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Evolutionary Biologists (evolutionary + biologist)
Selected AbstractsSYNTHESIS: Evolutionary consequences of fishing and their implications for salmonEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 2 2008Jeffrey J. Hard Abstract We review the evidence for fisheries-induced evolution in anadromous salmonids. Salmon are exposed to a variety of fishing gears and intensities as immature or maturing individuals. We evaluate the evidence that fishing is causing evolutionary changes to traits including body size, migration timing and age of maturation, and we discuss the implications for fisheries and conservation. Few studies have fully evaluated the ingredients of fisheries-induced evolution: selection intensity, genetic variability, correlation among traits under selection, and response to selection. Most studies are limited in their ability to separate genetic responses from phenotypic plasticity, and environmental change complicates interpretation. However, strong evidence for selection intensity and for genetic variability in salmon fitness traits indicates that fishing can cause detectable evolution within ten or fewer generations. Evolutionary issues are therefore meaningful considerations in salmon fishery management. Evolutionary biologists have rarely been involved in the development of salmon fishing policy, yet evolutionary biology is relevant to the long-term success of fisheries. Future management might consider fishing policy to (i) allow experimental testing of evolutionary responses to exploitation and (ii) improve the long-term sustainability of the fishery by mitigating unfavorable evolutionary responses to fishing. We provide suggestions for how this might be done. [source] Evolution on oceanic islands: molecular phylogenetic approaches to understanding pattern and processMOLECULAR ECOLOGY, Issue 6 2002B. C. Emerson Abstract By their very nature oceanic island ecosystems offer great opportunities for the study of evolution and have for a long time been recognized as natural laboratories for studying evolution owing to their discrete geographical nature and diversity of species and habitats. The development of molecular genetic methods for phylogenetic reconstruction has been a significant advance for evolutionary biologists, providing a tool for answering questions about the diversity among the flora and fauna on such islands. These questions relate to both the origin and causes of species diversity both within an archipelago and on individual islands. Within a phylogenetic framework one can answer fundamental questions such as whether ecologically and/or morphologically similar species on different islands are the result of island colonization or convergent evolution. Testing hypotheses about ages of the individual species groups or entire community assemblages is also possible within a phylogenetic framework. Evolutionary biologists and ecologists are increasingly turning to molecular phylogenetics for studying oceanic island plant and animal communities and it is important to review what has been attempted and achieved so far, with some cautionary notes about interpreting phylogeographical pattern on oceanic islands. [source] Teaching & Learning Guide for: Can a Darwinian Be a Christian?RELIGION COMPASS (ELECTRONIC), Issue 3 2008Gregory W. Dawes Author's Introduction The article was provoked by recent discussion of the so-called ,conflict thesis': the idea that the Christian faith and the findings of modern science are necessarily at odds. This thesis is generally attributed to John William Draper (1811,1882) and Andrew Dickson White (1832,1918). Recent opposition to their work dates from a 1979 publication by James Moore. Moore argues that the warfare metaphor employed by Draper and White misrepresents the historical reality, by suggesting that the religion and science debates were clashes between distinct groups of people who were sharply polarized and violently antagonistic. Since then, similar criticisms have been made by historians, such as David Livingstone, Ronald Numbers, and David Lindberg. A key question here is: what does the conflict thesis entail? If it holds that Christian thinkers have invariably opposed scientific progress, while the defenders of science have been non-believers, it would be demonstrably false. But there exist more interesting forms of conflict thesis, which are philosophical rather than historical. These suggest that there is some tension between what Christians have traditionally believed and the findings of modern science, particularly Darwin's theory of evolution by natural selection. Even if the two are not, strictly speaking, incompatible, the truth of one may constitute evidence against the truth of the other. Darwin's theory also undercuts traditional arguments from design, and highlights the epistemological divide between religious and scientific conceptions of authority. Online Materials The following sites contain audio and video files, as well as text and images. 1. http://www.meta-library.net/history/intro-frame.html This is a useful overview of the historical debate by Ronald Numbers, with links to other sites. Most presenters follow Moore in opposing the conflict thesis, narrowly defined, but neglect the conflicts that my article highlights. 2. http://www.pbs.org/wgbh/nova/id/program.html Here one can view an excellent, 2-h PBS television documentary on the Dover, Pennsylvania trial in December 2005 regarding the teaching of ,intelligent design' (ID) in public schools. 3. http://www.butler.edu/clergyproject/rel_evol_sun.htm This is a letter signed by more than 11,000 clergy, arguing that there is no conflict between religion and science, and encouraging (among other things) the liturgical celebration of evolution by natural selection. 4. http://www.discovery.org/csc/ At the other end of the theological spectrum, this is the website of the Discovery Institute, devoted to opposing Darwinism and promoting ,intelligent design' (ID). Controversially, it presents ID as a scientific theory, rather than a religious doctrine. 5. http://www.asa3.org/ Somewhere between the Clergy Letter Project and the Discovery Institute lies the American Scientific Affiliation (ASA). The ASA ,does not take a position when there is honest disagreement between Christians', so it embraces a variety of perspectives. Sample Syllabus The following could form the basis for a graduate seminar on religion and science, focusing on the Darwinian controversies. One could, for instance, devote two classes to each of these topics. 1. The Draper-White Thesis I recommend reading extracts from the two writers thought to be responsible for the conflict thesis, to establish what each actually said. John William Draper, The History of the Conflict between Religion and Science, International Scientific Series 13 (London: Henry S. King & Co., 1875), chap. 8. Andrew Dickson White, A History of the Warfare of Science with Theology in Christendom (1896; New York, NY: Dover Publications, 1960), vol. 1, chap. 1. 2. Criticism of the Draper-White Thesis Either of the following readings from historians critical of Draper and White's work would be a useful starting point for discussion. James R. Moore, The Post-Darwinian Controversies: A Study of the Protestant Struggle to Come to Terms with Darwin in Great Britain and America, 1870,1900 (Cambridge: Cambridge University Press, 1979), chap. 1. David N. Livingstone, ,Re-placing Darwinism and Christianity', in David C. Lindberg and Ronald L. Numbers (eds.), When Science and Christianity Meet, pp. 183,202 (Chicago, IL: University of Chicago Press, 2003). 3. The Incompatibility Thesis Many authors attempt to show that Darwinism and Christianity and compatible. But it would be useful to examine Pope John Paul II's statement on this topic, along with some responses by biologists and philosophers. John Paul II, ,The Pope's Message on Evolution and Four Commentaries', The Quarterly Review of Biology, 72:4 (1997): 375,406. 4. The Evidential Thesis Students might enjoy reading and discussing the following article by a leading evolutionary biologist. George C. Williams, ,Mother Nature Is a Wicked Old Witch', in Matthew H. Nitecki and Doris V. Nitecki (eds.), Evolutionary Ethics, 217,31 (Albany, NY: State University of New York Press, 1993). 5. The Replacement Thesis This is an important but often neglected book. Students would benefit from reading at least the first chapter. Neal C. Gillespie, Charles Darwin and the Problem of Creation (Chicago, IL: University of Chicago Press, 1979), chap. 1. 6. The Faith and Reason Thesis The following article by a well-known historian and philosopher of science touches on some of the key issues. Ernan McMullin, ,Evolution and Special Creation', Zygon 28:3 (1993): 299,335. Focus Questions 1There exist many Christian thinkers who accept Darwin's theory of evolution by natural selection. Does that mean there is no conflict between Darwinism and Christianity? 2Taken at face value, Genesis 1,3 tells the story of the origins of the world and of human beings. What aspects of that story would you consider essential to the Christian faith? 3If we have an entirely natural explanation of the origins of complex living organisms, do we still have reasons to believe in a creator God? 4If God could have created complex living beings by a simple command, why would he choose a lengthy and wasteful process such as natural selection? 5Could a Christian regard the existence of God in the same way as a scientific hypothesis, that is to say, to be accepted only in so far as it is supported by the evidence? Seminar Activity I would suggest a debate, in which students sympathetic to the creationist position are asked to defend Darwin's theory, while students sympathetic to evolution are asked to argue against it. [source] Molecular systematics and population genetics of biological invasions: towards a better understanding of invasive species managementANNALS OF APPLIED BIOLOGY, Issue 1 2009J. Le Roux Abstract The study of population genetics of invasive species offers opportunities to investigate rapid evolutionary processes at work, and while the ecology of biological invasions has enjoyed extensive attention in the past, the recentness of molecular techniques makes their application in invasion ecology a fairly new approach. Despite this, molecular biology has already proved powerful in inferring aspects not only relevant to the evolutionary biologist but also to those concerned with invasive species management. Here, we review the different molecular markers routinely used in such studies and their application(s) in addressing different questions in invasion ecology. We then review the current literature on molecular genetic studies aimed at improving management and the understanding of invasive species by resolving of taxonomic issues, elucidating geographical sources of invaders, detecting hybridisation and introgression, tracking dispersal and spread and assessing the importance of genetic diversity in invasion success. Finally, we make some suggestions for future research efforts in molecular ecology of biological invasions. [source] Assortative mating between adjacent populations of threespine stickleback (Gasterosteus aculeatus)ECOLOGY OF FRESHWATER FISH, Issue 1 2004R. J. Scott Abstract,,, The idea that sexual selection can lead to rapid evolution of premating isolation among independent populations (speciation) has been controversial, but is rapidly gaining acceptance among many evolutionary biologists as empirical examples accumulate. A survey of male signals and female preferences (mate recognition systems, MRSs) across the contact zone between divergent populations of threespine stickleback (Gasterosteus aculeatus) in Conner Creek, WA, revealed a spatial pattern of MRSs that is consistent with speciation via sexual selection. Females from locations that possessed melanic males preferred melanic males whereas females from populations possessing typical mosaic males (red chin, blue iris, and blue-green dorsum) preferred mosaic males. I argue that sensory drive sexual selection, acting through geographically varying spectral properties, is responsible for the observed population differences and premating isolation between the adjacent populations. [source] ADAPTIONISM,30 YEARS AFTER GOULD AND LEWONTINEVOLUTION, Issue 10 2009Rasmus Nielsen Gould and Lewontin's 30-year-old critique of adaptionism fundamentally changed the discourse of evolutionary biology. However, with the influx of new ideas and scientific traditions from genomics into evolutionary biology, the old adaptionist controversies are being recycled in a new context. The insight gained by evolutionary biologists, that functional differences cannot be equated to adaptive changes, has at times not been appreciated by the genomics community. In this comment, I argue that even in the presence of both functional data and evidence for selection from DNA sequence data, it is still difficult to construct strong arguments in favor of adaptation. However, despite the difficulties in establishing scientific arguments in favor of specific historic evolutionary events, there is still much to learn about evolution from genomic data. [source] INDIRECT GENETIC EFFECTS INFLUENCE ANTIPREDATOR BEHAVIOR IN GUPPIES: ESTIMATES OF THE COEFFICIENT OF INTERACTION PSI AND THE INHERITANCE OF RECIPROCITYEVOLUTION, Issue 7 2009Bronwyn H. Bleakley How and why cooperation evolves, particularly among nonrelatives, remains a major paradox for evolutionary biologists and behavioral ecologists. Although much attention has focused on fitness consequences associated with cooperating, relatively little is known about the second component of evolutionary change, the inheritance of cooperation or reciprocity. The genetics of behaviors that can only be expressed in the context of interactions are particularly difficult to describe because the relevant genes reside in multiple social partners. Indirect genetic effects (IGEs) describe the influence of genes carried in social partners on the phenotype of a focal individual and thus provide a novel approach to quantifying the genetics underlying interactions such as reciprocal cooperation. We used inbred lines of guppies and a novel application of IGE theory to describe the dual genetic control of predator inspection and social behavior, both classic models of reciprocity. We identified effects of focal strain, social group strain, and interactions between focal and group strains on variation in focal behavior. We measured ,, the coefficient of the interaction, which describes the degree to which an individual's phenotype is influenced by the phenotype of its social partners. The genetic identity of social partners substantially influences inspection behavior, measures of threat assessment, and schooling and does so in positively reinforcing manner. We therefore demonstrate strong IGEs for antipredator behavior that represent the genetic variation necessary for the evolution of reciprocity. [source] BROADENING THE APPLICATION OF EVOLUTIONARILY BASED GENETIC PEST MANAGEMENTEVOLUTION, Issue 2 2008Fred Gould Insect- and tick-vectored diseases such as malaria, dengue fever, and Lyme disease cause human suffering, and current approaches for prevention are not adequate. Invasive plants and animals such as Scotch broom, zebra mussels, and gypsy moths continue to cause environmental damage and economic losses in agriculture and forestry. Rodents transmit diseases and cause major pre- and postharvest losses, especially in less affluent countries. Each of these problems might benefit from the developing field of Genetic Pest Management that is conceptually based on principles of evolutionary biology. This article briefly describes the history of this field, new molecular tools in this field, and potential applications of those tools. There will be a need for evolutionary biologists to interact with researchers and practitioners in a variety of other fields to determine the most appropriate targets for genetic pest management, the most appropriate methods for specific targets, and the potential of natural selection to diminish the effectiveness of genetic pest management. In addition to producing environmentally sustainable pest management solutions, research efforts in this area could lead to new insights about the evolution of selfish genetic elements in natural systems and will provide students with the opportunity to develop a more sophisticated understanding of the role of evolutionary biology in solving societal problems. [source] HOW BRIGHT AND HOW NASTY: EXPLAINING DIVERSITY IN WARNING SIGNAL STRENGTHEVOLUTION, Issue 3 2007Michael P. Speed The conspicuous displays that warn predators of defenses carried by potential prey have been of interest to evolutionary biologists from the time of Wallace and Darwin to the present day. Although most studies implicitly assume that these "aposematic" warning signals simply indicate the presence of some repellent defense such as a toxin, it has been speculated that the intensity of the signal might reliably indicate the strength of defense so that, for example, the nastiest prey might "shout loudest" about their unprofitability. Recent phylogenetic and empirical studies of Dendrobatid frogs provide contradictory views, in one instance showing a positive correlation between toxin levels and conspicuousness, in another showing a breakdown of this relationship. In this paper we present an optimization model, which can potentially account for these divergent results. Our model locates the optimal values of defensive traits that are influenced by a range of costs and benefits. We show that optimal aposematic conspicuousness can be positively correlated with optimal prey toxicity, especially where population sizes and season lengths vary between species. In other cases, optimal aposematic conspicuousness may be negatively correlated with toxicity; this is especially the case when the marginal costs of aposematic displays vary between members of different populations. Finally, when displays incur no allocation costs there may be no single optimum value for aposematic conspicuousness, rather a large array of alternative forms of a display may have equal fitness. [source] WHY DOES A TRAIT EVOLVE MULTIPLE TIMES WITHIN A CLADE?EVOLUTION, Issue 1 2006REPEATED EVOLUTION OF SNAKELINE BODY FORM IN SQUAMATE REPTILES Abstract Why does a trait evolve repeatedly within a clade? When examining the evolution of a trait, evolutionary biologists typically focus on the selective advantages it may confer and the genetic and developmental mechanisms that allow it to vary. Although these factors may be necessary to explain why a trait evolves in a particular instance, they may not be sufficient to explain phylogenetic patterns of repeated evolution or conservatism. Instead, other factors may also be important, such as biogeography and competitive interactions. In squamate reptiles (lizards and snakes) a dramatic transition in body form has occurred repeatedly, from a fully limbed, lizardlike body form to a limbreduced, elongate, snakelike body form. We analyze this trait in a phylogenetic and biogeographic context to address why this transition occurred so frequently. We included 261 species for which morphometric data and molecular phylogenetic information were available. Among the included species, snakelike body form has evolved about 25 times. Most lineages of snakelike squamates belong to one of two ecomorphs, either short-tailed burrowers or long-tailed surface dwellers. The repeated origins of snakelike squamates appear to be associated with the in situ evolution of these two ecomorphs on different continental regions (including multiple origins of the burrowing morph within most continents), with very little dispersal of most limb-reduced lineages between continental regions. Overall, the number of repeated origins of snakelike morphology seems to depend on large-scale biogeographic patterns and community ecology, in addition to more traditional explanations (e.g., selection, development). [source] DO SUTURE ZONES EXIST?EVOLUTION, Issue 11 2004Nathan G. Swenson Abstract Remington (1968) argued that 13 suture zones exist in North America. Remington defined a suture zone as, "a band of geographic overlap between major biotic assemblages, including some pairs of species or semispecies which hybridize in the zone" (p. 322). Although initially controversial, the idea that suture zones exist has picked up momentum over the past decade, due largely to the phylogeographic work of Hewitt, Avise, and their colleagues. Nevertheless, the reality of suture zones has not yet been subjected to rigorous analysis using statistical and geographic information system (GIS) approaches. To test for the existence of Remington's suture zones, we first identified 117 terrestrial hybrid zones in Canada and the United States through a literature search for the key words "cline,""contact zone,""hybrid zone," and "hybridization" in articles published between 1970 and 2002. The 117 hybrid zones were mapped using a GIS approach and compared with a digitized version of Remington's original suture zone map. Overall, there does appear to be an association between hybrid zones and suture zones, but this association is largely attributable to clustering of hybrid zones in only two of the 13 suture zones recognized by Remington. The results suggest that evolutionary biologists should retain some skepticism toward Remington's suture zones. [source] FROM MICRO- TO MACROEVOLUTION THROUGH QUANTITATIVE GENETIC VARIATION: POSITIVE EVIDENCE FROM FIELD CRICKETSEVOLUTION, Issue 10 2004Mattieu Bégin Abstract . -Quantitative genetics has been introduced to evolutionary biologists with the suggestion that microevolution could be directly linked to macroevolutionary patterns using, among other parameters, the additive genetic variance/ covariance matrix (G) which is a statistical representation of genetic constraints to evolution. However, little is known concerning the rate and pattern of evolution of G in nature, and it is uncertain whether the constraining effect of G is important over evolutionary time scales. To address these issues, seven species of field crickets from the genera Gryllus and Teleogryllus were reared in the laboratory, and quantitative genetic parameters for morphological traits were estimated from each of them using a nested full-sibling family design. We used three statistical approaches (T method, Flury hierarchy, and Mantel test) to compare G matrices or genetic correlation matrices in a phylogenetic framework. Results showed that G matrices were generally similar across species, with occasional differences between some species. We suggest that G has evolved at a low rate, a conclusion strengthened by the consideration that part of the observed across-species variation in G can be explained by the effect of a genotype by environment interaction. The observed pattern of G matrix variation between species could not be predicted by either morphological trait values or phylogeny. The constraint hypothesis was tested by comparing the multivariate orientation of the reconstructed ancestral G matrix to the orientation of the across-species divergence matrix (D matrix, based on mean trait values). The D matrix mainly revealed divergence in size and, to a much smaller extent, in a shape component related to the ovipositor length. This pattern of species divergence was found to be predictable from the ancestral G matrix in agreement with the expectation of the constraint hypothesis. Overall, these results suggest that the G matrix seems to have an influence on species divergence, and that macroevolution can be predicted, at least qualitatively, from quantitative genetic theory. Alternative explanations are discussed. [source] Adaptation, extinction and global changeEVOLUTIONARY APPLICATIONS (ELECTRONIC), Issue 1 2008Graham Bell Abstract We discuss three interlinked issues: the natural pace of environmental change and adaptation, the likelihood that a population will adapt to a potentially lethal change, and adaptation to elevated CO2, the prime mover of global change. 1.,Environmental variability is governed by power laws showing that ln difference in conditions increases with ln elapsed time at a rate of 0.3,0.4. This leads to strong but fluctuating selection in many natural populations. 2.,The effect of repeated adverse change on mean fitness depends on its frequency rather than its severity. If the depression of mean fitness leads to population decline, however, severe stress may cause extinction. Evolutionary rescue from extinction requires abundant genetic variation or a high mutation supply rate, and thus a large population size. Although natural populations can sustain quite intense selection, they often fail to adapt to anthropogenic stresses such as pollution and acidification and instead become extinct. 3.,Experimental selection lines of algae show no specific adaptation to elevated CO2, but instead lose their carbon-concentrating mechanism through mutational degradation. This is likely to reduce the effectiveness of the oceanic carbon pump. Elevated CO2 is also likely to lead to changes in phytoplankton community composition, although it is not yet clear what these will be. We emphasize the importance of experimental evolution in understanding and predicting the biological response to global change. This will be one of the main tasks of evolutionary biologists in the coming decade. [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] Individual differences in allocation of funds in the dictator game associated with length of the arginine vasopressin 1a receptor RS3 promoter region and correlation between RS3 length and hippocampal mRNAGENES, BRAIN AND BEHAVIOR, Issue 3 2008A. Knafo Human altruism is a widespread phenomenon that puzzled evolutionary biologists since Darwin. Economic games illustrate human altruism by showing that behavior deviates from economic predictions of profit maximization. A game that most plainly shows this altruistic tendency is the Dictator Game. We hypothesized that human altruistic behavior is to some extent hardwired and that a likely candidate that may contribute to individual differences in altruistic behavior is the arginine vasopressin 1a (AVPR1a) receptor that in some mammals such as the vole has a profound impact on affiliative behaviors. In the current investigation, 203 male and female university students played an online version of the Dictator Game, for real money payoffs. All subjects and their parents were genotyped for AVPR1a RS1 and RS3 promoter-region repeat polymorphisms. Parents did not participate in online game playing. As variation in the length of a repetitive element in the vole AVPR1a promoter region is associated with differences in social behavior, we examined the relationship between RS1 and RS3 repeat length (base pairs) and allocation sums. Participants with short versions (308,325 bp) of the AVPR1a RS3 repeat allocated significantly (likelihood ratio = 14.75, P = 0.001, df = 2) fewer shekels to the ,other' than participants with long versions (327,343 bp). We also implemented a family-based association test, UNPHASED, to confirm and validate the correlation between the AVPR1a RS3 repeat and monetary allocations in the dictator game. Dictator game allocations were significantly associated with the RS3 repeat (global P value: likelihood ratio ,2 = 11.73, df = 4, P = 0.019). The association between the AVPR1a RS3 repeat and altruism was also confirmed using two self-report scales (the Bardi,Schwartz Universalism and Benevolence Value-expressive Behavior scales). RS3 long alleles were associated with higher scores on both measures. Finally, long AVPR1a RS3 repeats were associated with higher AVPR1a human post-mortem hippocampal messenger RNA levels than short RS3 repeats (one-way analysis of variance (ANOVA): F = 15.04, P = 0.001, df = 14) suggesting a functional molecular genetic basis for the observation that participants with the long RS3 repeats allocate more money than participants with the short repeats. This is the first investigation showing that a common human polymorphism, with antecedents in lower mammals, contributes to decision making in an economic game. The finding that the same gene contributing to social bonding in lower animals also appears to operate similarly in human behavior suggests a common evolutionary mechanism. [source] Plants intertwine fluvial landform dynamics with ecological succession and natural selection: a niche construction perspective for riparian systemsGLOBAL ECOLOGY, Issue 4 2009Dov Corenblit ABSTRACT Aim To contribute to the development of a macroevolutionary framework for riparian systems, reinforcing conceptual linkages between earth surface processes and biological and ecological processes. Location Riparian systems. Methods Literature review leading to an original proposition for perceiving the functioning of riparian systems in a new and different way. Results Riparian systems provide diverse landforms, habitats and resources for animals and plants. Certain organisms, defined as ,ecosystem engineers', significantly create and modify the physical components of riparian systems. Many studies have highlighted such engineering effects by animals on riparian systems, but the identification and understanding of the effects and responses of plants within fluvial corridors have emerged only recently. The modulation of matter, resources and energy flows by engineering plants helps establish characteristic sequences of fluvial landform creation and maintenance associated with synergetic ecological successions. We relate this process to the concept of niche construction, developed mainly by evolutionary biologists. Feedbacks between adaptive responses of riparian plants to flow regime and adjusting effects on biostabilization and bioconstruction are discussed in the context of niche construction at the scale of ecological succession and the evolution of organisms. Main conclusions Our conceptualization forges an integrated approach for understanding vegetated fluvial systems from a macroevolutionary perspective, for elucidating riparian ecosystem dynamics and potentially for establishing long-term stream conservation and restoration strategies. [source] Regeneration as an evolutionary variableJOURNAL OF ANATOMY, Issue 1-2 2001JEREMY P. BROCKES abstract Regeneration poses a distinctive set of problems for evolutionary biologists, but there has been little substantive progress since these issues were clearly outlined in the monograph of T. H. Morgan (1901). The champions at regeneration among vertebrates are the urodele amphibians such as the newt, and we tend to regard urodele regeneration as an exceptional attribute. The ability to regenerate large sections of the body plan is widespread in metazoan phylogeny, although it is not universal. It is striking that in phylogenetic contexts where regeneration occurs, closely related species are observed which do not possess this ability. It is a challenge to reconcile such variation between species with a conventional selective interpretation of regeneration. The critical hypothesis from phylogenetic analysis is that regeneration is a basic, primordial attribute of metazoans rather than a mechanism which has evolved independently in a variety of contexts. In order to explain its absence in closely related species, it is postulated to be lost secondarily for reasons which are not understood. Our approach to this question is to compare a differentiated newt cell with its mammalian counterpart in respect of the plasticity of differentiation. [source] Molecular clocks keep dispersal hypotheses afloat: evidence for trans-Atlantic rafting by rodentsJOURNAL OF BIOGEOGRAPHY, Issue 2 2010Diane L. Rowe Abstract Aim, In order to resolve disputed biogeographical histories of biota with Gondwanan continental distributions, and to assess the null hypothesis of vicariance, it is imperative that a robust geological time-frame be established. As an example, the sudden and coincident appearance of hystricognath rodents (Rodentia: Hystricognathi) on both the African and South American continents has been an irreconcilable controversy for evolutionary biologists, presenting enigmas for both Gondwanan vicariance and Late Eocene dispersal hypotheses. In an attempt to resolve this discordance, we aim to provide a more robust phylogenetic hypothesis and improve divergence-date estimates, which are essential to assessing the null hypothesis of vicariance biogeography. Location, The primary centres of distribution are in Africa and South America. Methods, We implemented parsimony, maximum-likelihood and Bayesian methods to generate a phylogeny of 37 hystricognath taxa, the most comprehensive taxonomic sampling of this group to date, on the basis of two nuclear gene regions. To increase phylogenetic resolution at the basal nodes, these data were combined with previously published data for six additional nuclear gene regions. Divergence dates were estimated using two relaxed-molecular-clock methods, Bayesian multidivtime and nonparametric rate smoothing. Results, Our data do not support reciprocal monophyly of African and South American lineages. Indeed, Old World porcupines (i.e. Hystricomorpha) appear to be more closely related to New World lineages (i.e. Caviomorpha) than to other Old World families (i.e. Bathyergidae, Petromuridae and Thryonomyidae). The divergence between the monophyletic assemblage of South American lineages and its Old World ancestor was estimated to have occurred c. 50 Ma. Main conclusions, Our phylogenetic hypothesis and divergence-date estimates are strongly at odds with Gondwanan-vicariance isolating mechanisms. In contrast, our data suggest that transoceanic dispersal has played a significant role in governing the contemporary distribution of hystricognath rodents. Molecular-clock analyses imply a trans-Tethys dispersal event, broadly confined to the Late Cretaceous, and trans-Atlantic dispersal within the Early Eocene. Our analyses also imply that the use of the oldest known South American rodent fossil as a calibration point has biased molecular-clock inferences. [source] The biology of insularity: an introductionJOURNAL OF BIOGEOGRAPHY, Issue 5-6 2002Donald R. Drake Insular environments, ranging from oceanic islands to fragments of once-contiguous natural systems, have long been used by biologists to test basic principles of ecology, evolution and biogeography. More recently, insular environments have figured prominently in conservation ecology, where the aim has usually been to conserve species or assemblages unique to isolated habitats. Improving the level of communication among the evolutionary biologists, theoretical ecologists and conservation biologists who study insular biotas will work to the benefit of all. This volume was inspired by a recent conference on the ecology of insular biotas, in which participants from a wide range of disciplines came together to compare ecological processes across a variety of taxonomic groups inhabiting a wide range of isolated environments. In this introduction, we point out the themes underlying these very diverse contributions. First we elaborate on the value of islands for elucidating processes underlying ecosystem functioning, population dynamics of reintroduced species, and restoration of disturbed habitats, and emphasize those areas where the use of islands could be expanded. The second section focuses on the link between ecology and evolutionary processes in insular systems and includes examples from oceanic islands, naturally patchy habitats and recently fragmented habitats. The third section illustrates some of the ways that invasive alien species on oceanic islands affect plant,animal mutualisms, particularly seed dispersal and pollination. The final section, on consequences of habitat fragmentation, focuses mainly on studies that describe the consequences that fragmentation has for plants and animals as they are forced into artificially insular environments. We close with a study that points out the differences among types of insular systems and identifies gaps in our knowledge of insular biotas, particularly the importance of explicitly incorporating patch type, age and patch,matrix contrasts in research. Finally, we recommend a greater emphasis on linking ecological theory and applied research, and improving communication between those who ask basic ecological questions and those who use insular systems for conservation. [source] What, if anything, is sympatric speciation?JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 6 2008B. M. FITZPATRICK Abstract Sympatric speciation has always fascinated evolutionary biologists, and for good reason; it pits diversifying selection directly against the tendency of sexual reproduction to homogenize populations. However, different investigators have used different definitions of sympatric speciation and different criteria for diagnosing cases of sympatric speciation. Here, we explore some of the definitions that have been used in empirical and theoretical studies. Definitions based on biogeography do not always produce the same conclusions as definitions based on population genetics. The most precise definitions make sympatric speciation an infinitesimal end point of a continuum. Because it is virtually impossible to demonstrate the occurrence of such a theoretical extreme, we argue that testing whether a case fits a particular definition is less informative than evaluating the biological processes affecting divergence. We do not deny the importance of geographical context for understanding divergence. Rather, we believe this context can be better understood by modelling and measuring quantities, such as gene flow and selection, rather than assigning cases to discrete categories like sympatric and allopatric speciation. [source] Bayesian approaches in evolutionary quantitative geneticsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2008R. B. O'HARA Abstract The study of evolutionary quantitative genetics has been advanced by the use of methods developed in animal and plant breeding. These methods have proved to be very useful, but they have some shortcomings when used in the study of wild populations and evolutionary questions. Problems arise from the small size of data sets typical of evolutionary studies, and the additional complexity of the questions asked by evolutionary biologists. Here, we advocate the use of Bayesian methods to overcome these and related problems. Bayesian methods naturally allow errors in parameter estimates to propagate through a model and can also be written as a graphical model, giving them an inherent flexibility. As packages for fitting Bayesian animal models are developed, we expect the application of Bayesian methods to evolutionary quantitative genetics to grow, particularly as genomic information becomes more and more associated with environmental data. [source] Mechanisms of pathogenesis and the evolution of parasite virulenceJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 2 2008S. A. FRANK Abstract When studying how much a parasite harms its host, evolutionary biologists turn to the evolutionary theory of virulence. That theory has been successful in predicting how parasite virulence evolves in response to changes in epidemiological conditions of parasite transmission or to perturbations induced by drug treatments. The evolutionary theory of virulence is, however, nearly silent about the expected differences in virulence between different species of parasite. Why, for example, is anthrax so virulent, whereas closely related bacterial species cause little harm? The evolutionary theory might address such comparisons by analysing differences in tradeoffs between parasite fitness components: transmission as a measure of parasite fecundity, clearance as a measure of parasite lifespan and virulence as another measure that delimits parasite survival within a host. However, even crude quantitative estimates of such tradeoffs remain beyond reach in all but the most controlled of experimental conditions. Here, we argue that the great recent advances in the molecular study of pathogenesis provide a way forward. In light of those mechanistic studies, we analyse the relative sensitivity of tradeoffs between components of parasite fitness. We argue that pathogenic mechanisms that manipulate host immunity or escape from host defences have particularly high sensitivity to parasite fitness and thus dominate as causes of parasite virulence. The high sensitivity of immunomodulation and immune escape arise because those mechanisms affect parasite survival within the host, the most sensitive of fitness components. In our view, relating the sensitivity of pathogenic mechanisms to fitness components will provide a way to build a much richer and more general theory of parasite virulence. [source] 20 Questions on Adaptive DynamicsJOURNAL OF EVOLUTIONARY BIOLOGY, Issue 5 2005D. WAXMAN Abstract Adaptive Dynamics is an approach to studying evolutionary change when fitness is density or frequency dependent. Modern papers identifying themselves as using this approach first appeared in the 1990s, and have greatly increased up to the present. However, because of the rather technical nature of many of the papers, the approach is not widely known or understood by evolutionary biologists. In this review we aim to remedy this situation by outlining the methodology and then examining its strengths and weaknesses. We carry this out by posing and answering 20 key questions on Adaptive Dynamics. We conclude that Adaptive Dynamics provides a set of useful approximations for studying various evolutionary questions. However, as with any approximate method, conclusions based on Adaptive Dynamics are valid only under some restrictions that we discuss. [source] Hemostasis and irreducible complexityJOURNAL OF THROMBOSIS AND HAEMOSTASIS, Issue 2 2003W. C. Aird Summary., Coagulation evolved as a means to stem the loss of blood and to defend against pathogens. The complexity of the clotting cascade has been cited as evidence for the existence of divine intervention. The objective of this review is to draw on the debate between creationists and evolutionary biologists to highlight important evolutionary principles that underlie the hemostatic mechanism. I propose the following: (a) as with all biological systems, the hemostatic mechanism displays non-linear complexity; (b) the cellular response represents primary hemostasis owing to its place in the evolutionary time scale and functional importance; and (c) the rapid evolution of the hemostatic mechanism in vertebrates is testimony to the power and versatility of gene duplications and exon shuffling. [source] Adapting to winter in wheat: a long-term study follows parallel phenotypic and genetic changes in three experimental wheat populationsMOLECULAR ECOLOGY, Issue 3 2008JARED L. STRASBURG Abstract Drawing a direct connection between adaptive evolution at the phenotypic level and underlying genetic factors has long been a major goal of evolutionary biologists, but the genetic characterization of adaptive traits in natural populations is notoriously difficult. The study of evolution in experimental populations offers some help , initial conditions are known and changes can be tracked for extended periods under conditions more controlled than wild populations and more realistic than laboratory or greenhouse experiments. In this issue of Molecular Ecology, researchers studying experimental wheat populations over a 12-year period have demonstrated evolution in a major adaptive trait, flowering time, and parallel changes in underlying genetic variation (Rhonéet al. 2008). Their work suggests that cis -regulatory mutations at a single gene may explain most of the flowering time variation in these populations. [source] Evolutionary genetics and biogeographic structure of Rhizobium gallicum sensu lato, a widely distributed bacterial symbiont of diverse legumesMOLECULAR ECOLOGY, Issue 13 2005CLAUDIA SILVA Abstract We used phylogenetic and population genetics approaches to evaluate the importance of the evolutionary forces on shaping the genetic structure of Rhizobium gallicum and related species. We analysed 54 strains from several populations distributed in the Northern Hemisphere, using nucleotide sequences of three ,core' chromosomal genes (rrs, glnII and atpD) and two ,auxiliary' symbiotic genes (nifH and nodB) to elucidate the biogeographic history of the species and symbiotic ecotypes (biovarieties) within species. The analyses revealed that strains classified as Rhizobium mongolense and Rhizobium yanglingense belong to the chromosomal evolutionary lineage of R. gallicum and harbour symbiotic genes corresponding to a new biovar; we propose their reclassification as R. gallicum bv. orientale. The comparison of the chromosomal and symbiotic genes revealed evidence of lateral transfer of symbiotic information within and across species. Genetic differentiation analyses based on the chromosomal protein-coding genes revealed a biogeographic pattern with three main populations, whereas the 16S rDNA sequences did not resolve that biogeographic pattern. Both the phylogenetic and population genetic analyses showed evidence of recombination at the rrs locus. We discuss our results in the light of the contrasting views of bacterial species expressed by microbial taxonomist and evolutionary biologists. [source] INVITED REVIEW: Quantitative trait locus mapping in natural populations: progress, caveats and future directionsMOLECULAR ECOLOGY, Issue 2 2005JON SLATE Abstract Over the last 15 years quantitative trait locus (QTL) mapping has become a popular method for understanding the genetic basis of continuous variation in a variety of systems. For example, the technique is now an integral tool in medical genetics, livestock production, plant breeding and population genetics of model organisms. Ten years ago, it was suggested that the method could be used to understand continuous variation in natural populations. In this review I: (i) clarify what is meant by natural population in the QTL context, (ii) discuss whether evolutionary biologists have successfully mapped QTL in natural populations, (iii) highlight some of the questions that have been addressed by QTL mapping in natural populations, (iv) describe how QTL mapping can be conducted in unmanipulated natural populations, (v) highlight some of the limitations of QTL mapping and (vi) try to predict some future directions for QTL mapping in natural populations. [source] Evolution on oceanic islands: molecular phylogenetic approaches to understanding pattern and processMOLECULAR ECOLOGY, Issue 6 2002B. C. Emerson Abstract By their very nature oceanic island ecosystems offer great opportunities for the study of evolution and have for a long time been recognized as natural laboratories for studying evolution owing to their discrete geographical nature and diversity of species and habitats. The development of molecular genetic methods for phylogenetic reconstruction has been a significant advance for evolutionary biologists, providing a tool for answering questions about the diversity among the flora and fauna on such islands. These questions relate to both the origin and causes of species diversity both within an archipelago and on individual islands. Within a phylogenetic framework one can answer fundamental questions such as whether ecologically and/or morphologically similar species on different islands are the result of island colonization or convergent evolution. Testing hypotheses about ages of the individual species groups or entire community assemblages is also possible within a phylogenetic framework. Evolutionary biologists and ecologists are increasingly turning to molecular phylogenetics for studying oceanic island plant and animal communities and it is important to review what has been attempted and achieved so far, with some cautionary notes about interpreting phylogeographical pattern on oceanic islands. [source] Vouchering DNA-barcoded specimens: test of a nondestructive extraction protocol for terrestrial arthropodsMOLECULAR ECOLOGY RESOURCES, Issue 6 2007DANIEL L. ROWLEY Abstract Morphology-based keys support accurate identification of many taxa. However, identification can be difficult for taxa that are either not well studied, very small, members of cryptic species complexes, or represented by immature stages. For such cases, DNA barcodes may provide diagnostic characters. Ecologists and evolutionary biologists deposit museum vouchers to document the species studied in their research. If DNA barcodes are to be used for identification, then both the DNA and the specimen from which it was extracted should be vouchered. We describe a protocol for the nondestructive extraction of DNA from terrestrial arthropods, using as examples members of the orders Acarina, Araneae, Coleoptera, Diptera, and Hymenoptera chosen to represent the ranges in size, overall sclerotization, and delicacy of key morphological characters in the group. We successfully extracted sequenceable DNA from all species after 1,4 h of immersion in extraction buffer. The extracted carcasses, processed and imaged using protocols standard for the taxon, were distinguishable from closely related species, and adequate as morphological vouchers. We provide links from the carcasses and DNA vouchers to image (MorphBank) and sequence (GenBank) databases. [source] An update on the honesty of melanin-based color signals in birdsPIGMENT CELL & MELANOMA RESEARCH, Issue 2 2008Kevin J. McGraw Summary The control mechanisms and information content of melanin-based color signals in birds have generated much recent interest and controversy among evolutionary biologists. Initial experimental studies on this topic manipulated coarse metrics of an individual's condition (i.e. food intake, disease state) and failed to detect significant condition-dependence of melanin ornament expression. However, three new lines of research appear profitable and target specific factors associated with the production of melanin pigments. These include the role of (i) metals, (ii) amino acids, and (iii) testosterone and social interactions in shaping the extent and intensity of melanin-colored plumage patches. Here, I review recent studies of and evidence for these honesty-reinforcing mechanisms. [source] | ||||||||||||||||||||||||||||