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Data from: Speciation in sympatry with ongoing secondary gene flow and an olfactory trigger in a radiation of Cameroon cichlids

Citation

Poelstra, Jelmer W.; Richards, Emilie J.; Martin, Christopher H. (2018), Data from: Speciation in sympatry with ongoing secondary gene flow and an olfactory trigger in a radiation of Cameroon cichlids, Dryad, Dataset, https://doi.org/10.5061/dryad.4s5dm31

Abstract

The process of sympatric speciation in nature remains a fundamental unsolved problem. Cameroon crater lake cichlid radiations were long regarded as one of the most compelling examples; however, recent work showed that their origins were more complex than a single colonization event followed by isolation. Here, we performed a detailed investigation of the speciation history of a radiation of Coptodon cichlids from Lake Ejagham using whole-genome sequencing data. The existence of this radiation is remarkable since this 0.5 km2 lake offers limited scope for divergence across a shallow depth gradient, disruptive selection is weak, and the species are sexually monochromatic. We infer that Lake Ejagham was colonized by riverine cichlids soon after its formation 9,000 years ago, yet speciation occurred only in the last 1,000-2,000 years. We show that secondary gene flow from riverine species has been ongoing, into ancestral and extant Lake Ejagham lineages, and identify and date river-to-lake admixture blocks. One of these contains a cluster of olfactory receptor genes that introgressed close to the time of the first speciation event and coincides with a higher overall rate of admixture into the recipient lineages. Olfactory signaling is a key component of mate choice and species recognition in cichlids. A functional role for this introgression event is consistent with previous findings that assortative mating appears much stronger than ecological divergence in Ejagham Coptodon. We conclude that speciation in this radiation took place in sympatry, yet may have benefited from ongoing riverine gene flow.

Usage Notes

Location

Cameroon
Lake Ejagham