species-and thus limits what we allow ourselves to imagine 'disabled' beings are capable of.
... Differently, fisher populations can decrease quickly if their habitat is degraded (Powell, 1993), which can disrupt the functioning of their ecosystem as mesopredators are essential drivers of ecosystem function (Roemer et al., 2009). Also, variations in life history traits are much larger across species than among individuals and can be represented by the slow-fast continuum of life history strategies (Pianka, 1970;Stearns, 1992). Ungulates are "slow" mammals having few offspring and higher survival rates, while mesocarnivores are relatively "fast" mammals with short lifespans (Heppell et al., 2000). ...
Harvested wildlife populations should ideally be monitored to inform harvest policies and decision‐making to help achieve management objectives. When the age of harvested individuals can be obtained, these data (i.e., age‐at‐harvest data) can be used to estimate trends of abundances, demographic rates, and harvest probabilities by the statistical reconstruction of the living population. This approach was developed primarily within the frequentist framework and requires the inclusion of auxiliary data (e.g., radiotelemetry data). We developed a novel Bayesian hierarchical approach allowing the population reconstruction from the definition of the species' life cycle without auxiliary data. The hierarchical model assumes that individuals are harvested from an open population whose fluctuations result from demographic processes, and the definition of a superpopulation composed of pseudo‐individuals from which the harvested population is drawn. We evaluated the ability of our model to estimate abundances, survival, recruitment, and harvest probabilities based on simulations guided by the demographic processes of a long‐lived mammal population. We considered model performance across scenarios, including varying age and temporal structures, superpopulation size, and prior information. We showed how prior information selected based on life history characteristics affects the accuracy of estimated parameters. We found that the model estimates accurate demographic parameters and abundances when the age‐at‐harvest matrix comprises more than two age classes. Furthermore, an increase in demographic information (number of age groups and years) increased the precision of the estimated parameters. We apply our model to a population of harvested (2012–2021) white‐tailed deer (Odocoileus virginianus) and a mammalian carnivore, the fisher (Pekania pennanti), from Rhode Island, USA. Our model estimated biologically realistic population size and demographic rates for both species. Our approach provides robustness to track the population abundance of harvested species through time and estimate fundamental demographic parameters. Such results can be used to monitor whether population objectives are being met and whether harvest policy changes are required. Furthermore, this information can be critical for evaluating the effect of harvest on population growth and projecting trajectories of age‐structured populations under different harvest scenarios. Therefore, our framework can help to guide management decisions and species conservation.
... P. dioica demonstrated a very high resilience against disturbances from harvesting and seasonal changes in environmental conditions, a typical trait for opportunistic life history strategies (Pianka, 1970;Grassle & Grassle, 1974;Stearns, 1989;Winemiller & Rose, 1992). Only mean thallus size decreased as a result of harvesting in summer and winter, although this could have further long-term implications. ...
Red macroalgae in the genus Porphyra are widely collected for human consumption and increasingly harvested along the North Atlantic coasts but their ability to withstand repeated harvesting and maintain high cover and abundance on natural shorelines remains poorly explored, raising sustainability concerns. Therefore, we investigated the effect of frequent hand-harvesting on Porphyra dioica in a population in South Wales, UK, where it is commercially harvested. Twelve control and twelve treatment quadrats were installed in spring and six control and treatment plots in autumn. Monthly hand-harvesting of P. dioica individuals larger than 5 cm was performed in the treatment plots, while the control plots remained undisturbed. We monitored P. dioica percentage cover, yield, thallus length and recruit density, as well as benthic flora and fauna. Harvesting only impacted P. dioica thallus length, resulting in 41% smaller thalli compared to unharvested plots during summer, with possible long-term implications (e.g. reproductive output). Strong seasonality of P. dioica cover and yield was observed, peaking during spring and summer. The results suggest high resilience of the opportunistic life strategy of P. dioica under frequent harvesting, but to allow for full recovery, we urge for a recovery period of more than the tested 4 weeks.
... Analyzing functional traits in the univariate analyses highlights how these differences are reflected in aspects that favor competition, such as lower values of height, seed mass, and leaf area, being more common among naturalized and invasive species. Possessing these traits also indicates that these species invest in reproductive load and recruitment (Westoby 1998), consistent with r-strategy in the r-K life-history continuum (Pianka 1970). These characteristics are particularly useful for invasive plants as they allow the formation of seed banks that compete with various annual life cycle native species employing the same strategy in the Caatinga (Fernandes et al. 2020). ...
Conflicting hypotheses regarding the factors underlying the invasibility of plant species persist, as portrayed by Darwin’s naturalization conundrum. This is particularly critical in arid and semiarid ecosystems, for which understanding remains elusive. We test how similarities between exotic and native plants in the Brazilian semiarid Caatinga affect the invasion stage and distribution of invasive species. We estimate diversity fields for exotic species, representing the composition of native species that co-occur with each exotic species and calculated phylogenetic metrics of the distance of focal species to its field. We also assess whether changes in stage from exotic to naturalized and from naturalized to invasive are influenced by phylogenetic relatedness and functional traits. We also test whether the observed phylogenetic distance values of the invasive species differ from those expected by chance. Finally, we analyze whether there are functional similarities between the stages of exotic species and native plants. Plants that are phylogenetically closer to the more frequent native species of the Caatinga are more likely to become naturalized and invasive. Among invasive species with a significant pattern of phylogenetic relatedness, those that are closer to native species are more prevalent. Naturalized and invasive plants are shorter and have smaller leaves and seeds than native plants. The observed functional differences suggest that naturalized and invasive species adopt strategies similar to those of competitive native plants, such as seed bank formation and dense populations.
... In contrast, the LDA treatment led to a higher relative abundance of Burkholderiaceae than those under the HDA and VDA treatment. The HDA and VDA treatments also (Pianka, 1970). Therefore, we assume that the nutritional strategies of most enriched soil microbial communities by the three organic amendments in this study were mainly r-strategies under the presence of readily available organic amendment-derived C sources and optimal environmental conditions (Malik et al., 2020). ...
Numerous studies have demonstrated the enhancement effects of organic amendment additions on soil organic carbon (SOC) accumulation in agroecosystems. However, the effects of different organic amendment types on stable SOC formation through belowground inputs remain poorly understood, especially under stress conditions. This study aims to investigate the effects of three organic amendment types, namely lignin- (LDA), humus- (HDA), and vetch-derived (VDA) organic amendments, on the transformation process of ¹³ C-rhizodeposits into SOC in sodic soil. Our results showed that the nitrogen (N) compounds in the organic amendments accounted for 0, 6.21, and 11.37% of the LDA, HDA, and VDA, respectively. Organic amendments with low C/N ratios (HDA and VDA) enhanced the transformation of ¹³ C-rhizodeposits into SOC, particularly into mineral-associated carbon ( ¹³ C-MAOC). In addition, HDA and VDA substantially decreased the exchangeable sodium percentage (ESP) and increased the soil nutrient contents (e.g., total N and total phosphorus) compared with LDA, providing more favorable environmental conditions for both the crop and rhizosphere microbial growth. These effects, consequently, enhanced the disposition of the crop root exudates into ¹³ C-MAOC in the sodic soil. Furthermore, compared with LDA, HDA and VDA enriched beneficial bacteria (e.g., Bacillaceae and Vermamoebidae) and inhibited pathogenic bacteria (Burkholderiaceae) through potential cross-trophic interactions, promoting crop growth and enhancing the production of root exudate deposition into ¹³ C-MAOC. Our study provides a novel approach to selecting organic amendments with suitable and effective chemical structures to promote stable SOC formation through belowground inputs, especially under sodic conditions.
... The dynamics of populations are usually described by the intrinsic rate of increase and the carrying capacity of a population. These two parameters are mostly used to describe different modes of life because fast population growth rates might result in poor competitive abilities (r-strategists), while K-strategists have slow-growing populations but may be superior competitors or efficient in using resources [17]. The reason behind these two strategies is that it is difficult to have both fast growth and be efficient in the use of resources at the same time; therefore, r and K strategies are often expected to be traded off against each other. ...
The determination of innate rate of increase (r) values under different grain storage conditions is critical for insect population predictions. The r values for Cryptolestes ferrugineus (Stephens) and Tribolium castaneum (Herbst) were calculated by using a new suggested method (continuous time analysis) and data from the literature, and these calculated r values were compared to identify the r values and carrying capacities under real grain storage conditions and times. The insects were reared in small glass vials (0.3 kg wheat), small PVC columns (2 kg wheat), large PVC columns (14 kg wheat), and shallow containers (14 kg wheat or wheat + cracked wheat). The wheat or cracked wheat had 13.8 to 14.5% moisture contents at different constant temperatures (17.5 to 42.5 °C) and fluctuating temperatures. The r values at the beginning of the population were the highest. Before r became negative, it gradually decreased with increasing time. After the r value became negative, it sometimes increased to positive; however, the rebounded r was much less than the initial r and gradually tended to stabilize within an up-and-down range. This up-and-down r was related to the carrying capacity. The larger the grain bulk, the higher the innate rate was for both species. The r values associated with 14 kg of wheat could be used to predict the insect population dynamics in stored grain bins.
... figure 1a vis-à-vis figure 2a). The general finding attached to these two points is that culture may drive the emergence of a typical r-strategist (boom-and-bust) population dynamics [60] in an otherwise K-strategist species because of rapid resource overexploitation. Since this dynamic is more likely to take place with little diverse resources, it may have had an important role in past human population crashes. ...
Over the history of humankind, cultural innovations have helped improve survival and adaptation to environmental stress. This has led to an overall increase in human population size, which in turn further contributed to cumulative cultural learning. During the Anthropocene, or arguably even earlier, this positive sociodemographic feedback has caused a strong decline in important resources that, coupled with projected future transgression of planetary boundaries, may potentially reverse the long-term trend in population growth. Here, we present a simple consumer/resource model that captures the coupled dynamics of stochastic cultural learning and transmission, population growth and resource depletion in a changing environment. The idealized stochastic mathematical model simulates boom/bust cycles between low-population subsistence, high-density resource exploitation and subsequent population decline. For slow resource recovery time scales and in the absence of climate forcing, the model predicts a long-term global population collapse. Including a simplified periodic climate forcing, we find that cultural innovation and population growth can couple with climatic forcing via nonlinear phase synchronization. We discuss the relevance of this finding in the context of cultural innovation, the anthropological record and long-term future resilience of our own predatory species.
... Whereas urbanization enhances economic output, it also acts as a sink for resources and might increase air pollution exposure for urbanites and other risks, such as low-nutrient, energy-dense, and proteinand fat-rich diets that promote diabetes and cardiovascular disease. In the network of events that lead to the reemergence of diseases and/or the emergence of a new pathogen in formerly biodiverse enclaves, social and economic factors in distant areas take preeminence when any of these two phenomena is usually preceded by environmental changes in land use, followed by r-strategist selection [14] and animal/human spheres getting closer and overlapping with each other. For example, exploitative deforestation leads to the introduction of agriculture and later cattle, which increase the external or environmental costs borne by local communities. ...
The global warming our generation is experiencing is just one of the great environmental crises of the Anthropocene, a geological period that began with the use of fossil fuels and that, in merely one century and a few decades of industrial activity, has altered ecosystemic processes that sustain human health and well-being. Beyond the loss of the "intrinsic value of nature", changes in the magnitude and direction of biogeochemical cycles and increases in temperature are phenomena that not only accompany the loss of habitats and species but impair resilience by ultimately generating greater and more complex numbers and types of exposures that constitute a danger to human health. In this study, we attempted to offer some notes about the margin, understood as that space with the greatest inequity and therefore the fastest growth of risk: the collision area where deprivation marks the social determinants of health and where the greatest interaction with causes of disease occur.
... Lethal methods of data collection are ethically objectionable to most researchers (Aron et al., 2000) and, for populations that are small or endangered, such methods are incompatible with the fundamental goals of conservation biologists. Such sampling also does not allow longitudinal studies which, given the K-selected lifehistory traits of cetaceans (i.e., having few young, long gestation and parental care periods, as well as reaching sexual maturity at relatively older ages; Wilson, 1967;Pianka, 1970), are essential to improve our understanding of cetacean biology and ecology. ...
... As a result, early-successional species live, grow, and reproduce fast, and die young after which they disperse in space or time to colonize new early-successional habitats. During succession, small species with fast life history traits (r-strategists) are therefore replaced by taller species with slow life history traits (K-strategists) (Pianka, 1970). For example, life history traits drive species replacement on temperate abandoned fields, where first summer annuals dominate (which germinate in spring, mature in summer, and die in late summer/autumn) followed by winter annuals (which germinate late in the growing season, overwinter as rosettes, and reproduce in spring), and biennials (which germinate in one year, overwinter often as rosettes, and reproduce the second year) until they are replaced by longer lived woody species . ...
Succession is defined as a directional change in species populations, the community, and the ecosystem at a site following a disturbance. Succession is a fundamental concept in ecology as it links different disciplines. An improved understanding of succession is urgently needed in the Anthropocene to predict the widespread effects of global change on succession and ecosystem recovery, but a comprehensive successional framework (CSF) is lacking. A CSF is needed to synthesize results, draw generalizations, advance successional theory, and make improved decisions for ecosystem restoration. We first show that succession is an integral part of socio‐ecological system dynamics and that it is driven by social and ecological factors operating at different spatial scales, ranging from the patch to the globe. We then present a CSF at the local scale (patch and landscape) at which succession takes place and explain the underlying successional processes and mechanisms operating at that scale. The CSF reflects the increasingly broader perspective on succession and includes recent theoretical advances by not only focusing on species replacement but also on ecosystem development, considering succession as part of a socio‐ecological system, and taking the effect of past and current land use, the landscape context, biotic interactions, and feedback loops into account. We discuss how the CSF can be used to integrate and synthesize successional studies, and its implications for ecosystem restoration.
... Typically, r-strategists have evolved in unpredictable environments and thus have low chances of surviving to old age. In contrast, K-strategists are adapted to predictable environments, where females reach sexual maturity at a relatively later age but have a relatively longer lifespan (5). The tradeoff between reproduction and somatic maintenance might be the key mechanism underlying the evolution of these divergent life history strategies. ...
... El éxito reproductivo en este pequeño estanque confirma la productividad de la especie y su adaptación al medio, donde han explotado los recursos como típica especie estratega r (PIANKA, 1970). Hemos podido observar larvas de P. flavescens en su último estadio, predando sobre ejemplares de su misma especie en estadios inferiores, incluso hemos observado varios ejemplares en avanzado estado de metamorfosis (hecho que ralentiza su movilidad) a los que les faltaba la cabeza, la ausencia de otros depredadores acuáticos en la charca y la voracidad de estas, nos hace sospechar de su autoría. ...
Reproducción de Pantala flavescens (Fabricius, 1798) (Odonata, Libellulidae) en la península ibérica y descripción de un posible corredor migratorio desde la costa occidental africana Reproduction of Pantala flavescens (Fabricius, 1798) (Odonata, Libellulidae) in the Iberian Peninsula and description of a possible dispersal pathway from the western African coast (versión impresa) RESUMEN Se describe un enjambre de Pantala flavescens (Fabricius, 1798) observado en un tramo del río Barbate, Cádiz. Además, se comprueba la reproducción de la especie en el Parque Natural de la Breña y Marismas del Barbate. Estos son los primeros registros de comportamiento migratorio y reproductor de la especie desde que se detectara por primera vez su presencia en la península ibérica (BERNAL-SÁNCHEZ & CONESA-GARCÍA, 2021). Se plantea también una posible ruta migratoria de dicho enjambre, así como su dispersión en territorio peninsular. Palabras clave: Odonata, Libellulidae, Pantala flavescens, enjambre, migración, reproducción, península ibérica, Cádiz, río Barbate, Parque Natural de la Breña y Marismas del Barbate. SUMMARY A swarm of Pantala flavescens (Fabricius, 1798) observed in a section of the Barbate River in Cádiz is described. In addition, the reproduction of the species is confirmed in the La Breña and Marismas del Barbate Natural Park. These are the first records of migratory and reproductive behaviour of the species since its presence was first detected in the Iberian Peninsula (BERNAL-SÁNCHEZ & CONESA-GARCÍA, 2021). A possible migratory path of this swarm is also proposed, as well as its dispersion in the Iberian Peninsula. INTRODUCCIÓN Pantala flavescens (Fabricius, 1798) es un libelúlido (Odonata) de talla media-grande y de amplia distribución mundial, que ocupa princi-palmente la zona de convergencia intertropical (ZCIT) (ASKEW, 1988). Es nómada en gran parte de su distribución geográfica, considerándose un migrante obligado. Las poblaciones de esta especie recorren grandes distancias utilizando convergen-cias climáticas y realizando su ciclo vital gracias a los encharcamientos producidos al paso de los frentes de lluvia (CORBET, 1999). Pueden alcan-zar su estado imaginal, desde la puesta hasta la emergencia, en tan solo 38 días (SUHLING et al., 2004) lo que le permite medrar en estos medios efímeros, ricos en presas (dípteros, cladóceros, copépodos o anostráceos) y donde están ausentes predadores como los peces o competidores que precisen más tiempo para su desarrollo.
... Although originally proposed for explaining animal behavior (MacArthur & Wilson, 1967;Pianka, 1970), life history theory has likewise been applied in studies of human behavior. Specifically, life history theory has been extended to address individual and group differences in humans, including differences in behavioral self-regulation, sexual promiscuity, and disregard for social rules (Figueredo et al., 2006), among other traits. ...
Population-level life history research on humans has proven to be a fruitful research program, establishing numerous socioeconomic and behavioral correlates of life history strategy. Herein, this research program is extended to the Republic of Poland. Life history speed is estimated for 380 powiats and cities with powiat status. To investigate how life history associates with socioeconomic development, the general socioeconomic factor (S factor) is also extracted. Presidential election results are used to emulate differences in political behavior. In line with previous research, the data show that fast life history strategy is negatively correlated with the S factor and percentage of votes for the conservative presidential candidate. Notably, powiats located within Western Borderlands (territories that were part of Germany prior to World War II) tend to have faster life history strategy. This pattern could be explained by forced population displacement of over 1.5 million people that were resettled from USSR into Western Borderlands, thus replacing prior German inhabitants. Forced population displacement can be understood as a disruptive life event that accelerates life history strategy. This can have long-lasting effects, and the present study provides additional insight into the detrimental consequences of population displacement.
... Other network structures, viz., scale-free and small-world networks, are also considered for the simulation (Barabási and Albert, 1999;Newman, 2018). At the same time, just like several previous researchers (Clark et al., 2010;Paul et al., 2022;Pianka, 1970;Bhowmick et al., 2015), we attempt to establish the relation between r-K status and density regulation parameter, although it involves several debates. ...
... Mammalian life history strategy is frequently visualized as an r-K continuum (Pianka 1970). In theory, at the r-endpoint animals experience environments with no competition, so that the optimal strategy is to focus on producing as much offspring as possible, even at the expense of caring less for each individual young. ...
... Unsurprisingly, the factorial analysis showed that the variables 'maximum longevity' and 'fertility per year' were negatively correlated. This is a good example of the r/K dichotomy (Pianka, 1970), which explains why there is always a trade-off between quality and quantity of offspring. The so-called r species (mainly represented by the amphibians in our study) have a reproductive strategy that enables them to deal with major variations in the availability of vital resources. ...
In urbanized areas, rivers and riparian ecosystems are often the only ecological corridors available for wildlife movement. There, riverbanks are often stabilised by civil engineering structures (dykes, riprap). This can lead to habitat degradation and loss of landscape connectivity. Fascines (willow bundles tied together) could be an alternative to riprap, since they maintain the quality of the natural ecosystems by using native vegetal species instead of rocks, but their potential positive impact needs to be assessed. We proposed a landscape-scale decision-making method for river managers who want to restore banks by transforming riprap into fascines to improve landscape connectivity. We applied our methodology to a case study involving a 25 km-stretch of the Arve River, France. We selected four target vertebrate species based on biological traits to cover a wide range of dispersal capacities. For each species, we used landscape graphs to assess habitat connectivity under different contrasted riverbank scenarios. Scenarios included replacing all-natural banks with ripraps or replacing all ripraps with fascines. In addition, we systematically tested the effect of replacing individual 100 or 500 m sections of ripraps by fascines, to locate where riverbank restoration would maximize connectivity gain. The four species selected responded very differently to the scenarios (up to +14% and +46% change in Probability of Connectivity for common toads and Eurasian beavers, respectively, 0% for common sandpipers and barred grass snakes). The restoration of specific riverbank sections could result in important gains in PC (up to +33% for one single section for one species) but no section maximized connectivity gain for all the target species.
... These results agree with previous studies that underlined that extant suids are relatively r-selected in comparison to other ungulates, especially considering the wild boar, S. scrofa [18,32,72]. The r/K selection theory is a generalization of the ecological continuum of reproduction strategies, according to which r-selected species are those that maximize the quantity of offspring, while K-selected species focus on the "quality" (i.e., fewer offspring but with a greater investment) [73,74]. Many shades exist between the hypothetical endmembers of the spectrum and the use of the r/K selection theory as a predictive model in a strict sense is now surpassed (e.g., [75,76]), but considering species adaptations in this conceptual framework and its relative deviations toward one of the other ends-with respect to other related species-is often useful for understanding its ecology and evolution. ...
It has been proposed that suids were absent from Europe during the post-Olduvai to pre-Jaramillo Early Pleistocene (from less than 1.8 to more than 1.2 Ma) and that their “re-appearance” in the late Early Pleistocene would mark the end of the late Villafranchian and the beginning of the Epivillafranchian. Arguments enumerated in favor of this “suid gap” are the lack of suid remains from extensively sampled fossil localities of this age and the high reproductive potential (r-strategy) of suids, which would translate in a high commonness of their remains in the fossil record. However, here it shown that while suids’ reproductive potential is certainly exceptional within artiodactyls, there is no direct relationship between the reproductive strategy and preservation rate of a taxon in the fossil record. In Early Pleistocene localities of Europe and adjoining areas, where suids are present in a fossil assemblage, they are always rare. In terms of number of occurrences (frequency), suids range from being moderately common (~2.0–1.8 Ma) to moderately rare (~1.1–1.0 Ma). Suid material is also described herein from Peyrolles (Issoire, France; reference locality for MNQ 19), a site dated at 1.47 Ma, providing direct evidence for the presence of suids within the purported “suid gap”. The case of suids underlines an important source of caveat in inferring faunal dynamics of the late Early Pleistocene of western Europe—including the dispersal of hominins—i.e., the unequal geographical distribution of the paleontological sites of post-Olduvai to pre-Jaramillo age. Indeed, Peyrolles is the only large mammal site in western Europe located outside the Iberian and Italian Peninsulas reliably dated around 1.5 Ma. In the post-Olduvai to pre-Jaramillo period, there is a paucity of radiometric estimates (or they have too coarse a resolution) and of paleomagnetic excursions detectable in continental deposits. Basically, for this time span, there is a high dependence on biochronological correlations, although, at the same time, these correlations are less reliable—because these are based on a few sites not covering the entire spectrum of environments present in Europe and the sites are not independently dated with methods that outperform biochronology—than those for other periods.
... LHS can be further simplified by models relating trade-offs in species' life history to their environments. These trade-offs have been described by frameworks, such as r-K selection (Pianka, 1970), and the fast-slow continuum (Franco & Silvertown, 1996), which has been used to describe how life history covaries with temperature in marine communities (Beukhof, Frelat, et al., 2019). ...
Aim
Human pressure in the oceans is pervasive and affects marine life. Understanding species' differing responses to human pressure, and how human pressure compares to other environmental variables in shaping marine communities is needed to facilitate the sustainable management of the seas. Despite theory and empirical evidence that fishing pressure affects marine life‐history strategies, several recent large‐scale studies have not shown strong relationships between fishing pressure and community composition. We aim to reconcile theory with data and explain these variable findings, testing the hypothesis that the signal of the effect of fishing pressure on marine communities depends on the scale at which the community is defined.
Location
North East Atlantic.
Time Period
2009 to 2021.
Major Taxa Studied
Marine vertebrates (Teleostei, Elasmobranchii, Petromyzonti, Holocephali).
Methods
We collate extensive scientific marine biodiversity surveys, published life‐history traits and high‐resolution annual fishing pressure data. Using frequentist Generalized Linear Mixed Models, we assess whether community mean weighted life‐history traits correlate with fishing pressure, sea surface temperature and depth and whether the strength of these relationships are scale dependant.
Results
We show fish community life‐history strategy correlates with fishing pressure, and the relative importance of fishing pressure compared to environmental variables increases with the scale at which a community is defined.
Main Conclusions
We suggest this scale dependence relates to the spatial extent over which covariates vary, and how fish movement moderates communities' experience of this variability. Our findings highlight the importance of explicit consideration of scale in ecological research, supporting the idea that studying systems at ecologically relevant scales is necessary to detect and appropriately interpret the effects of global change.
... The marked decline of warmoligotrophic taxa is likely related to a global transition toward cooler and higher nutrient conditions. During the precursor diversity-decrease phase, nannoplankton rapidly reacted to the cooler and eutrophic conditions displaying a contraction of the k-selected community and the expansion of select r-mode opportunist taxa (MacArthur & Wilson, 1967;Pianka, 1970). Major changes in calcareous nannofossil assemblages are also recorded by diversity indices, especially emphasized by the dramatic decrease in species richness (number of taxa) and Shannon indices. ...
The Eocene‐Oligocene transition (EOT; ∼34 Ma) was one of the most prominent global cooling events of the Cenozoic, coincident with the emergence of continental‐scale ice‐sheets on Antarctica. Calcareous nannoplankton experienced significant assemblage turnover at a time of long‐term surface ocean cooling and trophic conditions, suggesting cause‐effect relationships between Antarctic glaciation, broader climate changes, and the response of phytoplankton communities. To better evaluate the timing and nature of these relationships, we generated calcareous nannofossil and geochemical data sets (δ¹⁸O, δ¹³C and %CaCO3) over a ∼5 Myr stratigraphic interval recovered across the EOT from IODP Site U1509 in the Tasman Sea, South Pacific Ocean. Based on trends observed in the calcareous nannofossil assemblages, there was an overall decline of warm‐oligotrophic communities, with a shift toward taxa better adapted to cooler more eutrophic conditions. Assemblage changes indicate four distinct phases caused by temperature decrease and variations in paleocurrents: late Eocene warm‐oligotrophic phase, precursor diversity‐decrease phase, early Oligocene cold‐eutrophic phase, and a steady‐state cosmopolitan phase. The most prominent shift in the assemblages occurred during the ∼550 kyr‐long precursor diversity‐decrease phase, which has relatively high bulk δ¹⁸O and %CaCO3 values, and predates the phase of maximum glacial expansion (Earliest Oligocene Glacial Maximum–EOGM).
... The Naredi Formation, therefore, provides an ideal candidate for investigating r-type population dynamics with the reestablishment of the marine ecological niches in the basin. The r-selection (opportunistic colonization) develops after a major environmental disturbance and its consequent ecological vacuum under limited competition and favors a rapid reproductive rate, elevated growth rates with short lives, stunting, wide environment range, generalized trophic habits, high density (i.e., intensity of bioturbation for ichnological purpose), and low ichnodiversity (MacArthur and Wilson, 1967;Pianka, 1970;Miller and Johnson, 1981;Ekdale, 1985Ekdale, , 1988Bromley, 1996;Pemberton et al., 1992;Gaillard et al., 1999;Verde and Martínez, 2004). The turning of the era began after the marine encroachment over rugged volcanic terrain with the establishment of a restricted-marine settings in the shallowest paleotopographic furrows by depositing variegated shale beds. ...
The Early Eocene warm climatic episodes have a profound impact on the biotic assemblages. This study presents the distinct changes in trace-fossil signature within the Early Eocene Naredi Formation that consists of a marginal-marine mixed siliciclastic-carbonate succession. The foraminiferal assemblages earlier assigned the formation to the Shallow Benthic Zones (SBZ) 8-11, which incorporates the Eocene Thermal Maxima 2, Eocene Thermal Maxima 3, and Early Eocene Climatic Optimum. The lower part of the succession comprising interca-lation of green and red shales is characteristically unbioturbated with sparse bioerosion attributed to the Try-panites Ichnofacies restricted within the nodular horizons. The concretion layer immediately below the uppermost nodule horizon contains a localized remnant of a cohesive-debris-flow deposit characterized by a monospecific firmground Thalassinoides suite of the Glossifungites Ichnofacies. Glauconite-rich green shales, corresponding to the poorly fossiliferous SBZ 8 and barren SBZ 9/10 (?), represent oxygen-depleted bottom-water conditions, inhospitable to infauna. The hyperstressed to barren ichnological suites point to a eutrophic restricted-marine engulfment or lagoonal setting during ETM 2 and ETM 3. The upper part of the limestone-shale intercalated interval corresponding to the SBZ 11 was developed in the oligotrophic shallow open-marine condition during EECO. It is richer in trace fossils solely at the carbonate packstone intervals. The three intermittent packstone beds manifest three different ichnofabrics, viz., Cylindrichnus-Nummipera, Nummipera-Cylindrichnus, and monospecific Thalassinoides, which represent the depauperate expressions of Cruziana Ichnofacies. Recurrences of bioturbated and bioeroded intervals in an otherwise ichno-barren succession mark the repeated flooding events within a transgressive systems tract followed by a highstand systems tract. The environmentally stressed character of rarely preserved ichnofossil assemblages, which ameliorate upward, manifest the repercussions of warm climatic events previously well documented in the formation. The infaunal colonization records a gradual reestablishment of the endobenthic niche after the Mesozoic-to-Cenozoic transition in the basin.
... The main rstrategists found in the rearing water of fish larvae are γ-Proteobacteria such as Vibrio and Pseudoalteromonas (Vadstein et al., 2018b). Vibrio and Pseudoalteromonas also existed in the rearing water of crab larvae, coupled with two other r-strategists including Chryseobacterium and Polaribacter (Pianka, 1970). Unexpectedly, these four rstrategists had significantly higher relative abundances in RAS than in WES. ...
... we hypothesise two possible explanations for this relationship. Natural selection favors those individuals that achieve better competitiveness (Pianka, 1970). we suspect that larger bones increase competitiveness. ...
Appropriate growth of a nestling determines its subsequent reproductive ability. Numerous studies the influence of various factors on the growth rate; only a few deal with nocturnal species. Furthermore, no analyses have been carried out for this species group to show how the three parameters of the growth function, i.e., the expected final size, the start of rapid growth, and the growth rate constant. Therefore, in this study, we analyze the influence of breeding season and a likely correlate of sibling competition on the growth rate of Eagle owl nestlings. We found that the rapid mass growth phase started earlier and reached the final value earlier than for wing length. Furthermore, wing length growth over the season took longer in nests with more siblings but ultimately reached greater length than in the smaller broods. In the case of mass growth, we also found that as the season progressed, mass growth took longer and reached a smaller final size than in individuals who started breeding earlier. We have shown that time of breeding and brood size associate with specific parameters of the growth function in the eagle owl.
... By delineating size classes that define the onset of flowering and increased risk of poaching, respectively, we investigate genetic diversity at successive life history stages to examine whether fecundity in A. sinensis is sufficient to maintain gene flow despite ongoing poaching pressure. We hypothesise that attaining reproductive maturity and thus investment in recruitment from a relatively small size classboth traits associated with high fecundity and r-selection (Pianka, 1970;Singh, 2019) could together help mitigate the more extreme genetic impacts associated with the targeted removal of larger individuals due to poaching. Specifically, we address the following questions: (1) do genetic diversity metrics differ significantly among trees below and above the size-class threshold for onset of reproductive maturity; and (2) do genetic diversity metrics differ significantly among trees below and above the size-class threshold for increased poaching risk? ...
... Increasing the intensity and frequency of disturbances in natural systems theoretically reduces the recovery rate Veraart et al., 2011). Yet some studies indicate that if a system is to persist, recovery rates must rise in tandem with environmental stress (Pianka, 1970). Indeed, a paleontological study examining recovery rates in tropical rainforests over the past 20,000 years found that recovery rates increased with an increase in disturbance frequency (Cole et al., 2014). ...
Corals are being increasingly subjected to marine heatwaves. Theory suggests that increasing the intensity of disturbances reduces recovery rates, which inspired us to examine the recovery rates of coral cover following marine heatwaves, cyclones, and other disturbances at 1921 study sites, in 58 countries and three oceans, from 1977 to 2020. In the Atlantic Ocean, coral cover has decreased fourfold since the 1970s, and recovery rates following disturbances have been relatively slow, except in the Antilles. By contrast, reefs in the Pacific and Indian Oceans have maintained coral cover and recovery rates over time. There were positive relationships between rates of coral recovery and prior cyclone and heatwave frequency, and negative relationships between rates of coral recovery and macroalgae cover and distance to shore. A recent increase in the variance in recovery rates in some ecoregions of the Pacific and Indian Oceans suggests that some reefs in those ecoregions may be approaching a phase shift. While marine heatwaves are increasing in intensity and frequency, our results suggest that regional and local conditions influence coral recovery rates, and therefore, effective local management efforts can help reefs recover from disturbances.
... Organisms closer to the r endpoint channel their resources primarily into mating and producing numerous offspring, prioritizing quantity. Conversely, those closer to the K endpoint allocate resources predominantly to ensure their own long-term survival, investing in parenting and the well-being of a limited number of offspring, emphasizing quality over quantity (Pianka, 1970). The concept of r and K-strategies has been extrapolated to r-selectedfast history strategies and K-selectedslow history strategies, with specific developmental and reproductive behaviors related to each strategy (Del Giudice et al., 2015). ...
A life history strategy is a cohesive set of biological and psychosocial characteristics that reflect individual differences in how people adapt to their environment (Brumbach et al., 2009). Life history strategy refers to the set of reproductive and survival behaviors that organisms adopt to maximize their fitness in specific environments (Buss & Schmitt, 2019). This strategy involves the allocation of resources and energy by organ- isms to various life history traits, such as growth, reproduction, and survival. It encompasses trade-offs between these traits, where allocating more resources to one trait may come at the expense of another (Lu et al., 2022).
Many studies on memory emphasize the material substrate and mechanisms by which data can be stored and reliably read out. Here, I focus on complementary aspects: the need for agents to dynamically reinterpret and modify memories to suit their ever-changing selves and environment. Using examples from developmental biology, evolution, and synthetic bioengineering, in addition to neuroscience, I propose that a perspective on memory as preserving salience, not fidelity, is applicable to many phenomena on scales from cells to societies. Continuous commitment to creative, adaptive confabulation, from the molecular to the behavioral levels, is the answer to the persistence paradox as it applies to individuals and whole lineages. I also speculate that a substrate-independent, processual view of life and mind suggests that memories, as patterns in the excitable medium of cognitive systems, could be seen as active agents in the sense-making process. I explore a view of life as a diverse set of embodied perspectives—nested agents who interpret each other’s and their own past messages and actions as best as they can (polycomputation). This synthesis suggests unifying symmetries across scales and disciplines, which is of relevance to research programs in Diverse Intelligence and the engineering of novel embodied minds.
Energy transformation powers change in the universe. In physical systems, maximal power (rate of energy input or output) may occur only at submaximal efficiency (output/input), or conversely, maximal efficiency may occur only at submaximal power. My review of power and efficiency in living systems at various levels of biological organization reveals that (1) trade-offs (negative correlations) between power and efficiency, as expected in physical systems, chiefly occur for resource-supply systems; (2) synergy (positive correlations) between power and efficiency chiefly occurs for resource use systems, which may result from (a) increasing energy allocation to production versus maintenance as production rate increases and (b) natural selection eliminating organisms that exceed a maximal power limit because of deleterious speed-related effects; (3) productive power indicates species-wide ‘fitness’, whereas efficiency of resource acquisition for production indicates local ‘adaptiveness’, as viewed along a body size spectrum and within clades of related species; (4) covariation of the power and efficiency of living systems occurs across space and time at many scales; (5) the energetic power/efficiency of living systems relates to the rates and efficiencies/effectiveness of nutrient/water uptake/use, the functional performance of various activities, and information acquisition/processing; and (6) a power/efficiency approach has many useful theoretical and practical applications deserving more study.
(1) Background: Originally described as a single taxon, Peripatoides novaezealandiae (Hutton, 1876) are distributed across both main islands of New Zealand; the existence of multiple distinct lineages of live-bearing Onychophora across this spatial range has gradually emerged. Morphological conservatism obscured the true endemic diversity, and the inclusion of molecular tools has been instrumental in revealing these cryptic taxa. (2) Methods: Here, we review the diversity of the ovoviviparous Onychophora of New Zealand through a re-analysis of allozyme genotype data, mitochondrial DNA cytochrome oxidase subunit I sequences, geographic information and morphology. (3) Results: New analysis of the multilocus biallelic nuclear data using methods that do not require a priori assumptions of population assignment support at least six lineages of ovoviviparous Peripatoides in northern New Zealand, and mtDNA sequence variation is consistent with these divisions. Expansion of mitochondrial DNA sequence data, including representation of all existing taxa and additional populations extends our knowledge of the scale of sympatry among taxa and shows that three other lineages from southern South Island can be added to the Peripatoides list, and names are proposed here. In total, 10 species of Peripatoides can be recognised with current data.
Background
There is a burgeoning interest in using insects as a sustainable source of food and feed, particularly by capitalising on various waste materials and by-products that are typically considered of low value. Enhancing the commercial production of insects can be achieved through two main approaches: optimising environmental conditions and implementing selective breeding strategies. In order to successfully target desirable traits through selective breeding, having a thorough understanding of the genetic parameters pertaining to those traits is essential. In this study, a full-sib half-sib mating design was used to estimate variance components and heritabilities for larval size and survival at day seven of development, development time and survival from egg to adult, and to estimate correlations between these traits, within an outbred population of house flies ( Musca domestica ), using high-throughput phenotyping for data collection.
Results
The results revealed low to intermediate heritabilities and positive genetic correlations between all traits except development time and survival to day seven of development and from egg to adulthood. Surprisingly, larval size at day seven exhibited a comparatively low heritability (0.10) in contrast to development time (0.25), a trait that is believed to have a stronger association with overall fitness. A decline in family numbers resulting from low mating success and high overall mortality reduced the amount of available data which resulted in large standard errors for the estimated parameters. Environmental factors made a substantial contribution to the phenotypic variation, which was overall high for all traits.
Conclusions
There is potential for genetic improvement in all studied traits and estimates of genetic correlations indicate a partly shared genetic architecture among the traits. All estimates have large standard errors. Implementing high-throughput phenotyping is imperative for the estimation of genetic parameters in fast developing insects, and facilitates age synchronisation, which is vital in a breeding population. In spite of endeavours to minimise non-genetic sources of variation, all traits demonstrated substantial influences from environmental components. This emphasises the necessity of thorough attention to the experimental design before breeding is initiated in insect populations.
Essential soil functions such as plant productivity, C storage, nutrient cycling and the storage and purification of water all depend on soil biological processes. Given this insight, it is remarkable that in modeling of these soil functions, the various biological actors usually do not play an explicit role. In this review and perspective paper we analyze the state of the art in modeling these soil functions and how biological processes could more adequately be accounted for. We do this for six different biologically driven processes clusters that are key for understanding soil functions, namely i) turnover of soil organic matter, ii) N cycling, iii) P dynamics, iv) biodegradation of contaminants v) plant disease control and vi) soil structure formation. A major conclusion is that the development of models to predict changes in soil functions at the scale of soil profiles (i.e. pedons) should be better rooted in the underlying biological processes that are known to a large extent. This is prerequisite to arrive at the predictive models that we urgently need under current conditions of Global Change.
Multicopy sequences evolve adaptations for increasing their copy number within nuclei. The activities of multicopy sequences under constraints imposed by cellular and organismal selection result in a rich intranuclear ecology in germline cells. Mitochondrial and ribosomal DNA are managed as domestic herds subject to selective breeding by the genes of the single-copy genome. Transposable elements lead a peripatetic existence in which they must continually move to new sites to keep ahead of inactivating mutations at old sites and undergo exponential outbreaks when the production of new copies exceeds the rate of inactivation of old copies. Centromeres become populated by repeats that do little harm. Organisms with late sequestration of germ cells tend to evolve more “junk” in their genomes than organisms with early sequestration of germ cells.
Description
STP 974 is the latest offering in the continuing series on the subject of test methods development for materials used in controlling of managing vertebrate pests. Information on birds, rodents and predators/deer is presented in 18 papers. A majority of the papers in this volume are directed toward efficacy evaluation based on new or existing field test methods.
Aim
Functional trait space analyses are pivotal to describe and compare organisms' functional diversity across the tree of life. Yet, there is no single application that streamlines the many sometimes‐troublesome steps needed to build and analyse functional trait spaces.
Innovation
To fill this gap, we propose funspace, an R package to easily handle bivariate and multivariate functional trait space analyses. The six functions that constitute the package can be grouped in three modules: ‘Building and exploring’, ‘Mapping’ and ‘Plotting’. The building and exploring module defines the main features of a functional trait space (e.g. functional diversity metrics) by leveraging kernel density‐based methods. The mapping module uses general additive models to map how a target variable distributes within a trait space. The plotting module provides many options for creating flexible and publication‐ready figures representing the outputs obtained from previous modules. We provide a worked example to demonstrate a complete funspace workflow.
Main Conclusions
funspace will provide researchers working with functional traits across the tree of life with a new tool to easily explore: (i) the main features of any functional trait space, (ii) the relationship between a functional trait space and any other biological or non‐biological factor that might contribute to shaping species' functional diversity.
A population is the sum of individuals of the same species inhabiting one local habitat. Populations are to some extent isolated from individuals of the same species inhabiting neighbor localities. The term population is borrowed from genetics. In genetics, it comprises those members of a species which are not separated by physical barriers. There is an unrestricted exchange of genes within a population and the members of a population share common gene pool.
Obviously, this definition of a population is derived from the classic “biological” species concept based on fertile interbreeding within species. It does not work for species without sexual reproduction. Because such species are quite common, a practical definition of populations in ecology would be as follows: Populations comprise all individuals belonging to one species (defined in whichever way) and are isolated from other populations of the same species by dispersal barriers. However, “isolation” between populations is almost never absolute. Usually, there is some restricted exchange of individuals between local populations. The exchange between populations is minor relative to the exchange within populations. A group of populations connected by relatively frequent exchange of individuals is called metapopulation, while the single populations are then subpopulations of the metapopulation.
Subdoluseps is a recently described genus of Lygosomine skinks distributed in peninsular India and Southeast Asia. We conduct the first revision of Indian Subdoluseps based on range-wide sampling including 89 specimens from 33 localities. We use two mitochondrial and three nuclear markers, 58 morphological characters, and ecological data to reconstruct the evolutionary history of Indian Subdoluseps and assess their diversity and distribution, providing insights into lygosominin biogeography. We formally describe the Indian clade as a new genus, Dravidoseps gen. nov. and name five new species from Tamil Nadu, India in an integrative taxonomic framework – D. gingeeensis sp. nov. , D. jawadhuensis sp. nov. , D. kalakadensis sp. nov. , D. srivilliputhurensis sp. nov. , and D. tamilnaduensis sp. nov. . We transfer Riopa goaensis , Subdoluseps pruthi and S. nilgiriensis to the new genus and designate neotypes for the former two. Members of Dravidoseps gen. nov. are the first known viviparous skinks from peninsular India and the only known viviparous lygosominins apart from a few species of east African Mochlus . The Lygosomini have a Southeast Asian origin and began diversifying in the Eocene with three dispersals between India and Southeast Asia. Species level diversification in Dravidoseps gen. nov. was likely driven by a combination of niche conservatism, paleoclimate and past forest distribution. The discovery of a new genus and five new species reiterates the high levels of diversity and endemism present in peninsular India and how much more remains to be discovered.
Contrasting physiological mortality with predator‐induced mortality is of tremendous importance for the population dynamics of many organisms but is difficult to assess. This is especially true for tiny organisms, such as most protists, which do not leave any carcasses behind. I performed a meta‐analysis using planktonic ciliates as model organisms to estimate the maximum physiological mortality rates ( δ max ) across pelagic ecosystems in relation to environmental and biotic factors. The median δ max of planktonic ciliates was 0.62 d ⁻¹ and did not differ between marine and freshwater species. Maximum ciliate mortality rates were species‐specific and affected by their specific growth rates ( r max ), cell volume, and ability to encyst. Cyst‐forming species had, on average, higher δ max than species unable to encyst. Maximum mortality rates were positively related to r max , but, in contrast to the latter, δ max appeared unaffected by temperature. I conclude that (1) in the ocean, physiological mortality is more critical for controlling ciliate population size than ciliate losses imposed by microcrustacean predation, but (2) in many lakes, the opposite holds; (3) cyst formation is an effective ciliate trait to cope with the high mortality of motile cells upon starvation. The lack of a temperature effect on δ max deserves further study; if correct, planktonic ciliates may take advantage of rising ocean and lake temperatures, with important implications for the pelagic food web.
Avian communities composed of a total of 79 species were sampled repeatedly at different times of day throughout the breeding season in Norfolk, Virginia, USA. Estimates of taxonomic diversity (species richness, Shannon index and probability of interspecific encounter) were highest in the morning, whereas estimates of functional diversity (functional richness, evenness, Rao’s entropy and mean distinctiveness) did not vary significantly throughout the day. These results suggest that estimates of taxonomic diversity in avian communities are biased by time-of-day, but measures of functional diversity may be more robust to such bias.
The tremendous variation in the life-history patterns of organisms is best explained as adaptive.any organism has a limited amount of resources at its disposal, and these have to be partitioned between reproductive and nonreproductive activities. A larger share of resources to reproductive activities, that is, a higher reproductive effort at any age, leads to a better reproductive performance at that age; this may be considered a as profit function. This reproductive effort also leads to a reduction in survival and growth and consequent diminution of the reproductive contribution of the succeeding stages in the life history; this may be considered as a cost function. Natural selection would tend to an adjustment of the reproductive effort at every age such that the overall fitness of the life history would be maximized. A model of life history processes has been developed on the basis of these considerations. It leads to the following predictions: 1. If the form of the profit function is convex, or that o...
This book had its origin when, about five years ago, an ecologist (MacArthur) and a taxonomist and zoogeographer (Wilson) began a dialogue about common interests in biogeography. The ideas and the language of the two specialties seemed initially so different as to cast doubt on the usefulness of the endeavor. But we had faith in the ultimate unity of population biology, and this book is the result. Now we both call ourselves biogeographers and are unable to see any real distinction between biogeography and ecology.
MacAthur's model was derived to predict the relative abundance of species in adequately sampled sympatric associations in which niches are contiguous and nonoverlapping, the species are comparable in size and physiology and are maintained in equilibrium so that relative abundances are constant. The model is applicable only to homogeneously diverse biotopes in which the range of the environmental mosaic is small in relation to the requirements of the inhabitant species. These factors require that the niche arrangement be the outcome of competitive exclusion. Data are presented on the adequacy of the MacArthur model in describing the relative abundance of fish, ophiuroids, gastropods, pagurid crabs, and ciliates. In addition, summaries of previously reported tests are included. By comparing groups which are adequately and inadequately described by the MacArthur model, it is possible to examine the characteristics which may establish the equilibrium. It is hypothesized that characteristics of importance are length of life cycle, duration and frequency of reproduction, and relative (to generation time) constancy of environmental conditions. It is shown that when fish or gastropod species are tested, the goodness-of-fit to the model's predictions is related to the taxonomic affinity of the group being tested. Stable associations of species with high taxonomic affinity must be highly organized. A high degree of organization is required to maintain the random distribution of abundances. Density dependent competition for food is the most likely bases of this organization.
The results of laboratory studies on nine species of warehouse Ptinid beetles at 25° C. and 70% r.h . are used to calculate by Leslie's methods, the statistic r measuring the intrinsic rate of increase of each species. Ptinus tectus Boield. has the highest value of r —0–38, equivalent to a 39 % weekly increase or tenfold in under 2 months. Four species, Gibbium psylloides (Czemp.), Mezium affine Boield., Stethomezium squamosum Hinton and Trigonogenius globulus Sol., are capable of tenfold increase in 3 months and the remaining four multiply more slowly, either because of a low oviposition rate ( Eurostus ), high developmental mortality ( Niptus ), or slow development ( Ptinus fur (L.), P. sexpunctatus Panz.).
Generally the intrinsic rate of increase falls with temperature due to lengthening of development and reduction of oviposition, but near the maximum of development it also falls because of high developmental mortality. Niptus has a higher rate of increase at 20° C. than at 25° C. which is close to its developmental maximum. Relative humidity has little effect except at the limits of humidity tolerance, but water must be occasionally available for the adult to drink, or oviposition and thus rate of increase is markedly depressed. Food mainly affects the rate of increase through its effect on developmental speed. Other factors are briefly considered.
The statistic r applies to a population which has a stable age distribution. For Ptinids the stable age population was found by calculation to contain between 5 and 11% of adults, whereas in the warehouse never less than 15% of the population found were adults. In a warehouse actual observed rates of increase reached a value equivalent to r = 0.24 per week over a period of 8 weeks. From observed temperature means and laboratory results a maximum of r = 0.31 was predicted with a mean of 0.19 per week for a year. The value of r obtained using the oviposition rate estimated in the warehouse was 0.1. Warehouse values of r may be below those predicted from laboratory results because oviposition is restricted due to lack of drinking water and often to overcrowding, mortality increased due to disease, parasites, predators, and accidental cannibalism, and developmental speed retarded due to crowding.
In selecting from Deevey’s extensive review, we have tried to emphasize the different types of problems that arise in working with animal populations; our most serious omission is a detailed study of barnacles that examines crowding effects and mortality. Deevey begins his article with discussions of the life table and of different general survival patterns, which we also omit.
The part of Cole’s article included here outlines the relationship of Thompson’s work (1931, paper 20 above) to stable population theory. Omitted sections discuss the relationships between the rate of increase, numbers and spacing of offspring, and age structure, with their implications for species survival.
Size and cycle: an essay on the structure of biology
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Quantitative aspects of population growth, 2'i7-294 p
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The ilistlibution and abundance of animals
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Studies on beetles of the fanlily Ptinidae. VIII. The intrinsic rate of increase of some ptinid beetles
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Phyletic size increase-an important trend illustrated by fossil invertebrates
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