Genome evolution in parasitic wasps: comparisons of sexual and asexual species

Reproduction is a core organismal trait, and transitions between reproductive strategies may influence the evolutionary trajectory of a species. Sex is a costly reproductive strategy, yet it is ubiquitous in nature. The predominance of sex may be explained in part by passage of genetic material across generations during meiosis, particularly segregation and recombination. Sex enables parents to transmit genetic material without harmful mutations to offspring. Loss of sex may increase the accumulation of mutations in the genome. If harmful, these mutations could lead to the eventual extinction of an asexual lineage. A recent loss-of-sex event in Diachasma parasitic wasps offers a promising opportunity to compare patterns of genome-wide mutations between sexual and asexual species.

I used newly sequenced genomes from sexual and asexual Diachasma to investigate whether sex loss in an asexual wasp is associated with changes in meiosis genes. I identified a complete meiosis gene set in the asexual speices D. muliebre, supporting meiotic egg production despite sex loss. To assess whether reproductive mode influences Diachasma evolution more broadly, I retrieved a genome-wide dataset to calculate evolutionary rates between wasp species. I found evidence for greater mutation accumulation in asexual Diachasma, suggesting the modification of meiosis has an effect on the generation and maintenance of genetic variation. Future studies are needed to determine the extent to which this could affect the organism’s ability to survive in nature.