Diversity In Peripheral Populations Research Articles

Climatic and geographic effects on the spatial genetic pattern of a landbird species (Alectoris rufa) on the Iberian Peninsula

AbstractUnderstanding the spatial pattern of genetic diversity may be pivotal to adaptive conservation management of a given taxon. The red‐legged partridge (Alectorisrufa, Linnaeus 1758) is naturally widely distributed from the Mediterranean to humid temperate zones. According to a recent study, the genetic structure of this species comprises five clusters, three of which are in the Iberian Peninsula (glacial refugia). Partridge demographic expansion events and climatic shifts during Pleistocene glaciations have been used to test the hypotheses concerning Iberian red‐legged partridge distribution. We tested the existence of climatic and geographic relationships on genetic diversity/distances. We employed markers from two different genetic systems, such as part of the mitochondrial DNA control region (n = 113) and 20 species‐specific microsatellite DNA loci (n = 377), including climatic and geographic factors from the 14 Iberian localities where A. rufa populations were sampled. Our results showed a mitochondrial genetic diversity pattern associated with a thermic gradient, and a decrease of genetic diversity in peripheral populations that concurred with the ‘abundant centre’ hypothesis. Overall, current climatic variables reliably described genetic variation and differentiation in the red‐legged partridge, which may be a result of local species adaptation.

DIVERSITY OF DROUGHT-RESPONSIVE GENES IN CENTRAL AND PERIPHERAL POPULATIONS OF Trifolium purpureum Loisel

Drought-responsive genes may differ in structure and complexity in native populations of a species established in different ecosystems. Peripheral populations may be a source of genetic variability for breeding cultivated plants for abiotic stresses tolerance and the target for core collections in germplasm preservation programs. Genetic studies including both peripheral and central populations are still limited. This research evaluated genetic diversity of drought-responsive genes in peripheral and central populations of Trifolium purpureum Loisel. Genomic DNA isolated from leaves of three northern and three southern populations of Israel was digested with restriction enzymes and hybridized with four drought-induced and four drought-repressed gene fragments. RFLPs were analyzed for gene diversity, molecular variation and fixation indexes (FST). Gene diversity of drought-induced genes ranged from 0.1 to 0.42 but differences of individual or pooled genes between central and peripheral populations were nonsignificant. Gene diversity for drought-repressed genes ranged from 0.08 to 0.348. Even though there were no differences for individual genes, a joint analysis showed a significantly larger (P ≤ 0.05) gene diversity in peripheral populations of T. Purpureum than in central ones. Variation within populations for both drought-induced and drought-repressed genes was the main component of molecular variance. Fixation index (FST) for drought-induced genes was between 0.029 and 0.214 while for drought repressed genes it was between 0.04 and 0.33. Results of this study show that peripheral population might be a reservoir for drought-responsive genes.

Genetic diversity of the weed species,Stellera chamaejasme, inChina inferred from amplified fragment length polymorphism analysis

Stellera chamaejasmeis a perennial weed with a wide geographic range that is found from theAltai of easternRussia, northernChina andMongolia southwards as far as the westernHimalayas of theQinghai–Tibet andYunguiPlateaus. The genetic diversity and population structure of 17 populations ofS. chamaejasme, represented by 349 individuals, were assessed by using amplified fragment length polymorphism markers. The results showed a relatively high level of genetic variation at the species level. The proportion of total diversity among populations was 0.4370, suggesting significant genetic differentiation and a low gene flow among the populations of this species. TheMantel test indicated that genetic differentiation among populations was significantly correlated with geographic distance. Genetic drift through range expansion and a low gene flow among populations might result in a lower diversity in peripheral populations, compared to central populations. ABayesian analysis revealed two potential gene pools inS. chamaejasme, which was confirmed by neighbor‐joining clustering and principal coordinate analysis. These results demonstrate that it is necessary to develop suitable biocontrol agents for populations with different gene pools.

A peripheral view: post‐glacial history and genetic diversity of an amphibian in northern landscapes

AbstractAimWhere post‐glacial colonization and founder events are numerous, peripheral populations tend to have reduced genetic diversity as compared to their centrally located counterparts. Such decrease in genetic variability can limit their potential to adapt to changes in their environment. At northern latitudes for instance, populations are often living in conditions close to their physiological limits. Thus, identifying the levels of genetic diversity in peripheral populations is key to estimating the potential for adaptation to ongoing environmental change. In this context, we investigated the distribution of genetic diversity at the northern edge of the wood frog's (Lithobates sylvaticus) range by reconstructing its post‐glacial history in an area where phylogeographical data were lacking.LocationJames Bay area (north‐central Canada).MethodsDNAwas extracted from 463 wood frog tissue samples from 17 localities. Seven microsatellite loci were used to quantify genetic diversity and evaluate genetic structure through estimates of the fixation index, isolation‐by‐distance analyses and Bayesian clustering algorithms (tessandstructure). Phylogeographical relationships were investigated using single nucleotide polymorphisms in theND2/tRNATRPmitochondrial genes. Phylogenetic trees were built using the neighbour‐joining and the maximum likelihood inference methods implemented inmega5.ResultsOur analyses identified a contact zone between two colonizing lineages originating from one glacial refugium. Populations in this contact zone present sympatrically distributed haplotypes from both lineages and higher genetic variation than the surrounding populations. Population structure analyses revealed the differentiation of three genetic clusters, each covering large areas around the coast of James Bay.Main conclusionsOur study suggests that higher than expected genetic diversity and gene flow may be present in peripheral populations. Such adaptive potential is critical in areas of upcoming development and environmental changes. Thus, our study emphasizes the importance of understanding species post‐glacial history for the prediction of future evolutionary trends and species distributions.

Implications of isolation and low genetic diversity in peripheral populations of an amphi‐Atlantic coral

Limited dispersal and connectivity in marine organisms can have negative fitness effects in populations that are small and isolated, but reduced genetic exchange may also promote the potential for local adaptation. Here, we compare the levels of genetic diversity and connectivity in the coral Montastraea cavernosa among both central and peripheral populations throughout its range in the Atlantic. Genetic data from one mitochondrial and two nuclear loci in 191 individuals show that M. cavernosa is subdivided into three genetically distinct regions in the Atlantic: Caribbean-North Atlantic, Western South Atlantic (Brazil) and Eastern Tropical Atlantic (West Africa). Within each region, populations have similar allele frequencies and levels of genetic diversity; indeed, no significant differentiation was found between populations separated by as much as 3000 km, suggesting that this coral species has the ability to disperse over large distances. Gene flow within regions does not, however, translate into connectivity across the entire Atlantic. Instead, substantial differences in allele frequencies across regions suggest that genetic exchange is infrequent between the Caribbean, Brazil and West Africa. Furthermore, markedly lower levels of genetic diversity are observed in the Brazilian and West African populations. Genetic diversity and connectivity may contribute to the resilience of a coral population to disturbance. Isolated peripheral populations may be more vulnerable to human impacts, disease or climate change relative to those in the genetically diverse Caribbean-North Atlantic region.

Genetic diversity across the range of a temperate lizard

AbstractAim To examine range‐wide patterns of genetic diversity in association with range limits in a broadly distributed temperate lizard, and to identify the contributions of a series of environmental, geographical and historical variables to the observed patterns. Reduced genetic diversity may limit local adaptation in peripheral populations, thereby limiting their ability to adapt to marginal environmental conditions, possibly explaining the existence of temporally stable range limits.Location Various sampling locales throughout eastern and central USA and southern Ontario, Canada.Methods Genetic diversity of nuclear DNA microsatellites was estimated for each of 38 populations from across the range of eastern North America’s most broadly distributed lizard, the five‐lined skink, Plestiodon fasciatus (Linnaeus, 1758).Results Local climatic conditions and an interaction between distance from range border and glaciation history best predicted a population’s present‐day genetic diversity. Overall, peripheral populations had reduced genetic diversity relative to that of central populations, but this difference was attributable to the reduced genetic diversity in peripheral populations to the north and west that are not bordered by any obvious physical boundaries.Main conclusions Some, but not all, peripheral populations had reduced genetic diversity relative to that of more central populations, which probably arose through an interaction of ecological and historical factors. Peripheral populations that were bordered by an obvious boundary (e.g. an ocean) had higher diversity than peripheral populations that were not bordered by an obvious physical barrier to range expansion, suggesting that reduced intrapopulation genetic diversity is associated with range limits in the five‐lined skink.

Strong spatial genetic structure in peripheral but not core populations of Sitka spruce [Picea sitchensis (Bong.) Carr.

We examined spatial genetic structure within eight populations of Sitka spruce classified as core or peripheral based on ecological niche, and continuous or disjunct based on species distribution. In each population, 200 trees were spatially mapped and genotyped for eight cDNA-based sequence tagged site (STS) codominant markers. Spatial autocorrelation was assessed by estimating p(ij), the average co-ancestry coefficient, between individuals within distance intervals. The distribution of alleles and genotypes within core populations was almost random, with nonsignificant co-ancestry values among trees as close as 50 m in core populations. In contrast, the distribution of alleles and genotypes within peripheral populations revealed an aggregation of similar multilocus genotypes, with co-ancestry values greater than 0.20 among trees up to 50 m apart and significant, positive values between trees up to 500 m. The relatively high density of reproductive adults in core populations may lead to highly overlapping seed shadows that limit development of spatial genetic structure. However, in peripheral populations with a lower density of adults, the distribution of alleles and genotypes was highly structured, likely due to offspring establishment near maternal trees and subsequent biparental inbreeding, as well as more recent population establishment at the leading edge of post-Pleistocene range expansion. Conserving genetic diversity in peripheral populations may require larger reserves for in situ conservation than required in core populations. These data on spatial genetic structure can be used to provide guidance for sampling strategies for both ex situ conservation and research collections.

Gene diversity and demographic turnover in central and peripheral populations of the perennial herbGypsophila fastigiata

Within‐population gene diversity (HS) was estimated (using allozyme markers) for 16 populations of the perennial, outcrossing plant,Gypsophila fastigiata, on the Baltic island of Öland. The populations were characterized by data on extent, density, life‐stages, and habitat diversity. Populations were classed as central or peripheral in relation to the distribution of “alvar” (habitats with shallow, calcareous soils on limestone bedrock) on southern Öland. Three minimal adequate models were used to explain HSand the proportions of juveniles and dead adults. In the first model, HSwas significantly lower in peripheral populations and there were no significant additional effects of other explanatory variables. The lower diversity in peripheral populations can be explained by a combination of genetic drift (in populations that vary in size in response to habitat fragmentation) and lower levels of interpopulation gene flow than in central populations. In the two life‐stage models, peripheral populations had significantly larger proportions of both juveniles and dead adults – indicating a greater demographic turnover than in the central populations. There were also significant effects of HSand species diversity on the proportion of juveniles. The central or peripheral position of populations is the strongest predictor of both within‐population gene diversity and life‐stage dynamics in ÖlandG. fastigiata.