New publication: Balancing selection maintains hyper-divergent haplotypes in Caenorhabditis elegans 

Published on
April 28, 2021

The model nematode Caenorhabditis elegans reproduces mainly through self-fertilization. However, selfing has detrimental effects on the genetic diversity of a species, and therefore adaptive potential. Within the genus Caenorhabditis, selfing has evolved at least three times and within all three species indeed a substantially reduced genetic diversity relative to the outcrossing species is observed. The selfing and outcrossing Caenorhabditis species often occupy the same niches, but how the selfing species with their limited genetic diversity can adapt to these environments remains a question. This paper, recently published in Nature Ecology & Evolution provides an example of how a species can avoid this evolutionary dead-end.

In this publication the whole-genome sequences from 609 wild C. elegans strains isolated worldwide, including Wageningen, were examined and show that genetic variation is concentrated in punctuated hyper-divergent regions covering 20% of the C. elegans reference genome. These regions contain an over-abundance of environmental response genes. By constructing novel long-read genome assemblies for 15 wild strains, the paper shows that hyper-divergent haplotypes contain unique sets of genes and show levels of divergence comparable to levels found between Caenorhabditis species that diverged millions of years ago.