Rethinking Asexuality: The Enigmatic Case of Functional Sexual Genes in Lepraria (Stereocaulaceae)

Through having sex, organisms have the advantage to remove negative mutations and the opportunity to rapidly adjust to changes in the environment. Given most natural environments are variable, asexuality is a rare form of reproduction in naturally-occurring organisms and most of our knowledge of asexual genomes is based on mathematical models. These mathematical models predict dramatic consequences to genomes of asexual organisms such as an accumulation of deleterious mutations. Despite this potential danger, the lichen genus Lepraria shifted to strictly asexual reproduction while almost all other lichens, including Lepraria's sister genus Stereocaulon, retained the ability to reproduce sexually. Sequencing and comparing the genomes of Lepraria and Stereocaulon will show us how asexuality is represented in a genome, compared to its sexual relative. This study includes a representative high-quality annotated genome from each genus (Lepraria finkii and Stereocaulon virgatum), as well as 11 additional Lepraria and 9 additional Stereocaulon metagenomic seuquencing data sets. Comparison of our results with long-standing hypotheses about asexual genomes will help to answer why Lepraria shifted to this unusual form of reproduction and what advantages asexual vs. sexual reproduction carries for Lepraria.