NEW INSIGHT INTO THE PHYLOGENY AND BIOGEOGRAPHY OF THE CYPRINID FISHES LABEO (CYPRINIDAE; CYPRINIFORMES) IN AFRICA WITH EVIDENCE FOR CRYPTIC DIVERSITY IN ETHIOPIA

Abstract

To investigate the molecular phylogeny and biogeography of African Labeo and infer and date cladogenetic events that led to its diversification, a time-calibrated phylogeny was constructed based on analysis of mitochondrial cytochrome b (cyt b) gene sequences obtained from 18 African and 14 Asian Labeo species. Phylogenies were constructed under the GTR nucleotide substitution model employing Bayesian inference (BI) and Maximum Likelihood (ML) methods. A time calibrated phylogeny was generated using the GTR model with the Birth and Death speciation tree prior. Both Bayesian and ML phylogenies rendered African Labeo non-monophyletic with South African species grouped along with some Asian species suggesting multiple independent in-to-Africa dispersals of Labeo. Two exclusively African clades were recovered within Labeo; the first includes samples from lower and middle Congo and the eastern segment of Nilo-Sudanic river drainages, while the second comprised samples from the Congo and Nilo-Sudanic drainages. The separation of the Eastern Nilo-Sudanic + lower and middle Congo (clade 1) and Eastern and western Nilo-Sudanic + Congo clades (clade 2) may have occurred around 13.8 MYA with subsequent diversification in these clades leading to extant species diversity of Labeo in Africa. Overall, this study provides new insights into the taxonomy and biogeography of African Labeo with evidence for cryptic diversity within Ethiopia and incongruence between traditional taxonomy and molecular phylogeny. In addition, the study found a close correlation between the biogeographic history of the region and genetic diversity of Labeo in Africa.