Cytogenetics of South American Akodont Rodents (Cricetidae). X. Karyological Distances at Generic and Intergeneric Levels

Publisher Website
Google Scholar
Abstract
G-banding was employed to analyse the extent of chromosomal homology in seven akodontine species related at generic and suprageneric levels (Akodon molinae, A. dolores, A. varius, A. azarae, A. mollis, A. urichi, and Bolomys ohscurus). The size of the complement shared by two or more species varies from a minimum of 34% (A. urichi) to a maximum of 80% (A. molinae and A. dolores). This high rate of chromosomal divergence seems to indicate that akodont rodents underwent an active process of cladogenesis which was highly correlated with chromosomal rearrangements. Some chromosome arms are shared by the seven species under analysis, whereas others are shared only by two species or are not shared at all. It is proposed that: (a) chromosomes shared at the suprageneric level are the most primitive in this group of species, (b) highly adapted supergene complexes are an important cause preventing the remodeling of the strongly conserved arms, (c) non-shared chromosomes can be considered as evolutionary novelties derived from chromosomes prone to rearrangements. A mathematical equation is employed to analyse the karyological distances (KD) between any given pair of species. The denominator of the equation evaluates the degree of homology such as determined by G-banding and measurements of chromosomes, whereas the numerator takes into account the chromosomal rearrangements producing changes in the linkage groups. The results obtained with that equation show that in some cases intergeneric KDs are smaller than intrageneric ones. This finding stresses the fact that KDs do not necessarily correlate with phylogenetic distances. A sudden change in environmental conditions may allow survival and stabilization of a new series of chromosomal rearrangements which previously were not viable in the original stock, thus giving rise to marked karyological divergence of the offshoot.

This publication has 1 reference indexed in Scilit: