The evolutionary genomics of cichlid fishes: explosive speciation and adaptation in the postgenomic era

With more than 1,500 species, cichlid fishes provide textbook examples of recent and diverse adaptive radiations, rapid rates of speciation, and the parallel evolution of adaptive phenotypes among both recently and distantly related lineages. This extraordinary diversity has attracted considerable interest from researchers across several biological disciplines. Their broad phenotypic variation coupled with recent divergence makes cichlids an ideal model system for understanding speciation, adaptation, and phenotypic diversification. Genetic mapping, genome-wide analyses, and genome projects have flourished in the past decade and have added new insights on the question of why there are so many cichlids. These recent findings also show that the sharing of older DNA polymorphisms is extensive and suggest that linage sorting is incomplete and that adaptive introgression played a role in the African radiation. Here, we review the results of genetic and genomic research on cichlids in the past decade and suggest some potential avenues to further exploit the potential of the cichlid model system to provide a better understanding of the genomics of adaptation and speciation.