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Differential introgression from a sister species explains high F ST outlier loci within a mussel species
Author(s) -
Gosset C. C.,
Bierne N.
Publication year - 2013
Publication title -
journal of evolutionary biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.289
H-Index - 128
eISSN - 1420-9101
pISSN - 1010-061X
DOI - 10.1111/jeb.12046
Subject(s) - introgression , biology , gene flow , evolutionary biology , population , population genetics , genetics , genetic variation , gene , demography , sociology
Abstract Scanning genomes for loci with high levels of population differentiation has become a standard of population genetics. F ST outlier loci are most often interpreted as signatures of local selection, but outliers might arise for many other reasons too often left unexplored. Here, we tried to identify further the history and genetic basis underlying strong differentiation at F ST outlier loci in a marine mussel. A genome scan of genetic differentiation has been conducted between A tlantic and M editerranean populations of M ytilus galloprovincialis . The differentiation was low overall ( F ST = 0.03), but seven loci (2%) were strong F ST outliers. We then analysed DNA sequence polymorphism at two outlier loci. The genetic structure proved to be the consequence of differential introgression of alleles from the sister‐hybridizing species M ytilus edulis . Surprisingly, the M editerranean population was the most introgressed at these two loci, although the contact zone between the two species is nowadays localized along the A tlantic coasts of F rance and the B ritish I sles. A historical contact between M . edulis and M editerranean M . galloprovincialis should have happened during glacial periods. It proved difficult to disentangle two hypotheses: (i) introgression was adaptive, implying edulis alleles have been favoured in M editerranean populations, or (ii) the genetic architecture of the barrier to edulis gene flow is different between the two M . galloprovincialis backgrounds. Five of the seven outliers between M . galloprovincialis populations were also outliers between M . edulis and A tlantic M . galloprovincialis , which would support the latter hypothesis. Differential introgression across semi‐permeable barriers to gene flow is a neglected scenario to interpret outlying loci that may prove more widespread than anticipated.