Subterranean Fishes of the World

6933

2024

Populations that evolve the same traits in parallel due to the same strong selective pressure provide excellent opportunities to study the molecular basis of adaptation. While it is well recognized that copy number variation contributes to phenotypic diversity, its involvement in ecological adaptation is not readily obvious. By identifying genomic regions whose copy numbers repeatedly diverge between ancestral and derived ecotypes in multiple populations, the association of such CNVs with adaptation to the novel environment can be inferred. We employed this approach to pinpoint CNVs associated with recurrent adaptation to the cave environment in the natural populations of the Mexican tetra fish (Astyanax mexicanus), a well-known model for studying troglomorphy. We detected CNVs from publicly available genomic data of 44 individuals from two ancestral (surface form) and three recently derived (cave form) populations. We discovered 102 genes and 292 genomic regions that comprise 0.8% of the reference genome and exhibit recurring copy number divergence between the two ecotypes. Functional analysis uncovered their association with processes relevant for adaptation to subterranean life, such as visual processing, immune response, metabolism, nervous system functioning, and oxygen consumption. Most divergent CNVs are multiallelic, showing higher copy numbers in cavefish than in surface fish. Our findings suggest that selection draws from standing genetic variation at multiallelic CNVs to increase their copy number, providing a fast route to ecological adaptation

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26th International Conference on Subterranean Biology and 6th International Symposium on Anchialine Ecosystems: Cagliari 9-14 Sept 2024