Phylogeny of leavenworthia s-alleles suggests unidirectional mating system evolution and enhanced positive selection following an ancient population BOTTLENECK

Adam C. Herman, Jeremiah W. Busch, Daniel J. Schoen

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

The adoption of self-fertilization from an ancestral outcrossing state is one of the most common evolutionary transitions in the flowering plants. In the mustard family, outcrossing is typically enforced by sporophytic self-incompatibility (SI), but there are also many self-compatible species. The genus Leavenworthia contains taxa that either possess or lack SI. Here, we present data showing that SI is associated with strict outcrossing and that there is widespread trans-specific sequence polymorphism at the locus involved in the recognition of self-pollen (the S-locus). This ancestral polymorphism is consistent with the presence of an outcrossing mating system in the common ancestor of Leavenworthia species, and suggests that there have been several independent losses of SI in the group. When compared with other mustard species, the bulk of Leavenworthia S-allele sequences are highly diverged from those found in other Brassicaceae and show relatively low levels of nucleotide diversity, a pattern that suggests the common ancestor of the genus likely underwent a strong population bottleneck. The hypothesis of postbottleneck S-locus rediversification is supported by tests showing stronger positive selection acting on S-alleles from Leavenworthia than those found in other Brassicaceae.

Original languageEnglish (US)
Pages (from-to)1849-1861
Number of pages13
JournalEvolution
Volume66
Issue number6
DOIs
StatePublished - Jun 1 2012

Keywords

  • Mating system evolution
  • Positive selection
  • Self-incompatibility
  • Trans-specific polymorphism

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