Population genetic structure of Acanthoscelides obtectus and A. obvelatus (Coleoptera : Bruchidae) from wild and cultivated Phaseolus spp. (Leguminosae)

Allozyme electrophoresis was conducted on Acanthoscelides obtectus Say and A. obvelatus Bridwell collected from seeds of wild and cultivated populatio ns of Plaseolus vulgaris L. and P. coccineus L. from Mexico to test for evi dence of host-related and regional genetic differentiation. In total, live enzymes representing six different loci were resolved for the two beetle sp ecies. Significant genetic differentiation was found at the regional level for A. obtectus, but not among populations within regions or between hosts. In A. obvelatus, differentiation was not significant. Gene now values were high among insect populations within regions despite their association wit h different wild and cultivated species and subspecies of beans. Population s belonging to the same region cluster together in a unweighted pair-group method with arithmetic average dendrogram, based on Nei's unbiased genetic distances. A comparison of average expected heterozygosities revealed that A. obtectus had significantly higher levels of genetic variation than A. ob velatus, which may be explained by differences in life history traits and t he geographic ranges of the two bruchids.