Figure 4: Visualizing nuclear genetic change over time using principal component analysis.
From: Museum samples reveal rapid evolution by wild honey bees exposed to a novel parasite
(a) Principal component analysis and (b) changes in ancestral populations. In contrast to mitochondrial data, nuclear data do not show a major reduction in diversity, only a shift in the mean between the two populations. Although the proportions of different ancestral populations have changed, the number of ancestral populations has remained the same. The Fst between old and modern populations is 0.022±0.056. This suggests that in spite of colony level mortality caused by V. destructor, most of the nuclear genetic diversity has persisted, possibly through production of drones both by strong colonies and by colonies too weak to swarm (produce queens) but still strong enough to produce drones. Admixture analysis suggests that old and modern populations are largely descendants of Central European bees (Carniolan and Italian subspecies popular with beekeepers), though they also have genes from Western Europe and Central Asia. In addition, modern bees have a detectable component of African descent. Interestingly, the modern bees show an increase in genetic ancestry from the Arabian Peninsula, not typically found in domestic stock. These data suggest a mixture of immigration and genetic continuity in the modern population of wild colonies.
