title: Evolutionary shifts to self-fertilisation restricted to geographic range margins in North American Arabidopsis lyrata.
abstract: Cross-fertilisation predominates in eukaryotes, but shifts to self-fertilisation are common and ecologically and evolutionarily important. Reproductive assurance under outcross gamete limitation is one eco-evolutionary process held responsible for the shift to selfing. Although small effective population size is a situation where selfing plants could theoretically benefit from reproductive assurance, empirical tests of the role of population size are rare. Here, we show that selfing evolved repeatedly at range margins, where historical demographic processes produced low effective population sizes. Outcrossing populations of North American Arabidopsis lyrata have low genetic diversity at geographic margins, with a signature of post-glacial range expansion in the north and rear-edge isolation in the south. Selfing populations occur at the margins of two genetic groups and never in their interior. These results corroborate small effective population size as the promoter of self-fertilisation and have important implications for our understanding of species turnover, range limits and range dynamics.
authors.affiliation: Evolutionary Botany, Institute of Biology, University of Neuchâtel, Rue Emile-Argand 11, CH-2000, Neuchâtel, Switzerland.
authors.forename: P C
authors.initials: PC
authors.lastname: Griffin
authors.forename: Y
authors.initials: Y
authors.lastname: Willi
mesh_terms: D017360:Arabidopsis / Q000145:classification / Q000235:genetics / Q000502:physiology*; D005075:Biological Evolution; D014644:Genetic Variation; D005828:Genetics, Population; D018895:Microsatellite Repeats / Q000235:genetics; D009656:North America; D011156:Population Density; D057945:Self-Fertilization / Q000235:genetics / Q000502:physiology*
keywords: Central and marginal populations; demography; founder effects; genetic diversity; glacial refugia; migration; population differentiation; range edge; range expansion