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1.
The delimitation of populations, defined as groups of individuals linked by gene flow, is possible by the analysis of genetic markers and also by spatial models based on dispersal probabilities across a landscape. We combined these two complimentary methods to define the spatial pattern of genetic structure among remaining populations of the threatened Florida scrub-jay, a species for which dispersal ability is unusually well-characterized. The range-wide population was intensively censused in the 1990s, and a metapopulation model defined population boundaries based on predicted dispersal-mediated demographic connectivity. We subjected genotypes from more than 1000 individual jays screened at 20 microsatellite loci to two Bayesian clustering methods. We describe a consensus method for identifying common features across many replicated clustering runs. Ten genetically differentiated groups exist across the present-day range of the Florida scrub-jay. These groups are largely consistent with the dispersal-defined metapopulations, which assume very limited dispersal ability. Some genetic groups comprise more than one metapopulation, likely because these genetically similar metapopulations were sundered only recently by habitat alteration. The combined reconstructions of population structure based on genetics and dispersal-mediated demographic connectivity provide a robust depiction of the current genetic and demographic organization of this species, reflecting past and present levels of dispersal among occupied habitat patches. The differentiation of populations into 10 genetic groups adds urgency to management efforts aimed at preserving what remains of genetic variation in this dwindling species, by maintaining viable populations of all genetically differentiated and geographically isolated populations.  相似文献   

2.

Background

Data on spatial genetic patterns may provide information about the ecological and behavioural mechanisms underlying population structure. Indeed, social organization and dispersal patterns of species may be reflected by the pattern of genetic structure within a population.

Methodology/Principal Findings

We investigated the fine-scale spatial genetic structure of a roe deer (Capreolus capreolus) population in Trois-Fontaines (France) using 12 microsatellite loci. The roe deer is weakly polygynous and highly sedentary, and can form matrilineal clans. We show that relatedness among individuals was negatively correlated with geographic distance, indicating that spatially proximate individuals are also genetically close. More unusually for a large mammalian herbivore, the link between relatedness and distance did not differ between the sexes, which is consistent with the lack of sex-biased dispersal and the weakly polygynous mating system of roe deer.

Conclusions/Significance

Our results contrast with previous reports on highly polygynous species with male-biased dispersal, such as red deer, where local genetic structure was detected in females only. This divergence between species highlights the importance of socio-spatial organization in determining local genetic structure of vertebrate populations.  相似文献   

3.
东北马鹿(Cervus canadensis)种群面临着地理隔绝和生境破碎化等问题,对其种群遗传多样性和性别结构的研究,有助于了解其隔离种群的生存现状,为保护与管理工作提供科学依据。本研究利用8对微卫星分子标记,对内蒙古赛罕乌拉国家级自然保护区的456份马鹿粪便样品进行遗传多样性分析。结果识别出2015年冬季56只个体,2016年秋季41只个体;微卫星位点平均期望杂合度为0.650 1,平均多态信息含量为0.603 5,表明该地区马鹿种群的遗传多样性处于中等偏上水平。种群遗传分化系数为-0.053 99、近交系数为0.086 67、基因流为2.942 11,说明该马鹿种群基因交流普遍,近交水平低。基于SRY基因的方法进行性别鉴定,种群雌雄性比在冬季为1.8:1,秋季为0.71:1。本研究显示,该区域马鹿种群目前遗传多样性较为丰富,但现有种群集中分布于保护区内,处于相对隔离状态,长期发展则存在种群内部近交的风险。因此,加强对种群遗传结构和生存状态的监测,并促进与附近区域马鹿个体的交流,将有助于保持区域性东北马鹿种群长期繁盛。  相似文献   

4.
Red deer have been subjected to anthropogenic interference for many centuries. Most populations are managed according to hunting schedules, some have been kept long-term in enclosures and other populations have been restocked with foreign deer. The red deer in the Brittany region of north-western France only occupy the largest forests in the region, reaching quite high densities in restricted areas. Here, we aimed to assess the extent of the genetic variability of the populations in four forest fragments and investigate their population genetic structure. We show that, despite relatively large expected heterozygosity values, these geographically isolated populations are genetically impoverished relative to individuals from large continuous forests in other parts of Western Europe. We provide evidence for population genetic structure with large genetic differentiation between geographically close populations, suggesting the absence of effective exchange between the forests. Using samples from the most likely source population, we show that at least two populations were non-indigenous. In order to limit further loss of genetic diversity, it should be a management objective to reduce isolation of the different forests, rather than further increase it by fences and hunting practices that could limit free movement of red deer.  相似文献   

5.
The genetic structure of red deer populations is under strong influence of human activities such as game management and habitat fragmentation. Using multilocus genotypes from 193 geo-referenced individuals, we evaluated the population genetic structure of three red deer populations in Croatia. The effect of habitat fragmentation on genetic structure was tested using Bayesian non-spatial and spatial clustering methods. Our results indicate levels of genetic diversity similar to the ones previously reported by other authors for stable and appropriately managed populations within all populations analyzed. The spatial clustering model was able to detect the effect of habitat fragmentation on population differentiation, supporting the use of spatially explicit methods in landscape genetics, and giving important guidelines for future road planning.  相似文献   

6.
The spatial extent of Sitka black-tailed deer (Odocoileus hemionus sitkensis) populations below the regional scale is relatively unknown, as is dispersal between populations. Here, we use noninvasive samples to genotype 221 Sitka black-tailed deer in three watersheds on Prince of Wales Island, Alaska, separated by a maximum of 44 km, using traditional and spatial genetic approaches. We find that despite geographic proximity, multiple lines of evidence suggest fine-scale genetic structure among the three study sites. The 2 most geographically distant watersheds differed significantly in genetic composition, suggesting an isolation-by-distance pattern. Within study sites, deer exhibited spatial genetic structure within a radius of 1,000 m. Based on a reduced sample of known-sex individuals, females exhibited positive spatial genetic structure within a radius of 500 m but males showed no structure. Moreover, females were more likely to be related to their 5 nearest female neighbors, regardless of distance, than were males. Evidence indicates dispersal by both sexes although it may be more common, or dispersal distances are greater, in males. Nonetheless, analysis of assignment indices and comparison of sex-specific correlograms found no evidence of sex-biased dispersal between watersheds. Patterns of spatial relatedness and connectivity suggest limited dispersal among Sitka black-tailed deer, creating genetic structure on a fine spatial scale, perhaps as small as the watershed.  相似文献   

7.
Climate change causes species ranges to shift geographically as individuals colonise new suitable temperature zones or fail to reproduce where climate conditions fall below tolerance levels. Little is known about the potential loss of genetic diversity in such dynamic ranges. We investigated the level and distribution of neutral genetic diversity in shifting metapopulations during three scenarios of temperature increase projected for this century and at various degrees of weather variability. We used an individual‐based and spatially explicit metapopulation model in which temperature zones were simulated to move across a fragmented landscape following different climate change scenarios. Although the connectivity between habitat patches allowed the species, modelled after the middle spotted woodpecker Dendrocopos medius, to move along with the shifting temperature range, existing neutral genetic diversity was lost under all three temperature increase scenarios. This was independent of the loss of individuals. The explanation for this effect is that only a part of the original genetic variation moved into the newly colonised habitat. Under increased weather variability the number of individuals and the number of alleles per locus were persistently lower. However, the pattern of changes in allele distributions under temperature zone shifts was the same under all weather variability levels. Genetic differentiation between populations had a tendency to increase at metapopulation range margins, but decreased again when population sizes increased in time. Increased weather variability led to increased variation around the mean genetic differentiation across the metapopulation. Our results illustrate the usefulness of more realistic models for studying the effects of climate change on metapopulations. They indicate that biodiversity monitoring indices based on species occurrence and abundance are not a good proxy for the trend in the level of genetic diversity. Further, the results underline the importance of conserving areas where species have existed for a long time as modern refugia for genetic diversity.  相似文献   

8.
Dragonflies reside in both aquatic and terrestrial environments, depending on their life stage, necessitating the conservation of drastically different habitats; however, little is understood about how nymph and adult dragonflies function as metapopulations within connected habitat. We used genetic techniques to examine nymphs and adults within a single metapopulation both spatially and temporally to better understand metapopulation structure and the processes that might influence said structure. We sampled 97 nymphs and 149 adult Sympetrum obtrusum from eight locations, four aquatic, and four terrestrial, at the Pierce Cedar Creek Institute in Southwest Michigan over two summers. We performed AFLP genetic analysis and used the Bayesian analysis program STRUCTURE to detect genetic clusters from sampled individuals. STRUCTURE detected k = u4 populations, in which nymphs and adults from the same locations collected in different years did not necessarily fall into the same clusters. We also evaluated grouping using the statistical clustering analyses NMDS and MRPP. The results of these confirmed findings from STRUCTURE and emphasized differences between adults collected in 2012 and all other generations. These results suggest that both dispersal and a temporal cycle of emergence of nymphs from unique clusters every other year could be influential in structuring dragonfly populations, although our methods were not able to fully distinguish the influences of either force. This study provides a better understanding of local dragonfly metapopulation structure and provides a starting point for future studies to investigate the spatial and temporal mechanisms controlling metapopulation structure. The results of the study should prove informative for managers working to preserve genetic diversity in connected dragonfly metapopulations, especially in the face of increasing anthropogenic landscape changes.  相似文献   

9.
The genetic structure of metapopulations offers insights into the genetic consequences of local extinction and recolonization. We studied allozyme variation in rock pool metapopulations of two species of waterfleas (Daphnia) with the aim to understand how these dynamics influence genetic differentiation. We screened 138 populations of D. magna and 65 populations of D. longispina from an area in the archipelago of southern Finland. The pools from which they were sampled are separated by distances between 1.5 and 4710 m and located on a total of 38 islands. The genetic population structure of the two species was strikingly similar, consistent with their similar metapopulation ecology. The mean F(PT) value (differentiation among pools with respect to the total metapopulation) was 0.55 and a hierarchical analysis showed that genetic differentiation was strong (>0.25) among pools within islands as well as among whole islands. Within islands, pairwise genetic differentiation increased with geographic distance, indicating isolation by distance due to spatially limited dispersal. Previous studies have shown strong founder events occurring during colonization in our metapopulation. We suggest that the genetic population structure in the studied metapopulations is largely explained by three consequences of these founder events: (i) strong drift during colonization, (ii) local inbreeding, which results in hybrid vigour and increased effective migration rates after subsequent immigration, and (iii) effects of selection through hitchhiking of neutral genes with linked loci under selection.  相似文献   

10.
Amphibians are frequently characterized as having limited dispersal abilities, strong site fidelity and spatially disjunct breeding habitat. As such, pond‐breeding species are often alleged to form metapopulations. Amphibian species worldwide appear to be suffering population level declines caused, at least in part, by the degradation and fragmentation of habitat and the intervening areas between habitat patches. If the simplification of amphibians occupying metapopulations is accurate, then a regionally based conservation strategy, informed by metapopulation theory, is a powerful tool to estimate the isolation and extinction risk of ponds or populations. However, to date no attempt to assess the class‐wide generalization of amphibian populations as metapopulations has been made. We reviewed the literature on amphibians as metapopulations (53 journal articles or theses) and amphibian dispersal (166 journal articles or theses for 53 anuran species and 37 salamander species) to evaluate whether the conditions for metapopulation structure had been tested, whether pond isolation was based only on the assumption of limited dispersal, and whether amphibian dispersal was uniformly limited. We found that in the majority of cases (74%) the assumptions of the metapopulation paradigm were not tested. Breeding patch isolation via limited dispersal and/or strong site fidelity was the most frequently implicated or tested metapopulation condition, however we found strong evidence that amphibian dispersal is not as uniformly limited as is often thought. The frequency distribution of maximum movements for anurans and salamanders was well described by an inverse power law. This relationship predicts that distances beneath 11–13 and 8–9 km, respectively, are in a range that they may receive one emigrating individual. Populations isolated by distances approaching this range are perhaps more likely to exhibit metapopulation structure than less isolated populations. Those studies that covered larger areas also tended to report longer maximum movement distances – a pattern with implications for the design of mark‐recapture studies. Caution should be exercised in the application of the metapopulation approach to amphibian population conservation. Some amphibian populations are structured as metapopulations – but not all.  相似文献   

11.
The red fox (Vulpes vulpes) has the widest global distribution among terrestrial carnivore species, occupying most of the Northern Hemisphere in its native range. Because it carries diseases that can be transmitted to humans and domestic animals, it is important to gather information about their movements and dispersal in their natural habitat but it is difficult to do so at a broad scale with trapping and telemetry. In this study, we have described the genetic diversity and structure of red fox populations in six areas of north-eastern Poland, based on samples collected from 2002–2003. We tested 22 microsatellite loci isolated from the dog and the red fox genome to select a panel of nine polymorphic loci suitable for this study. Genetic differentiation between the six studied populations was low to moderate and analysis in Structure revealed a panmictic population in the region. Spatial autocorrelation among all individuals showed a pattern of decreasing relatedness with increasing distance and this was not significantly negative until 93 km, indicating a pattern of isolation-by-distance over a large area. However, there was no correlation between genetic distance and either Euclidean distance or least-cost path distance at the population level. There was a significant relationship between genetic distance and the proportion of large forests and water along the Euclidean distances. These types of habitats may influence dispersal paths taken by red foxes, which is useful information in terms of wildlife disease management.  相似文献   

12.
A growing literature now documents the presence of fine-scale genetic structure in wild vertebrate populations. Breeding population size, levels of dispersal and polygyny--all hypothesized to affect population genetic structure--are known to be influenced by ecological conditions experienced by populations. However the possibility of temporal or spatial variation in fine-scale genetic structure as a result of ecological change is rarely considered or explored. Here we investigate temporal variation in fine-scale genetic structure in a red deer population on the Isle or Rum, Scotland. We document extremely fine-scale spatial genetic structure (< 100 m) amongst females but not males across a 24-year study period during which resource competition has intensified and the population has reached habitat carrying capacity. Based on census data, adult deer were allocated to one of three subpopulations in each year of the study. Global F(ST) estimates for females generated using these subpopulations decreased over the study period, indicating a rapid decline in fine-scale genetic structure of the population. Global F(ST) estimates for males were not different from zero across the study period. Using census and genetic data, we illustrate that, as a consequence of a release from culling early in the study period, the number of breeding females has increased while levels of polygyny have decreased in this population. We found little evidence for increasing dispersal between subpopulations over time in either sex. We argue that both increasing female population size and decreasing polygyny could explain the decline in female population genetic structure.  相似文献   

13.
Metapopulation dynamics lead to predictable patterns of habitat occupancy, population density and trophic structure in relation to landscape features such as habitat patch size and isolation. Comparable patterns may occur in behavioural, physiological and life‐history traits but remain little studied. In the Glanville fritillary butterfly, females in newly established populations were more mobile than females in old populations. Among females from new populations, mobility decreased with increasing connectivity (decreasing isolation), but in females from old populations mobility increased with connectivity. The [ATP]/[ADP] ratio of flight muscles following controlled activity showed the same pattern as mobility in relation to population age and connectivity, suggesting that physiological differences in flight metabolic performance contribute to the observed variation in mobility. We demonstrate with an evolutionary metapopulation model parameterised for the Glanville fritillary that increasing spatial variation in landscape structure increases variance in mobility among individuals in a metapopulation, supporting the general notion that complex landscape structure maintains life‐history variation.  相似文献   

14.
Unraveling the relationship between demographic declines and genetic changes over time is of critical importance to predict the persistence of at‐risk populations and to propose efficient conservation plans. This is particularly relevant in spatially structured populations (i.e. metapopulations) in which the spatial arrangement of local populations can modulate both demographic and genetic changes. We used ten‐year demo‐genetic monitoring to test 1) whether demographic declines were associated with genetic diversity declines and 2) whether the spatial structure of a metapopulation can weaken or reinforce these demographic and genetic temporal trends. We continuously surveyed, over time and across their entire range, two metapopulations of an endemic freshwater fish species Leuciscus burdigalensis: one metapopulation that had experienced a recent demographic decline and a second metapopulation that was stable over time. In the declining metapopulation, the number of alleles rapidly decreased, the inbreeding coefficient increased, and a genetic bottleneck emerged over time. In contrast, genetic indices were constant over time in the stable metapopulation. We further show that, in the declining metapopulation, demographic and genetic declines were not homogeneously distributed across the metapopulation. We notably identify one local population situated downstream as a ‘reservoir’ of individuals and genetic variability that dampens both the demographic and genetic declines measured at the metapopulation level. We demonstrate the usefulness of long‐term monitoring that combines both genetic and demographic parameters to understand and predict temporal population fluctuations of at‐risk species living in a metapopulation context.  相似文献   

15.
Understanding how environmental variation influences population genetic structure is important for conservation management because it can reveal how human stressors influence population connectivity, genetic diversity and persistence. We used riverscape genetics modelling to assess whether climatic and habitat variables were related to neutral and adaptive patterns of genetic differentiation (population‐specific and pairwise FST) within five metapopulations (79 populations, 4583 individuals) of steelhead trout (Oncorhynchus mykiss) in the Columbia River Basin, USA. Using 151 putatively neutral and 29 candidate adaptive SNP loci, we found that climate‐related variables (winter precipitation, summer maximum temperature, winter highest 5% flow events and summer mean flow) best explained neutral and adaptive patterns of genetic differentiation within metapopulations, suggesting that climatic variation likely influences both demography (neutral variation) and local adaptation (adaptive variation). However, we did not observe consistent relationships between climate variables and FST across all metapopulations, underscoring the need for replication when extrapolating results from one scale to another (e.g. basin‐wide to the metapopulation scale). Sensitivity analysis (leave‐one‐population‐out) revealed consistent relationships between climate variables and FST within three metapopulations; however, these patterns were not consistent in two metapopulations likely due to small sample sizes (= 10). These results provide correlative evidence that climatic variation has shaped the genetic structure of steelhead populations and highlight the need for replication and sensitivity analyses in land and riverscape genetics.  相似文献   

16.
The endangered Black-faced Spoonbill Platalea minor has experienced drastic reductions in population size, geographic distribution, and habitat availability throughout East Asia. In the present study, we examined population genetic structure and genetic diversity of Black-faced Spoonbills inhabiting five sites off the west coast of South Korea encompassing a few of its major breeding sites. Ten microsatellite loci and the mitochondrial sequence were used to assess patterns of genetic variation based on 63 individuals. Three ND2 haplotypes were found among 61 individuals; the remaining two were identified as Eurasian Spoonbills, revealing an unexpected hybridization between these two species having different ecological niches in South Korea—the Eurasian Spoonbill overwinters in inland areas, whereas the Black-faced Spoonbill inhabits coastal areas during the summer. Analyses of microsatellite variation revealed no discrete population structure among the five breeding sites but very weak genetic differentiation among geographically distant regions. Assignment tests identified several possible migrants among sites. Our findings suggested that Black-faced Spoonbills from the five breeding sites could be managed as a single population and highlighted the importance of conserving the populations from Maedo, Suhaam, and Namdong reservoir, which are geographically close and have retained high levels of genetic diversity and large populations.  相似文献   

17.
The amount and spatial distribution of genetic variation that is maintained in a metapopulation depends critically on the colonization process. Here, we use molecular markers to determine the number and genetic relatedness of individuals establishing new local populations in a large metapopulation of the Glanville fritillary butterfly Melitaea cinxia. The empirical results are compared with the predictions of a dispersal model based on a diffusion approximation of correlated random walk, which serves as a base‐line hypothesis about the rate and pattern of colonization. The results show that half of the new local populations consisted of a single larval group of full sibs and hence necessarily of the offspring of a single female. If the colonization involved two or more larval groups, these were usually oviposited by two different females that were unrelated to each other. The pattern of colonizations is thus intermediate between the propagule pool and the migrant pool models. These results elucidate the generation of genetic stochasticity, which may influence the dynamics of small populations. The dispersal model predicted well the pattern of habitat occupancy and the pattern of colonizations in relation to landscape structure, though which particular habitat patches became colonized was influenced also by measures of habitat quality not included in the model.  相似文献   

18.
Habitat degradation can result in drastic environmental changes potentially affecting the life-history of populations and aspects of the reproductive biology and the genetic structure within and among populations. Here, we explore how life-history differences between subpopulations from contrasting habitats may affect mating availability, which in turn will indirectly affect the strength of spatial genetic structure within populations of a tropical rainforest cycad (Zamia fairchildiana). Subpopulations exposed to higher light availability in degraded-forest habitats had male individuals that grew faster, reproduced earlier, and invested more in reproduction than in native-forest habitat subpopulations. These differences in life history resulted in degraded-habitat subpopulations showing a higher proportion of reproductive adults and greater mate availability in a reproductive season. Subpopulations in the degraded habitat showed weaker SGS, i.e., a smaller slope in the linear regression of genetic relatedness on linear distance. Environmentally induced changes in life history and subsequent changes in the strength of the SGS after habitat degradation may have important consequences for population viability and should be of concern in conservation.  相似文献   

19.
Interpretation of spatially structured population systems is critically dependent on levels of migration between habitat patches. If there is considerable movement, with each individual visiting several patches, there is one ”patchy population”; if there is intermediate movement, with most individuals staying within their natal patch, there is a metapopulation; and if (virtually) no movement occurs, then the populations are separate (Harrison 1991, 1994). These population types actually represent points along a continuum of much to no mobility in relation to patch structure. Therefore, interpretation of the effects of spatial structure on the dynamics of a population system must be accompanied by information on mobility. We use empirical data on movements by ringlet butterflies, Aphantopus hyperantus, to investigate two key issues that need to be resolved in spatially-structured population systems. First, do local habitat patches contain largely independent local populations (the unit of a metapopulation), or merely aggregations of adult butterflies (as in patchy populations)? Second, what are the effects of patch area on migration in and out of the patches, since patch area varies considerably within most real population systems, and because human landscape modification usually results in changes in habitat patch sizes? Mark-release-recapture (MRR) data from two spatially structured study systems showed that 63% and 79% of recaptures remained in the same patch, and thus it seems reasonable to call both systems metapopulations, with some capacity for separate local dynamics to take place in different local patches. Per capita immigration and emigration rates declined with increasing patch area, while the resident fraction increased. Actual numbers of emigrants either stayed the same or increased with area. The effect of patch area on movement of individuals in the system are exactly what we would have expected if A. hyperantus were responding to habitat geometry. Large patches acted as local populations (metapopulation units) and small patches simply as locations with aggregations (units of patchy populations), all within 0.5 km2. Perhaps not unusually, our study system appears to contain a mixture of metapopulation and patchy-population attributes.  相似文献   

20.
Interactions between animal behaviour and the environment are both shaping observed habitat use. Despite the importance of inter-specific interactions on the habitat use performed by individuals, most previous analyses have focused on case studies of single species. By focusing on two sympatric populations of large herbivores with contrasting body size, we went one step beyond by studying variation in home range size and identifying the factors involved in such variation, to define how habitat features such as resource heterogeneity, resource quality, and openness created by hurricane or forest managers, and constraints may influence habitat use at the individual level. We found a large variability among individual's home range size in both species, particularly in summer. Season appeared as the most important factor accounting for observed variation in home range size. Regarding habitat features, we found that (i) the proportion of area damaged by the hurricane was the only habitat component that inversely influenced roe deer home range size, (ii) this habitat type also influenced both diurnal and nocturnal red deer home range sizes, (iii) home range size of red deer during the day was inversely influenced by the biomass of their preferred plants, as were both diurnal and nocturnal core areas of the red deer home range, and (iv) we do not find any effect of resource heterogeneity on home range size in any case. Our results suggest that a particular habitat type (i.e. areas damaged by hurricane) can be used by individuals of sympatric species because it brings both protected and dietary resources. Thus, it is necessary to maintain the openness of these areas and to keep animal density quite low as observed in these hunted populations to limit competition between these sympatric populations of herbivores.  相似文献   

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