Selfing is the safest sex for Caenorhabditis tropicalis

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Noble, Luke, M | Yuen, John | Stevens, Lewis | Moya, Nicolas | Persaud, Riaad | Moscatelli, Marc | Jackson, Jacqueline, L | Zhang, Gaotian | Chitrakar, Rojin | Baugh, L, Ryan | Braendle, Christian | Andersen, Erik, C | Seidel, Hannah, S | Rockman, Matthew, V

Edité par CCSD ; eLife Sciences Publication -

International audience. 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, Caenorhabditis 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 Medea-like elements, genetically consistent with maternal toxin/zygotic antidote systems. Loci with Medea activity harbor novel and duplicated genes, and their activity is modified by mito-nuclear background. Segregating Medea elements dramatically reduce fitness, and simulations show that selfing limits their spread. Frequent selfing in C. tropicalis may therefore be a strategy to avoid Medea-mediated outbreeding depression.

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