Rethinking evolution in self-fertilising species

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Determining the prevalence of natural selection (including the presence of deleterious and favourable variants) from genome sequence data is a major challenge in evolutionary genetics. A sizeable number of species in nature are hermaphrodites capable of self-fertilisation, where individuals produce both female and male gametes that can be used to reproduce. Emerging genome data from such species has yielded unusual selection signatures that cannot be explained by classic predictions, which assume selection acts on local genetic regions. Genetic variation is inherited as large linked regions in self-fertilising species, which can decrease diversity and cause linked selection to act over longer genetic distances. Yet punctuated regions of diversity also exist. SelectSelf will develop theoretical and genome-inference methods to determine how different selective forces interact with this reproductive mode. Work plan 1 will develop models and methods to establish the causes of punctuated diversity (balancing selection, introgression, exposure of deleterious mutations, or residual outcrossing) in self-fertilising species. Work plan 2 will investigate to what extent adaptation by a polygenic trait will lead to long-range selective sweeps and quantify the effect of pleiotropy on this process. Work plan 3 will quantify how the distribution of deleterious mutations are affected by linked selection due to either of these evolutionary mechanisms. Throughout, new methods and theory will be applied to data from Caenorhabditis species to infer the evolutionary impacts of hyperdiversity and linked selection in self-fertilising nematodes. This project will provide a step-change in knowledge of how natural selection and reproduction interact to determine how species persist in natural environments, resulting in new standards for analysing and interpreting genetic data from self-fertilising species.