Contrasting genetic patterns and population histories in three threatened redfin species (Cyprinidae) from the Olifants River system, western South Africa

Differentiation Occurred in different areas of the same river system in Pseudobarbus phlegethon and two sister species of the serrated redfin lineage (Barbus calidus and Barbus erubescens) of the Western Cape region of South Africa. In an analysis of 27 allozyme loci a deep divergence was found within P. phlegethon between the Olifants and Doring catchments (seven fixed allelic differences; 0.338 < D < 0.366; F-ST = 0.925). In contrast, speciation in the set-rated redfin lineage occurred within the Doring catchment between B. calidus and B. erubescens (one fixed allelic differences 0.008 < D < 0.052; F-ST = 0.760). Different niche preferences, behaviour and morphology probably played an important role in the formation of these contrasting patterns of genetic structure and suggest that B. calidus may have been better able to disperse between the Olifants and Doring catchments (no fixed allelic differences; 0 < D < 0.040; F-ST = 0.281) than P. phlegethon. (C) 2004 The Fisheries Society of the British Isles.