Recent ecological selection on regulatory divergence is shaping clinal variation in Senecio on Mount Etna

The hybrid zone on Mount Etna (Sicily) between Senecio aethnensis and Senecio chrysanthemifolius (two morphologically and physiologically distinct species) is a classic example of an altitudinal cline. Hybridization at intermediate altitudes and gradients in phenotypic and life-history traits occur along altitudinal transects of the volcano. The cline is considered to be a good example of ecological selection with species differences arising by divergent selection opposing gene flow. However, the possibility that the cline formed from recent secondary contact following an allopatric phase is difficult to exclude. We demonstrate a recent split between S. aethnensis and S. chrysanthemifolius (as recent as ∼32,000 years ago) and sufficient gene flow (2Nm > 1) to have prevented divergence (implicating a role for diversifying selection in the maintenance of the cline). Differentially expressed genes between S. aethnensis and S. chrysanthemifolius exhibit significantly higher genetic diver...

西西里岛埃特纳火山上的埃特纳千里光（Senecio aethnensis）与菊叶千里光（Senecio chrysanthemifolius）为两个形态与生理特征均存在显著差异的物种，二者之间的杂交带（hybrid zone）是海拔渐变群（altitudinal cline）的经典研究范例。该火山的海拔样带中，中间海拔区域存在杂交现象，同时表型与生活史性状呈现梯度分布。此渐变群被视为生态选择的典型案例，物种间的差异由对抗基因流（gene flow）的歧化选择（divergent selection）所塑造。然而，该渐变群是否形成于异域隔离阶段（allopatric phase）后的近期二次接触，这一可能性仍无法排除。本研究证实，埃特纳千里光与菊叶千里光的分化时间极近（仅约3.2万年前），且存在足够强度的基因流（2Nm > 1），足以阻止种群发生遗传分化，这暗示歧化选择在维持该渐变群过程中发挥了关键作用。两类物种间的差异表达基因（differentially expressed genes）展现出显著更高的遗传分化……