title: Reduced inbreeding depression after species range expansion.
abstract: Many species expanded their geographic ranges from core "refugium" populations when the global climate warmed after the Pleistocene. The bottlenecks that occur during such range expansions diminish genetic variation in marginal populations, rendering them less responsive to selection. Here, we show that range expansion also strongly depletes inbreeding depression. We compared inbreeding depression among 20 populations across the expanded range of a common European plant, and found that marginal populations had greatly reduced inbreeding depression. Similar patterns were also revealed by multilocus computer simulations. Low inbreeding depression is predicted to ease conditions for the evolution of self-fertilization, and selfing is known to be particularly frequent in marginal populations. Therefore, our findings expose a remarkable aspect of evolution at range margins, where a history of expansion can reverse the direction of selection on the mating system, providing a parsimonious explanation for the high incidence of selfing in marginal populations.
authors.affiliation: Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, United Kingdom.
authors.forename: Benoit
authors.initials: B
authors.lastname: Pujol
authors.forename: Shu-Rong
authors.initials: SR
authors.lastname: Zhou
authors.forename: Julia
authors.initials: J
authors.lastname: Sanchez Vilas
authors.forename: John R
authors.initials: JR
authors.lastname: Pannell
mesh_terms: D005075:Biological Evolution; D003198:Computer Simulation; D003710:Demography; D019665:Euphorbiaceae / Q000235:genetics* / Q000254:growth & development; D005828:Genetics, Population; D005843:Geography; D007178:Inbreeding; D016014:Linear Models; D009018:Morocco; D011174:Portugal; D013030:Spain