Showing papers in "The American Naturalist in 2006"
TL;DR: A Bayesian method for investigating correlated evolution of discrete binary traits on phylogenetic trees is described and the question of whether mating system and advertisement of estrus by females have coevolved in the Old World monkeys and great apes is illustrated.
Abstract: We describe a Bayesian method for investigating correlated evolution of discrete binary traits on phylogenetic trees. The method fits a continuous-time Markov model to a pair of traits, seeking the best fitting models that describe their joint evolution on a phylogeny. We employ the methodology of reversible-jump (RJ) Markov chain Monte Carlo to search among the large number of possible models, some of which conform to independent evolution of the two traits, others to correlated evolution. The RJ Markov chain visits these models in proportion to their posterior probabilities, thereby directly estimating the support for the hypothesis of correlated evolution. In addition, the RJ Markov chain simultaneously estimates the posterior distributions of the rate parameters of the model of trait evolution. These posterior distributions can be used to test among alternative evolutionary scenarios to explain the observed data. All results are integrated over a sample of phylogenetic trees to account for phylogenetic uncertainty. We implement the method in a program called RJ Discrete and illustrate it by analyzing the question of whether mating system and advertisement of estrus by females have coevolved in the Old World monkeys and great apes.
868 citations
TL;DR: In this black bear population, gene flow is facilitated by contiguous forest cover at middle elevations, and patterns of genetic structure are primarily related to landscape gradients of land cover and elevation.
Abstract: Predicting population‐level effects of landscape change depends on identifying factors that influence population connectivity in complex landscapes. However, most putative movement corridors and barriers have not been based on empirical data. In this study, we identify factors that influence connectivity by comparing patterns of genetic similarity among 146 black bears (Ursus americanus), sampled across a 3,000‐km2 study area in northern Idaho, with 110 landscape‐resistance hypotheses. Genetic similarities were based on the pairwise percentage dissimilarity among all individuals based on nine microsatellite loci (average expected \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc}
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655 citations
TL;DR: A general model encompassing these cases, numerical methods, and theoretical results, including stable population growth and sensitivity/elasticity analysis for density‐independent models, local stability analysis in density‐dependent models, and optimal/evolutionarily stable strategy life‐history analysis are presented.
Abstract: Matrix projection models occupy a central role in population and conservation biology. Matrix models divide a population into discrete classes, even if the structuring trait exhibits continuous variation (e.g., body size). The integral projection model (IPM) avoids discrete classes and potential artifacts from arbitrary class divisions, facilitates parsimonious modeling based on smooth relationships between individual state and demographic performance, and can be implemented with standard matrix software. Here, we extend the IPM to species with complex demographic attributes, including dormant and active life stages, cross‐classification by several attributes (e.g., size, age, and condition), and changes between discrete and continuous structure over the life cycle. We present a general model encompassing these cases, numerical methods, and theoretical results, including stable population growth and sensitivity/elasticity analysis for density‐independent models, local stability analysis in densi...
512 citations
TL;DR: It is shown that for different reproductive traits, either within‐individual improvement or selective appearance can result in a positive association between age and reproductive traits at the population level.
Abstract: Evolutionary questions regarding aging address patterns of within-individual change in traits during a lifetime. However, most studies report associations between age and, for example, reproduction based on cross-sectional comparisons, which may be confounded with progressive changes in phenotypic population composition. Unbiased estimation of patterns of age-dependent reproduction (or other traits) requires disentanglement of within-individual change (improvement, senescence) and between-individual change (selective appearance and disappearance). We introduce a new statistical model that allows patterns of variance and covariance to differ between levels of aggregation. Our approach is simpler than alternative methods and can quantify the relative contributions of within- and between-individual changes in one framework. We illustrate our model using data on a long-lived bird species, the oystercatcher (Haematopus ostralegus). We show that for different reproductive traits (timing of breeding and egg size), either within-individual improvement or selective appearance can result in a positive association between age and reproductive traits at the population level. Potential applications of our methodology are manifold because within- and between-individual patterns are likely to differ in many biological situations.
458 citations
TL;DR: It is concluded that although resource exploitation (diet), predatory habits, and taxonomy are influential in predisposing carnivores to attack each other, relative body size of the participants is overwhelmingly important.
Abstract: Interspecific killing is a key determinant of the abundances and distributions of carnivores, their prey, and nonprey community members. Similarity of body size has been proposed to lead competitors to seek similar prey, which increases the likelihood of interference encounters, including lethal ones. We explored the influence of body size, diet, predatory habits, and taxonomic relatedness on interspecific killing. The frequency of attacks depends on differences in body size: at small and large differences, attacks are less likely to occur; at intermediate differences, killing interactions are frequent and related to diet overlap. Further, the importance of interspecific killing as a mortality factor in the victim population increases with an increase in body size differences between killers and victims. Carnivores highly adapted to kill vertebrate prey are more prone to killing interactions, usually with animals of similar predatory habits. Family-level taxonomy influences killing interactions; carnivores tend to interact more with species in the same family than with species in different families. We conclude that although resource exploitation (diet), predatory habits, and taxonomy are influential in predisposing carnivores to attack each other, relative body size of the participants is overwhelmingly important. We discuss the implications of interspecific killing for body size and the dynamics of geographic ranges.
433 citations
TL;DR: Overall, this study illustrates how two general principles (niche conservatism and the time‐for‐speciation effect) may help explain the latitudinal diversity gradient as well as many other diversity patterns across taxa and regions.
Abstract: Why are there more species in the tropics than in temperate regions? In recent years, this long-standing question has been addressed primarily by seeking environmental correlates of diversity. But to understand the ultimate causes of diversity patterns, we must also examine the evolutionary and biogeographic processes that directly change species numbers (i.e., speciation, extinction, and dispersal). With this perspective, we dissect the latitudinal diversity gradient in hylid frogs. We reconstruct a phylogeny for 124 hylid species, estimate divergence times and diversification rates for major clades, reconstruct biogeographic changes, and use ecological niche modeling to identify climatic variables that potentially limit dispersal. We find that hylids originated in tropical South America and spread to temperate regions only recently (leaving limited time for speciation). There is a strong relationship between the species richness of each region and when that region was colonized but not between the latitudinal positions of clades and their rates of diversification. Temperature seasonality seemingly limits dispersal of many tropical clades into temperate regions and shows significant phylogenetic conservatism. Overall, our study illustrates how two general principles (niche conservatism and the time-for-speciation effect) may help explain the latitudinal diversity gradient as well as many other diversity patterns across taxa and regions.
406 citations
TL;DR: A comparative scaling analysis of a global data compilation detailing the N and P contents of leaves, stems, roots, and reproductive structures of 1,287 species in 152 seed plant families finds that P and N contents are generally highly correlated both within and across organs and that differences exist between woody and herbaceous taxa.
Abstract: Plant biomass and nutrient allocation explicitly links the evolved strategies of plant species to the material and energy cycles of ecosystems. Allocation of nitrogen (N) and phosphorus (P) is of particular interest because N and P play pivotal roles in many aspects of plant biology, and their availability frequently limits plant growth. Here we present a comparative scaling analysis of a global data compilation detailing the N and P contents of leaves, stems, roots, and reproductive structures of 1,287 species in 152 seed plant families. We find that P and N contents (as well as N : P) are generally highly correlated both within and across organs and that differences exist between woody and herbaceous taxa. Between plant organs, the quantitative form of the scaling relationship changes systematically, depending on whether the organs considered are primarily structural (i.e., stems, roots) or metabolically active (i.e., leaves, reproductive structures). While we find significant phylogenetic signals in the data, similar scaling relationships occur in independently evolving plant lineages, which implies that both the contingencies of evolutionary history and some degree of environmental convergence have led to a common set of rules that constrain the partitioning of nutrients among plant organs.
387 citations
TL;DR: It is shown that cold‐ Adapted insect species have much lower maximum rates of population growth than do warm‐adapted species, even when the authors control for phylogenetic relatedness, and that adaptation to temperature inevitably alters the population dynamics of insects.
Abstract: Diverse biochemical and physiological adaptations enable different species of ectotherms to survive and reproduce in very different temperature regimes, but whether these adaptations fully compensate for the thermodynamically depressing effects of low temperature on rates of biological processes is debated. If such adaptations are fully compensatory, then temperature-dependent processes (e.g., digestion rate, population growth rate) of cold-adapted species will match those of warm-adapted species when each is measured at its own optimal temperature. Here we show that cold-adapted insect species have much lower maximum rates of population growth than do warm-adapted species, even when we control for phylogenetic relatedness. This pattern also holds when we use a structural-equation model to analyze alternative hypotheses that might otherwise explain this correlation. Thus, although physiological adaptations enable some insects to survive and reproduce at low temperatures, these adaptations do not overcome the "tyranny" of thermodynamics, at least for rates of population increase. Indeed, the sensitivity of population growth rates of insects to temperature is even greater than predicted by a recent thermodynamic model. Our findings suggest that adaptation to temperature inevitably alters the population dynamics of insects. This result has broad evolutionary and ecological consequences.
297 citations
TL;DR: The number of individuals with a given size is found to be proportional to the weight raised to the power −2.05, independent of the predator/prey size ratio, the first time the spectrum exponent has been derived solely on the basis of processes at the individual level.
Abstract: The majority of higher organisms in the marine environment display indeterminate growth; that is, they continue to grow throughout their life, limited by an asymptotic size. We derive the abundance of species as a function of their asymptotic size. The derivation is based on size‐spectrum theory, where population structure is derived from physiology and simple arguments regarding the predator‐prey interaction. Using a hypothesis of constant satiation, which states that the average degree of satiation is independent of the size of an organism, the number of individuals with a given size is found to be proportional to the weight raised to the power −2.05, independent of the predator/prey size ratio. This is the first time the spectrum exponent has been derived solely on the basis of processes at the individual level. The theory furthermore predicts that the parameters in the von Bertalanffy growth function are related as \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{...
293 citations
TL;DR: Pleistocene rewilding would deliberately promote large, long‐lived species over pest and weed assemblages, facilitate the persistence and ecological effectiveness of megafauna on a global scale, and broaden the underlying premise of conservation from managing extinction to encompass restoring ecological and evolutionary processes.
Abstract: Large vertebrates are strong interactors in food webs, yet they were lost from most ecosystems after the dispersal of modern humans from Africa and Eurasia. We call for restoration of missing ecological functions and evolutionary potential of lost North American megafauna using extant conspecifics and related taxa. We refer to this restoration as Pleistocene rewilding; it is conceived as carefully managed ecosystem manipulations whereby costs and benefits are objectively addressed on a case‐by‐case and locality‐by‐locality basis. Pleistocene rewilding would deliberately promote large, long‐lived species over pest and weed assemblages, facilitate the persistence and ecological effectiveness of megafauna on a global scale, and broaden the underlying premise of conservation from managing extinction to encompass restoring ecological and evolutionary processes. Pleistocene rewilding can begin immediately with species such as Bolson tortoises and feral horses and continue through the coming decades wi...
293 citations
TL;DR: The hypotheses that herbivore resistance traits have introgressed from H. debilis to H. annuus and have increased adaptation in the latter suggest that introgression of biotic resistance traits was important in the adaptation of H.annuus to central and southern Texas.
Abstract: The role of hybridization in adaptive evolution is contentious. While many cases of adaptive trait introgression have been proposed, the relevant traits have rarely been identified, resulting in a lack of clear examples of this process. Here, we examine a purported case of adaptive introgression in which the annual sunflower Helianthus annuus annuus has captured alleles from a congener (Helianthus debilis) to form a stabilized hybrid, Helianthus annuus texanus. We tested the hypotheses that herbivore resistance traits have introgressed from H. debilis to H. annuus and have increased adaptation in the latter. In two common gardens, fitness (estimated by seed production) was on average 55% higher in H. a. texanus than in H. a. annuus. For H. a. texanus, three damage traits (of seven tested) differed significantly from the H. a. annuus parent in one or both sites and were shifted in the direction of the more resistant H. debilis. Natural selection favored H. a. \documentclass{aastex} \usepackage{am...
TL;DR: It is found that immigration increased local diversity, and in animal studies, diversity appears maximized at intermediate dispersal rates but not with plant studies; however, more standardized studies are needed.
Abstract: Species diversity in communities of interacting organisms is thought to be enhanced by dispersal, yet mechanisms predicting this have little to say about what effects differing rates of dispersal have on diversity and how dispersal affects diversity at larger spatial scales. I performed meta‐analyses on 23 studies comprising 50 experiments that manipulated species migration and measured community richness or diversity to test three hypotheses: that dispersal increases local diversity; that this effect depends on the rate of dispersal, specifically, that local diversity should be maximized at intermediate dispersal rates or else linearly related to dispersal rate; and that regional diversity may be either unaffected or negatively impacted by dispersal because dispersal tends to homogenize local communities. I found that immigration increased local diversity. Further, in animal studies, diversity appears maximized at intermediate dispersal rates but not with plant studies; however, more standardiz...
TL;DR: This work correlates estimates of current tree species diversity with a composite parameter integrating area over geological time for each continent’s tropical, temperate, and boreal biomes and finds significant positive correlations between current tree diversity and area‐time for periods since the Eocene, Oligocene, and Miocene.
Abstract: The greater area of tropical forest biomes has been proposed as a factor that drives the latitudinal gradient in species diversity by modulating speciation and extinction rates. But speciation and extinction are processes that operate over millions of years, so an adequate test of area’s contribution to diversity patterns must take into consideration that biome areas have changed through time in response to climate. Here we correlate estimates of current tree species diversity with a composite parameter integrating area over geological time for each continent’s tropical, temperate, and boreal biomes. We find significant positive correlations between current tree diversity and area‐time for periods since the Eocene, Oligocene, and Miocene, which we take as evidence for a time‐integrated species‐area effect on current patterns of species richness across biomes. These results contribute to explanations for why most lineages have tropical origins and why tropical forests are more diverse than extrat...
TL;DR: This article explores the proximate and ultimate reasons for why a temperate grasshopper, Chorthippus brunneus, is an exception to the temperature‐size rule, and shows that it is optimal for this species to mature at a larger size at higher temperatures.
Abstract: The majority of ectotherms mature at a larger size at lower rearing temperatures. Although this temperature-size rule is well established, a general explanation for this phenomenon has remained elusive. In this article, we address the problem by exploring the proximate and ultimate reasons for why a temperate grasshopper, Chorthippus brunneus, is an exception to the temperature-size rule. Using a complete set of life-history data to parameterize an established life-history model, we show that it is optimal for this species to mature at a larger size at higher temperatures. We also show that plasticity in adult size is determined by the relative difference between the minimum temperature thresholds for growth and development rates. The mechanism relates to aspects of the biophysical model of van der Have and de Jong. Ectotherms that obey the temperature-size rule are identified as having a higher temperature threshold for development rate than for growth rate; exceptions are identified as having a lower temperature threshold for development rate than for growth rate. The latter scenario may arise broadly in two ways. These are discussed in reference to the thermal biology of temperate grasshoppers and ectotherms in general.
TL;DR: It is demonstrated that cranial modularity is generally conserved in the evolution of therian mammals but differs between therians and monotremes, the two extant subclasses of Mammalia.
Abstract: The mammalian skull has been studied as several separate functional components for decades, but the study of modularity is a more recent, integrative approach toward quantitative examination of independent subsets of highly correlated traits, or modules. Although most studies of modularity focus on developmental and genetic systems, phenotypic modules have been noted in many diverse morphological structures. However, few studies have provided empirical data for comparing modules across higher taxonomic levels, limiting the ability to assess the broader evolutionary significance of modularity. This study uses 18-32 three-dimensional cranial landmarks to analyze phenotypic modularity in 106 mammalian species and demonstrates that cranial modularity is generally conserved in the evolution of therian mammals (marsupials and placentals) but differs between therians and monotremes, the two extant subclasses of Mammalia. Within therians, cluster analyses identify six distinct modules, but only three modules display significant integration in all species. Monotremes display only two highly integrated modules. Specific hypotheses of functional and developmental influences on cranial bones were tested. Theoretical correlation matrices for bones were constructed on the basis of shared function, tissue origin, or mode of ossification, and all three of these models are significantly correlated with observed correlation matrices for the mammalian cranium.
TL;DR: This work investigates the role of gene flow in modulating phenotypic response to selection by quantifying color variation and genetic variation across the ecotone and finds species differences in degree of background matching and in genetic connectivity of populations across the Ecotone.
Abstract: Ecological transition zones, where organismal pheno- types result from a delicate balance between selection and migration, highlight the interplay of local adaptation and gene flow. Here, I study the response of an entire species assemblage to natural selection across a common ecotone. Three lizard species, distributed along a dramatic environmental gradient in substrate color, display conver- gent adaptation of blanched coloration on the gypsum dunes of White Sands National Monument. I investigate the role of gene flow in modulating phenotypic response to selection by quantifying color variation and genetic variation across the ecotone. I find species differences in degree of background matching and in genetic con- nectivity of populations across the ecotone. Differences among spe- cies in phenotypic response to selection scale precisely to levels of genetic isolation. Species with higher levels of gene flow across the ecotone exhibit less dramatic responses to selection. Results also reveal a strong signal of ecologically mediated divergence for White Sands lizards. For all species, phenotypic variation is better explained by habitat similarity than genetic similarity. Convergent evolution of blanched coloration at White Sands clearly reflects the action of strong divergent selection; however, adaptive response appears to be modulated by gene flow and demographic history and can be pre- dicted by divergence-with-gene-flow models.
TL;DR: A hierarchical analytical approach is developed—using generalized linear mixed‐effects modeling of time series of home range sizes—that allows variance in home range size to be decomposed into components due to variation in temporal, spatial, and individual‐level processes, also facilitating intra‐ and interspecific comparative analyses.
Abstract: Animal home range use is a central focus of ecological research. However, how and why home range size varies between individuals is not well studied or understood for most species. We develop a hierarchical analytical approach—using generalized linear mixed‐effects modeling of time series of home range sizes—that allows variance in home range size to be decomposed into components due to variation in temporal, spatial, and individual‐level processes, also facilitating intra‐ and interspecific comparative analyses. We applied the approach to data from a roe deer population radiotracked in central Italy. Over multiple timescales, temporal variation is explained by photoperiod and climate and spatial variation by the distribution of habitat types and spatial variance in radiotracking error. Differences between individuals explained a substantial amount of variance in home range size, but only a relatively minor part was explained by the individual attributes of sex and age. We conclude that the choi...
TL;DR: It is suggested that estimates of emigration are important for delineating sources and sinks and, more generally, for evaluating how local populations interact to generate overall system dynamics.
Abstract: The interaction of local populations has been the focus of an increasing number of studies in the past 30 years. The study of source‐sink dynamics has especially generated much interest. Many of the criteria used to distinguish sources and sinks incorporate the process of apparent survival (i.e., the combined probability of true survival and site fidelity) but not emigration. These criteria implicitly treat emigration as mortality, thus biasing the classification of sources and sinks in a manner that could lead to flawed habitat management. Some of the same criteria require rather restrictive assumptions about population equilibrium that, when violated, can also generate misleading inference. Here, we expand on a criterion (denoted “contribution” or \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \use...
TL;DR: It is suggested that modest levels of intransitivity in nature, such as those that are thought to be characteristic of plant communities, can contribute to coexistence and, therefore, community‐scale biodiversity.
Abstract: Using a spatially explicit cellular automaton model with local competition, we investigate the potential for varied levels of competitive intransitivity (i.e., nonhierarchical competition) to promote species coexistence. As predicted, on average, increased levels of intransitivity result in more sustained coexistence within simulated communities, although the outcome of competition also becomes increasingly unpredictable. Interestingly, even a moderate degree of intransitivity within a community can promote coexistence, in terms of both the length of time until the first competitive exclusion and the number of species remaining in the community after 500 simulated generations. These results suggest that modest levels of intransitivity in nature, such as those that are thought to be characteristic of plant communities, can contribute to coexistence and, therefore, community-scale biodiversity. We explore a potential connection between competitive intransitivity and neutral theory, whereby competitive intransitivity may represent an important mechanism for "ecological equivalence."
TL;DR: This study is the first that uses a theoretical plant growth model to link leaf trade‐offs to whole‐plant performances and to differential performances across species in different light environments, and shows how leaf trade-offs influence differential tree performance and tree species' coexistence in a heterogeneous light environment.
Abstract: A dominant hypothesis explaining tree species coexistence in tropical forest is that trade-offs in characters allow species to adapt to different light environments, but tests for this hypothesis are scarce. This study is the first that uses a theoretical plant growth model to link leaf trade-offs to whole-plant performances and to differential performances across species in different light environments. Using data of 50 sympatric tree species from a Bolivian rain forest, we observed that specific leaf area and photosynthetic capacity codetermined interspecific height growth variation in a forest gap; that leaf survival rate determined the variation in plant survival rate under a closed canopy; that predicted height growth and plant survival rate matched field observations; and that fast-growing species had low survival rates for both field and predicted values. These results show how leaf trade-offs influence differential tree performance and tree species' coexistence in a heterogeneous light environment.
TL;DR: This analysis provides strong overall support for the theory that relatedness affects kin conflict over male parentage and shows that a significantly higher percentage of the males are workers’ sons in species where the workers are more related to other workers' sons.
Abstract: In many bees, wasps, and ants, workers police each other in order to prevent individual workers from selfishly producing their own male offspring. Although several factors can selectively favor worker policing, genetic relatedness is considered to be of special importance. In particular, kin selection theory predicts that worker policing should be more common in species where workers are more related to the queen’s sons than to other workers’ sons. Here we provide strong novel support for this theory based on a comparative analysis of policing and male parentage in 109 species of ants, bees, and wasps. First, an analysis of behavioral data confirms that worker policing occurs more frequently in species where workers are more related to the queen’s sons than to other workers’ sons. Second, an analysis of male parentage shows that a significantly higher percentage of the males are workers’ sons in species where the workers are more related to other workers’ sons. Both conclusions also hold if data...
TL;DR: A genetic algorithm is used to search for optimal combinations of 34 functional traits in a realistic model of tree seedling growth and survival and shows that separate lineages of seedlings evolving in identical environments result in many alternative functional designs of approximately equal fitness.
Abstract: According to conventional wisdom, functional diversity is exclusively a consequence of species having evolved adaptations to fill different niches within a heterogeneous environment. This view anticipates only one optimal combination of trait values in a given environment, but it is also conceivable that alternative designs of equal fitness in the same environment might evolve. To investigate that possibility, we use a genetic algorithm to search for optimal combinations of 34 functional traits in a realistic model of tree seedling growth and survival. We show that separate lineages of seedlings evolving in identical environments result in many alternative functional designs of approximately equal fitness.
TL;DR: It is suggested that disruption of mitochondrial function, known to result in a diverse set of human diseases, may frequently underlie reduced fitness in interpopulation and interspecies hybrids in animals.
Abstract: Through the processes of natural selection and genetic drift, allopatric populations diverge genetically and may ultimately become reproductively incompatible. In cases of prezygotic reproductive isolation, candidate systems for speciation genes logically include genes involved in mate or gamete recognition. However, where only postzygotic isolation exists, candidate speciation genes could include any genes that affect hybrid performance. We hypothesize that because mitochondrial genes frequently evolve more rapidly than the nuclear genes with which they interact, interpopulation hybridization might be particularly disruptive to mitochondrial function. Understanding the potential impact of intergenomic (nuclear and mitochondrial) coadaptation on the evolution of allopatric populations of the intertidal copepod Tigriopus californicus has required a broadly integrative research program; here we present the results of experiments spanning the spectrum of biological organization in order to demonstr...
TL;DR: The observation of a trade‐off within, but not between, populations suggests that the populations evolved different genetic solutions for growth in the selective environment, which in turn led to different physiological constraints.
Abstract: Theoretical studies have predicted a trade‐off between growth rate and yield in heterotrophic organisms. Here we test for the existence of this trade‐off by analyzing the growth characteristics of 12 E. coli B populations that evolved for 20,000 generations under a constant selection regime. We performed three different tests. First, we analyzed changes in growth rate and yield over evolutionary time for each population. Second, we tested for a negative correlation between rate and yield across the 12 populations. Finally, we isolated clones from four selected populations and tested for a negative correlation between rate and yield within these populations. We did not find evidence for a trade‐off based on the first two tests. However, we did observe a trade‐off based on the within‐population correlation of yield and rate. Our results indicate that, at least for the populations studied here, an analysis of the within‐population diversity might be the most sensitive test for the existence of a tr...
TL;DR: A standardized empirical approach to quantify prior‐residence effects is suggested, suggesting a self‐consistent model with feedbacks between individual behavior and population dynamics that produces qualitatively different frequency‐dependent selection on intruders (floaters) than on territory owners.
Abstract: Explaining the “prior‐residence effect” (automatic owner status of individuals who arrived first in an area) was one of the very first applications of game theory in animal behavior. These models, however, predict paradoxical solutions where intruders always win, with no satisfactory explanation for the absence of such cases in nature. We propose a solution based on new developments in evolutionary game theory. A self‐consistent model with feedbacks between individual behavior and population dynamics produces qualitatively different frequency‐dependent selection on intruders (floaters) than on territory owners. Starting with an ancestral population with no respect for ownership, the most likely evolutionary end point is complete or partial respect. Conventional rules of conflict resolution thus can rely on “uncorrelated asymmetries” without differences in resource‐holding power or territory value, although they will be strengthened by such differences. We also review the empirical literature on ...
TL;DR: The higher fitness of testosterone‐treated males in the absence of a comparable natural phenotype suggests that the natural phenotype may be constrained and the negative social effects on offspring and mates suggest that these effects might prevent high‐testosterone phenotypes from spreading in the population.
Abstract: Understanding physiological and behavioral mechanisms underlying the diversity of observed life‐history strategies is challenging because of difficulties in obtaining long‐term measures of fitness and in relating fitness to these mechanisms. We evaluated effects of experimentally elevated testosterone on male fitness in a population of dark‐eyed juncos studied over nine breeding seasons using a demographic modeling approach. Elevated levels of testosterone decreased survival rates but increased success of producing extra‐pair offspring. Higher overall fitness for testosterone‐treated males was unexpected and led us to consider indirect effects of testosterone on offspring and females. Nest success was similar for testosterone‐treated and control males, but testosterone‐treated males produced smaller offspring, and smaller offspring had lower postfledging survival. Older, more experienced females preferred to mate with older males and realized higher reproductive success when they did so. Treatme...
TL;DR: This work formalizes the alternative outcomes of multispecies interactions among plant enemies, plants, and mycorrhizal fungi, and explores the long‐term dynamics of the plant‐enemy interactions using a general model of interactions between plants and plant enemies.
Abstract: A number of studies have shown that an association with mycorrhizal fungi can alter the outcome of interactions between plants and their enemies. While the directions of these effects vary, their strength suggests the need for greater attention to multispecies interactions among plant enemies, plants, and mycorrhizal fungi. We recognize that mycorrhizal fungi could effect plant enemies by improving plant nutrition, modifying plant tolerance, or modifying plant defenses. In addition, mycorrhizal fungi could directly interfere with pathogen infection, herbivory, or parasitism by occupying root space. We formalize these alternative outcomes of multispecies interactions and explore the long‐term dynamics of the plant‐enemy interactions based on these different scenarios using a general model of interactions between plants and plant enemies. We then review the literature in terms of the assumptions of the alternative mechanisms and the predictions of these models. Through this effort, we identify new...
TL;DR: This work compared spatial patterns of endemism and conservation value for 22 species of Californian amphibians and reptiles with the 75 phylogeographic lineages that they contain to assess the extent to which the genetic component of diversity affects conservation assessments.
Abstract: Many phylogeographic studies have revealed strongly diverged lineages within species that are masked by a lack of congruent morphological differentiation. To assess the extent to which the genetic component of diversity affects conservation assessments, we compared spatial patterns of endemism and conservation value for 22 species of Californian amphibians and reptiles with the 75 phylogeographic lineages that they contain. We used bioclimatic distribution modeling with environmental layers to generate 5‐km spatial‐resolution maps of predicted distribution for each species and lineage. We found concentrations of lineage breaks across the Central Valley, San Francisco Bay, the Sierra Nevada, and the Tehachapi and Trinity ranges. Subdivision of the ranges of species into phylogeographic units revealed novel areas of endemism. Several areas of very high conservation value for lineages were not evident in the species‐level analysis. These observations illustrate the importance of considering multipl...
TL;DR: It is found that species with higher relative BMRs engage in less SWS, whereas species with larger relative brain masses engage in more REM sleep, and REM sleep was the only sleep variable strongly influenced by predation risk.
Abstract: Among mammalian species, the time spent in the two main “architectural” states of sleep—slow‐wave sleep (SWS) and rapid‐eye‐movement (REM) sleep—varies greatly. Previous comparative studies of sleep architecture found that larger mammals, those with bigger brains, and those with higher absolute basal metabolic rates (BMR) tended to engage in less SWS and REM sleep. Species experiencing a greater risk of predation also exhibited less SWS and REM sleep. In all cases, however, these studies lacked a formal phylogenetic and theoretical framework and used mainly correlational analyses. Using independent contrasts and an updated data set, we extended existing approaches with path analysis to examine the integrated influence of anatomy, physiology, and ecology on sleep architecture. Path model structure was determined by nonmutually exclusive hypotheses for the function of sleep. We found that species with higher relative BMRs engage in less SWS, whereas species with larger relative brain masses engage...
TL;DR: It is suggested that escape from soil pathogens may contribute to the disproportionately powerful effect of disturbance in introduced regions, as well as to the success of Eurasian native Centaurea solstitialis in invaded regions.
Abstract: Disturbance is one of the most important factors promoting exotic invasion. However, if disturbance per se is sufficient to explain exotic success, then “invasion” abroad should not differ from “colonization” at home. Comparisons of the effects of disturbance on organisms in their native and introduced ranges are crucial to elucidate whether this is the case; however, such comparisons have not been conducted. We investigated the effects of disturbance on the success of Eurasian native Centaurea solstitialis in two invaded regions, California and Argentina, and one native region, Turkey, by conducting field experiments consisting of simulating different disturbances and adding locally collected C. solstitialis seeds. We also tested differences among C. solstitialis genotypes in these three regions and the effects of local soil microbes on C. solstitialis performance in greenhouse experiments. Disturbance increased C. solstitialis abundance and performance far more in nonnative ranges than in the ...