Disentangling the divergence and cladogenesis in the freshwater crab species (Potamonautidae:<i>Potamonautes perlatus sensu lato</i>) in the Cape Fold Mountains, South Africa, with the description of two novel cryptic lineages

Abstract

River networks of major drainages can form barriers that shape the phylogeography of freshwater organisms, particularly those with low dispersal capabilities. Freshwater crab species' distributions can be used to examine hydrological patterns to expose historical drainage interconnectivity. We used molecular sequence data (mitochondrial and nuclear DNA) and divergence time estimations to determine the phylogeography of the freshwater crab, Potamonautes perlatus sensu lato, from six drainage systems along the Cape Fold Mountains, South Africa. Two major clades were detected: clade 1 comprised two geographically discrete haploclades occurring in southern flowing drainages, whereas clade 2 included specimens from western flowing drainages. Divergence time estimations suggested a Pleistocene (c. 2.61 Mya) divergence of P. perlatuss.l. The Pleistocene was associated with arid conditions and drainage contractions. However, it is likely that during the mesic conditions of the Pleistocene, P. perlatuss.l. migrated and diverged into contemporary patterns. We conclude that three lineages are nested within P. perlatus s.l., two representing novel species. Potamonautes perlatus sensu stricto is confined to western flowing drainages. The two novel species both occurring in southern flowing drainages are described here: Potamonautes barbarai sp. nov. occurs in the Gamtoos and Gourits Rivers and Potamonautes barnardi sp. nov. in the Breede River.