12/06/2025
This is a great paper focusing on the orange blotch (OB) phenotype in rock-dwelling cichlids or mbuna, in Lake Malawi. Researchers delve into the world of supergenes, clusters of two or more linked genes affecting multiple phenotype traits, showing a chromosome inversion created a supergene for s*x and colour in Lake Malawi cichlids
Open-access - https://onlinelibrary.wiley.com/doi/10.1111/mec.17821
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A Chromosome Inversion Creates a Supergene for S*x and Colour in Lake Malawi Cichlids
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Behrens, K.A., Jailwala, S., Clark, F.E., Meyer, A.C., Kumar, N.M., Konings, A.F., Roberts, R.B., Conte, M.A., Streelman, J.T., McGrath, P.T. and Kocher, T.D. (2025), A Chromosome Inversion Creates a Supergene for S*x and Colour in Lake Malawi Cichlids. Mol Ecol e17821. https://doi.org/10.1111/mec.17821
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Cichlid fishes have the highest rates of evolutionary turnover of s*x chromosomes among vertebrates. Many large structural polymorphisms in the radiation of cichlids in Lake Malawi are associated with s*x chromosomes and may also carry adaptive variation. Here, we investigate the structure and evolutionary history of an inversion polymorphism that includes both a ZW s*x locus and an orange-blotch colour polymorphism in the rock-dwelling cichlid fishes of Lake Malawi. We use long-read sequencing to characterise the sequence and breakpoints of the inversion. We quantify allele frequency differences across the inversion in population samples of the genera ๐๐๐ก๐๐๐๐๐๐๐๐ and ๐ฟ๐๐๐๐๐ก๐๐๐โ๐๐ข๐ . We also examine expression differences of genes in the inversion. The simple inversion spans 7 Mb and is flanked by CACTA transposons that may have catalysed the rearrangement. The region includes ~600 genes, several of which show large differences in expression. Some of these genes are candidates for the s*x and colour phenotypes. This inversion is an accessible model system for studying the role of structural polymorphisms and s*x chromosome turnover in the adaptive radiation of cichlids in the lakes of East Africa.
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An assessment of the frequency of OB males in populations around Lake Malawi. High frequencies are defined as populations with greater than 1% OB males, while low frequencies are defined as populations with less than 1% OB males. These frequencies were estimated through informal surveys by Ad Konings. Not indicated are many other populations segregating OB that do not have notable frequencies of OB males. Species/populations with OB poolseq data are indicated in bold.
Copyright ยฉ 2025 the Author(s). Published in Molecular Biology journal. This paper is released under a Creative Commons Attribution 4.0 International (CC BY 4.0) licence. https://creativecommons.org/licenses/by/4.0/
