The evolution and maintenance of sexual reproduction is one of the central questions of evolutionary biology, but we still know very little about how sex influences molecular evolution. The New Zealand freshwater snail Potamopyrgus antipodarum is ideally suited to address this knowledge gap because obligately sexual individuals often coexist with multiple independently-derived obligately asexual lineages. This project aims to describe the genomic effects of transitions from sexual to asexual reproduction in P. antipodarum.