Abstract
The South African coastline can be divided into at least four temperature-defined marine bioregions, including the
tropical north-east coast, the subtropical east coast, the warm-temperate south coast, and the cool-temperate west
coast. There are also two biogeographical transition zones, the south-west coast and the south-east coast (or Wild
Coast). The former is sometimes considered a distinct marine bioregion, but no such status has yet been suggested
for the Wild Coast. Previous data on the distribution of a recently described but very common coastal crab, Hymenosoma
longicrure, indicated that this species could be a Wild Coast endemic. If confirmed, this would be a first indication
that this region harbours unique fauna, and that additional research is required to determine whether the Wild
Coast constitutes a distinct bioregion that needs to be managed separately from other coastal regions. In the present
study, we generated novel genetic data for H. longicrure and compared the species’ range with that of its southern
African congeners. We found that H. longicrure occurs north of the Wild Coast, where its range overlaps with that of H.
projectum. This finding rejects the idea that the Wild Coast harbours endemic fauna and suggests that the ranges of
the two species may be linked to the subtropical and tropical bioregions, respectively, with some southward dispersal
facilitated by the southward-flowing Agulhas Current. We conclude that there is as yet no compelling evidence that
the Wild Coast is a distinct marine bioregion, and concur with previous biogeographical studies which have suggested
that the Wild Coast is an area in which species from the subtropical and warm-temperate bioregions have
overlapping ranges. Nonetheless, that fact that no biological information is available for the majority of the region’s
estuaries highlights the necessity of comprehensively documenting the biodiversity of this understudied region to
fully resolve this issue.