Molecular phylogenetic and phylogeographic evidence of unrecognized diversity within nominal species of Labeobarbus from Indian Ocean drainages and Endorheic Rivers of the Great Rift Valley of Kenya

Abstract

Studies of molecular phylogenetics and phylogeography of freshwater fishes from major river drainages of the Indian Ocean and endorheic basins of the Great Rift Valley of central, western and southern Kenya have revealed deep genetic divergences within several nominal species. The present study focuses on phylogeography of Kenyan populations of putative hexaploid cyprinid fishes, originally described as species of Barbus or Labeobarbus, and now regarded as species of Labeobarbus Rüppell. The nominal species under study here are the Ripon Barbel, Barbus altianalis Boulenger, the Pangani Barb, Barbus oxyrhynchus Pfeffer, and Labeobarbus intermedius Rüppell. All of the studied species and populations are recovered as a monophyletic group with strong bootstrap support. The most basal lineage is a population from the Yala River (Lake Victoria Basin), which is sister to a lineage comprising all other nominal species. Barbus altianalis and Labeobarbus intermedius for a group sister to Barbus oxyrhynchus, which itself comprises several divergent lineages. The phylogeny provides evidence that L. intermedius and B. altianalis are co-distributed in the Lake Victoria Basin. We present preliminary morphological evidence in an attempt to diagnose species.