RAPD analysis of Nectomys squamipes (Rodentia, Sigmodontinae) populations

Random amplified of polymorphic DNA (RAPD) analysis was used to assess gene tic distance and the genetic structure of populations of Nectomys squamipes , a semiaquatic rodent species distributed along watercourses. DNA samples of five populations were analyzed using three primers, producing 45 scorabl e bands, 31 of which were polymorphic, There was a significant differentiat ion among populations [F-ST = 0. 17; Phi (ST)= 0.14 (P<0.004)] but gene flo w (Nm=1.25) was sufficient to overcome genetic drift effects. No fixed spec ific markers were found for any population. The Mantel's test and UPGMA clu ster analysis showed a lack of relationship between genetic and geographic distances. The apparent homogeneity indicated by RAPD markers coincided wit h morphometric data, despite the wide geographic range of N. squamipes. Alt ernative hypotheses for explaining our results include recurrent processes of local extinction and recolonization or a recent and sudden increase in t he geographic distribution of this species.