Electrophoretic Analysis of the Contact Zone between Geomys breviceps and Geomys bursarius

Abstract

An analysis of the contact zone in Oklahoma between karyotypically and electro-phoretically distinct species, Geomys bursarius and G. breviceps , was made to demonstrate the dynamics of this zone. Electrophoretic variation at 17 loci revealed that the species are generally fixed for alternate alleles at four structural gene loci. However, populations of G. bursarius in northwestern Oklahoma have individuals with the G. breviceps allele at the LDH-1 locus, perhaps as a result of gene flow from Kansas G. bursarius . Hybridization was found in five populations, mostly along riverbottoms that form avenues for dispersal. One F1 hybrid was found, and all other hybrids were F2's or backcrosses. Shifts in allelic distributions are abrupt with no evidence of clinal variation. Levels of heterozygosity at the contact zone are not high, indicative of little hybridization. We conclude that the zone is dynamic and that the hybridization represents limited gene exchange that could result from single hybridization events.