Phylogeny and biogeography of the genus Pseudobarbus (Cyprinidae): Shedding light on the drainage history of rivers associated with the Cape Floristic Region

Abstract

Relationships among the historically isolated lineages of Pseudobarbus were reconstructed using molecular and morphological data. Contradictions between the molecular and morphological phylogenies suggest convergent evolution and homoplasy in some morphological characters. The earliest divergence in Pseudobarbus was between P. quathlambae in Lesotho and the rest of the genus associated with the Cape Foristic Region in South Africa. A close relationship between P. phlegethon from the Olifants River system on the west coast of South Africa and a lineage of P. afer from small river systems in Afrotemperate Forests on the south coast, can only be explained through previous occurrence and subsequent extinction of ancestral populations in the Gourits River system. Several river systems had confluences before reaching lower sea levels, most notably during the last glacial maximum about 18,000 years ago, explaining closely related populations across different river systems. Mainly river capture explains shared lineages across river systems that did not share a common confluence during lower sea levels.

The genetic legacy of lower sea levels: does the confluence of rivers during the last glacial maximum explain the contemporary distribution of a primary freshwater fish (Pseudobarbus burchelli, Cyprinidae) across isolated river systems?

“…Brito et al, 1997;Waters & Wallis, 2000;Mesquita et al, 2001;Craw et al, 2007;Swartz et al, 2007;Burridge et al, 2008), sea-level regressions (e.g. Ketmaier et al, 2004;Swartz et al, 2007Swartz et al, , 2009, intermittent freshwater connections (e.g. Burridge et al, 2008) and freshwater plumes into estuarine and marine environments (e.g.…”

“…1). Based on palaeoriver courses that were reconstructed by Swartz et al (2009), using the bathymetry of South African Navy Charts, seismic profiling of offshore sediments by Birch (1980) and reviews published on offshore stratigraphical, sedimentological and bathymetric studies (Dingle & Rogers, 1972;Dingle et al, 1987), it is proposed that exposure of the Agulhas Bank would have allowed adjacent rivers to coalesce before reaching the -130 m sea level, forming two major historical river systems (Fig. 1).…”

“…Bloomer & Impson (2000) proposed that the occurrence of P. burgi in the presently isolated Berg and Verlorenvlei river systems could be due to changes in the course of the Berg River system and that sea-level changes could have played a role. Swartz et al (2007Swartz et al ( , 2009 proposed that the confluence of river systems during periods of lower sea levels is the most plausible explanation for the close relationships between Pseudobarbus populations across presently isolated river systems in the CFR, based on reconstructions of possible palaeoriver systems during the LGM. They also suggested that river capture could explain the occurrence of closely related lineages in river systems that did not share a common confluence during periods of lower sea levels.…”

Morphometry and DNA barcoding reveal cryptic diversity in the genus Enteromius (Cypriniformes: Cyprinidae) from the Congo basin, Africa

“…For instance, in a study on African giant pouched rats (Cricetomys, Nesomyidae), the combined use of DNA barcoding and cranial measurements lead to the discovery of at least three new species (Olayemi et al 2012). Also for the fish genus Pseudobarbus (Cyprinidae) occurring in southern Africa, 15 separate lineages were identified, using cytb and 16S data, within the (at that time) seven valid species within the genus, most of which were confirmed by morphological results (Swartz et al 2009). Also in Neotropical frogs, a study based on 16S rDNA indicated a huge underestimation of the current species richness, as up to 115% additional species were discovered (Fouquet et al 2007).…”

The identity of Barbus capensis Smith, 1841 and the generic status of southern African tetraploid cyprinids (Teleostei, Cyprinidae)

“…We derived our phylogeny following methods of DNA extraction, amplification, mitochondrial DNA cytochrome b sequencing and analysis done in Swartz et al (2009). Thirteen sequences, representing eight species, were sourced from Genbank (from Tsigenopoulos & Berrebi 2000;Machordom & Doadrio 2001;Tsigenopoulos et al 2002;Durand et al 2002) and a further 19 individuals were sequenced specifically for the present study (Appendix 1).…”