Showing papers in "Trends in Ecology and Evolution in 1992"
TL;DR: New research is showing that species' effects can be as or more important than abiotic factors, such as climate, in controlling ecosystem fertility.
Abstract: Plant species create positive feedbacks to patterns of nutrient cycling in natural ecosystems. For example, in nutrient-poor ecosystems, plants grow slowly, use nutrients efficiently and produce poor-quality litter that decomposes slowly and deters herbivores. /n contrast, plant species from nutrient-rich ecosystems grow rapidly, produce readily degradable litter and sustain high rates of herbivory, further enhancing rates of nutrient cycling. Plants may also create positive feedbacks to nutrient cycling because of species' differences in carbon deposition and competition with microbes for nutrients in the rhizosphere. New research is showing that species' effects can be as or more important than abiotic factors, such as climate, in controlling ecosystem fertility.
1,214 citations
TL;DR: The core idea being that there exists a unique general fitness measure that concisely summarizes the overall time course of potential invasions by initially rare mutant phenotypes is summarized.
Abstract: Beginners in life history theory or evolutionary ecology seemingly face a variety of almost unrelated approaches Yet the biomathematical literature of the last 10–20 years reflects the implicit acceptance of a common evolutionary framework, the core idea being that there exists a unique general fitness measure that concisely summarizes the overall time course of potential invasions by initially rare mutant phenotypes Using such an invasion criterion to characterize fitness implicitly presupposes a scenario in which, during periods o f clear evolutionary change, the rate of evolution is set primarily by the random occurrence (and initial establishment) of favourable mutations Evolutionarily stable life history strategies ( ESSs ) may then be regarded as traps for the evolutionary random walk
987 citations
TL;DR: The study of intraguild predation will lead to a reconsideration of many classical topics, such as niche shifts, species exclusion and cascading interactions in food webs.
Abstract: There is a long-standing debate in ecology concerning the relative importance of competition and predation in determining community structure. Recently, a novel twist has been added with the growing recognition that potentially competing species are often engaged in predator-prey interactions. This blend of competition and predation is called intraguild predation (IGP). The study of IGP will lead to a reconsideration of many classical topics, such as niche shifts, species exclusion and cascading interactions in food webs. Theoretical models suggest that a variety of alternative stable states are likely in IGP systems, and that intermediate predators should tend to be superior in exploitative competition. Many field studies support these expectations. IGP is also important in applied ecological problems, such as the conservation of endangered species and fisheries management.
880 citations
TL;DR: There is typically at least a 10(5)-fold range of seed mass between species even within a single area, suggesting that much seed size variation is evolutionarily associated with other plant attributes.
Abstract: A seedling's chances of establishing successfully are likely to be affected by the quantity of metabolic reserves in the seed. Seed size is thought to evolve as a compromise between producing numerous smaller seeds, each with few resources, and fewer larger seeds, each with more resources. Seed size varies 10 11 -fold across plant species, so the compromise has been struck at very different levels. These basic ideas have been accepted for 50 years, and many studies have interpreted seed size differences between species by reference to larger seed size being adaptive under a variety of hazards. However, experimental tests of the benefits of large seed size in relation to particular hazards have been rare. More experiments are now being reported, but a consistent picture has yet to emerge. There is typically at least a 10 5 -fold range of seed mass between species even within a single area, suggesting that much seed size variation is evolutionarily associated with other plant attributes.
582 citations
541 citations
TL;DR: A review of existing models shows that differences in trophic conditions and mortality are the main sources of inter- and intraspecific variation in size.
Abstract: The schedule of growth and reproduction is crucial to maximization of fitness. Models of optimal allocation of limiting resources are useful tools for predicting age and size at maturity — key components of fitness — for all lifestyles. Early models considered annual plants. Recently, they have been generalized to other short-lived organisms and also to perennials in which growth and reproduction schedules following maturation can be predicted. A review of existing models shows that differences in trophic conditions and mortality are the main sources of inter- and intraspecific variation in size.
539 citations
528 citations
TL;DR: Recent results suggest an important role for transient isolation, gamete ecology and molecular evolution at gamete recognition loci in marine species at the scale of thousands to tens of thousands of kilometers.
Abstract: The scale of population structure in many marine species is on the order of thousands to tens of thousands of kilometers. How does speciation take place in oceans that are only about this same size? Recent results suggest an important role for transient isolation, gamete ecology and molecular evolution at gamete recognition loci. These factors have long been appreciated by plant biologists, and are likely to be a fruitful area of research for marine biologists as well.
522 citations
439 citations
TL;DR: The purpose of this review is to synthesize recent advances in research relating to nitrogen deposition effects on temperate zone forest ecosystems, and the further effects of nitrogen saturation on environmental quality.
Abstract: The last decade has seen a dramatic shift in the focus of nitrogen cycling research in forest ecosystems. Concerns over nitrogen deficiencies and effects of removal in harvest have given way to concerns over excess nitrogen availability and the potential for forest decline and surface water pollution. Driving this paradigm shift is the increase in atmospheric deposition of nitrogen to forests due to industrial and agricultural activity. At the core of the new paradigm is the concept of ‘nitrogen saturation' of forest ecosystems. The purpose of this review is to synthesize recent advances in research relating to nitrogen deposition effects on temperate zone forest ecosystems, and the further effects of nitrogen saturation on environmental quality.
432 citations
TL;DR: Plant hybrids formed following a plant invasion provide great potential for the study of 'evolution in action' and further study of these new taxa should aim to elucidate the factors that influence their subsequent establishment and spread, thus leading to a better understanding of the processes that lead to successful speciation.
Abstract: Interspecific hybridization between a native and an invading plant species, or two invading species, sometimes results in a new, sexually reproducing taxon. Several examples of such taxa have been confirmed by recent molecular and isozyme analyses. Further study of these new taxa, when recognized soon after their origin, should aim to elucidate the factors that influence their subsequent establishment and spread, thus leading to a better understanding of the processes that lead to successful speciation. Plant hybrids formed following a plant invasion provide great potential for the study of ‘evolution in action'.
TL;DR: The role of polyploidy in the origin of evolutionary novelty and the maintenance of diversity in plant populations has come to be recognized as an integral component of the ecological and evolutionary dynamics of plant species populations.
Abstract: The role of polyploidy in the origin of evolutionary novelty and the maintenance of diversity in plant populations has come to be recognized as an integral component of the ecological and evolutionary dynamics of plant species populations. Recent attempts to examine the evolutionary significance of polyploidy have focused on the processes responsible for the origin of polyploid plants and the conditions that favour their establishment and persistence. The importance of these issues is not simply limited to the evolutionary dynamics of polyploidy but is, in fact, central to our understanding of the population biology processes that act on the establishment of new ‘types' and the maintenance of biotic diversity at both the inter- and intraspecific levels.
TL;DR: New empirical data help to identify the physiological mechanisms constraining energy budgets and allow quantification of otherwise vague arguments in evolutionary optimization of life histories, foraging behaviours, and geographical distributions of species.
Abstract: fie physiological limitation of individual energy budgets has been suggested as one determinant of animal reproductive performance and survival, independent of extrinsic environmental factors. 7Iis postulate helps to explicate the evolutionary optimization of life histories, foraging behaviours, and geographical distributions of species. Models of optimal resource allocution and of optimal foraging have been proposed within this framework. New empirical data help to identify the physiological mechanisms constraining energy budgets and allow quantification of otherwise vague arguments. Nevertheless, many questions remain unanswered or clouded.
TL;DR: Recent advances in orchid pollination biology center mainly on floral evolutionary processes, pseudocopulation and other deceptive pollination systems, and flower and fruit production in relation to costs of sexual reproduction.
Abstract: Orchids display many unsurpassed floral specializations, as both rewarders and frauds in their interaction with animal pollinators. Accumulating evidence indicates that their floral evolution is driven by pollinator traits and that expenditure for maximized sexual reproduction is parcelled out over their lifetimes in strategies for coping with pollinator and resource limitations. Recent advances in orchid pollination biology center mainly on floral evolutionary processes, pseudocopulation and other deceptive pollination systems, and flower and fruit production in relation to costs of sexual reproduction.
TL;DR: A large number of conservation biologists are faced with the problem of whether to recommend the allocation of resources to corridors on the assumption that they may be important, and few studies have actually demonstrated that movement along corridors is important for any given species.
Abstract: Corridors are currently a major buzzword in conservation biology and landscape ecology. These linear landscape features may perform numerous functions, but it is their role in facilitating movement of fauna that has attracted much recent debate. The database supporting the idea of corridors acting as faunal conduits is remarkably small, and few studies have actually demonstrated that movement along corridors is important for any given species. Such data are very difficult to obtain, and conservation biologists are thus faced with the problem of whether to recommend the allocation of resources to corridors on the assumption that they may be important.
TL;DR: There are now experiments which demonstrate that there are different mechanisms underlying the response to an experimental manipulation versus a genetic correlation, so the two methods of estimating costs are not equivalent in estimating costs.
Abstract: The measurement of costs of reproduction is of interest because such costs are generally assumed by life history theory. There is some controversy concerning how to measure costs: common methods include experimental manipulations of life history, such as preventing some individuals from reproducing, or estimates of genetic correlations. These two methods often yield similar results, suggesting that one can serve as a substitute for the other. There are now experiments which demonstrate that there are different mechanisms underlying the response to an experimental manipulation versus a genetic correlation, so the two methods are not equivalent in estimating costs.
TL;DR: The evolution of wings is heralded as the most important event in the diversification of insects, yet flight-wing loss has occurred in nearly all pterygote insect orders.
Abstract: The evolution of wings is heralded as the most important event in the diversification of insects, yet flight-wing loss has occurred in nearly all pterygote insect orders. Flight loss is especially prevalent among taxa inhabiting historically stable habitats. Recent studies of wing-polymorphic species have revealed numerous selective trade-offs in the reproductive potentials of winged versus flightless forms. A diverse set of environmental factors, both biotic and abiotic, trigger flight loss in alary polyphenic taxa, presumably by influencing juvenile hormone titers. Phylogenetic comparisons promise to elucidate much about the historical contexts and consequences of flight loss.
TL;DR: Critical evaluation will require better data on the extent of movements of seabirds between colonies, the characteristics of those individuals that contribute disproportionately to the next generation, and the importance of year and/or cohort effects on population processes.
Abstract: Long-term studies of seabirds, some now 30–40 years old, have begun to reveal significant age-related changes in the survival and reproduction o f these long-lived animals. Evidence for density-dependent regulation of seabird numbers, however, remains sparse whereas unpredictable, disastrous breeding years may be an important influence. Critical evaluation will require better data on (1) the extent of movements of seabirds between colonies, (2) the characteristics of those individuals that contribute disproportionately to the next generation, and (3) the importance of year and/or cohort effects on population processes.
TL;DR: These studies emphasize that sex role reversal is not synonymous with male parental care and there is an apparent association between the mating pattern and the sex roles: polygamous species show reversed sex roles whereas monogamous species exhibit 'conventional' sex roles.
Abstract: The male pregnancy of pipefishes and seahorses has led to the inference that females compete most intensely for access to mates, because males limit female reproduction. However, recent work has shown that in different species either sex may be the predominant competitor for mates. In this family, there is an apparent association between the mating pattern and the sex roles: polygamous species show reversed sex roles whereas monogamous species exhibit 'conventional' sex roles. These studies emphasize that sex role reversal is not synonymous with male parental care.
TL;DR: The modifications of the ideal free distribution suggest ways in which behavioural properties of individuals might affect the distribution of competitors, and clear a path for further empirical tests.
Abstract: The ideal free distribution, a theoretical model of the distribution of competitors between habitat patches, has recently undergone a number of modifications and extensions. These fall into two main categories: those that assume that equilibrium is attained, and those that establish whether it is attained. The modifications suggest ways in which behavioural properties of individuals might affect the distribution of competitors, and clear a path for further empirical tests.
TL;DR: What Fisher really meant can be illustrated by looking in a new way at a recent model for the evolution of clutch size, which explains why Fisher was misunderstood.
Abstract: Fisher's Fundamental Theorem of natural selection is one of the most widely cited theories in evolutionary biology. Yet it has been argued that the standard interpretation of the theorem is very different from what Fisher meant to say. What Fisher really meant can be illustrated by looking in a new way at a recent model for the evolution of clutch size. Why Fisher was misunderstood depends, in part, on the contrasting views of evolution promoted by Fisher and Wright.
TL;DR: A series of problems and areas for new research that may be resolved are identified by the application of novel theoretical approaches, greater in situ experimentation, long-term monitoring of population dynamics and the use of new genetic techniques.
Abstract: Corals display a wide range of complex life histories. The evolutionary consequences of factors such as clonality, indeterminate growth, asexual reproduction coupled with various (sexual) breeding systems, different levels of gene flow, and strongly overlapping generations have only just begun to be explored. We identify a series of problems and areas for new research that may be resolved b y the application of novel theoretical approaches (including nonequilibrium population genetic models and demographic models incorporating modular processes such as colony fission and polyp mortality), greater in situ experimentation, long-term monitoring of population dynamics and the use of new genetic techniques.
TL;DR: Recent studies of a variety of polygynously mating animals indicate that females do not always choose mates independently, but instead may copy the choices of others, which is likely to affect the intensity of sexual selection.
Abstract: Recent studies of a variety of polygynously mating animals indicate that females do not always choose mates independently, but instead may copy the choices of others. Copying could serve either to increase the accuracy of mate assessment or to reduce its costs. It is also likely to affect the intensity of sexual selection.
TL;DR: The virtue of the papers by Service’ and Luckinbill etaL2, discussed in my TREE article3, is that they brought experiments to bear on discussion that otherwise could not be conclusive and theirs are the first experiments that directly address the potential difference between costs that result from selection experiments and those that are revealed by environmental manipulations.
Abstract: The virtue of the papers by Service’ and Luckinbill etaL2, discussed in my TREE article3, is that they brought experiments to bear on discussion that otherwise could not be conclusive. Theirs are the first experiments that directly address the potential difference between costs that result from selection experiments and those that are revealed by environmental manipulations. This is why I considered their work worthy of a more general discussion. First, Partridge4 notes that maintaining flies as virgins does not stop reproductive investment. Females continue to lay eggs. I assume that males also continue to produce sperm. Her thoughts on this were incomplete. If this continued investment accounts for Service’s or Luckinbill et a/.‘s results (Fig. 1 b and Ic in Ref. 3), then it must also be true that virgin males continue to invest as much in reproduction as virgin females, and that the B-line virgins invest much more than the O-line virgins. Both of these propositions are required to account for the same results for males and females and the deviation between the predicted result (Fig. la in Ref. 3) and the actual results. To illustrate how big the differences between 0 and B lines in sperm productivity by virgins must be, Service reports a difference in longevity of virgin 0 and B males (e.g. 89.2 versus 57.8 days, respectively hisTable 1) that isclose in magnitude tothe difference in longevity between virgin males and males mated daily with eightfemales (65versus40days, respectively) reported by Partridge and Farquhar5. These propositions are testable and I hope that they are evaluated some day. Partridge notes that reproductive activities other than egg laying may be involved; for progress to be made, it is essential that she state what these activities are and how they can be quantified. She made a similar criticism of my work on guppies6, but in this case I did quantify the energetic investment by nonreproducing females, so something else must account for my observations. Her more general criticisms of Service’s and Luckinbill et al.‘s studies, such as the observation that selection for decreased mating also increases lifespan, are beside the point for the issues discussed in my paper. Specifically, her claim that I fail ‘to point out that nongenetic work has given similar evidence for costs’ is simply not true. Her more general criticism of my essay casts me in the role of making black-and-white decisions about what sorts of data are correct for characterizing costs of
TL;DR: This work has suggested that flowering phenology is a trait that may not be under strong selection, and this may have allowed some variation to appear in populations by chance.
Abstract: Flowering phenology has normally been viewed as fundamental to a plant species' reproductive ecology. Researchers in the field have emphasized the adaptive importance of flowering at a particular time relative to other individuals in the population, or other species in the community. An alternative view, however, is that flowering phenology is a trait that may not be under strong selection, and this may have allowed some variation to appear in populations by chance.
TL;DR: Spiders are regarded with keen interest as model organisms in behavioral ecology because of their small size, short lifespan, and the strong influence of genetic control on their behavior.
Abstract: Abundant and ecologically important in many ecosystems as predators of insects (including agricultural pests), spiders have recently gained attention as a result of a number of significant studies. In addition, because of their small size, short lifespan, and the strong influence of genetic control on their behavior, spiders are regarded with keen interest as model organisms in behavioral ecology.
TL;DR: The new interest in correlated responses reflects more rigorous attempts to consider the organism as a whole, rather than dissecting it into a number of questionably separable traits.
Abstract: Many traits are genetically correlated with each other. Thus, selection that changes the mean value of one trait causes other traits to change as well. Recent comparative studies have emphasized the possible importance of such correlated responses in affecting the evolution of traits, including some behaviors, which are of little adaptive significance, or even maladaptive. However, it is also possible for traits with major effects on fitness, such as brain size, to evolve entirely by correlated response. Other traits that do not appear to have evolved at all may have been subject to much directional selection, simply to prevent their evolution by correlated response. The new interest in correlated responses reflects more rigorous attempts to consider the organism as a whole, rather than dissecting it into a number of questionably separable traits.
TL;DR: The quasispecies nature of HIV has formed the basis of a model that provides a mechanism for the pathogenesis of acquired immunodeficiency syndrome (AIDS) in humans and its implications for evolutionary biology and virology are discussed.
Abstract: A quasispecies is a well-defined distribution of mutants that is generated by a mutation-selection process. Selection does not act on a single mutant but on the quasispecies as a whole. Experimental systems have been designed to study quasispecies evolution under laboratory conditions. More recently, virus populations have been called quasispecies to indicate their extensive genetic heterogeneity. The most prominent examples are probably the human immunodeficiency viruses HIV-1 and HIV-2. The quasispecies nature of HIV has formed the basis of a model that provides a mechanism for the pathogenesis of acquired immunodeficiency syndrome (AIDS) in humans. This article focuses on the nature of the quasispecies concept and its implications for evolutionary biology and virology.