GENETIC DIFFERENTIATION OF CONTINENTAL AND ISLAND POPULATIONS OF BOMBUS-TERRESTRIS (HYMENOPTERA, APIDAE) IN EUROPE

Ten microsatellite loci and a partial sequence of the COII mitochondri al gene were used to investigate genetic differentiation in B. terrest ris, a bumble bee of interest for its high-value crop pollination. The analysis included eight populations from the European continent, five from Mediterranean islands (six subspecies altogether) and one from T enerife (initially described as a colour form of B. terrestris but rec ently considered as a separate species, B. canariensis). Eight of the 10 microsatellite loci displayed high levels of polymorphism in most p opulations. In B. terrestris populations, the total number of alleles detected per polymorphic locus ranged from 3 to 16, with observed alle lic diversify from 3.8 +/- 0.5 to 6.5 +/- 1.4 and average calculated h eterozygosities from 0.41 +/- 0.09 to 0.65 +/- 0.07. B. canariensis sh owed a significantly lower average calculated heterozygosity (0.12 +/- 0.08) and observed allelic diversity (1.5 +/- 0.04) as compared to bo th continental and island populations of B. terrestris. No significant differentiation was found among populations of B. terrestris from the European continent. In contrast, island populations were all signific antly and most of them strongly differentiated from continental popula tions. B. terrestris mitochondrial DNA is characterized by a low nucle otide diversity: 0.18% +/- 0.07%, 0.20% +/- 0.04% and 0.27% +/- 0.04% for the continental populations, the island populations and all popula tions together, respectively. The only haplotype found in the Tenerife population differs by a single nucleotide substitution from the most common continental haplotype of B. terrestris. This situation, identic al to that of Tyrrhenian islands populations and quite different from that of B. lucorum (15 substitutions between terrestris and lucorum mt DNA) casts doubts on the species status of B. canariensis. The large g enetic distance between the Tenerife and B. terrestris populations est imated from microsatellite data result, most probably, from a severe b ottleneck in the Canary island population. Microsatellite and mitochon drial DNA data call for the protection of the island populations of B. terrestris against importation of bumble bees of foreign origin which are used as crop pollinators.