Hybridization between European and Africanized honeybees (Apis mellifera L.) in tropical Yucatan, Mexico. I. Morphometric changes in feral and managed colonies

Abstract - Morphometrics of feral and managed honeybee colonies collected from tropical Yucatan, Mexico between 1986 and 1996, were analysed for changes in body size as an indicator of gene exchange between them. Twelve morphometric characters were analysed at the univariate level (ANOVA of single morphometric characters across years) and with a multivariate technique (principal component analysis, PCA ). The results from both types of approach give evidence for: 1) an initial increase in body size of feral honeybees due to a flow of genes from the large resident European population; 2) a subsequent constant reduction in body size in both types of honeybees as Africanization has progressed probably due to a disappearance of colonies with European morphometrics in both populations; and 3) the existence of European genes in both the managed and feral populations of Yucatecan honeybees 10 years after the report of the first Africanized swarm in the area. Bi-directional gene flow resulting in a convergence in quantitative traits towards an intermediate body size seems to better explain the morphological changes that have occurred between managed and feral populations of honeybees during the process of Africanization in Yucatan. However, the persistence of European genes in both populations across time needs to be further studied. © Inra/DIB/AGIB/Elsevier, Paris