The population genetic structure of a large temperate pollinator species, Bombus pascuorum (Scopoli) (Hymenoptera : Apidae)

The genetic population structure of the bumble bee Bombus pascuorum was stu died using six microsatellite loci and a partial sequence of the mitochondr ial gene cytochrome b. Eighteen populations from central and northern Europ e were included in the analysis. Observed levels of genetic variability and heterozygosity were high. Estimates of population differentiation based on F- and Phi-statistics revealed significant genetic differentiation among B . pascuorum populations and suggest that two partially isolated gene pools, separated by the Alps, do exist. The distribution of mtDNA haplotypes supp orts this view and presents direct evidence for gene flow across the Alps. Estimates of the number of migrants exchanged among populations north of th e Alps suggest that historical events may have left a strong imprint on pop ulation structure.