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Demographic history of speciation in a Senecio altitudinal hybrid zone on Mt. Etna
Author(s) -
Filatov Dmitry A.,
Osborne Owen G.,
Papadopulos Alexander S. T.
Publication year - 2016
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1111/mec.13618
Subject(s) - biology , genetic algorithm , hybrid zone , gene flow , senecio , adaptation (eye) , ecology , ecological speciation , divergence (linguistics) , evolutionary biology , genetic variation , gene , genetics , neuroscience , linguistics , philosophy
Hybrid zones typically form as a result of species coming into secondary contact, but can also be established in situ as an ecotonal hybrid zone, a situation which has been reported far less frequently. An altitudinal hybrid zone on Mount Etna between two ragwort species (the low elevation S enecio chrysanthemifolius and high elevation S . aethnensis ) could potentially represent either of these possibilities. However, a scenario of secondary contact vs. speciation with gene flow has not been explicitly tested. Here, we test these alternatives and demonstrate that the data do not support secondary contact. Furthermore, we report that the previous analyses of speciation history of these species were based on admixed populations, which has led to inflated estimates of ongoing, interspecific gene flow. Our new analyses, based on ‘pure’ S . aethnensis and S . chrysanthemifolius populations, reveal gene exchange of less than one effective migrant per generation, a level low enough to allow the species to accumulate neutral, genomewide differences. Overall, our results are consistent with a scenario of speciation with gene flow and a divergence time which coincides with the rise of Mt. Etna to altitudes above 2000 m (~150 KY ). Further work to quantify the role of adaptation to contrasting environments of high and low altitudes will be needed to support the scenario of recent ecological speciation in this system.