The genomic substrate for persistence without sex

• Applicant: Dr. Jens Bast
• Subject Area: Evolution, Anthropology
• Term: since 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 427993870

Why complicated and costly sex is maintained in natural populations, despite the existence of more straightforward routes to reproduction, is one of the most enigmatic questions in evolutionary biology. Theory predicts advantages for sex that could offset its costs, but empirical evidence remains largely equivocal. For example, sex is anticipated to be beneficial on the long-term because it facilitates effective purging of harmful mutations and adaptation to different ecological niches. Thus, species that abandoned sex, i.e. obligate asexuals, are considered evolutionary dead-ends. However, some few asexual lineages seem exceptions to this rule and have persisted over evolutionary time and diversified into distinct species. These ‘ancient asexuals’ are invaluable for developing insights into why sex exists, because identifying the singularities that allowed for their persistence will help to understand what the fundamental benefits of sex are.The most notorious ancient asexuals that were subject of intense studies are bdelloid rotifers, but recent research indicates that rotifers engage in non-canonical forms of sex. Thus, new model organisms to study the evolutionary persistence without sex are needed. The most promising organisms to take that role are oribatid mites, which feature several independently derived lineages of ancient asexuals that diversified into species and have sexual relatives at hand for comparative studies. With this proposal, using oribatid mites, the population genomic basis allowing for the persistence of asexuals will be identified. It will be understood, what fractions of genomes evolve truly clonal, how effective selection is maintained, how asexual speciation is achieved, and how important the amount of standing genetic variation is in these processes. Overall, using oribatid mites as model organisms, the work proposed here will contribute to understand the evolutionary persistence in the absence of sex and vice-versa provide invaluable contributions towards uncovering why sex exists.

• DFG Programme: Independent Junior Research Groups