The role of cytogenetic variation in Akodon cursor species complex speciation (Rodentia: Sigmodontinae)

Abstract

Chromosome polymorphism in populations of Akodon cursor complex (124 specimens) and the karyotypes of other Akodon species (92 specimens) from Brazil were analyzed. Five species were analyzed: Akodon cursor with 2n = 14, and Akodon aff. cursor with 2n = 16, Akodon montensis with 2n = 24, Akodon paranaensis with 2n = 44 and Akodon serrensis with 2n = 46. Chromosome polymorphism was observed in A. cursor and A. aff. cursor showing pericentric inversions, and also in A. paranaensis and A. montensis presenting supernumerary chromosomes. Pericentric inversion polymorphism affecting two autosomes pairs in A. cursor karyotype was found in Hardy-Weinberg equilibrium. Akodon with 2n = 16 occurred from Bahia to Rio Grande do Norte states and A. cursor with 2n = 14 from Bahia to Paraná states. Molecular analyses showed high genetic distance estimates between such set of samples, suggesting that karyomorphic type 2n = 16 is fixed in the northern part of the distribution of Akodon cursor complex. Captive hybrids males between Akodon [2n = 14] x [2n = 16] are apparently sterile, suggesting these populations may represent two full species.