In the United States, it has been speculated, but not shown, that Africanized honey bees would hybridize extensively with European honey bees. Herein we report a continuous 11- year study investigating temporal changes in the genetic structure of a feral population from the southern United States undergoing Africanization.

Prior to arrival of Africanized honey bees, the United States sustained large feral and managed populations of honey bees predominantly derived from eastern (A. m. ligustica, A. m. carnica, and A. m. caucasia) and western (A. m. mellifera) European subspecies. With the arrival and subsequent expansion of Africanized honey bees into Texas, New Mexico, Arizona, Nevada and California, the European honey bee gene pool in those areas is being converted to one with a substantial African component.

The overall pattern of Africanization that emerged from these studies is that Africanized honey bees may hybridize extensively when (managed) European honey bees are common. However, over time European alleles largely disappear mainly because of continued migration of African genotypes into the area, and possibly because hybrid workers exhibit reduced fitness.

By 1997 the genetic composition of the population had become predominantly A. m. scutellata. The turnover resulted primarily from a dramatic reduction in the number of colonies of non-A. m. scutellata matrilines that was not observed for colonies of A. m. scutellata matrilines (PINTO et al. 2004). The authors attributed this differential loss to the parasitic mite Varroa destructor, which was first detected in WWR in early 1995. The observed mortality was consistent with the observation that European honey bees are more susceptible to Varroa than Africanized honey bees. 

Africanization in the United States: Replacement of Feral European Honey Bees. Pinto, et al. Department of Entomology, Texas A&M University (2005)
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