Evolution of meiosis genes in sexual vs. asexual Potamopyrgus antipodarum

How asexual reproduction affects genome evolution, and how ancestrally sexual organisms alter their reproductive machinery upon becoming asexual are central unanswered questions in evolutionary biology. While these questions have been addressed to some extent in different asexual species, the most powerful tests of how sex and its absence influence evolution requires direct comparisons between closely related and otherwise similar sexual and asexual taxa. I address these questions by studying the evolution of genes critical to sexual reproduction in sexual and asexual lineages of Potamopyrgus antipodarum, a New Zealand freshwater snail. Because genes used only for sexual reproduction should have little or no functional relevance for asexuals, I can use this approach to study the effects of asexuality on the evolution of genes required only for sexual reproduction, which has implications for genome evolution in the absence of sex. I discovered that genes necessary for sexual reproduction show no evidence for being lost in asexual P. antipodarum. These results suggest asexuality may result in the loss of some, but not all, components of sexual reproductive machinery or that not enough time has passed for meiosis genes to be lost. Comparing evolutionary patterns between sexual and asexual organisms will help the scientific community understand the benefits and limitations of reproducing sexually. Understanding the consequences of sexual reproduction will illuminate fundamental biological and human health questions, ranging from the importance of biological diversity to the source and transmission of disease to dynamics between humans (who reproduce sexually) and parasites (which are often asexual).