CONICET | Buscador de Institutos y Recursos Humanos

South American rodents of the genus Ctenomys (tuco-tucos) constitute the most speciose group of all subterranean rodents. This extraordinary rate of divergence has been attributed to patchy distributions and spatial isolation, restricted mobility, territoriality, small effective population numbers, socially-structured mating systems and high karyotypic evolution. Within the genus, the Corrientes group, is a complex of three species and several forms whose taxonomic status has not yet been determined. Populations are patchy distributed in dry areas around the Esteros del Iberá in Northern Argentina, a wetland that covers more than 12,000 km2 consisting of a vast mosaic of marshes, swamps and lagoons, of which nearly 60% are permanently inundated. Fluctuations in the area of the lagoons are related to pluvial levels, rain, the effects of El Niño current, plus the Yacyretá dam on the Paraná River that has dramatically changed water volume in the esteros since 1989. The instability of the area, coupled with the particular characteristics of the subterranean rodents, create a situation where many evolutionary processes are actually occurring. We are trying to elucidate the forms and patterns of these processes through analysis of karyotypes and molecular markers, such as mitochondrial DNA and microsatellites. All results to date point to a complex scenario of diversification within species without chromosomal change and hybridization between the different species with incredible variation in chromosomal numbers. Boundaries between populations and species of the complex seem to be determined mainly by the geographic barriers to the dispersal of these rodents and indicate an ongoing and dynamical process.