Selfing is the safest sex for Caenorhabditis tropicalis

Tags: Other invertebrates, Toxin-antidote
L. M. Noble, J. Yuen, L. Stevens, N. Moya, R. Persaud, M. Moscatelli, J. Jackson, C. Braendle, E. C. Andersen, H. S. Seidel and M. V. Rockman, bioRxiv, 2020.08.07.242032. 2020.

Mating systems have profound effects on genetic diversity and compatibility. The convergent evolution of self-fertilization in three Caenorhabditis species provides a powerful lens to examine causes and consequences of mating system transitions. Among the selfers, C. tropicalis is the least genetically diverse and most afflicted by outbreeding depression. We generated a chromosomal-scale genome for C. tropicalis and surveyed global diversity. Population structure is very strong, and islands of extreme divergence punctuate a genomic background that is highly homogeneous around the globe. Outbreeding depression in the laboratory is caused largely by multiple gene drive elements, genetically consistent with maternal toxin/zygotic antidote systems. Driver loci harbor novel and duplicated genes, and their activity is modified by mito-nuclear background. Segregating drivers dramatically reduce fitness, and simulations show that selfing limits their spread. Frequent selfing in C. tropicalis may therefore be a strategy to avoid drive-mediated outbreeding depression.Competing Interest StatementThe authors have declared no competing interest.