Muller's Ratchet and Adaptation in Sympatric Sexual and Apomictic Boechera Lineages

We conducted whole-genome sequencing and multivariate phenotyping of eight sympatric pairs of apomictic (asexual) and sexual genotypes of Boechera spatifolia. Unlike many apomictic taxa, we find that apomictic Boechera spatifolia lineages are old and form a monophyletic group. To test the hypothesis that deleterious mutations have accumulated at a greater rate in asexual genomes, we compared the amount of derived mutations in sites under positive selection across the Brassicaceae to those at unconserved sites. Consistent with Muller’s Ratchet, we find that the ratio of mutations at conserved to neutral sites was significantly elevated in apomictic lineages relative to sexuals.