The African honey bee in the Americas

The African race of honey bees, Apis mellifera scutellata, was introduced into Brazil in the 1950s and spread throughout much of the New World within 50 years, giving rise to one of the most spectacular and best documented biological invasions known.  Throughout much of its range in New World, the African honey bee invasion has been characterized by a rapid rate of spread (up to 400-500 km/yr.), extensive hybridization with existing European races of honey bees, yet highly asymmetrical gene flow that has by-and-large favored the retention of the African genome and behavioral phenotype.   The factors contributing to the asymmetric introgression of African alleles into the European honey bee population and the retention of the African genome despite hybridization are not well understood, but include at least six different mechanisms, many of which convey survival and mating advantages to African reproductive castes.   However, despite the preponderance of African alleles in the genome of the New World African bee, hybridization with European honey bees has clearly occurred and European alleles typically comprise 25-35% of the nuclear genome throughout most colonized regions of South, Central and North America.  The maintenance and possible selective advantages of African/European hybrids with a predominantly African genome are discussed within the contexts of the “Enemy Release Hypothesis” and the “Evolution of Increase Competitive Ability.”