title: Africanization of a feral honey bee (Apis mellifera) population in South Texas: does a decade make a difference?
abstract: The arrival to the United States of the Africanized honey bee, a hybrid between European subspecies and the African subspecies Apis mellifera scutellata, is a remarkable model for the study of biological invasions. This immigration has created an opportunity to study the dynamics of secondary contact of honey bee subspecies from African and European lineages in a feral population in South Texas. An 11-year survey of this population (1991-2001) showed that mitochondrial haplotype frequencies changed drastically over time from a resident population of eastern and western European maternal ancestry, to a population dominated by the African haplotype. A subsequent study of the nuclear genome showed that the Africanization process included bidirectional gene flow between European and Africanized honey bees, giving rise to a new panmictic mixture of A. m. scutellata- and European-derived genes. In this study, we examined gene flow patterns in the same population 23 years after the first hybridization event occurred. We found 28 active colonies inhabiting 92 tree cavities surveyed in a 5.14 km(2) area, resulting in a colony density of 5.4 colonies/km(2). Of these 28 colonies, 25 were of A. m. scutellata maternal ancestry, and three were of western European maternal ancestry. No colonies of eastern European maternal ancestry were detected, although they were present in the earlier samples. Nuclear DNA revealed little change in the introgression of A. m. scutellata-derived genes into the population compared to previous surveys. Our results suggest this feral population remains an admixed swarm with continued low levels of European ancestry and a greater presence of African-derived mitochondrial genetic composition.
authors.affiliation: Department of Entomology Texas A&M University 2475 TAMU College Station Texas 77843-2475.
authors.forename: Juliana
authors.initials: J
authors.lastname: Rangel
authors.affiliation: Department of Biology Texas A&M University 3258 TAMU College Station Texas 77843-3258.
authors.forename: Melissa
authors.initials: M
authors.lastname: Giresi
authors.affiliation: Mountain Research Centre (CIMO) Polytechnic Institute of Bragança Campus de Sta. Apolónia Apartado 1172 Bragança 5301-855 Portugal.
authors.forename: Maria Alice
authors.initials: MA
authors.lastname: Pinto
authors.affiliation: Department of Zoology Oklahoma State University 501 Life Sciences West Stillwater Oklahoma 74078.
authors.forename: Kristen A
authors.initials: KA
authors.lastname: Baum
authors.affiliation: P.O. Box 2686 Edinburg Texas 78540.
authors.forename: William L
authors.initials: WL
authors.lastname: Rubink
authors.affiliation: Knowledge Engineering Laboratory Department of Entomology Texas A&M University College Station Texas 77843-2475.
authors.forename: Robert N
authors.initials: RN
authors.lastname: Coulson
authors.affiliation: Department of Entomology Texas A&M University 2475 TAMU College Station Texas 77843-2475.
authors.forename: John Spencer
authors.initials: JS
authors.lastname: Johnston
keywords: Apis mellifera; feral Africanized honey bee; hybridization; introgression; mitochondrial DNA; nuclear DNA