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Evolutionary Theory (evolutionary + theory)
Selected AbstractsPerinatal Sadness among Shuar Women: Support for an Evolutionary Theory of Psychic PainMEDICAL ANTHROPOLOGY QUARTERLY, Issue 1 2007Edward H. Hagen Psychiatry faces an internal contradiction in that it regards mild sadness and low mood as normal emotions, yet when these emotions are directed toward a new infant, it regards them as abnormal. We apply parental investment theory, a widely used framework from evolutionary biology, to maternal perinatal emotions, arguing that negative emotions directed toward a new infant could serve an important evolved function. If so, then under some definitions of psychiatric disorder, these emotions are not disorders. We investigate the applicability of parental investment theory to maternal postpartum emotions among Shuar mothers. Shuar mothers' conceptions of perinatal sadness closely match predictions of parental investment theory. [source] Kierkegaard's Socrates: a Venture in Evolutionary TheoryMODERN THEOLOGY, Issue 4 2001Mary-Jane Rubenstein This essay explores the shifts in Kierkegaard's conceptions of Socrates, looking to produce a more nuanced reading of Kierkegaardian indirect communication, faith, and subjectivity. Entirely bound up with his increasingly troubled view of Hegel and Hegelianism, Kierkegaard's relationship to Socrates can be traced through three of his major texts: The Concept of Irony, Philosophical Fragments, and The Concluding Unscientific Postscript. By examining these three works, this essay charts a path from a critique of the Socratic as un -speculative, through a deep resentment of the Socratic as proto -speculative, to admiration and imitation of the Socratic as anti -speculative. Ultimately, it is argued, Kierkegaard and the pseudonyms rely upon Socrates to rehabilitate subjectivity out of the undifferentiated totality of nineteenth century idealism. [source] Is There Life After Policy Streams, Advocacy Coalitions, and Punctuations: Using Evolutionary Theory to Explain Policy Change?POLICY STUDIES JOURNAL, Issue 4 2003Peter John This article reviews the current state of public policy theory to find out if researchers are ready to readdress the research agenda set by the classic works of Baumgartner and Jones (1993), Kingdon (1984) and Sabatier and Jenkins-Smith (1993). After reviewing the influences of institutional, rational choice, network, socio-economic and ideational approaches, the article pays tribute to the policy streams, punctuated equilibrium and policy advocacy coalition frameworks whilst also suggesting that future theory and research could identify more precisely the causal mechanisms driving policy change. The article argues that evolutionary theory may usefully uncover the micro-level processes at work, particularly as some the three frameworks refer to dymamic models and methods. After reviewing some evolutionary game theory and the study of memes, the article suggests that the benefits of evolutionary theory in extending policy theories need to be balanced by its limitations. [source] Metabolic age modelling: the lesson from centenariansEUROPEAN JOURNAL OF CLINICAL INVESTIGATION, Issue 10 2000G. Paolisso Evolutionary theories of ageing, and data emerging from cellular and molecular biology of ageing, suggested that animals and humans capable of reaching an age close to the extreme limit of the life span should be equipped with a very efficient network of anti-ageing mechanisms. Indeed several evidences have demonstrated that starting from young to very old subjects, ageing is associated with a progressive remodelling. Thus, a new paradigm, the remodelling theory of age, was proposed. This theory, focusing on the human immune system, suggested that immunosenescence is the net result of the continuous adaptation of the body to the deteriorative changes occurring over time. According to this hypothesis, body resources are continuously optimized, and immunosenescence must be considered a very dynamic process including both loss and gain. Whether the metabolic pathways and the endocrine functions are also part of the age remodelling is not investigated. The aim of this review is to focus on the age-related changes in metabolic pathways and endocrine functions and to demonstrate that healthy centenarians (HC) represent the best living example of successful age-remodelling in whom the age remodelling has occurred without problems. In order to design the clinical picture of such successful ageing, anthropometric, endocrine and metabolic characteristics of healthy centenarians (HC), compared with aged subject, have been outlined. [source] Sex differences in nutrient-dependent reproductive ageingAGING CELL, Issue 3 2009Alexei A. Maklakov Summary Evolutionary theories of aging predict that fitness-related traits, including reproductive performance, will senesce because the strength of selection declines with age. Sexual selection theory predicts, however, that male reproductive performance (especially sexual advertisement) will increase with age. In both bodies of theory, diet should mediate age-dependent changes in reproductive performance. In this study, we show that the sexes exhibit dramatic, qualitative differences in age-dependent reproductive performance trajectories and patterns of reproductive ageing in the cricket Teleogryllus commodus. In females, fecundity peaked early in adulthood and then declined. In contrast, male sexual advertisement increased across the natural lifespan and only declined well beyond the maximum field lifespan. These sex differences were robust to deviations from sex-specific dietary requirements. Our results demonstrate that sexual selection can be at least as important as sex-dependent mortality in shaping the signal of reproductive ageing. [source] ORIGINAL ARTICLE: Big dams and salmon evolution: changes in thermal regimes and their potential evolutionary consequencesEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 2 2008Michael J. Angilletta Jr Abstract Dams designed for hydropower and other purposes alter the environments of many economically important fishes, including Chinook salmon (Oncorhynchus tshawytscha). We estimated that dams on the Rogue River, the Willamette River, the Cowlitz River, and Fall Creek decreased water temperatures during summer and increased water temperatures during fall and winter. These thermal changes undoubtedly impact the behavior, physiology, and life histories of Chinook salmon. For example, relatively high temperatures during the fall and winter should speed growth and development, leading to early emergence of fry. Evolutionary theory provides tools to predict selective pressures and genetic responses caused by this environmental warming. Here, we illustrate this point by conducting a sensitivity analysis of the fitness consequences of thermal changes caused by dams, mediated by the thermal sensitivity of embryonic development. Based on our model, we predict Chinook salmon likely suffered a decrease in mean fitness after the construction of a dam in the Rogue River. Nevertheless, these demographic impacts might have resulted in strong selection for compensatory strategies, such as delayed spawning by adults or slowed development by embryos. Because the thermal effects of dams vary throughout the year, we predict dams impacted late spawners more than early spawners. Similar analyses could shed light on the evolutionary consequences of other environmental perturbations and their interactions. [source] Effects of ecogeographic variables on genetic variation in montane mammals: implications for conservation in a global warming scenarioJOURNAL OF BIOGEOGRAPHY, Issue 7 2007Amy M. Ditto Abstract Aim, Evolutionary theory predicts that levels of genetic variation in island populations will be positively correlated with island area and negatively correlated with island isolation. These patterns have been empirically established for oceanic islands, but little is known about the determinants of variation on habitat islands. The goals of this study were twofold. Our first aim was to test whether published patterns of genetic variation in mammals occurring on montane habitat islands in the American Southwest conformed to expectations based on evolutionary theory. The second aim of this research was to develop simple heuristic models to predict changes in genetic variation that may occur in these populations as a result of reductions in available mountaintop habitat in response to global warming. Location, Habitat islands of conifer forest on mountaintops in the American Southwest. Methods, Relationships between island area and isolation with measures of allozyme variation in four species of small mammal, namely the least chipmunk (Tamias minimus), Colorado chipmunk (Tamias quadrivittatus), red squirrel (Tamiasciurus hudsonicus), and Mexican woodrat (Neotoma mexicana), were determined using correlation and regression techniques. Significant relationships between island area and genetic variation were used to develop three distinct statistical models with which to predict changes in genetic variation following reduction in insular habitat area arising from global warming. Results, Patterns of genetic variation in each species conformed to evolutionary predictions. In general, island area was the most important determinant of heterozygosity, while island isolation was the most important determinant of polymorphism and allelic diversity. The heuristic models predicted widespread reductions in genetic variation, the extent of which depended on the population and model considered. Main conclusions, The results support a generalized pattern of genetic variation for any species with an insular distribution, with reduced variation in smaller, more isolated populations. We predict widespread reductions in genetic variation in isolated populations of montane small mammals in the American Southwest as a result of global warming. We conclude that climate-induced reductions in the various dimensions of genetic variation may increase the probability of population extinction in both the short and long term. [source] Mating preferences, sexual selection and patterns of cladogenesis in ray-finned fishesJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2007J. E. MANK Abstract Evolutionary theory predicts that sexual selection may increase taxonomic diversity when emergent mating preferences result in reproductive isolation and therefore speciation. This theory has been invoked to explain patterns of diversity in ray-finned fishes (most notably in the cichlids), but the theory has not been tested comparatively in fish. Additionally, several other unrelated factors have been identified as promoters of cladogenesis, so it is unclear how important sexual selection might be in diversification. Using sister-clade analysis, I tested the relationship between the presence of sexually selected traits and taxonomic diversification in actinopterygiian fishes, a large clade that shows substantial diversity in mating preferences and related sexually selected traits. In all identified sister-families that differed with regard to the proportion of species manifesting sexually selected traits, sexual selection was correlated with increased diversification, and this association was significant across all sister clades (P = 0.02). This suggests that sexual selection, when present, is a substantial driver of diversification in the ray-finned fishes, and lends further empirical support to the theoretical link between mating preferences and accelerated cladogenesis. [source] Resolving the Anti-Antievolutionism Dilemma: A Brief for Relational Evolutionary Thinking in AnthropologyAMERICAN ANTHROPOLOGIST, Issue 2 2009Emily Schultz ABSTRACT Anthropologists often disagree about whether, or in what ways, anthropology is "evolutionary." Anthropologists defending accounts of primate or human biological development and evolution that conflict with mainstream "neo-Darwinian" thinking have sometimes been called "creationists" or have been accused of being "antiscience." As a result, many cultural anthropologists struggle with an "anti-antievolutionism" dilemma: they are more comfortable opposing the critics of evolutionary biology, broadly conceived, than they are defending mainstream evolutionary views with which they disagree. Evolutionary theory, however, comes in many forms. Relational evolutionary approaches such as Developmental Systems Theory, niche construction, and autopoiesis,natural drift augment mainstream evolutionary thinking in ways that should prove attractive to many anthropologists who wish to affirm evolution but are dissatisfied with current "neo-Darwinian" hegemony. Relational evolutionary thinking moves evolutionary discussion away from reductionism and sterile nature,nurture debates and promises to enable fresh approaches to a range of problems across the subfields of anthropology. [Keywords: evolutionary anthropology, Developmental Systems Theory, niche construction, autopoeisis, natural drift] [source] Evolutionary Perspectives on the Development of Social ExchangesNEW DIRECTIONS FOR CHILD & ADOLESCENT DEVELOPMENT, Issue 95 2002Brad E. Sheese Evolutionary theory suggests that developmental context and genetic relatedness may fundamentally alter social exchange processes. [source] Women's fertility and mortality in late mid life: A comparison of three contemporary populationsAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 4 2009Emily Grundy Evolutionary theory suggests a trade-off between reproduction and somatic maintenance implying a negative relationship between parity and longevity, at least in natural fertility populations. In populations in which fertility control is usual, there are also a number of mechanisms that may link reproductive careers and later mortality, but evidence of associations between women's fertility patterns and their later life health has been judged inconclusive due to varying controls for socio-economic characteristics and marital status. Here, we build on three recent studies that followed a common framework to investigate associations between women's parity and timing of first and last birth with mortality in late middle age in three contemporary developed counties, Norway, England and Wales, and the USA. Data were drawn from whole population registers (Norway); a large census-based record linkage study (England and Wales), and a nationally representative survey linked to death records (USA). Results show that teenage childbirth was associated with higher mortality risks in late middle age in all three countries. Risks of death were significantly raised among nulliparous women in Norway and England and Wales, and also raised (although not significantly so) for childless US women. However, although higher parity was associated with a slight mortality disadvantage in England and Wales and the USA, the reverse seemed the case in Norway. These finding suggest that in populations in which fertility control is usual, contextual factors influencing the relative costs and benefits of childbearing may influence associations between fertility histories and later mortality. Am. J. Hum. Biol., 2009. © 2009 Wiley-Liss, Inc. [source] From imitation to invention: creating commodities in eighteenth-century BritainECONOMIC HISTORY REVIEW, Issue 1 2002Maxine Berg This article presents the history of new goods in the eighteenth century as a part of the broader history of invention and industrialization. It focuses on product innovation in manufactured commodities as this engages with economic, technological and cultural theories. Recent theories of consumer demand are applied to the invention of commodities in the eighteenth century; special attention is given to the process of imitation in product innovation. The theoretical framework for imitation can be found in evolutionary theories of memetic transmission, in archaeological theories of skeuomorphous, and in eighteenth-century theories of taste and aesthetics. Inventors, projectors, economic policy makers, and commercial and economic writers of the period dwelt upon the invention of new British products. The emulative, imitative context for their invention made British consumer goods the distinctive modern alternatives to earlier Asian and European luxuries. [source] An evolutionary concept for altered steroid hormone metabolism in patients with rheumatoid arthritisEXPERIMENTAL DERMATOLOGY, Issue 2 2005Rainer H. Straub The pathogenesis of chronic disabling inflammatory diseases (CDIDs) is partly understood. The presently used concepts focus mainly on abnormalities of the immune system but this view is incomplete. The presented concept is a new framework for the pathogenesis of CDIDs. It integrates evolutionary theories with the classical immunological standpoint, which is further linked with a neuroendocrine immune view of erroneous homeostatic adaptation of the other supersystems (nervous system, endocrine system, reproductive system): 1. In CDIDs, the loss of tolerance against self and harmless foreign antigens leads to continuous immune aggression which is dependent on a multifactorial genetically polymorph background (the initiation). 2. However, advantageous or disadvantageous adaptation to CDIDs were not evolutionary conserved because CDIDs severely impaired reproduction or appeared after the reproductive phase and, thus, imply a strong negative selection pressure. 3. Reactions of all supersystems are evolutionary conserved for transient inflammatory reactions such as the elimination of infectious agents, wound healing, foreign body reaction and many others. 4. The sum of the false reactions of all supersystems , conserved for transient inflammation , provide the pathogenetic background for the chronification of CDIDs because a continuous aggressive situation is created (the chronification). The human disease of rheumatoid arthritis is used as a prototypic CDID to illustrate the integrated view point. The synovial tissue innervation is in the focus of this concept. [source] The evolutionary ecology of senescenceFUNCTIONAL ECOLOGY, Issue 3 2008P. Monaghan Summary 1Research on senescence has largely focused on its underlying causes, and is concentrated on humans and relatively few model organisms in laboratory conditions. To understand the evolutionary ecology of senescence, research on a broader taxonomic range is needed, incorporating field, and, where possible, longitudinal studies. 2Senescence is generally considered to involve progressive deterioration in performance, and it is important to distinguish this from other age-related phenotypic changes. We outline and discuss the main explanations of why selection has not eliminated senescence, and summarise the principal mechanisms thought to be involved. 3The main focus of research on senescence is on age-related changes in mortality risk. However, evolutionary biologists focus on fitness, of which survival is only one component. To understand the selective pressures shaping senescence patterns, more attention needs to be devoted to age-related changes in fecundity. 4Both genetic and environmental factors influence the rate of senescence. However, a much clearer distinction needs to be drawn between life span and senescence rate, and between factors that alter the overall risk of death, and factors that alter the rate of senescence. This is particularly important when considering the potential reversibility and plasticity of senescence, and environmental effects, such as circumstances early in life. 5There is a need to reconcile the different approaches to studying senescence, and to integrate theories to explain the evolution of senescence with other evolutionary theories such as sexual and kin selection. [source] Panbiogeography from tracks to ocean basins: evolving perspectivesJOURNAL OF BIOGEOGRAPHY, Issue 4 2001John R. Grehan Misconceptions arising from efforts to translate panbiogeography into terms used in other biogeographic and evolutionary theories are discussed with respect to Cox's (1998, Journal of Biogeography, 25, 813,828) critique of panbiogeography. Croizat's rejection of ,Darwinian dispersal' applies only to efforts to utilize this concept as a general explanation for biogeographic patterns. The conceptual difference between distribution and panbiogeographic dispersal maps is illustrated to show that Croizat did not synonymize distribution and dispersal. Croizat's position on continental drift and plate tectonics does not support Cox's (1998) claim that Croizat ,for a long time' refused to accept the theory of plate tectonics. The methodological relationship between panbiogeographic analysis and geology suggests an independence of methodology that prevents geological theory from falsifying panbiogeographic predictions. Panbiogeographic predictions for the eastern Pacific are shown to be in agreement with current historical geological models. Claims by Cox (1998) that the panbiogeographic method is variable and questionable are evaluated with respect to the biogeographic homology of primitive frogs, ratite birds, and southern beeches to demonstrate the consistent application of minimal distance, main massing, phylogenetic affinity and baseline criteria. Panbiogeographic classification concepts are contrasted with the Darwinian system (supported by Cox) utilizing a concept of unitary geographical area based on the language of Roman military rule. Inconsistent positions expressed in recent critiques of panbiogeography may indicate an underlying and implicit acceptance of the empirical and theoretical progress generated by panbiogeography within modern biogeography. ,The formation of groups has an invigorating effect in all spheres of human striving, perhaps mostly due to the struggle between the convictions and aims represented by the different groups' (Einstein, 1938. Collier's, 26 November). [source] Representational Altruism: The Wary Cooperator as Authoritative Decision MakerAMERICAN JOURNAL OF POLITICAL SCIENCE, Issue 4 2006Kevin B. Smith What drives policymakers to put the interests of others above their own? If human nature is inherently selfish, it makes sense to institutionalize incentives that counter decision makers' temptations to use their positions to benefit themselves over others. A growing literature rooted in evolutionary theories of human behavior, however, suggests that humans, under certain circumstances, have inherent predispositions towards "representational altruism," i.e., to make an authoritative decision to benefit another at one's own expense. Drawing on Hibbing and Alford's conception of the wary cooperator, a theoretical case is made for such behavioral expectations, which are confirmed in a series of original laboratory experiments. [source] Theories in anthropology and ,anthropological theory'THE JOURNAL OF THE ROYAL ANTHROPOLOGICAL INSTITUTE, Issue 2 2010Roy Ellen What makes a theory ,anthropological' beyond it being a theory that anthropologists use? Assuming a framework that understands anthropology in its broadest sense, this article invites us to remind ourselves what theories are actually supposed to do. Distinguishing theories in terms of the scale of presumption in their claims, it argues for a pyramid of nested levels of explanation. As we move from the base to the tip of the pyramid, so our explanations and interpretation of data must become increasingly simple to accommodate the forms of measurement that each level demands. Given this model, how can evolutionary theories based on individual behaviour geared to immediate survival and reproduction be reconciled with theories that best explain the uncertainties of ,emergent systems', or that consider how individual actions are in turn constrained by the systems of which they are part? It is concluded that anthropology has always acquired its vitality by being critically ,conjunctural', and must be ultimately and necessarily a strategic cross-disciplinary theoretical compromise. Résumé Qu'est-ce qui rend une théorie « anthropologique », en dehors du fait que les anthropologues l'utilisent ? En posant une acception aussi large que possible de l'anthropologie, l'article invite à se rappeler à quoi servent en réalité les théories. En distinguant les théories par le niveau de conjecture de leurs affirmations, l'auteur propose une pyramide de niveaux d'explication imbriqués. En progressant de la base au sommet de la pyramide, les attentes et l'interprétation des données doivent devenir de plus en plus simples, afin de prendre en compte les formes de mesure exigées à chaque niveau. Sur la base de ce modèle, comment les théories évolutionnistes, basées sur des comportements individuels visant la survie et la reproduction immédiates, peuvent-elles être conciliées avec celles qui expliquent, au mieux, les incertitudes des « systèmes émergents » ou qui examinent la façon dont les actions individuelles sont contraintes par les systèmes dans lesquels elles s'inscrivent ? L'auteur conclut que l'anthropologie a toujours acquis sa vitalité par une approche « conjoncturelle » critique et qu'elle doit être en fin de compte, par nécessité, un compromis théorique stratégique transdisciplinaire. [source] Anomalous Experiences Reported by Field Anthropologists: Evaluating Theories Regarding ReligionANTHROPOLOGY OF CONSCIOUSNESS, Issue 2 2002James McClenon Ph.D. Content analysis of published accounts of 40 anomalous experiences reported by anthropologists allows qualitative evaluationof elements within evolutionary theories pertaining to religion . The analysis supports findings from previous studies indicating that certain anomalous experienceshave cross-culturally consistent features. Narrative and structural features within the anthropologists' accounts coincide with those gathered in northeastern North Carolina and many other areas. The data also reveal the capacity of these episodes to transform belief, supporting an experiential source theory regarding faith in spirits, souls, life after death, and magical abilities. The narratives indicate that anomalous perceptions cause some anthropologists to consider novel theories. This study supports evolutionary explanations for the origin of religion and provides predictions regarding research directions in anthropology. [source] Can behavioral evolution be measured on a staircase? a commentaryDEVELOPMENTAL PSYCHOBIOLOGY, Issue 1 2004Celia L. Moore Abstract The serious, comparative study of behavioral complexity that Greenberg et al. advocate is a progressive direction for the field, but their proposal to separate comparative psychology from its roots in evolutionary biology seems regressive. Modern evolutionary theory has been broadened within biology to include development and paleontology alongside natural selection, making closer integration with that discipline particularly timely. Such an integrated evolutionary approach in psychology would offer a useful alternative to the adaptationism popularized by evolutionary psychology. Although the differences between comparative psychologists and biologists may be blurred in the process, the behavioral sciences will be better served by a rich biological approach to evolution than by a uniquely psychological approach. © 2003 Wiley Periodicals, Inc. Dev Psychobiol 44: 16,20, 2004. [source] A Semantic View of Ecological Theories,DIALECTICA, Issue 1 2001David G.A. CastleArticle first published online: 23 JUN 200 Philosophical analysis of ecological theories has lagged behind the study of evolutionary theory. The semantic conception of scientific theories, which has been employed successfully in the analysis of evolutionary theory, is adopted here to analyse ecological theory. Two general problems in ecology are discussed. One arises from the continued use of covering law models in ecology, and the other concerns the applicability of ecological theory in conservation biology. The semantic conception of ecological theories is used to resolve these problems. [source] No Plastic Responses to Experimental Manipulation of Sperm Competition per se in a Free-Living FlatwormETHOLOGY, Issue 4 2010Peter Sandner In the absence of sperm competition evolutionary theory predicts low mating rates and low ejaculate expenditure per mating, and sex allocation theory for simultaneous hermaphrodites predicts a strongly female-biased sex allocation. In the presence of sperm competition a shift towards a more male-biased sex allocation and a higher ejaculate expenditure are predicted. The free-living flatworm Macrostomum lignano has been shown to respond plastically in mating rate, testis size, and sperm transfer to manipulation of the social group size, a proxy of the strength of sperm competition. However, manipulation of social group size may manipulate not only sperm competition, but also other factors, such as food supply and metabolite concentration. In this study we therefore manipulated sperm competition per se by repeatedly exposing individuals to partners that have either mated with rivals or not, while keeping the social group size constant. Our results suggest that M. lignano does not have the ability to detect sperm competition per se, as worms experimentally exposed to the presence or absence of sperm competition did not differ in sex allocation, sperm transfer or mating behavior. A response to our manipulation would have required individual recognition, the ability to detect self-referencing tags, or tags or traces left by rivals on or in the mating partners. We first discuss the possibility that highly efficient sperm displacement may have decreased the difference between the treatment groups and then propose three alternative cues that may allow M. lignano to respond plastically to the social group size manipulation used in earlier studies: assessment of the mating rate, chemical cues, or tactile cues. [source] ON THE EVOLUTION OF HARMING AND RECOGNITION IN FINITE PANMICTIC AND INFINITE STRUCTURED POPULATIONSEVOLUTION, Issue 11 2009Laurent Lehmann Natural selection may favor two very different types of social behaviors that have costs in vital rates (fecundity and/or survival) to the actor: helping behaviors, which increase the vital rates of recipients, and harming behaviors, which reduce the vital rates of recipients. Although social evolutionary theory has mainly dealt with helping behaviors, competition for limited resources creates ecological conditions in which an actor may benefit from expressing behaviors that reduce the vital rates of neighbors. This may occur if the reduction in vital rates decreases the intensity of competition experienced by the actor or that experienced by its offspring. Here, we explore the joint evolution of neutral recognition markers and marker-based costly conditional harming whereby actors express harming, conditional on actor and recipient bearing different conspicuous markers. We do so for two complementary demographic scenarios: finite panmictic and infinite structured populations. We find that marker-based conditional harming can evolve under a large range of recombination rates and group sizes under both finite panmictic and infinite structured populations. A direct comparison with results for the evolution of marker-based conditional helping reveals that, if everything else is equal, marker-based conditional harming is often more likely to evolve than marker-based conditional helping. [source] A TEST AND REVIEW OF THE ROLE OF EFFECTIVE POPULATION SIZE ON EXPERIMENTAL SEXUAL SELECTION PATTERNSEVOLUTION, Issue 7 2009Rhonda R. Snook Experimental evolution, particularly experimental sexual selection in which sexual selection strength is manipulated by altering the mating system, is an increasingly popular method for testing evolutionary theory. Concerns have arisen regarding genetic diversity variation across experimental treatments: differences in the number and sex ratio of breeders (effective population size; Ne) and the potential for genetic hitchhiking, both of which may cause different levels of genetic variation between treatments. Such differences may affect the selection response and confound interpretation of results. Here we use both census-based estimators and molecular marker-based estimates to empirically test how experimental evolution of sexual selection in Drosophila pseudoobscura impacts Ne and autosomal genetic diversity. We also consider effects of treatment on X-linked Nes, which have previously been ignored. Molecular autosomal marker-based estimators indicate that neither Ne nor genetic diversity differs between treatments experiencing different sexual selection intensities; thus observed evolutionary responses reflect selection rather than any confounding effects of experimental design. Given the increasing number of studies on experimental sexual selection, we also review the census Nes of other experimental systems, calculate X-linked Ne, and compare how different studies have dealt with the issues of inbreeding, genetic drift, and genetic hitchhiking to help inform future designs. [source] TESTS OF SEX ALLOCATION THEORY IN SIMULTANEOUSLY HERMAPHRODITIC ANIMALSEVOLUTION, Issue 6 2009Lukas Schärer Sex allocation is a crucial life-history parameter in all sexual organisms. Over the last decades a body of evolutionary theory, sex allocation theory, was developed, which has yielded capital insight into the evolution of optimal sex allocation patterns and adaptive evolution in general. Most empirical work, however, has focused on species with separate sexes. Here I review sex allocation theory for simultaneous hermaphrodites and summarize over 50 empirical studies, which have aimed at evaluating this theory in a diversity of simultaneous hermaphrodites spanning nine animal phyla. These studies have yielded considerable qualitative support for several predictions of sex allocation theory, such as a female-biased sex allocation when the number of mates is limited, and a shift toward a more male-biased sex allocation with increasing numbers of mates. In contrast, many fundamental assumptions, such as the trade-off between male and female allocation, and numerous predictions, such as brooding limiting the returns from female allocation, are still poorly supported. Measuring sex allocation in simultaneously hermaphroditic animals remains experimentally demanding, which renders evaluation of more quantitative predictions a challenging task. I identify the main questions that need to be addressed and point to promising avenues for future research. [source] DO WE NEED AN EXTENDED EVOLUTIONARY SYNTHESIS?EVOLUTION, Issue 12 2007Massimo Pigliucci The Modern Synthesis (MS) is the current paradigm in evolutionary biology. It was actually built by expanding on the conceptual foundations laid out by its predecessors, Darwinism and neo-Darwinism. For sometime now there has been talk of a new Extended Evolutionary Synthesis (EES), and this article begins to outline why we may need such an extension, and how it may come about. As philosopher Karl Popper has noticed, the current evolutionary theory is a theory of genes, and we still lack a theory of forms. The field began, in fact, as a theory of forms in Darwin's days, and the major goal that an EES will aim for is a unification of our theories of genes and of forms. This may be achieved through an organic grafting of novel concepts onto the foundational structure of the MS, particularly evolvability, phenotypic plasticity, epigenetic inheritance, complexity theory, and the theory of evolution in highly dimensional adaptive landscapes. [source] A CENTENNIAL CELEBRATION FOR QUANTITATIVE GENETICSEVOLUTION, Issue 5 2007Derek A. Roff Quantitative genetics is at or is fast approaching its centennial. In this perspective I consider five current issues pertinent to the application of quantitative genetics to evolutionary theory. First, I discuss the utility of a quantitative genetic perspective in describing genetic variation at two very different levels of resolution, (1) in natural, free-ranging populations and (2) to describe variation at the level of DNA transcription. Whereas quantitative genetics can serve as a very useful descriptor of genetic variation, its greater usefulness is in predicting evolutionary change, particularly when used in the first instance (wild populations). Second, I review the contributions of Quantitative trait loci (QLT) analysis in determining the number of loci and distribution of their genetic effects, the possible importance of identifying specific genes, and the ability of the multivariate breeder's equation to predict the results of bivariate selection experiments. QLT analyses appear to indicate that genetic effects are skewed, that at least 20 loci are generally involved, with an unknown number of alleles, and that a few loci have major effects. However, epistatic effects are common, which means that such loci might not have population-wide major effects: this question waits upon (QTL) analyses conducted on more than a few inbred lines. Third, I examine the importance of research into the action of specific genes on traits. Although great progress has been made in identifying specific genes contributing to trait variation, the high level of gene interactions underlying quantitative traits makes it unlikely that in the near future we will have mechanistic models for such traits, or that these would have greater predictive power than quantitative genetic models. In the fourth section I present evidence that the results of bivariate selection experiments when selection is antagonistic to the genetic covariance are frequently not well predicted by the multivariate breeder's equation. Bivariate experiments that combine both selection and functional analyses are urgently needed. Finally, I discuss the importance of gaining more insight, both theoretical and empirical, on the evolution of the G and P matrices. [source] THE MUTATION MATRIX AND THE EVOLUTION OF EVOLVABILITYEVOLUTION, Issue 4 2007Adam G. Jones Evolvability is a key characteristic of any evolving system, and the concept of evolvability serves as a unifying theme in a wide range of disciplines related to evolutionary theory. The field of quantitative genetics provides a framework for the exploration of evolvability with the promise to produce insights of global importance. With respect to the quantitative genetics of biological systems, the parameters most relevant to evolvability are the G -matrix, which describes the standing additive genetic variances and covariances for a suite of traits, and the M -matrix, which describes the effects of new mutations on genetic variances and covariances. A population's immediate response to selection is governed by the G -matrix. However, evolvability is also concerned with the ability of mutational processes to produce adaptive variants, and consequently the M -matrix is a crucial quantitative genetic parameter. Here, we explore the evolution of evolvability by using analytical theory and simulation-based models to examine the evolution of the mutational correlation, r,, the key parameter determining the nature of genetic constraints imposed by M. The model uses a diploid, sexually reproducing population of finite size experiencing stabilizing selection on a two-trait phenotype. We assume that the mutational correlation is a third quantitative trait determined by multiple additive loci. An individual's value of the mutational correlation trait determines the correlation between pleiotropic effects of new alleles when they arise in that individual. Our results show that the mutational correlation, despite the fact that it is not involved directly in the specification of an individual's fitness, does evolve in response to selection on the bivariate phenotype. The mutational variance exhibits a weak tendency to evolve to produce alignment of the M -matrix with the adaptive landscape, but is prone to erratic fluctuations as a consequence of genetic drift. The interpretation of this result is that the evolvability of the population is capable of a response to selection, and whether this response results in an increase or decrease in evolvability depends on the way in which the bivariate phenotypic optimum is expected to move. Interestingly, both analytical and simulation results show that the mutational correlation experiences disruptive selection, with local fitness maxima at ,1 and +1. Genetic drift counteracts the tendency for the mutational correlation to persist at these extreme values, however. Our results also show that an evolving M -matrix tends to increase stability of the G -matrix under most circumstances. Previous studies of G -matrix stability, which assume nonevolving M -matrices, consequently may overestimate the level of instability of G relative to what might be expected in natural systems. Overall, our results indicate that evolvability can evolve in natural systems in a way that tends to result in alignment of the G -matrix, the M -matrix, and the adaptive landscape, and that such evolution tends to stabilize the G -matrix over evolutionary time. [source] HOST LIFE SPAN AND THE EVOLUTION OF RESISTANCE CHARACTERISTICSEVOLUTION, Issue 1 2007Martin R. Miller There is a wide variety of resistance mechanisms that hosts may evolve in response to their parasites. These can be functionally classified as avoidance (lower probability of becoming infected), recovery (faster rate of clearance), tolerance (reduced death rate when infected), or acquired immunity. It is commonly thought that longer lived organisms should invest more in costly resistance. We show that due to epidemiological feedbacks the situation is often more complex. Using evolutionary theory we examine how the optimal investment in costly resistance varies with life span in a broad range of scenarios. In the absence of acquired immunity, longer lived populations do generally invest more in resistance. If hosts have acquired immunity, the optimal resistance may either increase or decrease with increasing life span. In addition, there may be evolutionary bistability with high and low investments in avoidance or tolerance. The optimal investment in the duration of acquired immunity always increases with life span, and due to bistability, shorter lived hosts may commonly not evolve any immunity. In contrast, the optimal investment in the probability of acquiring immunity initially increases and then decreases with life span. Our results have important implications for the evolution of invertebrate and vertebrate immunity, and for the evolution of acquired immunity itself. [source] A GENERAL MULTIVARIATE EXTENSION OF FISHER'S GEOMETRICAL MODEL AND THE DISTRIBUTION OF MUTATION FITNESS EFFECTS ACROSS SPECIESEVOLUTION, Issue 5 2006Guillaume Martin Abstract The evolution of complex organisms is a puzzle for evolutionary theory because beneficial mutations should be less frequent in complex organisms, an effect termed "cost of complexity." However, little is known about how the distribution of mutation fitness effects (f(s)) varies across genomes. The main theoretical framework to address this issue is Fisher's geometric model and related phenotypic landscape models. However, it suffers from several restrictive assumptions. In this paper, we intend to show how several of these limitations may be overcome. We then propose a model of f(s) that extends Fisher's model to account for arbitrary mutational and selective interactions among n traits. We show that these interactions result in f(s) that would be predicted by a much smaller number of independent traits. We test our predictions by comparing empirical f(s) across species of various gene numbers as a surrogate to complexity. This survey reveals, as predicted, that mutations tend to be more deleterious, less variable, and less skewed in higher organisms. However, only limited difference in the shape of f(s) is observed from Escherichia coli to nematodes or fruit flies, a pattern consistent with a model of random phenotypic interactions across many traits. Overall, these results suggest that there may be a cost to phenotypic complexity although much weaker than previously suggested by earlier theoretical works. More generally, the model seems to qualitatively capture and possibly explain the variation of f(s) from lower to higher organisms, which opens a large array of potential applications in evolutionary genetics. [source] PHYLOGENETIC RELATIONSHIPS AND MORPHOLOGICAL DIVERSITY IN DARWIN'S FINCHES AND THEIR RELATIVESEVOLUTION, Issue 6 2002Kevin J. Burns Abstract Despite the importance of Darwin's finches to the development of evolutionary theory, the origin of the group has only recently been examined using a rigorous, phylogenetic methodology that includes many potential outgroups. Knowing the evolutionary relationships of Darwin's finches to other birds is important for understanding the context from which this adaptive radiation arose. Here we show that analysis of mitochondrial DNA sequence data from the cytochrome b gene confirm that Darwin's finches are monophyletic. In addition, many taxa previously proposed as the sister taxon to Darwin's finches can be excluded as their closest living relative. Darwin's finches are part of a well-supported monophyletic group of species, all of which build a domed nest. All but two of the non-Darwin's finches included in this clade occur on Caribbean islands and most are Caribbean endemics. These close relatives of Darwin's finches show a diversity of bill types and feeding behaviors similar to that observed among Darwin's finches themselves. Recent studies have shown that adaptive evolution in Darwin's finches occurred relatively quickly. Our data show that among the relatives of Darwin's finches, the evolution of bill diversity was also rapid and extensive. [source] | ||||||||||||||||||||||||||||||||||||||||