COMPARATIVE KARYOLOGY IN AKODON (RODENTIA, SIGMODONTINAE) FROM SOUTHEASTERN BRAZIL

Karyotypic comparisons among five Akodon species showed that they shar ed a substantial proportion of their chromosome complements, indicated by distinct homologies between chromosomes, arms, or arm regions desp ite that this genus is karyotypically rearranged. A comparison with a related outgroup (Bolomys lasiurus) allowed for the recognition of anc estral and derived karyotypic traits as well as for inferring the dire ction of several chromosome rearrangements. This study indicated that species with lower diploid chromosome number are derived from species with higher diploid number, mainly by 11 fusions and 1 pericentric inv ersion while the direction of 5 other rearrangements could not be dete rmined (fusions or fissions). UPGMA analyses of karyologic data indica ted a topology like (Bolomys lasiurus (Akodon sp. (A. lindberghi (A. m ontensis (A. aff. cursor, A. cursor))))).