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.