Showing papers in "Trends in Ecology and Evolution in 1994"
TL;DR: With the explicit recognition of the genetic component of biodiversity in conservation legislation of many countries and in the Convention on Biological Diversity, the ESU concept is set to become increasingly significant for conservation of natural as well as captive populations.
Abstract: writing in the first issue of TREE, Ryder’ brought the term ‘Evolutionarily Significant Unit’ (ESU) to the attention of a broad audience of ecologists and evolutionary biologists. The ESU concept was developed to provide a rational basis for prioritizing taxa for conservation effort (e.g. captive breeding), given that resources are limited and that existing taxonomy may not adequately reflect underlying genetic diversity*. With the explicit recognition of the genetic component of biodiversity in conservation legislation of many countries and in the Convention on Biological Diversity, the ESU concept is set to become increasingly significant for conservation of natural as well as captive populations.
3,130 citations
TL;DR: Evidence for the importance of positive interactions - facilitations - in community organization and dynamics has accrued to the point where it warrants formal inclusion into community ecology theory, as it has been in evolutionary biology.
Abstract: Current concepts of the role of interspecific interactions in communities have been shaped by a profusion of experimental studies of interspecific competition over the past few decades. Evidence for the importance of positive interactions — facilitations — in community organization and dynamics has accrued to the point where it warrants formal inclusion into community ecology theory, as it has been in evolutionary biology.
3,107 citations
TL;DR: Important advances seem likely from quantifying synchrony within a population, and examining species with very constant reproduction between years, but the other theories have less support.
Abstract: The past seven years have seen a revolution in understanding the causes of mast seeding In perennial plants. Before 1987, the two main theories were resource matching (i.e. plants vary their reproductive output to match variable resources) and predator satiation (i.e. losses to predators are reduced by varying the seed crop). Today, resource matching is restricted to a proximate role, and predator satiation is only one of many theories for the ultimate advantage of masting. Wind pollination, prediction of favourable years for seedling establishment, animal pollination, animal dispersal of fruits, high accessory costs of reproduction and large seed size have all been advanced as possible causes of masting. Of these, wind pollination, predator satiation and environmental prediction are important in a number of species, but the other theories have less support. In future, Important advances seem likely from quantifying synchrony within a population, and examining species with very constant reproduction between years.
942 citations
TL;DR: The shy-bold continuum is a fundamental axis of behavioral variation in humans and at least some other species, but its taxonomic distribution and evolutionary implications are unknown as mentioned in this paper, and models of optimal risk, density- or frequency-dependent selection, and phenotypic plasticity can provide a theoretical framework for understanding shyness and boldness as a product of natural selection.
Abstract: The shy-bold continuum is a fundamental axis of behavioral variation in humans and at least some other species, but its taxonomic distribution and evolutionary implications are unknown. Models of optimal risk, density- or frequency-dependent selection, and phenotypic plasticity can provide a theoretical framework for understanding shyness and boldness as a product of natural selection. We sketch this framework and review the few empirical studies of shyness and boldness in natural populations. The study of shyness and boldness adds an interesting new dimension to behavioral ecology by focusing on the nature of continuous behavioral variation that exists within the familiar categories of age, sex and size.
893 citations
889 citations
TL;DR: Interspecific interactions are traditionally displayed in a grid in which each interaction is placed according to its outcome, but the full range of natural outcomes may reveal far more about its ecological and evolutionary dynamics than does the average outcome at a given place and time.
Abstract: Interspecific interactions are traditionally displayed in a grid in which each interaction is placed according to its outcome (positive, negative or neutral) for each partner. However, recent field studies consistently find the costs and benefits that determine net effects to vary greatly in both space and time, inevitably causing outcomes within most interactions to vary as well. Interactions show ‘conditionality' when costs and benefits, and thus outcomes, are affected in predictable ways by current ecological conditions. The full range of natural outcomes of a given association may reveal far more about its ecological and evolutionary dynamics than does the average outcome at a given place and time.
861 citations
859 citations
TL;DR: Comparing plants as a function of plant size or developmental stage, as well as afunction of age, broadens the understanding of phenotypic variation between plants.
Abstract: Plant ecologists and evolutionary biologists frequently examine patterns of phenotypic variation across variable environments or genetic identities. Too often, we ignore the fact that most phenotypic traits change throughout growth and development of individual plants, and that rates of growth and development are highly variable. Plants growing in different environments are likely to grow at different rates, and will be of different sizes and stages of development at a particular age. When we compare plants as a function of plant size or developmental stage, as well as a function of age, we broaden our understanding of phenotypic variation between plants.
630 citations
TL;DR: Tolerance is the capacity of a plant to maintain its fitness through growth and reproduction after sustaining herbivore damage, which often may Influence the evolution of plant defence and the composition of plant communities.
Abstract: Damage to plants by herbivores is ubiquitous and sometimes severe. Tolerance is the capacity of a plant to maintain its fitness through growth and reproduction after sustaining herbivore damage. Recent physiological and ecological work indicates that tolerance mechanisms are numerous and varied. Some of the plant traits involved may reflect selection by herbivores, while others are likely to be by-products of selection for other ecological functions. Similarly, some tolerance mechanisms may participate In trade-offs with plant defence, while many do not. Regardless of its ultimate origin or physiological relationship to plant defence, tolerance often may Influence the evolution of plant defence and the composition of plant communities.
565 citations
TL;DR: Recent ecological studies on species borders have used a number of approaches to establish causation for specific environmental factors and to identify the traits involved, including interspecific comparisons, detailed investigations of marginal populations, and experimental manipulation.
Abstract: Recent ecological studies on species borders have used a number of approaches to establish causation for specific environmental factors and to identify the traits involved. These include interspecific comparisons, detailed investigations of marginal populations, and experimental manipulation. Species borders continue to be largely ignored in evolutionary biology, although some work suggests that marginal populations may often be relatively better-adapted to unfavourable conditions but perform poorly under most other conditions.
544 citations
TL;DR: This work focuses on intraspecific variability in the distribution of reproduction within animal societies, and the available data suggest that this variability might be greater than previously suspected.
Abstract: A key feature differentiating cooperative animal societies Is the apportionment of reproduction among individuals. Only recently have studies started to focus on intraspecific variability in the distribution of reproduction within animal societies, and the available data suggest that this variability might be greater than previously suspected. How can one account for intra-and interspecific variability in partitioning of reproduction? This Is one of the most intriguing problems in the study of social behaviour, and understanding the factors underlying this variability is one of the keys to understanding the properties of complex animal societies.
TL;DR: A family of Incidence-function models can be constructed for particular kinds of metapopulations that can be parameterized with field data on patch occupancy, and used to make quantitative predictions about specific metapipulations.
Abstract: Recent work on the dynamics of species living In fragmented landscapes has produced much Information on patterns of habitat patch occupancy in a wide range of organisms. Building on an elementary Markov chain model of patch occupancy, a family of Incidence-function models can be constructed for particular kinds of metapopulations. These models can be parameterized with field data on patch occupancy, and the models can be used to make quantitative predictions about specific metapopulations. This approach provides a potentially powerful tool for the management of reserve networks and species living in fragmented landscapes.
TL;DR: Improvements in computer power and software are making computers more inviting as a primary tool for modelling, and ecologists have started to recognize the importance of local interactions between individuals in ecological systems.
Abstract: Recent advances of three different kinds are driving a change in the way that modelling Is being done in ecology. First, the theory of chaos tells us that short-term predictions of nonlinear systems will be difficult, and long-term predictions will be impossible. The grave Implications this has for ecology are only just beginning to be understood. Second, ecologists have started to recognize the importance of local interactions between individuals in ecological systems. And third, improvements in computer power and software are making computers more inviting as a primary tool for modelling. The combination of these factors may have far-reaching consequences for ecological theory.
TL;DR: The initiation of speciation through a habitat shift in animals which mate within a preferred habitat (such as many phytophagous and parasitic invertebrates and some vertebrates) requires few genetic changes.
Abstract: Recent research on natural host races and sympatric sister species, comparative phylogenetic analyses, laboratory experiments and theoretical models has greatly strengthened the case for sympatric speciation. Traits evolving in response to divergent selection experienced by subpopulations adapting to different habitats provide sufficient intrinsic premating isolation for sympatric speciation to occur. The initiation of speciation through a habitat shift in animals which mate within a preferred habitat (such as many phytophagous and parasitic invertebrates and some vertebrates, including birds) requires few genetic changes.
TL;DR: Two core ideas in the study of mating systems and sexual selection are the existence of a conflict between the sexes over mating decisions and that variation in ecological conditions drives the evolution of adaptive mating strategies and the diversification of mating system.
Abstract: Two core ideas in the study of mating systems and sexual selection are (1) the existence of a conflict between the sexes over mating decisions, and (2) that variation in ecological conditions drives the evolution of adaptive mating strategies and the diversification of mating systems. A recent burst of experimental studies of mating behavior and sexual selection in water striders has focused on the interaction of these ideas and led to new insights into the evolutionary ecology of mating systems and sexual selection.
TL;DR: Behavioral ecologists are being attracted to the study of within-individual morphological variability, manifested in random deviations from bilateral symmetry, as a means of ascertaining the stress susceptibility of developmental regulatory mechanisms.
Abstract: Behavioral ecologists are being attracted to the study of within-individual morphological variability, manifested in random deviations from bilateral symmetry, as a means of ascertaining the stress susceptibility of developmental regulatory mechanisms. Several early successes Indicate that incorporating measures of symmetry into sexual-selection studies may help link individual sexual success to a basic component of viability — developmental stability.
TL;DR: The development of a phylogenetic system of nomenclature requires reformulating these concepts and principles so that they are no longer based on the Linnean categories but on the tenet of common descent.
Abstract: Despite the widely held belief that modem biological taxonomy is evolutionary, some of the most fundamental concepts and principles in the current system of biological nomenclature are based on a nonevolutionary convention that pre-dates widespread acceptance of an evolutionary world view by more than a century. The development of a phylogenetic system of nomenclature requires reformulating these concepts and principles so that they are no longer based on the Linnean categories but on the tenet of common descent.
TL;DR: Comparative studies of two species of mole-rat are helping to clarify the ecological correlates of mammalian eusociality, and ecological factors and kin selection have apparently interacted in the evolution of eussociality in these species.
Abstract: Comparative studies of two species of mole-rat are helping to clarify the ecological correlates of mammalian eusociality. Both species live in social groups composed of close kin, within which breeding is restricted to one female and one to three males. They inhabit xeric areas with dispersed, patchy food and unpredictable rainfall. During droughts, they can neither expand their tunnel systems nor disperse. In brief periods after rain the animals must cooperate and dig furiously to locate rich food patches. By living in groups, arid-zone mole-rats can take full advantage of windows of opportunity when conditions are right for burrowing. Thus, ecological factors and kin selection have apparently interacted in the evolution of eusociality in these species.
TL;DR: The world's oceans are now attracting the serious attention of conservationists as discussed by the authors. But as the value of marine biological diversity is recognized, the ecosystems that harbor this diversity are fast becoming degraded.
Abstract: The world's oceans are now attracting the serious attention of conservationists. Paradoxically, as the value of marine biological diversity is recognized, the ecosystems that harbor this diversity are fast becoming degraded. New thinking about how to conserve coastal areas has resulted in protected-area models that incorporate principles of landscape ecology, adaptive and ecosystem management, and zoning in protected-area plans.
TL;DR: Studying seagrass-dominated landscapes may provide a novel approach to investigating questions regarding self-similarity of spatial patterns, and offers a new perspective for analysing habitat change in a variety of marine environments.
Abstract: Subtidal seagrass habitats are prime candidates for the application of principles derived from landscape ecology. Although seagrass systems are relatively simple compared to their terrestrial counterparts in terms of species diversity and structural complexity, seagrasses do display variation in spatial patterns over a variety of scales. The presence of a moving water layer and its influence on faunal dispersal may be a distinguishing feature impacting ecological processes in the subtidal zone. Studying seagrass-dominated landscapes may provide a novel approach to investigating questions regarding self-similarity of spatial patterns, and offers a new perspective for analysing habitat change in a variety of marine environments.
TL;DR: Molecular phylogenetics has recently yielded striking findings for two cases: the mutualistic endosymbionts of aphids and relatives, and some of the cytoplasmically inherited organisms that induce reproductive abnormalities in various arthropods.
Abstract: Associations with cytoplasmically inherited microorganisms are fundamental to the ecology and reproductive biology of many insects. Molecular phylogenetics now provides a window into the previously obscure history of these associations. This approach has recently yielded striking findings for two cases: the mutualistic endosymbionts of aphids and relatives, and some of the cytoplasmically inherited organisms that induce reproductive abnormalities in various arthropods. These examples provide useful reference points for future extensions of molecular phylogenetic methods to other prokaryote-eukaryote associations.
TL;DR: If body size distributions can be described with certainty, this will allow assessment of the mechanisms proposed to generate them, and will be an important step towards understanding the structure and dynamics of animal assemblages.
Abstract: Documenting the shape of the frequency distribution of species body sizes for an animal taxon appears at first sight a straightforward task. However, a variety of patterns has been reported, and a consensus is only now being reached through an understanding of how potential biases may affect observed shapes of distributions. A new body of evidence suggests that, at large scales, size distributions are right-skewed, even on logarithmic axes. If body size distributions can be described with certainty, this will allow assessment of the mechanisms proposed to generate them, and will be an important step towards understanding the structure and dynamics of animal assemblages.
TL;DR: Several recent studies have uncovered different lines of evidence suggesting that an organism's thermal habit, or metabolic rate, can influence the evolution of mtDNA.
Abstract: The hallmarks of animal mitochondrial DNA (mtDNA) are a rapid rate of sequence evolution, a small genome carrying the same set of homologous genes, maternal inheritance and lack of recombination. Over the past few years, a variety of different observations has challenged these accepted notions of mitochondrial biology. Notable examples include evidence for variable rates of mtDNA sequence evolution among taxa, evidence for large and variable mitochondrial genome sizes in certain groups, and a growing number of cases in metazoans of 'paternal leakage' in the inheritance of mtDNA. Several recent studies have uncovered different lines of evidence suggesting that an organism's thermal habit, or metabolic rate, can influence the evolution of mtDNA.
TL;DR: This paper argues that one- and two-tailed tests are simply extremes in a continuum of testing options and can be used in ecology and evolution to handle large parameter changes in the unanticipated direction.
Abstract: Whenever experiments make a priori predictions about the direction of change in some parameter, one-tailed test statistics offer a potentially large gain in power over the corresponding two-tailed test. This gain is rarely used in ecology and evolution because of (1) the belief that one-tailed procedures are unavailable for most statistical tests and (2) an inherent dilemma in one-tailed tests: how do we handle large parameter changes in the unanticipated direction? The first problem is a misconception, whereas the second is easily resolved by recognizing that one- and two-tailed tests are simply extremes in a continuum of testing options.
TL;DR: In this article, the authors show that nutrient fluxes are often pulsed in tropical forests, and that pulsed versus gradual inputs have different effects on the fates of nutrients in the ecosystem.
Abstract: Recent research shows that nutrient fluxes are often pulsed In tropical forests, and that pulsed versus gradual inputs have different effects on the fates of nutrients in the ecosystem. Synchrony of nutrient mineralization with plant uptake can lower competition between microbes and plants for limiting nutrients while maintaining tight nutrient cycling, whereas asynchrony can lead to losses of nutrients from the system. Thus, nutrient pulses may play a critical role in maintaining productivity in tropical forests with tight nutrient cycling.
TL;DR: In both cases, the presence of pathogens can lead to changes in the relative abundance of the species in a plant community, which are discernible for many years after the initial disease outbreak has passed.
Abstract: There is increasing interest in the direct and indirect effects of pathogens and parasites on the structure of plant communities. The direct influence of pathogens is seen in cases where pathogens reduce the populations of adult and seedling plants or prevent the recruitment of seeds. Indirect effects occur when epidemic outbreaks or endemic parasites of herbivores lead to reductions in grazing pressure, which temporarily allow plants to escape from the detrimental effects of their herbivores. In both cases, the presence of pathogens can lead to changes in the relative abundance of the species in a plant community, which are discernible for many years after the initial disease outbreak has passed.
TL;DR: Of course, inclusive-fitness models explain the generalities of cooperative breeding, but differences in ecology, physiology and life history may result in distinctive processes operating in different taxa-data only likely to emerge from long-term field studies.
Abstract: Cooperative breeding in mammals covers a diversity of breeding systems. In all cases, however, Individuals assist in the rearing of offspring other than their own. Recent research has highlighted some of the factors responsible for variation both within and between species. While it is possible to generalize about the selective pressures leading to cooperative breeding, doing so may obscure important contrasts between taxa. Of course, inclusive-fitness models explain the generalities of cooperative breeding, but differences in ecology, physiology and life history may result in distinctive processes operating in different taxa-data only likely to emerge from long-term field studies.
TL;DR: A recent threshold model for delayed dispersal helps clarify the confused semantics of 'benefits of philopatry' and 'ecological constraints' schools and demonstrates the complimentarity of the two approaches.
Abstract: Families form when offspring delay dispersal and remain associated with their parents into adulthood. What are the ultimate causes of such philopatry and prolonged association? Two schools of thought have emerged, providing seemingly opposing answers to this question - the 'benefits of philopatry' and the 'ecological constraints' schools. A recent threshold model for delayed dispersal helps clarify the confused semantics of these arguments and demonstrates the complimentarity of the two approaches. Many of the current advantages of family living may have evolved secondarily, however, suggesting that the initial origin of families occurred under conditions of severe competition for breeding vacancies.
TL;DR: The distinction between a species' effect on resources and its response to reduced resource levels might help to solve the questions on which traits can be considered to contribute to competitive ability in different species.
Abstract: Few ecologists today doubt that competition is an important structuring factor in plant communities, but researchers disagree on the circumstances where it is most intense, and on which traits can be considered to contribute to competitive ability in different species The distinction between a species' effect on resources and its response to reduced resource levels might help to solve these questions Whereas classical competition theory predicts competitive exclusion of species with similar requirements, recent ideas stress that species diversity may be explained by a multitude of processes acting at different scales, and that similarities in competitive abilities often may facilitate coexistence