Genetic diversity of wild and managed honey bees (Apis mellifera) in Southwestern Pennsylvania, and prevalence of the microsporidian gut pathogens Nosema ceranae and N. apis

The populations of wild honey bee (Apis mellifera) colonies in the USA were decimated after the arrival of a parasitic mite Varroa destructor in the 1980s. However, in some places, wild honey bee colonies survived. In this 3-year study, we analyzed 32 wild and 11 managed colonies in Southwestern Pennsylvania for their maternal genetic ancestries and their levels of Nosema spp. infection. We detected nine mtDNA haplotypes in the 32 wild colonies sampled: six belonged to the Eastern European lineage (C) and three belonged to the Western European lineage (M). We found only three mtDNA haplotypes in the eleven managed colonies sampled, all belonging to the C lineage. Infection levels of N. ceranae were relatively high and fluctuated over time while those of N. apis remained relatively low and constant. There were no differences in N. ceranae or N. apis levels between wild and managed colonies. This study shows that wild honey bee colonies can represent old lineages despite being susceptible to Nosema.