A review of the Pseudobarbus afer (Peters, 1864) species complex (Teleostei, Cyprinidae) in the eastern Cape Fold Ecoregion of South Africa

The Eastern Cape redfin, Pseudobarbus afer, has long been considered to be a single widespread and variable species occurring in multiple isolated river systems in the Cape Fold Ecoregion (CFE) at the southern tip of Africa. Mitochondrial cytochrome b and control region sequence data of individuals from populations currently assigned to P. afer across the species' distribution range revealed existence of four deeply divergent taxonomic units: (i) the Mandela lineage confined to the Sundays, Swartkops and Baakens river systems, (ii) the Krom lineage endemic to the Krom River system, (iii) the St Francis lineage occurring in the Gamtoos and adjacent river systems, and (iv) the Forest lineage occurring in several coastal river systems from the Tsitsikamma to the Klein Brak River system. The Forest lineage is closely related to P. phlegethon from the Olifants River system on the west coast of South Africa, suggesting that it does not belong to P. afer s.l. Herein we focus on the three lineages within the P. afer s.l. complex and provide new diagnosis for P. afer s.s (Mandela lineage), revalidate P. senticeps (Krom lineage) as a distinct species, and describe a new species P. swartzi (St Francis lineage). The three species exhibit subtle differences, which explains why they were previously considered to represent a single variable and widespread species. Pseudobarbus senticeps differs from both P. afer and P. swartzi by having fewer (i.e. larger) scales (25-33, mode 29 lateral line scale series; 10-12, mode 11 circumpeduncular scales) and presence of a lateral stripe which terminates in a conspicuous triangular blotch at the base of the caudal fin. Long barbels which reach or surpass the vertical through the posterior edge of the eye further separate P. senticeps from P. afer s. s. which possesses simple short barbels which do not reach the vertical through the posterior margin of the eye. Pseudobarbus afer s. s differs from P. swartzi sp. n. by possession of fewer scale rows along the lateral line (29-35, mode 32 vs 34-37, mode 36 in P. swartzi), fewer scales around the caudal peduncle (12-16, mode 12 vs 13-17, mode 16 in P. swartzi) and a distinct mesh or net-like pigmentation pattern on latero-ventral scales.