Phylogeographic structure and continued surveys of a Vulnerable South African freshwater crab (Potamonautidae, Potamonautes lividus): Implications for the IUCN Red Listing of the Afrotropical fauna

In the present study, the phylogeography of the only southern African freshwater crab listed as Vulnerable (VU) on the International Union for Conservation of Nature (IUCN) Red List, Potamonautes lividus, was investigated by surveying several localities in the Eastern Cape and KwaZulu‐Natal provinces in South Africa. Both nuclear and mitochondrial DNA (nDNA and mtDNA) markers were used and, as it was hypothesized that marked genetic differentiation should be present, niche modelling was undertaken to explore the distribution of the species along the east coast of South Africa. In addition, shortfalls in the present approach to IUCN Red Listing, as illustrated by this Vulnerable species of crab, are discussed. Results from the mtDNA revealed the presence of two haploclades, confined to specimens from the two provinces, respectively, and the general absence of maternal dispersal, a fact that was further validated by the fixation index (FST) data and high ΦST values. Within the Eastern Cape haploclade, low‐frequency maternal dispersal occurred, corroborated by the low value of FST. In contrast, no haplotypes were shared in the KwaZulu‐Natal haploclade, as corroborated by the marked differences in FST. The microsatellite data demonstrated the presence of higher frequency, possibly paternally biased, dispersal of specimens between the Eastern Cape and KwaZulu‐Natal provinces. The results suggest the presence of two distinct management units within P. lividus. An estimate of divergence time suggests a late Pleistocene cladogenesis between the Eastern Cape and KwaZulu‐Natal haploclades. Considering the presence of P. lividus in several newly formed nature conservation areas in both provinces, and its potential presence in the intermediary area, based on maximum entropy (Maxent) niche modelling, our data suggest that the species status in the IUCN Red List should be downgraded to Least Concern. A comparison of all the Endangered, Vulnerable, and Critically Endangered IUCN Red Listed freshwater crabs for the entire Afrotropical region reveals the lack of recent sampling in the three biodiversity hot spots in West, Central, and East Africa, with mountainous areas containing a disproportionate number of species but with most species being devoid of phylogeographical study.