Biochemical polymorphisms and phenetic relationships in rodents of the genusCtenomys from Southern Brazil

Protein variation at 20 loci was analyzed by starch gel electrophoresis in population samples of Ctenomys flamarioni, C. torquatus, C. sp., and C. minutus collected in 25 localities of Southern Brazil. Results show that these four species exhibit higher levels of genetic variability (He = 0.11-0.17) than those reported for most other fossorial rodents. Estimates of similarity coefficients indicate that C. minutus and C. sp. (S = 0.91) are the closest species, while C. flamarioni (S = 0.77) is the most distant from the others. The data presented here support the hypothesis of a relatively recent disjunction of C. minutus from C. sp. Within-species similarity indices are of the same order of magnitude as those found between species. The relatively high levels of heterozygosity observed are not in accordance with the view that subterranean taxa should be less variable than aboveground species due to the uniformity of their environment.