Investigating the consequences of the mating system for drug resistance evolution in C. elegans

The rise of anthelmintic-resistant strains in livestock threatens both animal and human health. Understanding the factors influencing anthelmintic resistance is crucial to mitigate the threat posed by these parasites. Due to difficulties in studying parasitic worms in the laboratory, the non-parasitic nematode Caenorhabditis elegans is used as a model organism to investigate anthelmintic resistance evolution. However, the suitability of this free-living nematode as a model for parasitic worms is debatable due to its rare androdioecious reproductive system, raising questions about the generalizability of findings from evolutionary experiments in C. elegans to other species. In this study, we developed a polygenic, population genetic model combined with pharmacodynamic approaches to investigate the effects of reproductive strategy and other aspects, such as dominance, mutational effects, the number of loci, and population size, on determining the dynamics and outcome of evolutionary processes. We found that androdioecious populations showed both rapid initial adaptation typical for hermaphrodites and tolerance to high drug concentrations observed in dioecious populations. They also exhibited the highest diversity and shortest time for the fixation of the beneficial allele. These results suggest that androdioecious populations can harness the advantages of both selfing and outcrossing, optimizing their reproductive strategy in response to drug selection.