Evolution of phyllotines (Rodentia, Muridae) in the southern Andes

The tribe Phyllotini is an advanced group of 46 endemic species among the M uridae of South America, that being adapted to its xeric environments, seem s to have the Southern Altiplano as its original differentiation area (Reig 1986). This hypothesis is tested by examining the geographic distributions and cytogenetic data from 35 species, including the Andinomys edax and Eun eomys chichilloides G band descriptions: its comparison with Phyllotis, AgN OR bands and rDNA FISH in seven species, as well as protein electrophoresis data (118 electro-alleles in 12 species) and cytochrome b gen sequences in the mtDNA (407 bp in 14 species). All karyotypes were chromosomically diff erent, except in two cases with unknown G bands. A general association betw een altiplanic distribution of species with ancestral character states (tel ocentric chromosomes, high 2n, basal positions in phylogenies based on prot ein and cytochrome b gene sequences) was found, as well as between non-alti planic distribution with derived states. Different combinations of Altdinom ys-like chromosomal arms that would have suffer ed centric fusions to form the metacentric chromosomes of Euneomys and Phyllotis, respectively, are do cumented here, and also a reduction of the number of structural NOR in Auli scomys compared to Loxodontomys, all derived features showing a diversifica tion to the south and another to the north respectively, from a center in t ile southern Altiplano.