GEOGRAPHIC-VARIATION OF CHROMOSOMAL-POLYMORPHISM IN 9 POPULATIONS OF CTENOMYS-AZARAE, TUCO-TUCOS OF THE CTENOMYS-MENDOCINUS GROUP (RODENTIA, OCTODONTIDAE)

Previous studies of Ctenomys species from Central and Western Argentin a, referred to as the mendocinus-group, which included a single C. aza rae specimen, showed that they share a similar karyotype of 2n = 47-48 , a complex chromosomal polymorphism and heterochromatic short arms in most of biarmed autosomes. In this study karyotypes of 46 specimens o f C. azarae from nine local populations From La Pampa and Cordoba Prov inces (Argentina) were analyzed. Diploid numbers ranged from 2n=46 to 2n=48 and the G-banding pattern was identical to the other species of the mendocinus-group. As in C. mendocinus and C. porteousi, heterochro matin was highly variable, exhibiting a large number of polymorphisms that involved C-positive blocks. Our data also revealed that the same polymorphism displayed in pair Al, was present in five C. azarae popul ations. Another significant finding was the presence of the homomozygo us karyotype (2n = 46), which was absent in 106 previously studied spe cimens of C. porteousi and C. mendocinus, in two C. nmr-ae populations . Cytogenetic, morphometric, and sperm morphology studies of the mendo cinus-group suggest recent allopatric speciation events, in which chro mosomal rearrangements did not play a central role.