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

The striped-mouse, Rhabdomys pumilio, is widely distributed throughout sout hern 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 taxono mic status of populations within this species. Fifteen of the 26 loci exami ned 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 m ean value for local genetic differentiation (F-st) of 0.459 and the low mea n value for the effective number of migrants (Nm) of 0.179 indicated low le vels of gene flow between the different localities of R. pumilio. The negat ive, near zero F-is value of -0.01 indicated a balance between heterozygote s and homozygotes. Rogers (1972) genetic similarity ranged between 0.796 an d .0.988, and Nei's (1978) unbiased genetic distance varied between 0.000 a nd 0.189 between the samples of R. pumilio. The phenogram based on Nei's (1 978) unbiased genetic distance showed some degree of geographical subgroupi ng. The Mantel test indicated a significant relationship between the F-st v alues and the geographical distances between sample pairs, supporting an is olation 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.