Do genomic regions under selection have hybrid origins in cichlids?

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Hybridization is increasingly recognised as a creative evolutionary force because ecologically useful genomic attributes from one species can be easily obtained from another without waiting for mutation and fixation. However, we currently lack evidence that such genetic contributions could be preferentially retained through natural selection- hybridization maybe a consequence rather than a cause of speciation. In particular, the role that hybridization plays in the generation of hundreds of species in adaptive radiations is unclear. Recent advances in genome technologies make studying this process in detail an exciting possibility - DNA technology can identify "genomic islands of speciation"- loci under selection (or linked to regions under selection) which show divergence between species relative to the rest of the genome. Crucially, the genetic contributions of these adaptively important genetic regions from divergent founding lineages can then be identified in adaptive radiations. In this proposal, I plan to demonstrate that the "text book" Lake Malawi cichlid fish radiation consists of collections of adaptively important genomic regions from different sources. The project will capitalise on the recent Astatotilapia burtoni cichlid genome sequence, advancing our understanding by genome-wide screening of more than 20 species at once in order to identify tens of thousands of single nucleotide polymorphisms (SNPs) using RAD-tag sequencing. Genome scans will identify regions of the genome important in adaptation, and I will then test whether these regions in the endemic radiation lineages show a signal of hybridization with putative seeding lineages, compared to "neutral" regions. This approach will be the first evidence to demonstrate that loci under selection in an adaptive radiation have distinct origins, confirming the importance of hybridization as a driving force for adaptive change.