title: Nuclear microsatellites reveal contrasting patterns of genetic structure between western and southeastern European populations of the common ash (Fraxinus excelsior L.).
abstract: To determine extant patterns of population genetic structure in common ash and gain insight into postglacial recolonization processes, we applied multilocus-based Bayesian approaches to data from 36 European populations genotyped at five nuclear microsatellite loci. We identified two contrasting patterns in terms of population genetic structure: (1) a large area from the British Isles to Lithuania throughout central Europe constituted effectively a single deme, whereas (2) strong genetic differentiation occurred over short distances in Sweden and southeastern Europe. Concomitant geographical variation was observed in estimates of allelic richness and genetic diversity, which were lowest in populations from southeastern Europe, that is, in regions close to putative ice age refuges, but high in western and central Europe, that is, in more recently recolonized areas. We suggest that in southeastern Europe, restricted postglacial gene flow caused by a rapid expansion of refuge populations in a mountainous topography is responsible for the observed strong genetic structure. In contrast, admixture of previously differentiated gene pools and high gene flow at the onset of postglacial recolonization of western and central Europe would have homogenized the genetic structure and raised the levels of genetic diversity above values in the refuges.
authors.affiliation: Centre de Recherche Public-Gabriel Lippmann, CREBS Research Unit, L-1511 Luxembourg, Luxembourg. myriamheuertz@gmx.net
authors.forename: Myriam
authors.initials: M
authors.lastname: Heuertz
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Hausman
authors.forename: Olivier J
authors.initials: OJ
authors.lastname: Hardy
authors.forename: Giovanni G
authors.initials: GG
authors.lastname: Vendramin
authors.forename: Nathalie
authors.initials: N
authors.lastname: Frascaria-Lacoste
authors.forename: Xavier
authors.initials: X
authors.lastname: Vekemans
mesh_terms: D001499:Bayes Theorem; D005075:Biological Evolution; D016000:Cluster Analysis; D003710:Demography; D005060:Europe; D031661:Fraxinus / Q000235:genetics*; D005787:Gene Frequency; D014644:Genetic Variation; D005828:Genetics, Population; D005843:Geography; D015810:Linkage Disequilibrium; D018895:Microsatellite Repeats / Q000235:genetics