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Ancestral Hybridization Facilitated Species Diversification in the Lake Malawi Cichlid Fish Adaptive Radiation

Svardal, Hannes and Quah, Fu Xiang and Malinsky, Milan and Ngatunga, Benjamin P. and Miska, Eric A. and Salzburger, Walter and Genner, Martin J. and Turner, George F. and Durbin, Richard. (2020) Ancestral Hybridization Facilitated Species Diversification in the Lake Malawi Cichlid Fish Adaptive Radiation. Molecular biology and evolution, 37 (4). pp. 1100-1113.

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Abstract

The adaptive radiation of cichlid fishes in East African Lake Malawi encompasses over 500 species that are believed to have evolved within the last 800,000 years from a common founder population. It has been proposed that hybridization between ancestral lineages can provide the genetic raw material to fuel such exceptionally high diversification rates, and evidence for this has recently been presented for the Lake Victoria region cichlid superflock. Here, we report that Lake Malawi cichlid genomes also show evidence of hybridization between two lineages that split 3-4 Ma, today represented by Lake Victoria cichlids and the riverine Astatotilapia sp. "ruaha blue." The two ancestries in Malawi cichlid genomes are present in large blocks of several kilobases, but there is little variation in this pattern between Malawi cichlid species, suggesting that the large-scale mosaic structure of the genomes was largely established prior to the radiation. Nevertheless, tens of thousands of polymorphic variants apparently derived from the hybridization are interspersed in the genomes. These loci show a striking excess of differentiation across ecological subgroups in the Lake Malawi cichlid assemblage, and parental alleles sort differentially into benthic and pelagic Malawi cichlid lineages, consistent with strong differential selection on these loci during species divergence. Furthermore, these loci are enriched for genes involved in immune response and vision, including opsin genes previously identified as important for speciation. Our results reinforce the role of ancestral hybridization in explosive diversification by demonstrating its significance in one of the largest recent vertebrate adaptive radiations.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften > Integrative Biologie > Evolutionary Biology (Salzburger)
UniBasel Contributors:Salzburger, Walter
Item Type:Article, refereed
Article Subtype:Research Article
Publisher:Oxford University Press
ISSN:0737-4038
e-ISSN:1537-1719
Note:Publication type according to Uni Basel Research Database: Journal article
Language:English
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Last Modified:07 Feb 2021 13:43
Deposited On:07 Feb 2021 13:43

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