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

Abstract

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 Pseudobarbus 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 Pseudobarbus phlegethon from the Olifants River system on the west coast of South Africa, suggesting that it does not belong to Pseudobarbus afer s.l. Herein we focus on the three lineages within the Pseudobarbus afer s.l. complex and provide new diagnosis for Pseudobarbus afer s.s (Mandela lineage), revalidate Pseudobarbus senticeps (Krom lineage) as a distinct species, and describe a new species Pseudobarbus 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 Pseudobarbus afer and Pseudobarbus 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 Pseudobarbus senticeps from Pseudobarbus 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 Pseudobarbus swartzi sp. n. by possession of fewer scale rows along the lateral line (29–35, mode 32 vs 34–37, mode 36 in Pseudobarbus swartzi), fewer scales around the caudal peduncle (12–16, mode 12 vs 13–17, mode 16 in Pseudobarbus swartzi) and a distinct mesh or net-like pigmentation pattern on latero-ventral scales.

Evidence of hidden diversity and taxonomic conflicts in five stream fishes from the Eastern Zimbabwe Highlands freshwater ecoregion

“…Results of the present study thus add to the growing board of evidence that shows that a large proportion of freshwater fishes in southern Africa remain scientifically undocumented, because many river systems remain poorly explored as much of the previous research effort and application of molecular approaches has predominantly focussed on fishes of the Cape Fold Ecoregion (Ellender et al 2017). Despite being one of the geographically and taxonomically well explored regions in southern Africa, new species and deeply divergent genetic lineages continue to be discovered within almost all fish taxonomic groups of the Cape Fold Ecoregion Chakona and Skelton, 2017;Chakona et al , 2014Wishart et al 2006), and estimates indicate that there are about 43 undescribed species within the 21 currently recognised fish species of this region (Linder et al 2010). The discovery of hidden diversity in the EZH freshwater ecoregion adds to the growing evidence for the existence of high species-level diversity within a number of fish species from high altitude streams in southern, east and west Africa (e.g., Friel and Vigliotta 2011;Morris et al 2016;Schmidt and Pezold 2011;Schmidt et al 2014Schmidt et al , 2015Schmidt et al , 2016Thomson 2013;Thomson and Page 2010).…”

“…Growing evidence from previous and ongoing DNA-based studies shows that many species of freshwater fishes that were previously considered to have wide geographic ranges are instead complexes comprising several genetically divergent lineages (e.g., Goodier et al 2011;Kramer et al 2004;Kramer and Wink 2013;Linder et al 2010;Swartz et al 2007Swartz et al , 2009). These studies have stimulated renewed interest in the systematics of freshwater fishes in the region as evidenced by the recent revalidation of some junior synonyms as well as the identification and description of several new species (e.g., Chakona et al 2014;Chakona and Skelton 2017;Kramer et al 2003Kramer et al , 2007Kramer et al , 2012Kramer et al , 2013Kramer et al , 2014Kramer and Swartz 2010;Kramer and van der Bank 2011;Maake et al 2014). There is thus need for expanding the application of molecular approaches as these may lead to the identification of presently unrecognised diversity and provide insights on the patterns of endemism of stream fishes from other understudied regions in southern Africa such as the EZH freshwater ecoregion.…”

“…Map of the Eastern Zimbabwe Highlands (EZH) freshwater ecoregion showing the river systems (Lower Zambezi, Pungwe, Buzi and Save) that drain this region and the sampling localities for the present study. Chakona and Skelton 2017;Decru et al 2012Decru et al , 2013Decru et al , 2015Zengeya et al 2011), as well as their peculiar disjunct distribution patterns (i.e., discontinuous and separated by wide geographic distance) in the case of A. natalensis and H. ansorgii (Marshall 2011;Skelton 2001).…”

Evidence of hidden diversity and taxonomic conflicts in five stream fishes from the Eastern Zimbabwe Highlands freshwater ecoregion

“…Growing evidence from previous and ongoing DNA-based studies shows that many species of freshwater fishes that were previously considered to have wide geographic ranges are instead complexes comprising several genetically divergent lineages (e.g., Chakona et al 2013; Goodier et al 2011; Kramer et al 2004; Kramer and Wink 2013; Linder et al 2010; Swartz et al 2007, 2009). These studies have stimulated renewed interest in the systematics of freshwater fishes in the region as evidenced by the recent revalidation of some junior synonyms as well as the identification and description of several new species (e.g., Chakona and Swartz 2013; Chakona et al 2014; Chakona and Skelton 2017; Kramer et al 2003, 2007, 2012, 2013, 2014; Kramer and Swartz 2010; Kramer and van der Bank 2011; Maake et al 2014). There is thus need for expanding the application of molecular approaches as these may lead to the identification of presently unrecognised diversity and provide insights on the patterns of endemism of stream fishes from other understudied regions in southern Africa such as the EZH freshwater ecoregion.…”

“…1). These taxa were selected due to uncertainties about their taxonomic status (Marshall 2011), their perceived broad geographic distribution ranges that are surprising considering recent evidence from studies of other freshwater fishes that were previously thought to be wide ranging species (e.g., Chakona and Skelton 2017; Decru et al 2012, 2013, 2015; Zengeya et al 2011), as well as their peculiar disjunct distribution patterns (i.e., discontinuous and separated by wide geographic distance) in the case of A. natalensis and H. ansorgii (Marshall 2011; Skelton 2001). …”