The Neotropical region is among the world richest in biodiversity; however, it still holds poorly known and understudied biota. Furthermore, comparative phylogeographic syntheses of the Southern Hemisphere fauna are needed to understand the current and historical patterns of populations (Beheregaray, 2008). Particularly, eastern South America’s coastal areas and river basins were impacted by marine transgression during the Pleistocene and post-Pleistocene resulting in habitat modications and fragmentations (Sprechman, 1978).