title: Ancient hybridization fuels rapid cichlid fish adaptive radiations.
abstract: Understanding why some evolutionary lineages generate exceptionally high species diversity is an important goal in evolutionary biology. Haplochromine cichlid fishes of Africa's Lake Victoria region encompass >700 diverse species that all evolved in the last 150,000 years. How this 'Lake Victoria Region Superflock' could evolve on such rapid timescales is an enduring question. Here, we demonstrate that hybridization between two divergent lineages facilitated this process by providing genetic variation that subsequently became recombined and sorted into many new species. Notably, the hybridization event generated exceptional allelic variation at an opsin gene known to be involved in adaptation and speciation. More generally, differentiation between new species is accentuated around variants that were fixed differences between the parental lineages, and that now appear in many new combinations in the radiation species. We conclude that hybridization between divergent lineages, when coincident with ecological opportunity, may facilitate rapid and extensive adaptive radiation.
authors.affiliation: Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland.|Department of Fish Ecology and Evolution, Centre for Ecology, Evolution &Biogeochemistry, Eawag: Swiss Federal Institute of Aquatic Science and Technology, 6047 Kastanienbaum, Switzerland.|Computational and Molecular Population Genetics Lab, Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland.
authors.forename: Joana I
authors.initials: JI
authors.lastname: Meier
authors.affiliation: Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland.|Department of Fish Ecology and Evolution, Centre for Ecology, Evolution &Biogeochemistry, Eawag: Swiss Federal Institute of Aquatic Science and Technology, 6047 Kastanienbaum, Switzerland.|Computational and Molecular Population Genetics Lab, Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland.
authors.forename: David A
authors.initials: DA
authors.lastname: Marques
authors.affiliation: Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland.|Department of Fish Ecology and Evolution, Centre for Ecology, Evolution &Biogeochemistry, Eawag: Swiss Federal Institute of Aquatic Science and Technology, 6047 Kastanienbaum, Switzerland.
authors.forename: Salome
authors.identifier: 0000-0002-0241-1685
authors.initials: S
authors.lastname: Mwaiko
authors.affiliation: Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland.|Department of Fish Ecology and Evolution, Centre for Ecology, Evolution &Biogeochemistry, Eawag: Swiss Federal Institute of Aquatic Science and Technology, 6047 Kastanienbaum, Switzerland.|Biodiversity Institute &Department of Botany, University of Wyoming, Laramie Wyoming 82071, USA.
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Wagner
authors.affiliation: Computational and Molecular Population Genetics Lab, Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland.|Swiss Institute of Bioinformatics, 1015 Lausanne, Switzerland.
authors.forename: Laurent
authors.identifier: 0000-0002-7507-6494
authors.initials: L
authors.lastname: Excoffier
authors.affiliation: Aquatic Ecology and Evolution, Institute of Ecology and Evolution, University of Bern, 3012 Bern, Switzerland.|Department of Fish Ecology and Evolution, Centre for Ecology, Evolution &Biogeochemistry, Eawag: Swiss Federal Institute of Aquatic Science and Technology, 6047 Kastanienbaum, Switzerland.
authors.forename: Ole
authors.identifier: 0000-0001-6598-1434
authors.initials: O
authors.lastname: Seehausen
mesh_terms: D000222:Adaptation, Physiological / Q000235:genetics*; D000349:Africa; D000818:Animals; D023681:Cichlids / Q000145:classification / Q000235:genetics*; D004272:DNA, Mitochondrial / Q000145:classification / Q000235:genetics; D019143:Evolution, Molecular; D049810:Genetic Speciation; D014644:Genetic Variation; D006824:Hybridization, Genetic; D060106:Lakes; D010802:Phylogeny; D017422:Sequence Analysis, DNA / Q000379:methods
chemical_list: D004272:DNA, Mitochondrial