MtDNA lineage diversity of a potamonautid freshwater crab in KwaZulu-Natal, South Africa

Five species of freshwater crab (genus Potamonautes) are known from KwaZulu-Natal, South Africa, whilst a sixth (Potamonautes isimangaliso) was recently described from the iSimangaliso Wetland Park. Earlier molecular studies of crab diversity in the province were largely limited in geographic scope or employed genetic markers, ill-suited for identifying intraspecific diversity. Possible species-level diversity or cryptic taxa may have thus remained undetected. In this study, lineage diversity was examined in a widespread species, Potamonautes sidneyi, using mitochondrial sequence data, to determine whether this species harbours cryptic diversity that could be of conservation importance in the province, particularly with respect to the iSimangaliso Wetland Park. The taxonomic status of P. isimangaliso was also assessed. Mitochondrial sequence data were generated and analysed to identify unique lineages and to examine their distributions. Phylogenetic analyses were used to determine whether these lineages represented known or potentially novel species, using comparative data from southern African Potamonautes species. Seven independent networks were identified within P. sidneyi and substantial structure was observed amongst sampling localities. Phylogenetic analyses revealed two distinct, divergent lineages in P. sidneyi. One was positively assigned to P. sidneyi, whereas the placement of the other suggested a novel species. These results suggested possible species diversity within P. sidneyi, with one lineage occurring in the north-east of the province, around the iSimangaliso Wetland Park. Potamonautes isimangaliso was clearly allied to Potamonautes lividus, but genetic divergences suggested that P. isimangaliso is a distinct taxon and that P. lividus may represent a species complex. Conservation implications: This study confirmed unique freshwater crab diversity, both within KwaZulu-Natal and associated with the iSimangaliso Wetland Park.