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Abstract

Sexual reproduction is widespread among eukaryotes, but asexual lineages have repeatedly evolved from sexual ancestors across a wide range of taxa. Despite extensive research on the evolution of sex, the molecular changes underpinning the switch to asexual reproduction remain elusive, particularly in organisms with haploid sexual systems such as bryophytes, red and brown algae. Here, we explore three independent events of emergence of asexuality from sexual ancestors in brown algal natural populations of Scytosiphon species complex to examine the nature, evolution and degree of convergence of gene expression changes that accompany the breakdown of sexuality. We show that asexual, female-only populations arose in cold water environments and consistently exhibit a decay of sexual traits, including loss of capacity to fuse with male gametes, rapid trigger of parthenogenic development from unfertilized eggs, larger gamete size and loss of pheromone production. The decay in sexual traits is accompanied by dramatic changes in gene expression patterns, and an overall defeminization and masculinization of asexual female gamete transcriptomes. We will show how these data is being used to test the importance of sexual conflict on gene expression changes following loss of sexual reproduction and to tackle the molecular genetic mechanisms underlying pheromone production in these organisms.