Phylogeography reveals unexpectedly low genetic diversity in a widely distributed species: The case of the freshwater crab Aegla platensis (Decapoda: Anomura)

Abstract

Habitat and taxon-specific properties could affect the propensity for cryptic species to be formed. For example, anomurans of the genus Aegla possess characteristics that suggest the existence of cryptic diversity. The widelydistributed species Aegla platensis, besides having been considered paraphyletic, shows a considerable amount of morphological variation in the carapace shape among populations. Thus, the aim of this study was to test the hypothesis that A. platensis encompasses a large complex of cryptic species. Seventeen populations of A. platensis from Argentina and Brazil were analysed using three molecular markers. Contrary to our expectations, 16 populations seem to belong to a single species. Only one population of A. platensis might represent an unrecognized new species. These results are intriguing because they do not fit the phylogeographical pattern seen in other aeglids, which usually have narrow distributions. Although intrinsic characteristics and/or historical biogeographical events could be related to these findings, the factors driving the broad distribution of A. platensis still need to be clarified. Finally, we highlight the fact that taxonomic issues in aeglids are far from being fully understood, and the use of a broad population-based sampling can be useful to improve our understanding of the group?s systematics and evolution.