TY - JOUR

T1 - Demographic history of speciation in a Senecio altitudinal hybrid zone on Mt. Etna

AU - Filatov, Dmitry A

AU - Osborne, Owen G

AU - Papadopulos, Alexander S T

N1 - NERC. Grant Number: NE/K004352/1 Gatsby Charitable Foundation

PY - 2016/6

Y1 - 2016/6

N2 - 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 Senecio 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.

AB - 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 Senecio 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.

KW - Adaptation, Physiological

KW - Altitude

KW - DNA, Plant

KW - Gene Flow

KW - Genetic Speciation

KW - Genetics, Population

KW - Hybridization, Genetic

KW - Models, Genetic

KW - Phenotype

KW - Polymorphism, Single Nucleotide

KW - Senecio

KW - Sequence Analysis, DNA

KW - Sicily

KW - Journal Article

U2 - 10.1111/mec.13618

DO - 10.1111/mec.13618

M3 - Article

C2 - 26994342

VL - 25

SP - 2467

EP - 2481

JO - Molecular Ecology

JF - Molecular Ecology

SN - 1365-294X

IS - 11

ER -