Molecular phylogenetic evidence of unrecognized diversity within Barbus kerstenii and a broad zone of introgression with Barbus neumayeri in Kenya

Abstract

Ongoing studies of molecular phylogenetics of freshwater fishes from major river drainages and endorheic basins across central and southern Kenya (Lake Victoria, Lake Naivasha, Ewaso Nyiro, Ewaso Ngiro, Athi, Tana and Pangani basins) have revealed evidence of unrecognized diversity within the Redspot Barb, Barbus kerstenii Peters. Here we present results of sequencing of nuclear and mitochondrial genetic markers for populations of Barbus kerstenii and B. neumayeri from throughout the study area, and a preliminary analysis of morphological differences between the two species. Barbus kerstenii was described from the Paganini Basin in Tanzania. The reported range of B. kernstenii in Kenya extends across southern Kenya from the Pangani system to Lake Victoria. We detected genetically distinct populations of B. kernstenii in the Athi River system and the Lake Victoria basin. Barbus neurmayeri Fischer was described from rivers of the Lake Natron Basin, Kenya. The reported distribution of B. neumayeri in Kenya extends from Lake Victoria to the Athi Basin. Barbus kerstenii and B. neumayeri are not closely related genetically, yet our genetic results provide clear evidence of ongoing hybridization and/or past mitochondrial introgression between B. kerstenii and B. neumayeri across an area, extending from Lake Naivasha to the Athi River system.