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Proc Natl Acad Sci U S A. 2009 Sep 8;106(36):15379-83. doi: 10.1073/pnas.0902257106. Epub 2009 Aug 27.

Reduced inbreeding depression after species range expansion.

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1
Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, United Kingdom.

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.

PMID:
19717421
PMCID:
PMC2741259
DOI:
10.1073/pnas.0902257106
[Indexed for MEDLINE]
Free PMC Article
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