ArticleLiterature Review

Molecular ecological approaches to studying the evolutionary impact of selective harvesting in wildlife

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Abstract

Harvesting of wildlife populations by humans is usually targeted by sex, age or phenotypic criteria, and is therefore selective. Selective harvesting has the potential to elicit a genetic response from the target populations in several ways. First, selective harvesting may affect population demographic structure (age structure, sex ratio), which in turn may have consequences for effective population size and hence genetic diversity. Second, wildlife-harvesting regimes that use selective criteria based on phenotypic characteristics (e.g. minimum body size, horn length or antler size) have the potential to impose artificial selection on harvested populations. If there is heritable genetic variation for the target characteristic and harvesting occurs before the age of maturity, then an evolutionary response over time may ensue. Molecular ecological techniques offer ways to predict and detect genetic change in harvested populations, and therefore have great utility for effective wildlife management. Molecular markers can be used to assess the genetic structure of wildlife populations, and thereby assist in the prediction of genetic impacts by delineating evolutionarily meaningful management units. Genetic markers can be used for monitoring genetic diversity and changes in effective population size and breeding systems. Tracking evolutionary change at the phenotypic level in the wild through quantitative genetic analysis can be made possible by genetically determined pedigrees. Finally, advances in genome sequencing and bioinformatics offer the opportunity to study the molecular basis of phenotypic variation through trait mapping and candidate gene approaches. With this understanding, it could be possible to monitor the selective impacts of harvesting at a molecular level in the future. Effective wildlife management practice needs to consider more than the direct impact of harvesting on population dynamics. Programs that utilize molecular genetic tools will be better positioned to assess the long-term evolutionary impact of artificial selection on the evolutionary trajectory and viability of harvested populations.

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... Trait changes consistent with evolutionarily relevant hunter selection are often accompanied by confounding environmental influences (Coltman et al. 2003, Coltman 2008, P erez et al. 2011, Pigeon et al. 2016. Clear evidence of negative evolutionary consequences of selective trophy harvest in ungulates is rare (Mysterud 2011, Kuparinen andFesta-Bianchet 2016). ...
... Coltman et al. (2003) was subsequently criticized for analysis methods and inadequate consideration of nutritional and environmental influences that may have had much greater influence on the reduction in horn size (Heimer 2004, Postma 2006, Hadfield et al. 2010, Traill et al. 2014. Indeed, Coltman (2008) later acknowledged that the selective effect on the genetic contribution to horn size reduction could have been overestimated because they could not fully account for environmental effects due to changes in population density and nutrition. Additionally, the estimated breeding values in Coltman et al. (2003) were likely overestimated, exaggerating the amount of change due to genetics , Pigeon et al. 2016. ...
... Biologists know that horn, antler, and pronghorn (Antilocapra americana) development is heavily influenced by nutrition in ungulates, including mountain sheep (Jorgenson et al. 1998, Coltman 2008, Pigeon et al. 2016, elk (Cervus canadensis), red deer (Cervus elaphus; Wang et al. 1999, Kruuk et al. 2002, deer (French et al. 1956, Brown 1990, Lockwood et al. 2007, Foley et al. 2012, Michel et al. 2016b), pronghorn (O'Gara 1990, and caribou (Cronin et al. 2003, Mahoney et al. 2011. Substandard and variable nutrition, caused by weather patterns, independent habitat degradation, or the density-dependent effects of high population density, results in animals not expressing their genetic potential for horn or antler size. ...
Article
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Differentially harvesting individual animals with specific traits has led some to argue that such selection can cause evolutionary change that may be detrimental to the species, especially if those traits are related positively to individual fitness. Most hunters are not selective in the type of animal they take, satisfied instead to harvest any legal animal. In a few exceptions, however, regulations may limit hunters to harvest animals of a minimum size or age regardless of their personal choice. Using information from a broad range of aquatic and terrestrial systems exposed to a myriad of potential and operational selective pressures, several authors have made expansive generalizations about selective harvest and its applicability to ungulates. Harvest-based selection can potentially be intensive enough to be relevant in an evolutionary sense, but phenotypic changes consistent with hunter selection are otherwise confounded with multiple environmental influences. Factors such as age, genetic contribution of females, nutrition, maternal effects, epigenetics, patterns of mating success, gene linkage, gene flow, refugia, date of birth, and other factors affecting selection interact with harvest to impede unidirectional evolution of a trait. The intensity of selection determines potential for evolutionary change in a meaningful temporal framework. Indeed, only under severe intensity, and strict selection on a trait, could human harvest prompt evolutionary changes in that trait. Broad generalizations across populations or ecological systems can yield erroneous extrapolations and inappropriate assumptions. Removal of males expressing a variety of horn or antler sizes, including some very large males, does not inevitably represent directional artificial selection unless the selective pressures are intensive enough to cause a unidirectional shift in allele frequencies that may act on some relevant life-history trait or process. Here I review the topic of harvest-based selection in male ungulates and discuss the inefficiency of trophy hunting in changing genetic expression of phenotype. © 2017 The Wildlife Society.
... Cette mortalité additionnelle peut être en soi la cause de changements évolutifs, par exemple lorsque les taux d'exploitation réduisent significativement la taille effective de la population, engendrant des changements génétiques par dérive (Hauser et al. 2002, Hutchinson et al. 2003, Hoarau et al. 2005. De tels changements génétiques peuvent aussi se produire lorsque des populations qui ont dès le départ de faibles nombres d'effectifs sont exploitées (Coltman 2008). Par contre, presque toute forme de récolte est sélective ; l'exploitation cible presque toujours ses proies selon certaines caractéristiques, par exemple le sexe, la taille ou l'âge. ...
... Ainsi, la détection d'un changement dans la fréquence allélique de marqueurs ou de gènes associés à l'expression de traits phénotypiques au sein d'une population exploitée serait une indication manifeste de changements évolutifs induits par la récolte sélective. À cette fin, la cartographie génétique, les études d'association, ainsi qu'une approche par gènes candidats sont autant de méthodes pouvant servir à identifier des marqueurs moléculaires associés aux variations phénotypiques ou fonctionnelles (Coltman 2008). Bien que ces différentes méthodes génomiques n'aient pas encore été appliquées à l'étude de changements évolutifs causés par l'exploitation, des exemples tirés de la littérature plus fondamentale illustrent bien leur potentiel. ...
... La première est intuitive et consiste à éviter l'exploitation sélective, peu importe le trait qui est sélectionné (taille, comportement, sexe). De même, imposer des tailles limites maximales ou encore modifier les engins de capture sont des mesures envisageables et facilement applicables (Law 2007), tout comme prélever les plus gros individus seulement lorsque la reproduction a eu lieu (Coltman 2008). Une deuxième mesure consiste en la création d'aires protégées servant de refuges, à partir desquels le pool génique peut être reconstitué. ...
... One consequence of intensive hunting is a change in the sex ratio of the population. A highly skewed sex ratio in the population would affect population viability by reducing the effective population size (N e ) (Coltman 2008). Although N e is always lower than the census population size, if sex ratios are highly skewed by bush meat hunting, then N e may become much lower than predicted by census population size (Gaggiotti 2003). ...
... Although N e is always lower than the census population size, if sex ratios are highly skewed by bush meat hunting, then N e may become much lower than predicted by census population size (Gaggiotti 2003). In small isolated populations such as island populations where the immigration rate is very low, having a low N e reduces population viability and in extreme cases could result in population extinction (Gaggiotti 2003;Coltman 2008;Milner-Gullard et al. 2010). The hunting of C. p. buettikoferi will also reduce the genetic diversity of the population resulting in decreased resilience to future changes in environment '" " and disease. ...
... This will provide information on the sustainability of the bushmeat trade in Guinea-Bissau. Molecular sexing to infer sexbiased hunting should be undertaken, as papers by Gaggiotti (2003); Coltman (2008) and Milner-Gullard et al. (2010) have indicated that N e in selectively-hunted populations may be considerably lower than predicted by census population size, corresponding to an increased risk of extinction. " ...
... Additionally, 20-30% of males hunted across Alberta were taken at 4-5 years old, before peaking reproductively (Festa-Bianchet 2012, Festa-Bianchet et al. 2014). The horn size-based definition of a legal male across much of Canada (Pelletier et al. 2012, Festa-Bianchet et al. 2014) means that individuals with higher breeding values are more likely to be hunted before the reproductive peak, thus imposing selection in favor of males with small breeding values for horn size (Coltman 2008, Schindler et al. 2017) across a large part of the range of Rocky Mountain bighorn sheep (Ovis canadensis canadensis). Changes in age structure due to hunting can result in smaller mean weapon size in ungulates that have nothing to do with an evolutionary response to hunting. ...
... Heffelfinger (2018) did not consider the effects of genetic drift due to small effective population size (N e ), which can reduce to the evolutionary response to selective hunting. The response to selection is less predictable in small populations because genetic drift generates random changes in allele frequency, whereas positive selection increases the frequency of a favorable allele (Robertson 1960, Coltman 2008). This is a particularly important factor to account for when considering the potential for evolutionary responses to selective hunting in small hunted populations (Coltman 2008). ...
... The response to selection is less predictable in small populations because genetic drift generates random changes in allele frequency, whereas positive selection increases the frequency of a favorable allele (Robertson 1960, Coltman 2008). This is a particularly important factor to account for when considering the potential for evolutionary responses to selective hunting in small hunted populations (Coltman 2008). Rapid evolution of horn size in an apparent response to selective hunting in the Ram Mountain bighorn sheep population illustrates the power of human actions to cause rapid evolution in wildlife, even in very small populations. ...
... The vulnerability of a species to overexploitation is influenced by its life-history traits, compensatory responses to increased mortality, dispersal capabilities, and population structure (Allendorf et al. 2008;Coltman 2008;Harris et al. 2002). In regards to life history, the conservation of long-lived species subject to harvest presents particular challenges. ...
... Whether genetic diversity is lost or retained in harvested populations will also be greatly influenced by the population-level structure that is in turn shaped by the topography of the landscape, local patterns of distribution, and the species' dispersal capability. If opportunity for dispersal is plentiful and contemporary gene flow between populations is high, the detrimental effects of harvesting on any one population are lowered because the impacts will be diffused across all populations that constitute the metapopulation (Allendorf et al. 2008;Coltman 2008;McCullough 1996). If, however, gene flow is unequal and a population is harvested intensively it can act as a sink population and thereby reduce the overall effective population size, alter the rates of gene flow within, and adversely affect the functioning of, the entire metapopulation (Coltman 2008;McCullough 1996;Pannell and Charlesworth 2000). ...
... If opportunity for dispersal is plentiful and contemporary gene flow between populations is high, the detrimental effects of harvesting on any one population are lowered because the impacts will be diffused across all populations that constitute the metapopulation (Allendorf et al. 2008;Coltman 2008;McCullough 1996). If, however, gene flow is unequal and a population is harvested intensively it can act as a sink population and thereby reduce the overall effective population size, alter the rates of gene flow within, and adversely affect the functioning of, the entire metapopulation (Coltman 2008;McCullough 1996;Pannell and Charlesworth 2000). An alternative scenario is that the harvested population is genetically isolated from unharvested regions because of a barrier to dispersal or poor dispersal capability of the species. ...
... Our findings suggest that the differences in the spatial organization of female black bears in the Milan and Pittsburg populations can be explained by differences in the hunting pressure that they experience, but not by differences in landscape features or anthropogenic development. Human exploitation of natural populations adds selective pressures that can have life history, demographic and evolutionary consequences (Allendorf et al. 2008;Coltman 2008;Coltman et al. 2003;Milner et al. 2007). Previous research has shown that populations with differing levels of exploitation may exhibit different demographic tactics (Servanty et al. 2011). ...
... Nonetheless, our findings may have important implications for other exploited mammal populations, especially managed populations that allow sex-biased hunting. Understanding not only the demographic, but also the genetic, behavioral and evolutionary consequences of hunting is important for sustainable management (Allendorf et al. 2008), especially if we are to accept as a goal the adoption of harvest practices that minimize their evolutionary impact (Coltman 2008). ...
Article
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Anthropogenic influences such as hunting pressure and habitat fragmentation can alter the demographic and spatial patterns of wildlife populations. Understanding the consequences of these impacts is a challenge for natural resource managers, which can be overcome by investigations using spatial genetic techniques. We used spatial autocorrelation and landscape genetic analyses to compare the impacts of anthropogenic forces on the spatial genetic structure of two female black bear (Ursus americanus) populations in northern New Hampshire with similar bear densities but varying human densities, hunting pressure and sex ratios. We found evidence of an impact of hunting mortality on the spatial genetic structure of female black bears. The population with greater hunting pressure and a heavily male-biased sex ratio (Milan) exhibited greater spatial genetic structure represented by a pattern of isolation by distance, kin clustering, and reduced dispersal in comparison to the population with a balanced sex ratio (Pittsburg). We did not find a strong effect of fragmenting landscape features on female spatial structure. Major roads were correlated with spatial genetic structure, but only in the population with lower human density and development (Pittsburg). Slope and elevation were also correlated with spatial genetic structure, suggesting terrain plays a role in structuring seasonal female home range boundaries. Our study revealed the utility of using spatial genetic techniques to identify anthropogenic influences on female social organization. These findings highlight the importance of monitoring the impacts of harvest pressure not only on demographics but also the spatial genetic structure of animal populations.
... Furthermore, the bulk of the current evidence supporting an effect of selective harvest on ungulate species has been obtained from studies of mountain sheep, where extensive pedigrees and assessments of phenotypic and genotypic changes in horn size have demonstrated that harvest can reduce the size of weaponry through time (Coltman 2008, Pigeon et al. 2016). This evidence, however, largely has stemmed from a single population (Ram Mountain, Alberta, Canada) with unique characteristics and a harvest regime that is not ...
... employed in other jurisdictions across most of mountain sheep range, with the notable exception of management areas in most of Alberta, Canada. Ideally, assessing the effect of selective harvest on wild populations would include sophisticated molecular approaches (Coltman 2008). Such data are not readily available, however, and conducting molecular analyses at the temporal and spatial scales necessary to encompass variation in harvest practices and evolutionary change in a long-lived mammal is expensive. ...
Article
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The influence of human harvest on evolution of secondary sexual characteristics has implications for sustainable management of wildlife populations. The phenotypic consequences of selectively removing males with large horns or antlers from ungulate populations have been a topic of heightened concern in recent years. Harvest can affect size of horn-like structures in two ways: (a) shifting age structure toward younger age classes, which can reduce the mean size of horn-like structures, or (b) selecting against genes that produce large, fast-growing males. We evaluated effects of age, climatic and forage conditions, and metrics of harvest on horn size and growth of mountain sheep (Ovis canadensis ssp.) in 72 hunt areas across North America from 1981 to 2016. In 50% of hunt areas, changes in mean horn size during the study period were related to changes in age structure of harvested sheep. Environmental conditions explained directional changes in horn growth in 28% of hunt areas, 7% of which did not exhibit change before accounting for effects of the environment. After accounting for age and environment, horn size of mountain sheep was stable or increasing in the majority (~78%) of hunt areas. Age-specific horn size declined in 44% of hunt areas where harvest was regulated solely by morphological criteria, which supports the notion that harvest practices that are simultaneously selective and intensive might lead to changes in horn growth. Nevertheless, phenotypic consequences are not a foregone conclusion in the face of selective harvest; over half of the hunt areas with highly selective and intensive harvest did not exhibit age-specific declines in horn size. Our results demonstrate that while harvest regimes are an important consideration, horn growth of harvested male mountain sheep has remained largely stable, indicating that changes in horn growth patterns are an unlikely consequence of harvest across most of North America.
... Environmental influences can be accounted for in an analysis of a pedigreed population with phenotypic data; however, strong environmental effects on phenotype still make hunter selection less efficient than it might be if phenotype were influenced only by genetics, which was my primary point. Even at Ram Mountain, much of the decline in horn size was due to non-genetic phenotypic plasticity related to increasing sheep densities and subsequent densitydependent declines in nutrition (Pigeon et al. 2016), resulting in exaggerated effects of hunter selection (Postma 2006, Coltman 2008, Pigeon et al. 2016, Douhard et al. 2017. Kardos et al. (2018) correctly state that I considered many nongenetic factors as obstacles to an evolutionary response to selective hunting but then go on to argue erroneously that I suggested they preclude an evolutionary response. ...
... I did not address this factor because small N e may also increase the response to selection. A large selection differential can be imposed on a small population by removing a few males with high phenotypic values because they make up a relatively larger proportion of the breeding population (Coltman 2008). The number of males in the Ram Mountain population during 1973-2011 ranged from 8 to 61, with 50% of the annual lamb recruitment typically sired by 2-3 dominant males . ...
... Sophisticated modeling techniques can be used to parse genetic, environmental, and maternal contributions to horn and antler size (Coltman 2008, Wilson et al. 2010). Nonetheless, manipulative experiments have demonstrated the overriding influence of nutrition on growth of male ungulates by varying nutrition while controlling for the genetic contributions to growth. ...
... Results published by Coltman et al. (2003) were, thereafter, the subject of criticism and concern over inadequate consideration of environmental effects on horn size (Heimer 2004, Festa-Bianchet et al. 2006b, Postma 2006, Coltman 2008, Traill et al. 2014. A subsequent reanalysis of those data from Ram Mountain indicated that such severe and selective harvest led to genetically based reductions in horn size, and indicated that this effect was reduced with a regulation that changed the definition of a legal sheep to full curl in 1997 (Pigeon et al. 2016). ...
Article
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Horns, antlers, and other horn-like structures are products of sexual selection, confer reproductive advantages, and are heritable and honest indicators of individual quality. In addition to serving key biological functions, horns and antlers garner societal interest that, when combined with the powerful motivation to acquire trophy animals, likely has spawned a growing hornographic culture fixated on males with exceptional horn-like structures. The concern that harvest of large, fast-growing males may cause evolutionary change to the very trait being sought has been the source of controversy in the popular and scientific literature over the past 2 decades. Mountain sheep (i.e., bighorn and thinhorn; Ovis spp.), possibly the only large ungulates in North America managed almost exclusively as trophy species throughout their ranges, embody this controversy, which has led to polarizing views among scientists and stakeholders as to how mountain sheep should be managed. Our goal in this commentary was to discuss the relative contributions of the key ecological and intrinsic factors that influence horn growth, how those factors might interact with harvest strategies, and identify what determinants of horn size are most amenable to management and most effective in achieving desired outcomes. Despite repeated results demonstrating that age or nutrition frequently override genetic contributions to size of horns, attention has been given to the role of genetics and its relationship to harvest of mountain sheep. Given the hyperbole surrounding trophy management and big horns, we suggest the importance of females in the management of mountain sheep has been largely forgotten. Maternal condition can instigate life-long effects on size and growth of males (via maternal effects), and abundance of females, in turn, affects nutritional limitation within populations through density-dependent feedbacks. If production of males with large horns is an objective, we contend that management programs should, integrate monitoring of nutritional status of populations, and where evidence indicates nutritional limitation through density dependence, seek to regulate abundance and per capita nutrition via harvest of females. We propose that extrinsic regulation (i.e., removal by harvest or translocation) is the most effective way to manage per capita availability of forage resources and, thus, nutritional limitation on growth of males. Not only can female harvest improve growth in body size and horns of males through enhanced nutrition of growing males and their mothers, such management also 1) may yield a nutritional buffer against environmental stochasticity and erratic population fluctuations, 2) be employed in areas where other management alternatives such as habitat manipulation may not be feasible, 3) may reduce frequency or magnitude of epizootic die-offs, and 4) will increase hunter opportunity and involvement in management. Ultimately, we call for greater recognition of the pervasive role of the ewe, and other female ungulates, in the production of trophy males, and that accordingly, females be better integrated into harvest and management programs. © 2017 The Wildlife Society.
... However, gene flow within a patchy metapopulation can counteract these effects to some extent, particularly when mature adult males are contributing to gene flow (Hard et al. 2006). To further counteract these effects, managers could reduce harvest levels through permit harvests (i.e., reduce harvest of adult males- Hard et al. 2006;Allendorf et al. 2008;Coltman 2008). ...
... Here we focused on the level of genetic similarity among elk populations in Idaho to describe their metapopulation structure. Our results suggest a network (i.e., patchy metapopulation structure) of elk populations linked by extensive gene flow and exhibiting little to no differences in genetic variation, which is common among cervids (Coltman 2008). The lack of geographic barriers and the dispersal capabilities of elk support our results based on genetics (Shoesmith 1980;O'Gara 2002). ...
Article
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Wildlife managers are challenged to manage spatially structured populations efficiently and effectively, therefore dispersal and gene flow are vital to understand and manage, particularly for a harvested species. We used a genetic approach to describe the metapopulation structure of Rocky Mountain elk (Cervus elaphus) in Idaho to assess past patterns of population distribution and influences of harvest. We used elk tissue and DNA samples (n=216) to examine genetic dissimilarity between 7 regions and 9 elk management zones throughout Idaho using microsatellite loci (n=11). Using 5 approaches, including pairwise FST-values, assignment tests, and a Bayesian model–based clustering of genotypes, we examined the distribution of genetic variation. The distribution of genetic variation between elk populations indicated low levels of genetic differentiation among regions (expected heterozygosity [HE]=0.55–0.61, overall FST=0.011) and elk management zones (HE=0.54–0.60, overall FST=0.017). Assignment tests and migration rates indicated directional gene flow between elk populations. A patchy metapopulation best describes the distribution of genetic variation among Idaho elk populations because likely enough individual interchange occurs between geographically separated populations. The elk populations we sampled could be part of a geographically larger patchy metapopulation potentially stretching from Yellowstone National Park through Idaho into western Canada. Because of historical translocations of elk from Yellowstone National Park, insufficient time may have passed to detect differences in genetic variation. Subtle differences in the distribution of genetic variation were observed in 2 of the 9 elk management zones within 2 different regions of the state. Our findings indicate management of Idaho elk populations and dispersal are maintaining sufficient gene flow. Metapopulation structure of a harvested species based on the distribution of genetic variation is an indicator of potential genetic consequences of harvesting and sustainable harvest levels.
... Phenotypic changes resulting from exploitative selection have been reported in several instances (reviewed by Allendorf et al., 2008). However, obtaining evidence for a genetic basis of the observed changes is not straightforward (Kuparinen & Merilä, 2007), as genetic and environmental causes of phenotypic change need to be disentangled (Coltman et al., 2003;Coltman, 2008). ...
... Thus, estimation of additive genetic variation (i.e. narrow sense heritability) for the traits that may be targeted by selection is necessary to predict the potential genetic impact of fishing (see Coltman, 2008). ...
Article
1. There is growing evidence that sexually mature but morphologically juvenile males of Atlantic salmon (precocious or mature male parr) actively participate in reproduction and, therefore, in the genetic composition of the populations of this species. The impact of mature male parr on the effective population size (Ne) of such populations has been previously studied under experimental settings, but no studies have been performed directly on natural populations. 2. Continuous monitoring and sampling of all sea returns is possible in the Lérez River (northwest of Spain). From demographic data on variances of reproductive success and genetic data from six microsatellite marker loci we carried out parentage assignment and assessed the impact of male parr on demographic and genetic estimates of Ne in two consecutive years. 3. Our results reveal that: (i) approximately 60% of the total sire paternity is attributable to mature parr; (ii) mature parr decrease the variance of reproductive success of males by a threefold factor and increase the effective population size of males by a 10-fold factor; (iii) however, they do not substantially affect the variance of reproductive success and the effective size of females; (iv) mature parr increase two-to threefold the overall effective size of the population but the ratio Ne/N, where N is the population size including or not mature parr in each case, is not affected.
... Phenotypic changes resulting from exploitative selection have been reported in several instances (reviewed by Allendorf et al., 2008). However, obtaining evidence for a genetic basis of the observed changes is not straightforward (Kuparinen & Merilä, 2007), as genetic and environmental causes of phenotypic change need to be disentangled (Coltman et al., 2003; Coltman, 2008). The natural southern range of distribution of the Atlantic salmon in Europe corresponds to rivers located in the north of Spain (Brañ a et al., 1995a). ...
... Thus, estimation of additive genetic variation (i.e. narrow sense heritability) for the traits that may be targeted by selection is necessary to predict the potential genetic impact of fishing (see Coltman, 2008). The objective of this study was to predict the expected response in body length and weight because of angling in the River Bidasoa (Navarra, NW Spain) population of Atlantic salmon. ...
Article
1. Recreational angling activities in wild populations of Atlantic salmon may induce a selection pressure towards a reduction in body size and length if the angling season coincides with the return of the largest sea age fish class. 2. Using estimates of heritability for growth traits and estimates of the selection pressure from angling operating on growth, we predicted the response to selection expected to occur in a wild population of Atlantic salmon. 3. The dataset used here comprised individuals from two consecutive generations (parents and offspring) from the River Bidasoa (NW Spain). Offspring were assigned to parents using six highly polymorphic microsatellite loci. Use of restricted maximum likelihood methodology and the animal model allowed us to estimate the heritability for body length and body weight as well as their genetic correlation. 4. Estimated heritabilities (0.32 ± 0.12 for length and 0.32 ± 0.11 for weight) and selection pressure caused by angling were used to obtain predictions of response to selection because of angling. Our results suggested a decline of 1.9 mm in body length and 103.3 g in body weight per generation because of angling pressure. 5. The results derived from this study suggest that the angling season should be annually delayed in order to avoid selective angling of the multi-year class and further reductions in body weight and length.
... The impact of hunting on wildlife populations can include changes in demographic and genetic structure, effects that are less obvious than observable population declines and direct extinction caused by over-harvesting (Harris et al. 2002;Coltman 2008;Allendorf and Hard 2009). ...
... To create demographic sinks, individuals are removed by hunting and individuals dispersing from less exploited areas may become proportionately more abundant, altering allele frequencies (Harris et al. 2002). Potential consequences of demographic sinks are: (i) a local decrease in effective population size (Coltman 2008) and (ii) contact zones, where allopatrically differentiated sub-populations exchange genes causing genetic ''swamping'' and loss of local adaptation (Allendorf et al. 2008). Thus, locally restricted hunting practices can potentially impact the genetic diversity of the populations at a broader scale than appreciated. ...
Article
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Guinea baboons are heavily hunted for bushmeat consumption in Guinea-Bissau. We investigated whether hunting-driven mortality has affected population structure in this generalist primate using two genetic markers. Sampling was conducted in protected areas separated by anthropogenic landscape features. We predicted significant genetic differentiation between samples and investigated whether genetic discontinuities in the data were concordant with the location of human infrastructures. Genetic diversity was not significantly reduced when compared with a neighbouring population in Senegal and female-biased dispersal was inferred with recent contact between localities. Evidence was found for a contact zone between genetically differentiated populations where gene-flow is unidirectional, admixed individuals are at a higher proportion and individuals differentiated for both genetic markers co-exist within the same social units. Genetic discontinuities were, however, unrelated to anthropogenic dispersal barriers and we could not explain the existence of a contact zone by geographic distance, habitat type or the effect of social structure. We propose that hunting practices have affected the population structure by increasing dispersal distances, facilitating contact between previously separated gene pools within social groups. We suggest that hunting-related density sinks found in areas where the quality of the habitat remains adequate could precipitate the immigration of genetically distinct individuals from distant populations. Alternatively, migrants found in protected areas might be avoiding hunters, in locations they may perceive as less disturbed. This study suggests that hunting practices must be considered when investigating genetic patterns in primates and underlines the utility of molecular approaches to detect population perturbations due to bushmeat hunting.
... 3.5, the existing Markov chain Monte Carlo (MCMC) methods are prone to producing very different answers in independent simulations, and they fail to adequately capture the uncertainty in its solutions. For many population genetics applications such as wildlife conversation (Coltman, 2007), it is crucial to accurately characterize the confidence in a solution. ...
... Maintenance of gene flow among populations is increasingly emphasized as an important tactic in the conservation and management of wildlife species, including bats (Ashley et al. 2003;Coltman 2008;Racey and Entwistle 2003). Various aspects of the mating systems and habitat requirements of temperate-zone cavernicolous bat species could influence the spatial scales at which gene flow occurs. ...
Article
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Although groups of bats may be genetically distinguishable at large spatial scales, the effects of forest disturbances, particularly permanent land use conversions on fine-scale population structure and gene flow of summer aggregations of philopatric bat species are less clear. We genotyped and analyzed variation at 10 nuclear DNA microsatellite markers in 182 individuals of the forest-dwelling northern myotis (Myotis septentrionalis) at multiple spatial scales, from within first-order watersheds scaling up to larger regional areas in West Virginia and New York. Our results indicate that groups of northern myotis were genetically indistinguishable at any spatial scale we considered, and the collective population maintained high genetic diversity. It is likely that the ability to migrate, exploit small forest patches, and use networks of mating sites located throughout the Appalachian Mountains, Interior Highlands, and elsewhere in the hibernation range have allowed northern myotis to maintain high genetic diversity and gene flow regardless of forest disturbances at local and regional spatial scales. A consequence of maintaining high gene flow might be the potential to minimize genetic founder effects following population declines caused currently by the enzootic White-nose Syndrome.
... Coltman et al. 2003;Edeline et al. 2007;Garel et al. 2007). Recent reviews caution that the effects of selective harvesting are relevant in efforts to sustain wild animal populations (Coltman 2008;Fenberg & Roy 2008;Allendorf & Hard 2009;Dunlop et al. 2009;Mysterud 2011). In fisheries, especially, it has been documented that size-selective harvesting causes phenotypic and genetic change in such traits as body size (Conover & Munch 2002;Carlson et al. 2007;Swain, Sinclair & Hanson 2007), reproductive scheduling (Olsen et al. 2004;Dieckmann & Heino 2007) and other parameters (Walsh et al. 2006;Biro & Post 2008). ...
Conference Paper
Although selective fishing often causes plastic life history changes of target species, there is little evolutionary perspective on those changes. We examined a facultative sex-change of the protandrous shrimp (Pandalus latirostris) to the skew of population structure by unintentional female-selective fishing due to a favoring for large size. Our 12-year survey showed that annual fluctuation of the sex ratio was diminished in the maturing season by occurrences of females that changed sex early or males that postponed sex-change. Both field observation and laboratory experiment confirmed that those sex-changes were induced by the skew of age and sex structures, suggesting sex ratio adjustment. Sex ratio adjustment is not sufficient, however, because large individuals that can change sex have been selectively removed by fishing in the previous year. Moreover, such adjusted sex ratio is skewed again by subsequent fishing acting as female-selective, suggesting that the sex ratio adjustment often becomes rather maladaptive. A consideration of facultative changes in the life history of harvested animals would be more important than our recognition to conserve wild animal resources.
... As scientists, we look for signal and temporal shifts in a heritable trait, such as horn size within a hunted population can signal undesirable change (Coltman, 2008). We did not find any signal, but given our caveats, cannot draw any strong conclusions. ...
... Harvest-associated plasticity could also occur in response to environmental effects because fishing causes other confounding environmental changes that could influence phenotypic expression (9,21), such as the reduction of population density over time. Indeed, intense harvesting can remove so much biomass from the environment that the density for the remaining population is altered. ...
Article
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Fisheries induce one of the strongest anthropogenic selective pressures on natural populations, but the genetic effects of fishing remain unclear. Crucially, we lack knowledge of how capture-associated selection and its interaction with reductions in population density caused by fishing can potentially shift which genes are under selection. Using experimental fish reared at two densities and repeatedly harvested by simulated trawling, we show consistent phenotypic selection on growth, metabolism, and social behavior regardless of density. However, the specific genes under selection—mainly related to brain function and neurogenesis—varied with the population density. This interaction between direct fishing selection and density could fundamentally alter the genomic responses to harvest. The evolutionary consequences of fishing are therefore likely context dependent, possibly varying as exploited populations decline. These results highlight the need to consider environmental factors when predicting effects of human-induced selection and evolution.
... In small populations, harvesting may cause significant genetic drift as age structures are altered, sex-ratios skewed and effective sizes decreased, but to assess these effects requires a correct assessment of population genetic structure, which acts as an enforcing factor (Frankham 1996;Coltman 2008). Harvest may in MGR have involved genetic drift and differentiation, as compared to the protected SNP. ...
Article
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Wildlife species exposed to habitat fragmentation are often in need of a conservation effort. The African buffalo (Syncerus caffer) is one of the key species in the Serengeti ecosystem as they form a large part of the herbivore biomass, providing ecotourism and valuable trophies. The ecosystem is a part of Tanzanias protected areas and is administrated under different management practices. Among these, we have analysed the genetic structure of buffalo (n = 68) from the Serengeti National Park (SNP), the Ngorongoro conservation area (NCA) and the Maswa game reserve (MGR). Both the sequence variation in a 493 base pair fragment of the mitochondrial D-loop and the allele frequency-distribution in 15 microsatellites suggest genetic structuring of the buffalo populations within the ecosystem. Both the allele frequency-distribution and the amount of genetic variation were high and similar in SNP and MGR, suggesting a high degree of gene flow between these locations. By comparison, the NCA buffaloes had significantly lower genetic variation and were genetically differentiated from SNP and MGR. Approximate Bayesian computation estimates suggest that the observed genetic structure is of a recent origin, indicating that the recent increases in developmental activity in the region may have influenced the genetic structure of the buffalo within the Serengeti ecosystem.
... Consequently, about 40% of males that attained legal size were harvested each year, allowing males with slow-growing horns to reach older age classes ( Bonenfant et al. 2009b) and, thus, do a disproportionate amount of mating ( Coltman et al. 2003). Such heavy harvest resulted in selection against males with fast-growing horns before their reproductive peak, and thereby reduced their genetic contribution to the population ( Coltman et al. 2003), although declining horn size may have been confounded by increasing population density ( Coltman 2008). Other factors decreasing the potential influence of trophy hunting on selection for horn and antler size among artiodactyls are skewed sex ratios, and age structures of young males that are biased downward as a result of heavy harvest ( Laurian et al. 2000, Jenks et al. 2002, Webb et al. 2012). ...
Article
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Hunting remains the cornerstone of the North American model of wildlife conservation and management. Nevertheless, research has indicated the potential for hunting to adversely influence size of horn-like structures of some ungulates. In polygynous ungulates, mating success of males is strongly correlated with body size and size of horn-like structures; consequently, sexual selection has favored the development of large horns and antlers. Horn-like structures are biologically important and are of great cultural interest, both of which highlight the need to identify long-term trends in size of those structures, and understand the underlying mechanisms responsible for such trends. We evaluated trends in horn and antler size of trophy males (individuals exhibiting exceptionally large horns or antlers) recorded from 1900 to 2008 in Records of North American Big Game, which comprised >22,000 records among 25 trophy categories encompassing the geographic extent of species occupying North America. The long-term and broad-scale nature of those data neutralized localized effects of climate and population dynamics, making it possible to detect meaningful changes in size of horn-like structures among trophy males over the past century; however, ages of individual specimens were not available, which prevented us from evaluating age-class specific changes in size. Therefore, we used a weight-of-evidence approach based on differences among trophy categories in life-history characteristics, geographic distribution, morphological attributes, and harvest regimes to discriminate among competing hypotheses for explaining long-term trends in horn and antler size of trophy ungulates, and provide directions for future research. These hypotheses were young male age structure caused by intensive harvest of males (H1), genetic change as a result of selective male harvest (H2), a sociological effect (H3), effects of climate (H4), and habitat alteration (H5). Although the number of entries per decade has increased for most trophy categories, trends in size of horn-like structures were negative and significant for 11 of 17 antlered categories and 3 of 8 horned categories. Mean predicted declines during 1950–2008 were 1.87% and 0.68% for categories of trophy antlers and horns, respectively. Our results were not consistent with a sociological effect (H3), nutritional limitation imposed by climate (H4), or habitat alteration (H5) as potential explanations for long-term trends in size of trophies. In contrast, our results were consistent with a harvest-based explanation. Two of the 3 species that experienced the most conservative harvest regimes in North America (i.e., bighorn sheep [Ovis canadensis] and bison [Bison bison]) did not exhibit a significant, long-term trend in horn size. In addition, horn size of pronghorn (Antilocapra americana), which are capable of attaining peak horn size by 2–3 years of age, increased significantly over the past century. Both of those results provide support for the intensive-harvest hypothesis, which predicts that harvest of males has gradually shifted age structure towards younger, and thus smaller, males. The absence of a significant trend for mountain goats (Oreamnos americanus), which are difficult to accurately judge size of horns in the field, provided some support for the selective-harvest hypothesis. One other prediction that followed from the selective-harvest hypothesis was not supported; horned game were not more susceptible to reductions in size. A harvest-induced reduction in age structure can increase the number of males that are harvested prior to attaining peak horn or antler size, whereas genetic change imposed by selective harvest may be less likely to occur in free-ranging populations when other factors, such as age and nutrition, can override genetic potential for size. Long-term trends in the size of trophy horn-like structures provide the incentive to evaluate the appropriateness of the current harvest paradigm, wherein harvest is focused largely on males; although the lack of information on age of specimens prevented us from rigorously differentiating among causal mechanisms. Disentangling potential mechanisms underpinning long-term trends in horn and antler size is a daunting task, but one that is worthy of additional research focused on elucidating the relative influence of nutrition and effects (both demographic and genetic) of harvest.
... For instance, ungulate populations in Ngorongoro can be compared with other ungulate populations, such as those occurring in several Serengeti areas (Estes et al. 2006). Moreover, the method can be applied to studying the effects of male-biased harvesting on mating-system features and, hence, on evolutionary and conservation processes (Martínez et al. 2002;Hard et al. 2006;Coltman 2008). In conclusion, our comparison shows that Ripley's K analysis can be used in a wide range of studies on mating systems and with many species, in which it can notably improve other grid-sampling spatial methods. ...
Article
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Context. Mating systems are of central importance to the operation of sexual selection, with consequences for evolution and for the maintenance of genetic diversity. Female aggregation is one of the most important elements of mating systems because female distribution can influence the degree of polygyny. Measuring female aggregation requires finding the scale for the distribution pattern. Several spatial methods can be used to determine the scale of a point pattern; however, only one of them has been applied to mating-system research. Aims. Here, we assess three different spatial methods to determine the best one in finding the scale of female distribution for female-aggregation measures in a mating-system context. Methods. We describe and compare the spatial methods by applying them to 30 Iberian red deer (Cervus elaphus hispanicus) populations. We use spatial analyses for point patterns. Key results. Ripley's K analysis was found to be the best method for determining the scale of female distribution and for quantifying female-aggregation parameters in our populations. Conclusions. Ripley's K analysis, a distance method based on circles centred in individuals and that is widely used in ecological studies, allows the estimation of female aggregation and, hence, it can be used to measure sexual selection. Implications. This work describes the use of a distance method that can be applied to mating-system research (at least for ungulate populations) to obtain models with behavioural and evolutionary implications.
... Although the current hunt in the Greenland Sea is almost 2 orders of magnitude smaller than the Canadian hunt, the Greenland Sea population has been reduced to a smaller proportion of its initial population size than the Canadian population (Hammill & Stenson 2007, Skaug et al. 2007) and current pup production in the Greenland Sea is approximately an order of magnitude smaller than that in Canadian waters (Haug et al. 2006). Harvesting might have evolutionary consequences depending on the intensity of the hunt and the age classes targeted (Coltman 2008, Wirsing et al. 2008). Geographic location and density might also affect maternal behavior as there was a large difference in the sizes of the Greenland Sea and Front breeding patches. ...
Article
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All harp seal populations form breeding aggregations on the Arctic pack ice. However, pack ice conditions vary spatially and temporally among these aggregations with variation in environmental and oceanographic conditions, which may affect the behavioral interactions between mothers and their newborn pups. We investigated the variation in mother-pup behavior between harp seal breeding aggregations in the NE (Greenland Sea) and NW Atlantic coastal shelf region (Front). Acoustic cues provided by the pups are thought to be important in facilitating reunions with their mothers. Consequently, we measured variation in vocal parameters among seals to investigate geographic differences in pup vocalizations. Classification trees showed a distinctive split between Front and Greenland Sea pup vocalizations. There were no clear differences between male and female pups at the Front, where 42% of male and 38% of female pup calls could be attributed to a given individual. This contrasts with the Greenland Sea, where 55% of vocalizations of female pups were attributed to individuals compared with only 8% for males. Analyses of behavioral observations of mother-pup pairs made in the afternoon and evening showed that pups in the Greenland Sea suckled more and were more alert than pups in the Front. Further, mother-pup attendance patterns differed between sites. Mothers at the Front attended their pups 85.1% of the time, whereas mothers in the Greenland Sea attended their pups 52.2% of the time. These substantial differences between sites might be related to evolutionary changes in behavior resulting from commercial hunting or variable environmental conditions.
... Wide ranging habitat generalists such as deer are often expected to exhibit low levels of population structure and a high potential for gene flow (Coltman 2008). Exceptions include species with a history of introductions and other types of human interference, such as white-tailed deer (DeYoung et al. 2003) and Alpine ibex (Biebach and Keller 2009). ...
Article
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Human influence typically impacts on natural populations of conservation interest. These interactions are varied and sometimes complex, and may be negative and unintended or associated with conservation and management strategy. Understanding the details of how these interactions influence and are influenced by natural evolutionary processes is essential to the development of effective conservation strategies. In this study, we investigate a species in Britain that has experienced both negative impact through overhunting in historical times and management efforts through culls and translocations. At the same time, there are regional populations that have been less affected by human influence. We use mtDNA and nuclear microsatellite DNA markers to investigate patterns of connectivity and diversity and find multiple insular populations in Britain that probably evolved within the Holocene (when the habitat was free of ice). We identify three concurrent processes. First, surviving indigenous populations show highly provincial patterns of philopatry, maintaining and generating population structure on a small geographic scale. Second, founder populations into habitat extirpated of native populations have expanded, but remained largely insular. Third, introductions into established populations generate some admixture. We discuss the implications for the evolution of diversity of the integration of natural processes with anthropogenic influences on population size and distribution.
... For instance, the animal model [80] is now commonly used in the wild to estimate additive genetic variation, a critical component of the evolutionary potential of a trait. To our knowledge, no examples of the application of the animal model to ER yet exist; however, several authors have highlighted its potential [81][82][83]. High throughput genomic techniques with large sets of microsatellites loci and/or high-density SNP data provide helpful tools to achieve this objective [80]. For example, a recent study of bighorn sheep used 195 loci genotyped for 219 individuals and genomic positioning of loci on a linkage map to assess the effects of genetic rescue in this species [58]. ...
Article
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The current rapid rate of human-driven environmental change presents wild populations with novel conditions and stresses. Theory and experimental evidence for evolutionary rescue present a promising case for species facing environmental change persisting via adaptation. Here, we assess the potential for evolutionary rescue in wild vertebrates. Available information on evolutionary rescue was rare and restricted to abundant and highly fecund species that faced severe intentional anthropogenic selective pressures. However, examples from adaptive tracking in common species and genetic rescues in species of conservation concern provide convincing evidence in favour of the mechanisms of evolutionary rescue. We conclude that low population size, long generation times and limited genetic variability will result in evolutionary rescue occurring rarely for endangered species without intervention. Owing to the risks presented by current environmental change and the possibility of evolutionary rescue in nature, we suggest means to study evolutionary rescue by mapping genotype → phenotype → demography → fitness relationships, and priorities for applying evolutionary rescue to wild populations.
... Coltman et al. 2003;Edeline et al. 2007;Garel et al. 2007). Recent reviews caution that the effects of selective harvesting are relevant in efforts to sustain wild animal populations (Coltman 2008;Fenberg & Roy 2008;Allendorf & Hard 2009;Dunlop et al. 2009;Mysterud 2011). In fisheries, especially, it has been documented that size-selective harvesting causes phenotypic and genetic change in such traits as body size (Conover & Munch 2002;Carlson et al. 2007;Swain, Sinclair & Hanson 2007), reproductive scheduling (Olsen et al. 2004;Dieckmann & Heino 2007) and other parameters (Walsh et al. 2006;Biro & Post 2008). ...
Article
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Selective harvesting is acknowledged as a serious concern in efforts to conserve wild animal populations. In fisheries, most studies have focused on gradual and directional changes in the life-history traits of target species. While such changes represent the ultimate response of harvested animals, it is also well known that the life history of target species plastically alters with harvesting. However, research on the adaptive significance of these types of condition-dependent changes has been limited. We explored the adaptive significance of annual changes in the age at sex-change of the protandrous (male-first) hermaphroditic shrimp and examined how selective harvesting affects life-history variation, by conducting field observations across 13 years and a controlled laboratory experiment. In addition, we considered whether plastic responses by the shrimp would be favourable, negligible or negative with respect to the conservation of fishery resources. The age at sex-change and the population structure of the shrimp fluctuated between years during the study period. The results of the field observations and laboratory experiment both indicated that the shrimp could plastically change the timing of sex-change in accordance with the age structure of the population. These findings provide the first concrete evidence of adult sex ratio adjustment by pandalid shrimp, a group that has been treated as a model in the sex allocation theory. The sex ratio adjustment by the shrimp did not always seem to be sufficient, however, as the supplement of females is restricted by their annual somatic growth rate. In addition, adjusted sex ratios are further skewed by the unintentional female-selectivity of fishing activity prior to the breeding season, indicating that the occurrence of males that have postponed sex-change causes sex ratio adjustment to become unfavourable. We conclude that the plastic responses of harvested animals in selective fishing environments must be considered in efforts to conserve wild animal resources, because such responses can become maladaptive.
... The selective effect on salmon life-history traits is another potential impact of the Greenland fishery on exploited populations . Growing evidence indicates that evolutionary changes in life-history traits in response to selective harvesting may be more common than previously thought (Stokes and Law 2000; Coltman 2008a; Hard et al. 2008). Namely, traits such as body size and migration timing have received considerable attention in salmonids (Hard et al. 2008 ). ...
Article
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Mixed-stock fisheries refer to the exploitation of admixed fish stocks coming from different origins. We identified the North American origin of 2835 Atlantic salmon (Salmo salar) in the Greenland mixed-stock fishery during I I years (1995-2006) at three localities using 13 microsatellites. The study included 52 baseline populations representing nine genetically distinct regional groups. The contribution of each group ranged from <1% (Maine) to 40% (Southern Quebec). Decreasing temporal contributions were observed for Southern Quebec (-22.0%) and New Brunswick (-17.4%), whereas an increasing contribution for Labrador (+14.9%) was observed during the time course of the study. The estimated regional contribution to the Greenland fishery was significantly correlated to the number of multi-sea-winter salmon regionally produced in 2002 (r = 0.79) and 2004 (r = 0.92). No difference in contribution was found between the three Greenland sampling localities. Ungava and Southern Quebec regions showed the highest-mortality estimates caused by the fishery, ranging from 12.10% to 18.08%, for both years tested. No regional group was overrepresented in landings compared with their respective productivity. Yet, management precautions should still be taken as the fishery strongly selects large females, which could have evolutionary impacts on populations over the long term.
... Quantifying the amount and spatial distribution of genetic diversity in a continuously distributed population can help guide the geographic scale for monitoring and harvest management, and inform longterm conservation strategies (Palsbøll et al. 2007). Wildlife populations are generally managed at a local level within political boundaries, which do not necessarily correspond to their genetic configuration (Coulon et al. 2006;Coltman 2008). Because Dall's sheep occur throughout relatively continuous habitats at ancestral levels of population density and distribution, increased understanding of their fine-scale genetic structure provides useful assessments of natural patterns of genetic variability in alpine ungulates, especially in comparison to those that have experienced population declines and inhabit fragmented landscapes (Valdez and Krausman 1999). ...
Article
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Identifying patterns of fine-scale genetic structure in natural populations can advance understanding of critical ecological processes such as dispersal and gene flow across heterogeneous landscapes. Alpine ungulates generally exhibit high levels of genetic structure due to female philopatry and patchy configuration of mountain habitats. We assessed the spatial scale of genetic structure and the amount of gene flow in 301 Dall’s sheep (Ovis dalli dalli) at the landscape level using 15 nuclear microsatellites and 473 base pairs of the mitochondrial (mtDNA) control region. Dall’s sheep exhibited significant genetic structure within contiguous mountain ranges, but mtDNA structure occurred at a broader geographic scale than nuclear DNA within the study area, and mtDNA structure for other North American mountain sheep populations. No evidence of male-mediated gene flow or greater philopatry of females was observed; there was little difference between markers with different modes of inheritance (pairwise nuclear DNA F ST = 0.004–0.325; mtDNA F ST = 0.009–0.544), and males were no more likely than females to be recent immigrants. Historical patterns based on mtDNA indicate separate northern and southern lineages and a pattern of expansion following regional glacial retreat. Boundaries of genetic clusters aligned geographically with prominent mountain ranges, icefields, and major river valleys based on Bayesian and hierarchical modeling of microsatellite and mtDNA data. Our results suggest that fine-scale genetic structure in Dall’s sheep is influenced by limited dispersal, and structure may be weaker in populations occurring near ancestral levels of density and distribution in continuous habitats compared to other alpine ungulates that have experienced declines and marked habitat fragmentation.
... Сейчас известно уже много примеров генетически обусловленных адаптаций в современных популяциях. Популяции приспосабливаются к обитанию в мегаполисах (Макеева и др., 2011, 2013; Северцова и др., 2015), химическому загрязнению (Большаков, Моисеенко, 2009), искусственным условиям обитания (Артамонова, Махров, 2006), влиянию промысла (обзоры: Allendorf et al., 2008;Allendorf, Hard, 2009;Coltman, 2008;Рожков, Проняев, 2012), изменению климата (Parmesan, 2006;Reusch, Wood, 2007;Bradshaw, Holzapfel, 2008), появлению чужеродных видов (Altizer et al., 2003;Carroll, 2008); чужеродные виды, в свою очередь, адаптируются к новым для них местообитаниям (Sax et al., 2007;Орлова, 2011). ...
Conference Paper
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As alternative to application of neurotoxins in neurobiological studies, the article considers immunochemical approach for the purpose of blocking the activity of secondary messengers of aminergic systems, particularly, to studying input of serotonergic system in formation of mutagenic changes, epileptic seizures and drug addiction. Key words: aminergic systems, antibodies, serotonin-modulating anticonsolidation protein.
... data). This type of selective harvesting can have significant impacts on many different aspects of the population, including genetics, behavior, life history, and demography over a short ecological time scale, particularly for long-lived species with low fecundity such as Carettochelys (Clark and Tait 1982;Coltman 2008;Fenberg and Roy 2008). ...
... Understanding the population structure of a species is an important factor in making informed management decisions (Coltman 2008). This knowledge allows managers to track an animal's gene flow through the environment and evaluate how differential harvest on subsets of the population (e.g., sex, age) may affect the effective population size and hence genetic diversity of the population. ...
Article
Lynx rufus (Bobcat) is a wide-ranging and highly adaptable predator whose populations are increasing throughout much of its natural range including in the New England states, yet there are only limited empirical ecological studies there. How Bobcats are responding to the unique modern landscape of southern New England with its highly forested landscape coupled with high density of humans is unknown. This lack of spatial and population ecological information impedes evaluating recovery and management objectives and identifying necessary management actions. Our objectives were to better understand the spatial and population structure of Bobcats in Rhode Island. We specifically examined space use, resource selection, and population genetics. We trapped Bobcats across 5 field seasons from April 2015 to March 2019, totaling 2232 trap nights. We captured 8 Bobcats, equipped GPS collars to a subset (n = 3), and collected locations for 4 to 9 months. We used GPS locations to estimate annual and seasonal home-range size and individual-level seasonal resource selection within the home range for each individual. Further, we used tissue samples collected from trapped individuals and opportunistically collected roadkill (n = 30) to examine the population genetic structure and effective population size of Bobcats in the state. We found the mean winter and summer home-range sizes were 219.3 km2 and 51.7 km2, respectively. Bobcats selected for forested wetland habitats and were associated with areas closer to wetlands and young forests, according to resource-selection models. They also selected for areas with higher road densities, yet avoided developed areas. We found that Bobcats in Rhode Island are part of 1 genetic population and estimated their effective population size to be 82 individuals (95% CI: 44329). Our study highlights the importance of examining a widely distributed species at a local scale in order to employ evidence-based management practices.
... This influence is especially severe in stressful environments, i.e. with fluctuating environmental conditions (Markert et al., 2010). Many factors play substantial roles in the accumulation of genetic diversity with ecological (Banks et al., 2013) and anthropogenic disturbance being two of them (Coltman, 2008). ...
Article
European populations of common reed (Phragmites australis) are considered to build a single metapopulation with an extensive gene pool. Here we characterize the pattern of genetic diversity of 24 common reed populations in northeastern Germany and test how a disturbance by water salinity and mowing influences population genetic and morphological parameters. The investigation of in total 720 samples revealed them as uniformly tetraploid. The four haplotypes found and a set of eight SSR loci combined freely corroborating the hypothesis of a single large metapopulation. A MEMGENE plot based on pairwise genetic and geographic distances explained only 3.27% of genetic variation. Most of the genetic diversity was found within populations implying that gene flow over distances exceeding 10 km seems to be effectively mediated via seeds and pollen. Only in two cases, we encountered spread via rhizomes among different populations. Populations influenced by brackish water salinity show consistently higher values for Nei's unbiased gene diversity index, which we explain by higher disturbance (water salinity, water currents, stronger winds) creating more room for seedling establishment, and/or lower extension of clones. A structural equation model revealed both mowing and higher water salinity, but not genetic parameters, to have a negative effect on stem width, and put an effect on haplotype composition. Our results point towards a very effective gene flow in this species, a high degree of plasticity, and the importance of disturbance for the accumulation of genetic diversity, perhaps via seedling recruitment. Data Availability Statement Sequence data that support the findings of this research have been deposited in GenBank with the accession code OK666430. Raw data for all samples, used in this study, and the quality plots of assignment loci as isoloci, have been deposited in Figshare [DOI: 10.6084/m9.figshare.16438668; 10.6084/m9.figshare.16438812].
... Harvest-associated selection is one of the most important humaninduced evolutionary pressures for natural populations (Darimont et al., 2015;Hendry et al., 2017). Phenotypic changes in life-history traits (such as reduced body size-at-age and/or earlier maturation) have been observed in many targeted populations, threatening their resilience (Coltman, 2008;Jorgensen et al., 2007;Law, 2000;Marty et al., 2015;Sharpe & Hendry, 2009). While individual behaviour is the first line of defence to human-induced stressors, evidence for harvest-associated behavioural changes has so far been limited. ...
Article
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Fishing-associated selection is one of the most important human-induced evolutionary pressures for natural populations. However, it is unclear if fishing leads to heritable phenotypic changes in the targeted populations, as the heritability and genetic correlations of traits potentially under selection have received little attention. In addition, phenotypic changes could arise from fishing-associated environmental effects, such as reductions in population density. Using fish reared at baseline and reduced group density and repeatedly harvested by simulated trawling, we show that trawling can induce direct selection on fish social behaviour. As sociability has significant heritability, and is also genetically correlated with activity and exploration, trawling has the potential to induce both direct and indirect selection on a variety of fish behaviours, potentially leading to evolution over time. However, while trawling selection was consistent between density conditions, the heritability and genetic correlations of behaviours changed according to the population density. Fishing-associated environmental effects can thus modify the evolutionary potential of fish behaviour, revealing the need to use a more integrative approach to address the evolutionary consequences of fishing.
... Anthropogenic barriers, such as highways, block gene flows [108][109][110]. Sex-biased harvesting changes population structures and reduces effective population sizes [111,112]. These processes tend to decrease ungulate genetic diversity and, hence, affect species conservation and the probability of infectious disease emergence and spread. ...
Article
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Host genetic diversity tends to limit disease spread in nature and buffers populations against epidemics. Genetic diversity in wildlife is expected to receive increasing attention in contexts related to disease transmission and human health. Ungulates such as wild boar (Sus scrofa) and red deer (Cervus elaphus) are important zoonotic hosts that can be precursors to disease emergence and spread in humans. Tuberculosis is a zoonotic disease with relevant consequences and can present high prevalence in wild boar and red deer populations. Here, we review studies on the genetic diversity of ungulates and determine to what extent these studies consider its importance on the spread of disease. This assessment also focused on wild boar, red deer, and tuberculosis. We found a disconnection between studies treating genetic diversity and those dealing with infectious diseases. Contrarily, genetic diversity studies in ungulates are mainly concerned with conservation. Despite the existing disconnection between studies on genetic diversity and studies on disease emergence and spread, the knowledge gathered in each discipline can be applied to the other. The bidirectional applications are illustrated in wild boar and red deer populations from Spain, where TB is an important threat for wildlife, livestock, and humans.
... Wide-ranging habitat generalists such as different deer species are expected to exhibit low levels of population structure and a high potential for gene flow [100]. In our case, the evolution of population structure has been facilitated by the apparent historical extirpation of roe deer from much of their natural range (areas in the north-east and south), together with the existence of a relatively undisturbed remnant population (in the central part). ...
Article
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Simple Summary: We determined the genetic variability, population structure, and influence of genetic factors on two parameters of fitness (body mass and reproductive ability) in roe deer females in the contact zone between the Alps and the Dinaric Mountains by utilizing microsatellite variations in 214 individuals collected throughout Slovenia, Central Europe. Spatial differences in the genetic diversity of the species can be explained by population history, different approaches to population management and/or different connectivity among subpopulations. The population genetic structure confirms the high side fidelity of roe deer, but also shows the existence of admixtures of genes among different areas. We found evidence that genetic factors, including individual heterozygosity, influence body mass, confirming that heterozygosity positively affects fitness in wild populations. However, as the effect of genetic factors is usually masked or overruled by the influence of environmental factors, i.e., availability of resources, data on the joint influence of external and intrinsic factors on fitness and other life-history traits are needed to better predict the population dynamics of targeted species, which would enable sustainable, science-based population management. Abstract: Across its pan-European distribution, the European roe deer (Capreolus capreolus) faces a wide diversity of environmental and climatic conditions; therefore, several factors, including intrinsic ones, shape life-history traits and cause significant variability in parameters of fitness. By utilizing microsatellite variations in 214 roe deer females collected throughout Slovenia, Central Europe, we determined the genetic variability and population structure of this species in the contact zone between the Alps and the Dinaric Mountains, i.e., over a wider area where data on the genetic outlook for this-the most common and widespread European wild ungulate-have been completely lacking so far. Throughout the country, we found moderate microsatellite diversity (Ho = 0.57-0.65) in relation to the observed heterozygosity reported for other roe deer populations in Europe. Spatial differences in genetic diversity of the species in Slovenia can be explained by population history linked to varying approaches to population management and/or different connectivity among subpopulations in topographically differentiated habitats. A country-wide pattern of genetic structure is clearly defined by separation of the populations into three groups present in the following regions: (i) Southern sub-Mediterranean and Karst regions, (ii) Central Slovenia, and (iii) the Sub-Pannonian Region in the northeast. This is also confirmed by evidencing a moderate isolation by distance, especially by separating southern samples (coastal Slovenia) from others. Levels of genetic differentiation vary among populations, which can be explained by the effect of natural geographical barriers Animals 2020, 10, 2276 2 of 25 or the presence of anthropogenic barriers such as urban areas and highways. In the subset of 172 yearling females, we analyzed the influence of genetic advantage (individual heterozygosity) and other genetic data (reflected in the structuring of the population) on body mass and reproductive ability. We found evidence that genetic factors influence the body mass of roe deer yearling females (explaining altogether 18.8% of body mass variance), and the level of individual heterozygosity alone also positively affected body mass, which is in accordance with the theory that heterozygosity is commonly positively correlated with fitness in wild populations. However, we did not uncover any effect of heterozygosity on two parameters of reproductive ability (fertility and potential reproductive outcome), indicating that several other factors, especially environmental ones, have a predominant effect on the parameters of fitness in roe deer.
... The extent to which trophy hunting may have contributed to elephant trophy decline needs further investigation given the selectivity of this form of hunting in areas with low animal populations of some species (Damm 2008). Coltman (2008) suggested that harvesting of wild animal populations by humans is usually targeted by sex, age or phenotypic criteria, and is therefore selective. This assertion concurs with the present study findings as only male species were legally hunted. ...
... The extent to which trophy hunting may have contributed to elephant trophy decline needs further investigation given the selectivity of this form of hunting in areas with low animal populations of some species (Damm 2008). Coltman (2008) suggested that harvesting of wild animal populations by humans is usually targeted by sex, age or phenotypic criteria, and is therefore selective. This assertion concurs with the present study findings as only male species were legally hunted. ...
Article
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This study was based on a temporal analysis of trophy quality trends and hunting effort in Chewore South Safari Area (CSSA), Zimbabwe, for the period 2009-2012. We selected four of the big five species, namely; buffalo (Syncerus caffer), elephant (Loxodonta africana), the leopard (Panthera pardus) and lion (Panthera leo) for analysis. Existing database of 188 trophies from 2009 to 2011 was reviewed and recorded using the Safari Club International (SCI) scoring system. Further, 50 trophies for 2012 were measured and recorded based on the SCI scoring system. Local ecological knowledge on trophy quality and hunting effort in CSSA was obtained through semi-structured questionnaires from 22 conveniently selected professional hunters in 2012. The results indicated no significant change in trophy quality trends of buffalo, leopard and lion (p > 0.05) over the study period. In contrast, there was a significant decline in elephant trophy quality trend over the same period (p < 0.05). The results showed no significant change in hunting effort over the study period for all the four study species (p > 0.05). Furthermore, seventy-two percent (72%, n = 13) of the professional hunters confirmed that elephant population was declining in CSSA and this was likely due to poaching. Professional hunters perceived trophy hunting as a source of financial capital generation for wildlife conservation (61%, n = 11), as well as positively contributing to the local economy (56%, n = 10). It was concluded that hunting has limited negative impact on species trophy quality trends when a sustainable hunting system is consistently followed in CSSA. CSSA management need to continuously monitor trophy hunting, animal populations and employ adaptive management approach to quota setting and species conservation.
... Quantifying h 2 of specific traits in wild species that are farmed or harvested can be valuable for breeding design (Guo et al. 2018) and management decisions (Coltman 2008). White-tailed deer (Odocoileus virginianus) are a big-game species of economic and cultural value across North America. ...
Article
Estimating heritability (h2) is required to predict the response to selection and is useful in species that are managed or farmed using trait information. Estimating h2 in free-ranging populations is challenging due to the need for pedigrees; genomic-relatedness matrices (GRMs) circumvent this need and can be implemented in nearly any system where phenotypic and genome-wide single nucleotide polymorphism (SNP) data are available. We estimated the heritability of five body and three antler traits in a free-ranging population of white-tailed deer (Odocoileus virginianus) on Anticosti Island, Quebec, Canada. We generated classic and robust GRMs from >10,000 SNPs: hind foot length, dressed body mass and peroneus muscle mass had high h2 values of 0.62, 0.44 and 0.55, respectively. Heritability in male-only antler features ranged from 0.07 to 0.33 and had high standard errors. We explored the influence of filtering by minor allele frequency and data completion on h2: GRMs derived from fewer SNPs had reduced h2 estimates and the relatedness coefficients significantly deviated from those generated with more SNPs. As a corollary, we discussed limitations to the application of GRMs in the wild, notably how skewed GRMs, specifically many unrelated individuals, can increase variance around h2 estimates. This is the first study to estimate h2 on a free-ranging population of white-tailed deer and should be informative for breeding designs and management as these traits should respond to selection.
... The first paper to claim an evolutionary response to hunter selection (Coltman et al. 2003) used a quantitative genetic animal model but failed to eliminate the possible influence of change in environment as an alternative explanation for phenotypic change (Postma 2006, Hadfield et al. 2010. Coltman (2008) acknowledged the limitations identified by Postma (2006), yet the original Coltman et al. (2003) paper continues to be cited heavily as definitive evidence of the evolutionary effect of trophy hunting (Darimont et al. 2009, Pelletier et al. 2012; >350 papers from 2007-2017 in Web of Science). Coulson et al. (2018) examine how horn size is likely to respond to trophy hunting in a quantitative genetics model, concluding that selection must be intensive over several generations to produce a measurable evolutionary response. ...
... Сейчас известно уже много примеров генетически обусловленных адаптаций в современных популяциях. Популяции приспосабливаются к обитанию в мегаполисах (Макеева и др., 2011, 2013; Северцова и др., 2015), химическому загрязнению (Большаков, Моисеенко, 2009), искусственным условиям обитания (Артамонова, Махров, 2006), влиянию промысла (обзоры: Allendorf et al., 2008;Allendorf, Hard, 2009;Coltman, 2008;Рожков, Проняев, 2012), изменению климата (Parmesan, 2006;Reusch, Wood, 2007;Bradshaw, Holzapfel, 2008), появлению чужеродных видов (Altizer et al., 2003;Carroll, 2008); чужеродные виды, в свою очередь, адаптируются к новым для них местообитаниям (Sax et al., 2007;Орлова, 2011). ...
... At the species level, many different population structures exist. It has been thought that large-bodied habitat generalists, such as large carnivores, exhibit lower levels of genetic structuring and higher migration rates than habitat specialists, with more restricted ranges (Coltman 2008). Large-bodied habitat generalists are often top predators, and by virtue of their high resource requirements, they occur at low densities, have large home ranges and require vast areas to harbor viable populations (Purvis et al. 2000, Gittleman et al. 2001. ...
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Tigers are endangered in the wild and face increasing threats from habitat loss and fragmentation. The majority of their range occurs in the Indian subcontinent, which is therefore a critical area for tiger conservation. Bengal tigers are distributed across many small protected areas in India. Two important Bengal tiger landscapes – Terai Arc Landscape (TAL) and Sundarbans in India were lacking in basic genetic information and needed to address the impact of anthropogenic pressure and climate change on their genetic makeup in order to identify conservation units. Therefore, I employed nuclear and mitochondrial genetic markers on TAL and Sundarbans tiger individuals to respond these demands for the first time. Thirty-nine heterologous microsatellite loci were screened on Bengal tigers and thirteen of these loci were selected to genotype Bengal tiger samples from western TAL (WTAL) and Sundarbans. After I had genotyped seventy-one Bengal tiger individuals from WTAL, I found cryptic population genetic structure, moderate gene flow and asymmetric migration among the subpopulation. Genetic diversity was moderate and there were no signs of population bottlenecks. In order to maintain the connectivity of subpopulations and avoid human–wildlife conflict, relocation of villages is necessary. Preventive measures against habitat encroachment and a ban on sand and boulder mining in the corridor area should also be implemented. Noninvasively-collected tiger samples from Sundarbans were analyzed for mitochondrial and microsatellite markers and compared with mainland (northern and peninsular) Bengal tiger populations in India. Sundarbans tigers were found to be genetically distinct and had lower genetic variation in comparison to other mainland tiger populations. Demographic analysis indicated recent historical isolation (600–2000 years ago) of the Sundarbans tiger from the mainland. Both historical and genetic evidence supported that the Sundarbans tiger was genetically connected to other mainland tigers until recently. Conclusively, genetic isolation from the mainland tiger population and adaptation to the mangrove ecosystem might have jointly shaped the genetic architecture of the Sundarbans tiger. Hence, the Sundarbans tiger needs special conservation attention for the preservation of its unique ability to adapt and for its genetic individuality. It should be managed as an evolutionary significant unit (ESU) under the adaptive evolutionary conservation (AEC) criteria. I also addressed a problem in the previously suggested sex-specific gene flow estimation method and recommended an alternative approach for a more precise estimation.
... Science-based harvest management is often effective at regulating population sizes and reducing humanwildlife conflicts, but excessive harvest can lead to reduced genetic diversity or altered population structure (Allendorf et al. 2008). Specifically, excessive harvest can substantially reduce a species' ability to respond to environmental change or anthropogenic disturbances and alter a species' evolutionary trajectory (Coltman 2008;Frankham 2005). ...
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The genetic effects of harvest may be especially important in species that form social groups, such as gray wolves (Canis lupus). Though much research exists on the ecology and population dynamics of gray wolves, little research has focused on how anthropogenic harvest relates to the genetics of wolf populations. To analyze the short-term genetic consequences of the first two years of public wolf harvest in Minnesota following delisting under the Endangered Species Act, we genotyped harvested individuals at 18 microsatellite loci and quantified changes in population genetic structure and diversity in the first post-harvest year. If the harvest rate was high enough to create detectable genetic changes, population structure and differentiation between clusters could both increase because of decreased natal dispersal and increased disperser mortality, or they could decrease because of increased immigration from outside the population. In the Minnesota population, heterozygosity and allelic richness were not significantly different between years. However, population genetic structure increased and effective migration decreased among the sampled wolves. While the role of anthropogenic harvest in these changes cannot be distinguished from other confounding factors, this analysis suggests that harvest has a non-negligible effect and indicates the need for continued study to determine whether harvest-induced changes in genetic structure affect the evolutionary trajectory of harvested populations.
... No strong evidence was obtained for possible ancestry relationships between Italian, Canadian and French populations based on our genetic clustering inferred in STRUCTURE. The analysis highlights that such a pattern may be the consequence of the species ecological characters: A. artemisiifolia is awide-ranging habitat generalist exhibiting a high potential for gene flow (Coltman, 2008;Kočiš Tubić et al., 2015). On the other hand, a degree of differentiation between French and Italian populations can be observed (prevalence of cluster displayed by green colour in the French populations; prevalence of the other cluster displayed by red colour in the Italian populations). ...
Article
Investigations of the genetic pattern and colonisation sources and the routes of invasion by alien species populations are crucial for identifying invasion mechanisms and the reasons for the bio-ecological success of invasive species. The aim of our work was to study the genetic pattern of Italian populations of Ambrosia artemisiifolia in comparison with that of some French and Canadian populations and to use herbarium records to characterise the colonisation areas of A. artemisiifolia across Italy. Molecular investigations were based on a set of nuclear SSR marker loci, which we used to analyse a number of Italian, Canadian and France populations. The time-spatial spread of A. artemisiifolia was reconstructed through the distributional pathway of 194 herbarium specimens.
... Determinar la proporción de sexos es primordial en poblaciones sometidas a aprovechamiento realizado de manera selectiva, porque existe una afectación directa a la estructura de edades y de sexos. Este manejo impacta de manera significativa el número de nacimientos en la población, lo que ocasiona al paso del tiempo un desbalance tanto en el tamaño de la población como en la proporción de sexos (Coltman, 2008;Milner, Nilsen y Andreassen, 2007). ...
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Se obtuvieron excretas de venado cola blanca (Odocoileus virginianus) en cautiverio dentro de unidades de manejo para la conservación de la vida silvestre, ubicadas en Mérida y Ticul, Yucatán, México, para medir las concentraciones de los metabolitos de testosterona, progesterona y estrógeno con la técnica de radioinmunoanálisis y se relacionaron mediante índices. Se obtuvieron concentraciones detectables de los 3 metabolitos y se analizaron los índices mediante la teoría del valor predictivo. Los índices de progesterona /testosterona —ambos a dilución 1:2 y dilución 1:20/1:2, respectivamente— tuvieron la mayor eficiencia (77.5%) para asignar correctamente el sexo en la época no reproductiva. En la época reproductiva el índice progesterona / testosterona —dilución 1:2/1:20, respectivamente— tuvo la mayor eficiencia (68.75%). Estas eficiencias son superiores a las obtenidas mediante métodos indirectos para determinar la proporción de sexos en venado cola blanca. El método de determinación del sexo por estimación de los metabolitos de hormonas fecales es factible de ser aplicado en poblaciones silvestres de venado cola blanca.
... The philopatric nature of salmonids, including Lake Whitefish (e.g., Scheerer et al. 1985;Walker et al. 1993), could potentially limit gene flow between these basins similar to other lacustrine salmonids (Fraser et al. 2004;Hendry et al. 2004;Ramstad et al. 2004;Golder Associates 2006), yet such population genetic patterns were not evident over two distinct time periods in our study. Additionally, microsatellites revealed more temporal than spatial variation in allele frequencies, which may be significant in the context of our inferred changes in N e (Coltman 2008). ...
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Size-selective harvest may lead to over-exploitation of commercial fisheries, but the population genetic and evolutionary consequences of such practices remain poorly understood. We investigated the role of within-generation selection in a historically over-exploited Lake Whitefish (Coregonus clupeaformis) population associated with fisheries-induced evolution in Lesser Slave Lake, Alberta, Canada. DNA from archived scales of Lake Whitefish collected between 1986 and 1999 were genotyped at 20 microsatellites and 51 gene-coding SNPs associated with growth and reproduction. We found that the Lake Whitefish in Lesser Slave Lake consisted of a single genetic stock, with microsatellites revealing more temporal than spatial variation in allele frequencies. A comparative genome scan among replicate cohorts from commercially harvested versus random survey samples identified one candidate SNP under divergent selection. This SNP localized within a gene encoding nucleoside diphosphate kinase A, a protein associated with differential growth. Collectively, the results highlight the utility of within-generation genome scans towards investigating the evolutionary consequences of harvest in the wild.
... The premise that predators can generate evolutionary change in their prey has been persuasively demonstrated in natural systems (e.g., Reznick et al. 2008) and some anthropogenically influenced systems (e.g., Grift et al. 2003; Hard 2004; Swain et al. 2007; Coltman 2008). Nonetheless, the hypothesis that fishing can effect genetic responses by fish prey, having been seriously considered since the late 1970s (Handford et al. 1977; Ricker 1981), is one that remains controversial despite its logical premises (Dieckmann and Heino 2007; Marshall and McAdam 2007; Hutchings and Fraser 2008). ...
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I examined how the fitness (r) associated with early- and late-maturing genotypes varies with fishing mortality (F) and age-/size-specific probability of capture. Life-history data on Newfoundland’s northern Atlantic cod (Gadus morhua) allowed for the estimation of r for individuals maturing at 4 and 7 year in the absence of fishing. Catch selectivity data associated with four types of fishing gear (trap, gillnet, handline, otter trawl) were then incorporated to examine how r varied with gear type and with F. The resulting fitness functions were then used to estimate the F above which selection would favour early (4 year) rather than delayed (7 year) maturity. This evolutionarily-sensitive threshold, Fevol, identifies a limit reference point somewhat similar to those used to define overfishing (e.g., Fmsy, F0.1). Over-exploitation of northern cod resulted in fishing mortalities considerably greater than those required to effect evolutionary change. Selection for early maturity is reduced by the dome-shaped selectivities characteristic of fixed gears such as handlines (the greater the leptokurtosis, the lower the probability of a selection response) and enhanced by the knife-edged selectivities of bottom trawls. Strategies to minimize genetic change are consistent with traditional management objectives (e.g., yield maximization, population increase). Compliance with harvest control rules guided by evolutionarily-sensitive limit reference points, which may be achieved by adherence to traditional reference points such as Fmsy and F0.1, should be sufficient to minimize the probability of fisheries-induced evolution for commercially exploited species.
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The Union Island Gecko Gonatodes daudini is a Critically Endangered gecko, endemic to Union Island, Saint Vincent and the Grenadines. This species is occurring in an area less than 1 km² in one of the Grenadines only remaining stands of mature forest. Illegal trade in this species was first reported in 2011 and over-harvesting for the international pet trade is now considered the single most important threat to the continued survival of this species. The Union Island Gecko was proposed for a CITES Appendix I listing for Cop18, to be held in Sri Lanka in 2019. Here we support this proposed listing by showing that international trade in this species is ongoing. We documented the advertisement of 36 Union Island Geckos in 19 advertisements between September 2014 and December 2018. Germany (39%), Netherlands (22%) and Austria (14%) were the most frequent reported origin of advertisements. For 5 animals a wild-caught origin was reported. Our findings support those of previous trade surveys. Recent surveys suggest a sharp (80%) decline in the most accessible habitats of the wild population and any offtake could have detrimental consequences. As such, there is strong justification for an immediate listing of the Union Island Gecko in Appendix I.
Article
Genetic polymorphism varies among species and within genomes, and has important implications for the evolution and conservation of species. The determinants of this variation have been poorly understood, but population genomic data from a wide range of organisms now make it possible to delineate the underlying evolutionary processes, notably how variation in the effective population size (N e) governs genetic diversity. Comparative population genomics is on its way to providing a solution to 'Lewontin's paradox'-the discrepancy between the many orders of magnitude of variation in population size and the much narrower distribution of diversity levels. It seems that linked selection plays an important part both in the overall genetic diversity of a species and in the variation in diversity within the genome. Genetic diversity also seems to be predictable from the life history of a species.
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Here we report the first population genetic examination of a fungus in Hawaii and, to our knowledge, the only investigation of a saprotrophic fungal population distributed across an oceanic archipelago. Rhodocollybia laulaha fruits abundantly in the native rain forests of Hawaii from June through December. Its range includes the geographic extent of the Hawaiian Archipelago; however, this range is highly fragmented because of the discontinuous distribution of the native forest habitat where R. laulaha occurs. We hypothesized that significant patterns of population structure would be recovered within the geographic range of the Hawaiian mushroom R. laulaha resulting from divergence between isolated subpopulations. We tested for population structure and related inferred patterns of restricted gene flow to geographic distance, major geographic features such as mountain peaks and oceans, elevation zones, and spore morphology. We included 120 R. laulaha collections using data from the rRNA IGS1 region, two microsatellite loci, and 184 AFLP loci. Analyses of these genetic data suggest limited genetic structure among R. laulaha subpopulations in Hawaii correlated mostly with geographic distance. Patterns associated with specialization to elevation or spore morphology were not recovered. The limited geographic structure observed in R. laulaha is consistent with relatively recent population fragmentation.
Thesis
Intraspecific variability is now recognized for its importance on ecosystem functioning. In the context of biological invasions, which can strongly impact ecological processes, it is of high importance to understand the determinants and the patterns of genetic and phenotypic variability to fully apprehend the consequences of invasive individuals on recipient ecosystems. We demonstrated a high variability among and within populations of two crayfish species, Procambarus clarkii and Faxonius limosus, with distinct life-history traits and colonization histories in a narrow-invaded area. We highlighted that colonization history and environmental conditions were the main drivers of the contrasting patterns of genetic and phenotypic variability between the two species. Genetic analyses provided a great inference of local invasion pathways for P. clarkii, which had a great genetic variability, compared to F. limosus for which the local invasion pathways were more cryptic. We found that neutral and adaptive processes shaped the phenotypic variability of the two species in differing proportions. Then, we demonstrated the existence of a stable resource polymorphism along the benthic littoral-pelagic axis within populations of P. clarkii, suggesting that invaders could have contrasting impacts on ecosystem functioning between littoral and pelagic trophic chains. Finally, in an experiment context using a multi-traits approach, we demonstrated that the structure of trait covariations differed between species in a sympatric population, suggesting that P. clarkii impacts would be more predictable than F. limosus, and that P. clarkii could affect a higher range of ecological processes or impact the ecosystem functioning with a greater intensity than F. limosus. Overall, our findings stress the need to integrate intraspecific variability in the context of biological invasions to better understand their impacts on ecosystem functioning.
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Abstract The phylogeography history and contemporary agents of selection for many marine fisheries, characterized by widespread species distributions in the face of significant harvest, remains poorly understood. Chub mackerel (Scomber japonicus) are a widespread species in the Indo-Pacific and represent one of the top five commercially fished species in the world, yet their phylogeographic history remains unknown. We characterized the genetic diversity, structure and demographic history of S. japonicus throughout adjacent Chinese seas (from the Yellow Sea to the South China Sea). Using 220 individuals from 11 sites, we inferred 55 distinct haplotypes from complete mitochondrial cytochrome b gene sequences. Haplotype diversity ranged from 0.505 to 0.967 and nucleotide diversity ranged from 0.00056 to 0.01042. Genetic differentiation (Fst) statistics suggested that the highest level of differentiation existed between the SanYa and SanSha localities (Fst = 0.86977), while the lowest levels of differentiation occurred between the DongGang and ShiDao localities (Fst ∼ 0). Kimura's genetic distances ranged from 0.001 to 0.011 within and from 0.001 to 0.018 between populations. Hierarchical analysis of molecular variance, Neighbor-joining and median-joining network analyses identified significant phylogeographic structure with two localities (SanYa, Hainan of the South China Sea and LianYunGang, Jiangsu of the East China Sea) explaining most of the genetic variation observed, while the remaining populations were poorly differentiated.
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We evaluate methods for measuring and specifying rates of microevolution in the wild, with particular regard to studies of contemporary, often deemed "rapid," evolution. A considerable amount of ambiguity and inconsistency persists within the field, and we provide a number of suggestions that should improve study design, inference, and clarity of presentation. (1) Some studies measure change over time within a population (allochronic) and others measure the difference between two populations that had a common ancestor in the past (synchronic). Allochronic studies can be used to estimate rates of "evolution," whereas synchronic studies more appropriately estimate rates of "divergence." Rates of divergence may range from a small fraction to many times the actual evolutionary rates in the component populations. (2) Some studies measure change using individuals captured from the wild, whereas others measure differences after rearing in a common environment. The first type of study can be used to specify "phenotypic" rates and the later "genetic" rates. (3) The most commonly used evolutionary rate metric, the darwin, has a number of theoretical shortcomings. Studies of microevolution would benefit from specifying rates in standard deviations per generation, the haldane. (4) Evolutionary rates are typically specified without an indication of their precision. Readily available methods for specifying confidence intervals and statistical significance (regression, bootstrapping, randomization) should be implemented. (5) Microevolutionists should strive to accumulate time series, which can reveal temporal shifts in the rate of evolution and can be used to identify evolutionary patterns. (6) Evolutionary rates provide a convenient way to compare the tempo of evolution across studies, traits, taxa, and time scales, but such comparisons are subject to varying degrees of confidence. Comparisons across different time scales are particularly tenuous. (7) A number of multivariate rate measures exist, but considerable theoretical development is required before their utility can be determined. We encourage the continued investigation of evolutionary rates because the information they provide is relevant to a wide range of theoretical and practical issues.
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Commercial harvest of red sea urchins began in Washington state in 1971. Harvests peaked in the late 1980s and have since declined substantially in Washington and other areas of the U.S. west coast. We studied effects of experimental harvest on red sea urchins in San Juan Channel (SJC), a marine reserve in northern Washington. We recorded changes in density and size distribution of sea urchin populations resulting from three levels of experimental harvest: 1) annual size-selective harvest (simulating current commercial urchin harvest regulations), 2) monthly complete (non-sizeselective) harvest, and 3) no harvest (control) sites. We also examined re-colonization rates of harvested sites. The red sea urchin population in SJC is composed of an accumulation of large, old individuals. Juvenile urchins represent less than 1% of the population. Lower and upper size limits for commercial harvest protect 5% and 45% of the population, respectively. Complete harvest reduced sea urchin densities by 95%. Annual size-selective harvest significantly decreased sea urchin densities by 67% in the first year and by 47% in the second year. Two years of size-selective harvest significantly altered the size distribution of urchins, decreasing the density of legal-size urchins. Recolonization of harvested sites varied seasonally and occurred primarily through immigration of adults. Selective harvest sites were recolonized to 51% and 38% of original densities, respectively, six months after the first and second annual harvests. Yields declined substantially in the second year of size-selective harvest because of the fishing down of the population and because of low re-colonization rates of harvested sites. We recommend that managers consider the potential efficacy of marine harvest refuges and reevaluate the existing upper and lower size limits for commercial harvest to improve long-term management of the sea urchin fishery in Washington.
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The Hamilton and Zuk hypothesis1 that the intensity of male ornamentation allows females to assess a male's ability to resist parasites has been much debated recently2-12. Much of the empirical work to test this hypothesis has been with insect2, fish3,4, reptilian5 or avian6-9 hosts. In a southern Indian population, we show that the length of tusks of male Asian elephants (Elephas maximus), corrected for differences due to age, is significantly negatively correlated with intestinal parasite loads. The less aggregated distribution of parasites in this elephant population, as compared to other mammalian species, indicates that ivory poaching may have already selectively removed a significant proportion of parasite-resistant individuals. Ivory poaching which targets larger-tusked elephants may thus affect the health status of the population.
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Population genomics has the potential to improve studies of evolutionary genetics, molecular ecology and conservation biology, by facilitating the identification of adaptive molecular variation and by improving the estimation of important parameters such as population size, migration rates and phylogenetic relationships. There has been much excitement in the recent literature about the identification of adaptive molecular variation using the population-genomic approach. However, the most useful contribution of the genomics model to population genetics will be improving inferences about population demography and evolutionary history.
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Waterbird hunting is a widespread human activity over wetlands of the Eurasian continent. It has two components that can influence the population dynamics of migratory species : mortality and disturbance. Disturbance is the focus of an increasing number of detailed studies, using both experimental and theoretical approaches. They are synthesized herein. Disturbance is considered important when induced changes influence the fitness of the individuals of a species (decrease in survival or breeding success). Studies show that disturbance almost always change the geographical distribution of birds, conducting to an under-exploitation of food resources available in hunting areas. Disturbance can also favour an increase in the turnover rate of individuals on their migratory stopover. These changes in bird distribution, although precisely quantified at a local scale, have an unknown impact on the population size of the concerned species. The wide distribution of several of these species ranging over several continents makes the precise evaluation of this impact difficult. Disturbance changes behaviour either by increasing time spent in activities more costly than those done without disturbance or by decreasing time spent gaining energy. Estimation or simulation of these lost can reach 25% of the daily energy expenses. Facing disturbance, birds can develop several physiological adaptations, for instance an increased food intake, an increased efficiency of energy assimilation or an augmentation of corticosterone secretion stimulating food searching. The direct evaluation of the energy balance of these adaptations has not been made yet and it can be acknowledged that they allow birds to maintain energy gains similar to those obtained without disturbance. However, the long-term cost of this compensation is high. A recent study of the Greater Snow Goose Anser caerulescens atlantica on their spring stopover in Canada indicates that hunting disturbance makes geese use lower quality habitats, decreases their body condition (fat and protein) when they depart to the breeding sites and decreases their breeding success relative to individuals that have not experienced hunting. Uncertainties remain, for instance at the species level (few studies on waders), but all authors that emphasized them also agree to acknowledge that protection measures must be taken to counter-balance the effects of hunting disturbance. They recommend the increase of protected areas (hunt-free areas), the elaboration of a network of reserves and the establishment of non hunted zones around existing reserves to reduce to the minimum the negative effects of disturbance on birds that use these reserves. The implementation of these management actions must favour the widening of the distribution of these populations and facilitate the local and regional increase of their numbers. These protection measures are positive responses to the recommendations of the European Union birds and habitats directives.
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Sexual traits are usually more phenotypically variable than non-sexual traits. We show that additive genetic variation is also higher in sexual traits, and often greater than in the same, non-sexually selected trait in females or other comparable traits in the same species. In contrast there is no difference in residual variation (environmental and non-additive) or heritability. The higher genetic variability of sexual traits is contrary to the expectations of the lek paradox. This hypothesis predicts that strong sexual selection, due to female choice, leads to fixation of most genetic variation in male sexual characters. High genetic variability in sexual traits can be explained if they are subject to directional selection that is greater than linear because this selects for greater phenotypic variation. It favours modifiers that increase the number of genes and the average contribution of a locus to phenotypic variance in sexual traits. These results provide a general resolution of the lek paradox.
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By estimating probabilistic reaction norms for age and size at maturation, we show that maturation schedules of Atlantic cod (Gadus morhua) off Labrador and Newfoundland shifted toward earlier ages and smaller sizes during the late 1980s and early 1990s, when these populations underwent a severe collapse in biomass and subsequently were closed for directed commercial fishing. We also demonstrate that this trend towards maturation at younger ages and smaller sizes is halted and even shows signs of reversal during the closure of the fisheries. In addition, our analysis reveals that males tend to mature earlier and at a smaller size than females and that maturation age and size decrease with increasing latitude. Importantly, the maturation reaction norms presented here are robust to variation in survival and growth (through phenotypic plasticity) and are thus strongly indicative of rapid evolutionary changes in cod matu- ration as well as of spatial and sex-specific genetic variation. We therefore suggest that maturation reaction norms can provide helpful reference points for managing harvested populations with evolving life histories.
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Changes to life history traits are often concomitant with prolonged periods of exploitation. In the Northwest Atlantic, 30- to 40-year declines of more than 90% of Atlantic cod (Gadus morhua) have been associated with signifi- cant reductions in age and length at maturity, changes most parsimoniously explained as genetic responses to fishing. Increased survival costs of reproduction associated with earlier maturity, resulting in higher natural mortality and shorter life span, negatively affect population growth rate and rate of recovery. Coupled with lower hatching rate among first-time spawners and smaller size at maturity, a modest reduction in age from 6 to 4 years can reduce annual population growth in Atlantic cod by 25%-30%, based on the output of a stochastic, age-structured life history model. Earlier maturity more than doubles the probability of negative population growth every generation. These results under- score the potential for fishing-induced changes to life history traits alone to generate slow or negligible recovery in marine fishes, exacerbating negative impacts on population growth resulting from ecosystem-level alterations to interspecific competition and predation. Résumé : Des changements de caractéristiques démographiques accompagnent souvent les longues périodes
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Two major factors are likely to have caused recent elephant population declines: carrying capacity reductions and hunting for ivory. A model is developed to disentangle the effects of these two factors on elephant population dynamics since 1814. The model suggests that carrying capacity reductions were a major cause of elephant population declines in the 19th Century and first half of the 20th Century, but that, since 1950, hunting for ivory has been the cause of an increasingly rapid population decline. These results are extremely robust to changes in parameter values within a reasonable range.
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A new Bayesian method that uses individual multilocus genotypes to estimate rates of recent immigration (over the last several generations) among populations is presented. The method also estimates the posterior probability distributions of individual immigrant ancestries, population allele frequencies, population inbreeding coefficients, and other parameters of potential interest. The method is implemented in a computer program that relies on Markov chain Monte Carlo techniques to carry out the estimation of posterior probabilities. The program can be used with allozyme, microsatellite, RFLP, SNP, and other kinds of genotype data. We relax several assumptions of early methods for detecting recent immigrants, using genotype data; most significantly, we allow genotype frequencies to deviate from Hardy-Weinberg equilibrium proportions within populations. The program is demonstrated by applying it to two recently published microsatellite data sets for populations of the plant species Centaurea corymbosa and the gray wolf species Canis lupus. A computer simulation study suggests that the program can provide highly accurate estimates of migration rates and individual migrant ancestries, given sufficient genetic differentiation among populations and sufficient numbers of marker loci.
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We describe extensions to the method of Pritchard et al. for inferring population structure from multilocus genotype data. Most importantly, we develop methods that allow for linkage between loci. The new model accounts for the correlations between linked loci that arise in admixed populations (“admixture linkage disequilibium”). This modification has several advantages, allowing (1) detection of admixture events farther back into the past, (2) inference of the population of origin of chromosomal regions, and (3) more accurate estimates of statistical uncertainty when linked loci are used. It is also of potential use for admixture mapping. In addition, we describe a new prior model for the allele frequencies within each population, which allows identification of subtle population subdivisions that were not detectable using the existing method. We present results applying the new methods to study admixture in African-Americans, recombination in Helicobacter pylori, and drift in populations of Drosophila melanogaster. The methods are implemented in a program, structure, version 2.0, which is available at http://pritch.bsd.uchicago.edu.
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We present a statistical method for identifying species hybrids using data on multiple, unlinked markers. The method does not require that allele frequencies be known in the parental species nor that separate, pure samples of the parental species be available. The method is suitable for both markers with fixed allelic differences between the species and markers without fixed differences. The probability model used is one in which parentals and various classes of hybrids (F1's, F2's, and various backcrosses) form a mixture from which the sample is drawn. Using the framework of Bayesian model-based clustering allows us to compute, by Markov chain Monte Carlo, the posterior probability that each individual belongs to each of the distinct hybrid classes. We demonstrate the method on allozyme data from two species of hybridizing trout, as well as on two simulated data sets.
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A new method is described for estimating genetic relatedness from genetic markers such as protein polymorphisms. It is based on Grafen's (1985) relatedness coefficient and is most easily interpreted in terms of identity by descent rather than as a genetic regression. It has several advantages over methods currently in use: it eliminates a downward bias for small sample sizes; it improves estimation of relatedness for subsets of population samples; and it allows estimation of relatedness for a single group or for a single pair of individuals. Individual estimates of relatedness tend to be highly variable but, in aggregate, can still be very useful as data for nonparametric tests. Such tests allow testing for differences in relatedness between two samples or for correlating individual relatedness values with another variable.
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A marker-based method for studying quantitative genetic characters in natural populations is presented and evaluated. The method involves regressing quantitative trait similarity on marker-estimated relatedness between individuals. A procedure is first given for estimating the narrow sense heritability and additive genetic correlations among traits, incorporating shared environments. Estimation of the actual variance of relatedness is required for heritability, but not for genetic correlations. The approach is then extended to include isolation by distance of environments, dominance, and shared levels of inbreeding. Investigations of statistical properties show that good estimates do not require great marker polymorphism, but rather require significant variation of actual relatedness; optimal allocation generally favors sampling many individuals at the expense of assaying fewer marker loci; when relatedness declines with physical distance, it is optimal to restrict comparisons to within a certain distance; the power to estimate shared environments and inbreeding effects is reasonable, but estimates of dominance variance may be difficult under certain patterns of relationship; and any linkage of markers to quantitative trait loci does not cause significant problems. This marker-based method makes possible studies with long-lived organisms or with organisms difficult to culture, and opens the possibility that quantitative trait expression in natural environments can be analyzed in an unmanipulative way.
Article
Genetic divergence and gene flow among closely related populations are difficult to measure because mutation rates of most nuclear loci are so low that new mutations have not had sufficient time to appear and become fixed. Microsatellite loci are repeat arrays of simple sequences that have high mutation rates and are abundant in the eukaryotic genome. Large population samples can be screened for variation by using the polymerase chain reaction and polyacrylamide gel electrophoresis to separate alleles. We analyzed 10 microsatellite loci to quantify genetic differentiation and hybridization in three species of North American wolflike canids. We expected to find a pattern of genetic differentiation by distance to exist among wolflike canid populations, because of the finite dispersal distances of individuals. Moreover, we predicted that, because wolflike canids are highly mobile, hybrid zones may be more extensive and show substantial changes in allele frequency, relative to nonhybridizing populations. We demonstrate that wolves and coyotes do not show a pattern of genetic differentiation by distance. Genetic subdivision in coyotes, as measured by theta and Gst, is not significantly different from zero, reflecting persistent gene flow among newly established populations. However, gray wolves show significant subdivision that may be either due to drift in past Ice Age refugia populations or a result of other causes. Finally, in areas where gray wolves and coyotes hybridize, allele frequencies of gray wolves are affected, but those of coyotes are not. Past hybridization between the two species in the south-central United States may account for the origin of the red wolf.
Article
We describe a model-based clustering method for using multilocus genotype data to infer population structure and assign individuals to populations. We assume a model in which there are K populations (where K may be unknown), each of which is characterized by a set of allele frequencies at each locus. Individuals in the sample are assigned (probabilistically) to populations, or jointly to two or more populations if their genotypes indicate that they are admixed. Our model does not assume a particular mutation process, and it can be applied to most of the commonly used genetic markers, provided that they are not closely linked. Applications of our method include demonstrating the presence of population structure, assigning individuals to populations, studying hybrid zones, and identifying migrants and admixed individuals. We show that the method can produce highly accurate assignments using modest numbers of loci—e.g., seven microsatellite loci in an example using genotype data from an endangered bird species. The software used for this article is available from http://www.stats.ox.ac.uk/~pritch/home.html.
Article
Recent empirical evidence indicates that although fitness and fitness components tend to have low heritability in natural populations, they may nonetheless have relatively large components of additive genetic variance. The molecular basis of additive genetic variation has been investigated in model organisms but never in the wild. In this article we describe an attempt to map quantitative trait loci (QTL) for birth weight (a trait positively associated with overall fitness) in an unmanipulated, wild population of red deer (Cervus elaphus). Two approaches were used: interval mapping by linear regression within half-sib families and a variance components analysis of a six-generation pedigree of >350 animals. Evidence for segregating QTL was found on three linkage groups, one of which was significant at the genome-wide suggestive linkage threshold. To our knowledge this is the first time that a QTL for any trait has been mapped in a wild mammal population. It is hoped that this study will stimulate further investigations of the genetic architecture of fitness traits in the wild.
Article
Many empirical studies have assessed fine-scale spatial genetic structure (SGS), i.e. the nonrandom spatial distribution of genotypes, within plant populations using genetic markers and spatial autocorrelation techniques. These studies mostly provided qualitative descriptions of SGS, rendering quantitative comparisons among studies difficult. The theory of isolation by distance can predict the pattern of SGS under limited gene dispersal, suggesting new approaches, based on the relationship between pairwise relatedness coefficients and the spatial distance between individuals, to quantify SGS and infer gene dispersal parameters. Here we review the theory underlying such methods and discuss issues about their application to plant populations, such as the choice of the relatedness statistics, the sampling scheme to adopt, the procedure to test SGS, and the interpretation of spatial autocorrelograms. We propose to quantify SGS by an ' Sp ' statistic primarily dependent upon the rate of decrease of pairwise kinship coefficients between individuals with the logarithm of the distance in two dimensions. Under certain conditions, this statistic estimates the reciprocal of the neighbourhood size. Reanalysing data from, mostly, published studies, the Sp statistic was assessed for 47 plant species. It was found to be significantly related to the mating system (higher in selfing species) and to the life form (higher in herbs than trees), as well as to the population density (higher under low density). We discuss the necessity for comparing SGS with direct estimates of gene dispersal distances, and show how the approach presented can be extended to assess (i) the level of biparental inbreeding, and (ii) the kurtosis of the gene dispersal distribution.
Article
Abstract Parasite resistance and body size are subject to directional natural selection in a population of feral Soay sheep (Ovis aries) on the island of St. Kilda, Scotland. Classical evolutionary theory predicts that directional selection should erode additive genetic variation and favor the maintenance of alleles that have negative pleiotropic effects on other traits associated with fitness. Contrary to these predictions, in this study we show that there is considerable additive genetic variation for both parasite resistance, measured as fecal egg count (FEC), and body size, measured as weight and hindleg length, and that there are positive genetic correlations between parasite resistance and body size in both sexes. Body size traits had higher heritabilities than parasite resistance. This was not due to low levels of additive genetic variation for parasite resistance, but was a consequence of high levels of residual variance in FEC. Measured as coefficients of variation, levels of additive genetic variation for FEC were actually higher than for weight or hindleg length. High levels of additive genetic variation for parasite resistance may be maintained by a number of mechanisms including high mutational input, balancing selection, antagonistic pleiotropy, and host-parasite coevolution. The positive genetic correlation between parasite resistance and body size, a trait also subject to sexual selection in males, suggests that parasite resistance and growth are not traded off in Soay sheep, but rather that genetically resistant individuals also experience superior growth.
Article
Abstract Maternal effects are widespread and can have dramatic influences on evolutionary dynamics, but their genetic basis has been measured rarely in natural populations. We used cross-fostering techniques and a long-term study of a natural population of red squirrels, Tamiasciurus hudsonicus, to estimate both direct (heritability) and indirect (maternal) influences on the potential for evolution. Juvenile growth in both body mass and size had significant amounts of genetic variation (mass h2= 0.10; size h2= 0.33), but experienced large, heritable maternal effects. Growth in body mass also had a large positive covariance between direct and maternal genetic effects. The consideration of these indirect genetic effects revealed a greater than three-fold increase in the potential for evolution of growth in body mass (h t2= 0.36) relative to that predicted by heritability alone. Simple heritabilities, therefore, may severely underestimate or overestimate the potential for evolution in natural populations of animals.
Article
Microsatellite markers are routinely used to investigate the genetic structuring of natural populations. The knowledge of how genetic variation is partitioned among populations may have important implications not only in evolutionary biology and ecology, but also in conservation biology. Hence, reliable estimates of population differentiation are crucial to understand the connectivity among populations and represent important tools to develop conservation strategies. The estimation of differentiation is c from Wright's FST and/or Slatkin's RST, an FST -analogue assuming a stepwise mutation model. Both these statistics have their drawbacks. Furthermore, there is no clear consensus over their relative accuracy. In this review, we first discuss the consequences of different temporal and spatial sampling strategies on differentiation estimation. Then, we move to statistical problems directly associated with the estimation of population structuring itself, with particular emphasis on the effects of high mutation rates and mutation patterns of microsatellite loci. Finally, we discuss the biological interpretation of population structuring estimates.
Article
We review commonly used population definitions under both the ecological paradigm (which emphasizes demographic cohesion) and the evolutionary paradigm (which emphasizes reproductive cohesion) and find that none are truly operational. We suggest several quantitative criteria that might be used to determine when groups of individuals are different enough to be considered ‘populations'. Units for these criteria are migration rate ( m ) for the ecological paradigm and migrants per generation ( Nm ) for the evolutionary paradigm. These criteria are then evaluated by applying analytical methods to simulated genetic data for a finite island model. Under the standard parameter set that includes L = 20 High mutation (microsatellitelike) loci and samples of S = 50 individuals from each of n = 4 subpopulations, power to detect departures from panmixia was very high (∼ 100%; P < 0.001) even with high gene flow ( Nm = 25). A new method, comparing the number of correct population assignments with the random expectation, performed as well as a multilocus contingency test and warrants further consideration. Use of Low mutation (allozyme-like) markers reduced power more than did halving S or L . Under the standard parameter set, power to detect restricted gene flow below a certain level X (H 0 : Nm < X ) can also be high, provided that true Nm ≤ 0.5 X . Developing the appropriate test criterion, however, requires assumptions about several key parameters that are difficult to estimate in most natural populations. Methods that cluster individuals without using a priori sampling information detected the true number of populations only under conditions of moderate or low gene flow ( Nm ≤ 5), and power dropped sharply with smaller samples of loci and individuals. A simple algorithm based on a multilocus contingency test of allele frequencies in pairs of samples has high power to detect the true number of populations even with Nm = 25 but requires more rigorous statistical evaluation. The ecological paradigm remains challenging for evaluations using genetic markers, because the transition from demographic dependence to independence occurs in a region of high migration where genetic methods have relatively little power. Some recent theoretical developments and continued advances in computational power provide hope that this situation may change in the future.