Adaptation and divergence in edaphic specialists and generalists: serpentine soil endemics in the California flora occur in barer serpentine habitats with lower soil calcium levels than serpentine tolerators

• Premise of the study: Adaptation to harsh edaphic substrates has repeatedly led to the evolution of edaphic specialists and generalists. Yet, it is unclear what factors promote specialization versus generalization. Here, we search for habitat use patterns associated with serpentine endemics (specialists) and serpentine tolerators (generalists) to indirectly test the hypothesis that trade-offs associated with serpentine adaptation promote specialization. We predict that 1) endemics have adapted to chemically harsher and more bare serpentine habitats than tolerators, and 2) edaphic endemics show more habitat divergence from their sister species than tolerators do among on- and off-serpentine populations. • Methods: We selected 8 serpentine endemic and 9 serpentine tolerator species representing independent adaptation to serpentine. We characterized soil chemistry and microhabitat bareness from one serpentine taxon of each species and from a paired nonserpentine sister taxon, resulting i...

• 研究前提：对严苛土壤基质生境的适应反复催生了生态特化种（specialist）与广适种（generalist）的演化。然而，目前尚不明确哪些因素推动了特化而非广适的演化方向。本研究旨在探寻与蛇纹岩（serpentine）特有种（特化种）及蛇纹岩耐受种（广适种）相关的生境利用模式，以间接验证与蛇纹岩适应相关的权衡效应推动特化演化这一假说。我们提出两项预测：1）相较于耐受种，特有种更适应化学特性更严苛、裸岩程度更高的蛇纹岩生境；2）相较于耐受种，在蛇纹岩与非蛇纹岩种群间，生态特有种与其姊妹物种（sister species）间的生境分化程度更高。
• 研究方法：我们选取了8个蛇纹岩特有种与9个蛇纹岩耐受种，这些类群均独立演化出对蛇纹岩生境的适应。我们针对每个物种的一个蛇纹岩类群及其配对的非蛇纹岩姊妹类群，分别测定了土壤化学特性与微生境裸岩率，最终得到……