Genic Differentiation of two Chromosome Races of the Geomys bursarius Complex

Abstract

Electrophoretic variation in proteins encoded by 21 loci was analyzed for 37 populations of Geomys bursarius sampled across the ranges and at two contact zones of chromosomal races D (2N = 72, FN = 70) and E (2N = 74, FN = 72). Previous electrophoretic studies at a contact zone of these races in central Texas indicated a high degree of genic differentiation between the two forms. Four loci, ADH-1, MDH-2, LDH-1, and IDH-1, exhibited patterns of alternately fixed or predominant alleles between the races. This pattern was consistent across the ranges of both races and at a contact zone near Norman, Oklahoma. Genic identities among populations of chromosomal races D and E were 0.938 and 0.953, respectively, while interracial genic identity was 0.685. Additionally, the races have significantly different levels of heterozygosity, along with differences in interpopulation heterogeneity. Intensive study of the contact zone near Norman, Oklahoma, revealed the chromosomal races are generally parapatric, except in one area where a local population was comprised of both races and a F1 hybrid. No backcross individuals were found. It is concluded that the two races are maintaining separate gene pools and that chromosomal race E be recognized as a separate species, Geomys breviceps .