title: Mutation Accumulation in an Asexual Relative of Arabidopsis.
abstract: Asexual populations experience weaker responses to natural selection, which causes deleterious mutations to accumulate over time. Additionally, stochastic loss of individuals free of deleterious mutations can lead to an irreversible increase in mutational load in asexuals (the "click" in Muller's Ratchet). Here we report on the genomic divergence and distribution of mutations across eight sympatric pairs of sexual and apomictic (asexual) Boechera (Brassicaceae) genotypes. We show that apomicts harbor a greater number of derived mutations than sympatric sexual genotypes. Furthermore, in phylogenetically constrained sites that are subject to contemporary purifying selection, the ancestral, conserved allele is more likely to be retained in sexuals than apomicts. These results indicate that apomictic lineages accumulate mutations at otherwise conserved sites more often than sexuals, and support the conclusion that deleterious mutation accumulation can be a powerful force in the evolution of asexual higher plants.
authors.affiliation: Department of Integrative Biology, University of Texas at Austin, Austin, TX, United States of America.
authors.forename: John T
authors.identifier: 0000-0002-8938-1166
authors.initials: JT
authors.lastname: Lovell
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Robert J
authors.identifier: 0000-0001-9732-0964
authors.initials: RJ
authors.lastname: Williamson
authors.affiliation: Department of Ecology and Evolutionary Biology, University of Toronto, Toronto, Ontario, Canada.
authors.forename: Stephen I
authors.initials: SI
authors.lastname: Wright
authors.affiliation: Department of BioAgricultural Sciences and Pest Management, Colorado State University, Fort Collins, CO, United States of America.
authors.forename: John K
authors.initials: JK
authors.lastname: McKay
authors.affiliation: Apomixis Research Group, Leibniz Institute for Plant Genetics and Crop Plant Research, Gatersleben, Germany.
authors.forename: Timothy F
authors.identifier: 0000-0002-3450-2733
authors.initials: TF
authors.lastname: Sharbel
mesh_terms: D019607:Brassicaceae / Q000145:classification / Q000235:genetics*; D019143:Evolution, Molecular; D018745:Genome, Plant; D059645:Mutation Rate; D010802:Phylogeny; D012100:Reproduction, Asexual; D012641:Selection, Genetic