New studies on allozyme genetic distance and variability in akodontine rodents (Cricetidae) and their systematic implications

Abstract

Allozyme genetic distance and variability were studied by horizontal starch gel electrophoresis in 11 species of rodents of the tribe Akodontini representing four different genera. One species of the phyllotine Calomys was used as an outgroup for comparisons. Thirty presumptive loci were assessed in a total of 172 specimens. Only three of 30 loci were found to be monomorphic in the whole sample. Levels of polymorphism ( P) and mean heterozygosity ( H) were dependent on esterase loci which increase H values by 6.26% on average. Nei's jackknife genetic distances among conspecific populations were found not to differ significantly with geographic distance. Phenetic and cladistic interspecific analysis coincided in indicating the monophyletic nature of the akodontine clade, and its splitting into two sharply differentiated subclades: one comprising species referred to as Abrothrix, Chelemys and Geoxus, another comprising species of Akodon (including Deltamys) and Oxymycterus. Thus, the separateness of a southern Andean branch in the cladogenesis of the Akodontini was confirmed, as well as the early recognition of Abrothrix as a full genus, and the recent claim of Spotorno to include in this genus other species formerly classified as Akodon jelskii, Ak. andinus and Ak. olivaceus.