Systematic Relationships of the Bolivian Tuco-Tucos, Genus Ctenomys (Rodentia: Ctenomyidae)

Evolutionary relationships and taxonomic identity of seven nominal species (Ctenomys boliviensis, C. conoveri, C. frater, C. leucodon, C. lewisi, C. opimus, C. steinbachi) and an undescribed species of Bolivian tuco-tuco were examined using allozymes. These species represent all previously described subgenera of Ctenomys. Twenty-one presumptive genetic loci were resolved and, among the species of Ctenomys, 17 of these were polymorphic. Patterns of intraspecific and interspecific variation, in general, agreed with the current taxonomy for members of this group, although little differentiation was found between C. frater and C. lewisi. The allozymic data suggest that C. boliviensis, as currently recognized, may be paraphyletic. Octodon degus was included as an outgroup for phylogenetic analyses. Phenetic and cladistic analyses of these data indicate that C. opimus was the earliest species to diverge from the group, followed by C. leucodon, and then two lineages, one that included C. boliviensis and C. steinbachi and one that included C. lewisi, C. frater, Ctenomys sp., and C. conoveri. These species are distributed either in the lowlands or highlands in Bolivia and the proposed evolutionary relationships indicate that the historical zoogeography of tuco-tucos has been more complex than a simple lowland-highland vicariant event.