Our Domesticated Honey Bee-Originally from Europe-Is Slow to Sting, Requires

Our domesticated honey bee-originally from Europe-is slow to sting, requires abundant flower nectar, gets up late in the morning, and stores much honey but only produces enough new brood to swarm once a year. Because the European honey bee was performing poorly as a honey producer in South America, the African subspecies was imported in a breeding experiment. The African honey bee formed small nests, foraged earlier and on smaller nectar sources, produced less honey stores and more brood, swarmed four or five times a year, and was fast to sting. However, when the African queens escaped, the two populations interbred and the African genotype spread several hundred miles north each year. Surprisingly, a hundred miles behind the expanding range of the African honey bees, the European and hybrid strains died out and the bees were essentially 100 percent African. How would this be explained in evolutionary genetics terms?

A) Gene flow is not occurring and therefore these are two separate species.
B) This is a natural consequence of the Hardy-Weinberg equilibrium.
C) Obviously the African bee genes are dominant over the European honey bee alleles.
D) Gene flow is occurring between these subspecies but the African bee is "ecologically better suited".
E) This can be understood as a classic case of genetic drift.