No Sex No Conflict · Evolutionary Consequences of Arrested Genomic Conflict in Asexual Species

Genomic conflicts are major drivers of evolutionary innovation and play an increasingly recognized role in human disease. Intra-genomic conflicts arise because self-promoting elements such as driving centromeres or transposable elements (TEs) can spread in a population without increasing the fitness of their carriers. Inter-genomic conflicts arise when genes have opposite fitness effects in different carriers, as is the case for genes underlying traits with distinct optimal values in males and females. Here I propose to use asexual species as a novel system to studying intra- and inter-genomic conflicts. Because there is no recombination or segregation under asexual reproduction, intra-genomic conflict disappears as the interests of all genetic elements become aligned with those of their host. This allows us to test the predictions that intra-genomic conflict drives the evolution of TE virulence, centromeres, and centromere-binding proteins. Furthermore, because asexual species are comprised of only females, male phenotypes are no longer under selection and sexual conflict over optimal trait values therefore disappears. This proposal leverages the replicated loss of conflicts in independently evolved asexual lineages of Timema stick insects to identify conflict driven aspects of genomic and phenotypic evolution in sexual species. Because Timema have an XX:XO sex determination system, males can be recovered from asexual lineages via X-chromosome losses. This allows for the study of male reproductive traits, sexual dimorphism and sex-biased gene expression in species where selection has been acting solely on females for prolonged time periods, and for the identification of traits and biological processes subject to sexual conflict. By combining phenotypic, experimental and next-generation sequencing approaches, we will generate a cohesive understanding of how intra- and inter-genomic conflict shape phenotype and genome evolution.