Allozyme diversity and genetic structure of European populations of Sorbusaucuparia L. (Rosaceae : Maloideae)

Genetic diversity at 10 loci encoding six enzymes was studied in 17 Europea n populations of Sorbus aucuparia L. (the rowan), distributed among five re gions, from Finland to the Pyrenees. Levels of genetic diversity were high both at the species level (H-e = 0.229) and within populations (mean H-e = 0.212), whereas levels of differentiation among populations were very low ( G(ST) = 0.060). These values were comparable to those observed in other woo dy species with similar ecological traits. Populations from the Plateau des Tailles (Belgium) exhibited an unexpectedly high level of differentiation among populations, which was tentatively explained by the recent history of colonization experienced by these populations. Despite the low overall dif ferentiation, geographical patterns were observed. Gene flow estimates and geographical distances between pairs of populations appeared to be correlat ed (r = -0.483), resulting in a pattern of isolation by distance, which was disrupted to some extent by the local dynamics of the Tailles populations. Cluster analysis revealed that populations were genetically more similar t o populations from the same region compared to populations from other geogr aphical groups. Finnish populations, in particular, appeared to be highly d ifferentiated from more southerly populations.