Genetic markers that differ in mode of inheritance and rate of evolution (a sex-linked Z-specific microsatellite locus, five biparentally inherited microsatellite loci, and maternally inherited mitochondrial [mtDNA] sequences) were used to evaluate the degree of spatial genetic structuring at macro- and microgeographic scales, among breeding regions and local nesting populations within each region, respectively, for a migratory sea duck species, the spectacled eider (Somateria fisheri). Disjunct and declining breeding populations coupled with sex-specific differences in seasonal migratory patterns and life history provide a series of hypotheses regarding rates and directionality of gene flow among breeding populations from the Indigirka River Delta, Russia, and the North Slope and Yukon-Kuskokwim Delta, Alaska. The degree of differentiation in mtDNA haplotype frequency among breeding regions and populations within regions was high (phiCT = 0.189, P < 0.01; phiSC = 0.059, P < 0.01, respectively). Eleven of 17 mtDNA haplotypes were restricted to a single breeding region. Genetic differences among regions were considerably lower for nuclear DNA loci (sex-linked: phiST = 0.001, P > 0.05; biparentally inherited microsatellites: mean theta = 0.001, P > 0.05) than was observed for mtDNA. Using models explicitly designed for uniparental and biparentally inherited genes, estimates of spatial divergence based on nuclear and mtDNA data together with elements of the species' breeding ecology were used to estimate effective population size and degree of male and female gene flow. Differences in the magnitude and spatial patterns of gene correlations for maternally inherited and nuclear genes revealed that females exhibit greater natal philopatry than do males. Estimates of generational female and male rates of gene flow among breeding regions differed markedly (3.67 x 10(-4) and 1.28 x 10(-2), respectively). Effective population size for mtDNA was estimated to be at least three times lower than that for biparental genes (30,671 and 101,528, respectively). Large disparities in population sizes among breeding areas greatly reduces the proportion of total genetic variance captured by dispersal, which may accelerate rates of inbreeding (i.e., promote higher coancestries) within populations due to nonrandom pairing of males with females from the same breeding population.
"Genetic markers have been employed to characterise patterns of genetic variation within and among populations, and to examine the processes of dispersal and the patterns of mating that influence levels of genetic differentiation in ecosystems (Nevo et al., 1984, Parker et al., 1998). To achieve these aims in waterfowl species various techniques have been used: protein polymorphism (Kuznetsov et al., 1995, 1998; Rhodes et al., 1996; Sruoga et al., 1998; 2005), microsatellite polymorphism (McCracken et al., 2001; Williams et al., 2002; Slavenaite et al., 2004; Sruoga et al., 2005; Ahmadi et al., 2007), RAPD (Kulikova et al., 2003), mtDNA haplotypes (Scribner et al., 2001; Pearce et al., 2004; Kulikova et al., 2005), genetic maps (Huand et al., 2006), and MHC genes (Xia et al., 2004). These studies have contributed an evolutionary dimension to our understanding of contemporary ecological processes and the role of various organisms in ecosystems. "
"Indeed, differences in the genetic picture drawn by mitochondrial and nuclear markers are expected when sex-biased dispersal occurs . Studies focusing on the application of population genetic tools to infer sex-biased dispersal are well known for vertebrates, more frequently in birds and mammals (e.g.: eiders , rodents ) than in amphibians and reptiles (e.g.: frogs , turtles ). Nevertheless, as exhaustively discussed by Møller et al.
, dispersal of migratory birds is poorly studied because routes can greatly complicate the interpretation of the genetic scenario . "
[Show abstract][Hide abstract] ABSTRACT: Dispersal affects the distribution, dynamics and genetic structure of natural populations, and can be significantly different between sexes. However, literature records dealing with the dispersal of migratory birds are scarce, as migratory behaviour can notably complicate the study of dispersal. We used the barn swallow Hirundo rustica as model taxon to investigate patterns of genetic variability in males and in females of a migratory species showing sex-biased dispersal. We collected blood samples (n = 186) over the period 2006 to 2011 from adults (H. r. rustica subspecies) nesting in the same breeding site at either high (Ireland, Germany and Russia) or low (Spain, Italy and Cyprus) latitude across Europe. We amplified the Chromo Helicase DNA gene in all birds in order to warrant a sex-balanced sample size (92 males, 94 females). We investigated both uniparental (mitochondrial ND2 gene) and biparental (microsatellite DNA: 10 loci) genetic systems. The mtDNA provided evidence for demographic expansion yet no significant partition of the genetic variability was disclosed. Nevertheless, a comparatively distant Russian population investigated in another study, whose sequences were included in the present dataset, significantly diverged from all other ones. Different to previous studies, microsatellites highlighted remarkable genetic structure among the studied populations, and pointed to the occurrence of differences between male and female barn swallows. We produced evidence for non-random patterns of gene flow among barn swallow populations probably mediated by female natal dispersal, and we found significant variability in the philopatry of males of different populations. Our data emphasize the importance of taking into account the sex of sampled individuals in order to obtain reliable inferences on species characterized by different patterns of dispersal between males and females.
PLoS ONE 06/2014; 9(6):e98574. DOI:10.1371/journal.pone.0098574 · 3.23 Impact Factor
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