Genetic variation in Rhabdomys pumilio (Sparrman 1784) - an allozyme study

Abstract

The striped-mouse, Rhabdomys pumilio, is widely distributed throughout southern Africa. It prefers grasslands but is also found in vlei areas and dry river beds and its attraction to cultivated land has resulted in extensive damage to plants. An allozyme study of R. pumilio populations in different regions of southern Africa was undertaken to evaluate the genetic structure within and between 23 populations and to draw conclusions about the taxonomic status of populations within this species. Fifteen of the 26 loci examined were polymorphic. The mean heterozygosity (0.073) was high for a mammal, although relatively low heterozygosities (0.036–0.054) were recorded for three localities from the peninsular region of the Western Cape. The high mean value for local genetic differentiation (F_st) of 0.459 and the low mean value for the effective number of migrants (Nm) of 0.179 indicated low levels of gene flow between the different localities of R. pumilio.The negative, near zero F_is value of -0.01 indicated a balance between heterozygotes and homozygotes. Rogers (1972) genetic similarity ranged between 0.796 and 0.988, and Nei's (1978) unbiased genetic distance varied between 0.000 and 0.189 between the samples of R. pumilio. The phenogram based on Nei's (1978) unbiased genetic distance showed some degree of geographical subgrouping. The Mantel test indicated a significant relationship between the Fst values and the geographical distances between sample pairs, supporting an isolation by distance model for R. pumilio. Although the genetic evidence for geographical divergence does suggest the possible existence of subspecies, this remains to be substantiated.