title: Geographical ancestry of Lake Malawi's cichlid fish diversity.
abstract: The Lake Malawi haplochromine cichlid flock is one of the largest vertebrate adaptive radiations. The geographical source of the radiation has been assumed to be rivers to the south and east of Lake Malawi, where extant representatives of the flock are now present. Here, we provide mitochondrial DNA evidence suggesting the sister taxon to the Lake Malawi radiation is within the Great Ruaha river in Tanzania, north of Lake Malawi. Estimates of the time of divergence between the Lake Malawi flock and this riverine sister taxon range from 2.13 to 6.76 Ma, prior to origins of the current radiation 1.20-4.06 Ma. These results are congruent with evaluations of 2-3.75 Ma fossil material that suggest past faunal connections between Lake Malawi and the Ruaha. We propose that ancestors of the Malawi radiation became isolated within the catchment during Pliocene rifting that formed both Lake Malawi and the Kipengere/Livingstone mountain range, before colonizing rivers to the south and east of the lake region and radiating within the lake basin. Identification of this sister taxon allows tests of whether standing genetic diversity has predisposed Lake Malawi cichlids to rapid speciation and adaptive radiation.
authors.affiliation: School of Biological Sciences, University of Bristol, Life Sciences Building, Bristol BS81TQ, UK m.genner@bristol.ac.uk.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Genner
authors.affiliation: Tanzania Fisheries Research Institute (TAFIRI), PO Box 9750, Dar-es-Salaam, Tanzania.
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Ngatunga
authors.affiliation: Tanzania Fisheries Research Institute (TAFIRI), PO Box 9750, Dar-es-Salaam, Tanzania.
authors.forename: Semvua
authors.initials: S
authors.lastname: Mzighani
authors.affiliation: School of Biological, Biomedical and Environmental Science, University of Hull, Hull HU67RX, UK.
authors.forename: Alan
authors.initials: A
authors.lastname: Smith
authors.affiliation: School of Biological Sciences, Bangor University, Bangor, Gwynedd LL572UW, UK.
authors.forename: George F
authors.initials: GF
authors.lastname: Turner
mesh_terms: D063147:Animal Distribution; D000818:Animals; D044822:Biodiversity; D023681:Cichlids / Q000235:genetics* / Q000502:physiology; D019143:Evolution, Molecular; D029941:Fish Proteins / Q000235:genetics; D049810:Genetic Speciation; D060106:Lakes; D008295:Malawi; D008969:Molecular Sequence Data; D009073:Mozambique; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D013636:Tanzania
chemical_list: D029941:Fish Proteins
keywords: African fishes; adaptive radiation; phylogeny