Allozymic variation and systematic relationships of the Octodontidae and allied taxa (Mammalia, Rodentia)

Genetic variation and the allozymic relationships of five families comprisi ng 23 species of hystricognath rodents were examined using electrophoretic data from 19 presumptive gene loci. Direct-count heterozygosity ranged from 0% to 13.6%, and polymorphism varied from 0% to 36.8%. Fixed allele differ ences were instrumental for the segregation of taxa as summarized by the Di stance Wagner procedure and by majority-rule consensus trees. The monophyly of the Octodontidae, and the family rank of the Abrocomidae and Ctenomyida e is supported by the data. Monotypic Myocastor coypus is not resolved as a distinct family but appeared within the Caviidae. Within the Octodontidae, paraphyly was detected in polytypic Octodon, whereas a high bootstrap valu e supported the node containing the desert specialists O.mimax (2n = 56) an d Tympanoctomys barreare (2n = 102). The implications of allozymic data as a robust phylogenetic signal that connected biochemical associations to the prediction of tetraploidy in T. barrerae are discussed.