A key role for deleterious mutations

Congratulations to Paul Jay and Mathieu Chouteau for their amazing study now published in Nature Genetics !

The chromosomal inversions bringing great mimicry benefits in Heliconius numata are full of deleterious mutations and insertions of transposable elements. Individual with a homozygous inversion genotype shave very poor larval survival. This means those inversion only bring their mimicry advantage when heterozygous. Therefore, selection caused by these deleterious effects maintains the standard (non-inverted) arrangements in the population, and balances the amazing wing-pattern polymorphism observed.

Figure: Larval survival according to inversion genotype. Both chromosome types bearing inversions have a low survival rate. All heterozygotes have good survival, similar to individuals lack inversions altogether.

This illustrates the dual effect of recombination suppression associated with inversions: they lock together beneficial mutations, forming greatly favourable haplotypes, but are also prone to capturing and accumulating deleterious variation, acting against their fixation. This could be a very general mechanism underlying inversion polymorphisms throughout the tree of life.

Nature Genetics. doi:10.1038/s41588-020-00771-1
Read online: https://rdcu.be/cebgl

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