Sexual Selection and Speciation in Cichlid Fishes

Cichlid fishes of the African Great Lakes represent one of the most rapid and extensive adaptive radiations known in vertebrates. Sexual selection, chiefly mediated through male nuptial coloration and female mate choice, has driven the diversification of hundreds of sympatric species within remarkably short evolutionary timescales. Divergent visual environments at varying depths have favoured distinct colour signals, reinforcing prezygotic isolation. Concurrently, genetic architecture—such as loci of large effect or physical linkage between colour traits and preference—facilitates speciation despite ongoing gene flow. Ecological heterogeneity, sensory drive and behavioural assortative mating interact to generate and maintain reproductive barriers. These processes not only underpin the extraordinary biodiversity of cichlid assemblages but also offer a model for understanding speciation dynamics in other taxa and inform conservation strategies in rapidly changing aquatic habitats.

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Sexual Selection and Speciation in Cichlid Fishes publication trend

The graph below shows the total number of articles in sexual selection and speciation in cichlid fishes across all publications each year (not limited to Nature Index journals).

Technical terms

Sexual selection: An evolutionary process in which differential mating success leads to the exaggeration of traits that increase attractiveness to the opposite sex.

Speciation: The formation of distinct species through the accumulation of reproductive barriers that prevent gene flow between populations.

Assortative mating: A non-random mating pattern in which individuals preferentially mate with others that share similar phenotypic or genotypic traits.

Nuptial coloration: The bright or distinctive colour patterns exhibited by males during breeding, used to attract females or deter rivals.

Sensory drive: A mechanism of divergence in which environmental variation in signalling conditions shapes both the sensory system and mating signals, promoting reproductive isolation.

Quantitative trait loci (QTL): Genomic regions that contribute to variation in a quantitative phenotype, such as colour intensity or mate-choice behaviour.

References

1. Genetic architecture of a key reproductive isolation trait differs between sympatric and non-sympatric sister species of Lake Victoria cichlids. Proceedings of the Royal Society B (2020).
2. Developmental effects of environmental light on male nuptial coloration in Lake Victoria cichlid fish. PeerJ (2018).
3. Strong species structure but weak geographical structure in demersal Lake Victoria cichlids. Ecology and Evolution (2022).
4. Sympatric and allopatric Alcolapia soda lake cichlid species show similar levels of assortative mating. Frontiers in Ecology and Evolution (2023).
5. Constraints to speciation despite divergence in an old haplochromine cichlid lineage. Evolution (2023).