Population dynamics in the subterranean rodent Ctenomys from the Iberá wetland, Argentina

P MIROL; M GIMÉNEZ; M ROSSI; C BIDAU; J SEARLE; C FAULKES

Memphis, USA

Congreso; 91st Ecological Society of America Meeting; 2006

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. This work seeks to investigate the resulting impact of habitat fragmentation on the patterns of genetic differentiation among population and species of tuco-tucos within these environments. Eighteen polymorphic microsatellite loci were tried in 135 individuals from 24 populations of the complex of species. Principal component analysis (PCA) showed three significant components, which separated the populations in 6 main groups. A neighbor joining tree based on Nei's genetic distance (Ds) showed very similar relationships that correlate with karyotypic differences. Boundaries between the populations 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.