Genomic architecture of phenotypic divergence between two hybridizing plant species along an elevational gradient

Pictures from Mount Etna, Italy, showing Senecio chrysanthemifolius at <1000 m.a.s. (left panel) and S. aethnensis at >2000 m.a.s. (right panel).
Senecio chrysanthemifolius and S. aethnensis, Mount Etna, Italy.

Hybrid zones that occur across environmental gradients provide excellent opportunities for studying the maintenance of divergent adaptations in the presence of gene flow. They also provide insight into the biodiversity implications of future species contact and hybridization in a changing world. In a new study published in AoB PLANTS, Brennan et al. used a quantitative trait locus (QTL) mapping approach to study divergent morphology between two Senecio (ragwort) species that form a natural hybrid zone with respect to elevation on Mount Etna, Italy. They found signals of divergent selection with increased genetic differentiation close to QTLs. Extensive interactions between QTLs and traits suggested a QTL architecture that is resistant to hybridization.

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