GENETIC VARIATION IN THE AFRICAN VLEI RAT OTOMYS IRRORATUS (MURIDAE: OTOMYINAE)

ABSTRACT

Starch gel electrophoresis was used to analyse genetic variation at 24 enzyme and protein loci in 12 South African populations of vlei rats Otomys irroratus. Mean heterozygosity ([Hbar]: 0.071) was relatively high for a mammal. Allelic variation within populations conformed to Hardy-Weinberg expectations, and the mean value for Wright's F _IS statistic (0.048) indicated no evidence of inbreeding within populations. There was significant local differentiation in allelic frequencies (Wright's F _ST = 0.375). However, genetic distances between populations were low (mean for Nei's D = 0.034), and cluster analysis of genetic distances failed to identify groups consistent with geographical position or karyotypic differences between populations. A single population (Hogsback, eastern Cape), bearing a chromosomal tandem fusion and demonstrating a high measure of reproductive isolation, showed no allozymic differences from other populations, suggesting that chromosomally-mediated speciation may precede phenotypic and genie divergence. However, the population genetic structure of O. irroratus was not consistent with the conditions required for amodel of speciation by chromosomal transilience (i.e., stasipatric speciation of White).