Evolution of plant growth and defense in a continental introduction

Substantial research has addressed adaptation of nonnative biota to novel environments, yet surprisingly little work has integrated population genetic structure and the mechanisms underlying phenotypic differentiation in ecologically important traits. We report on studies of the common milkweed Asclepias syriaca, which was introduced from North America to Europe over the past 400 years and which lacks most of its specialized herbivores in the introduced range. Using 10 populations from each continent grown in a common environment, we identified several growth and defense traits that have diverged, despite low neutral genetic differentiation between continents. We next developed a Bayesian modeling approach to account for relationships between molecular and phenotypic differences, confirming that continental trait differentiation was greater than expected from neutral genetic differentiation. We found evidence that growth-related traits adaptively diverged within and between continents. ...

已有诸多研究探讨了外来生物类群对新生境的适应性演化，但鲜有研究同时整合种群遗传结构与生态关键性状表型分化的潜在调控机制。本研究以普通马利筋（Asclepias syriaca）为研究对象：该物种于400余年前从北美传入欧洲，且在其引入分布区内几乎缺失了绝大多数专食性植食昆虫。我们在共同栽培环境下栽培两大洲各10个种群，结果发现尽管两大陆间的中性遗传分化（neutral genetic differentiation）水平较低，但已有多个生长与防御相关性状发生了分化。随后我们开发了一种贝叶斯建模方法，用以解析分子差异与表型差异间的关联，证实两大陆间的性状分化程度高于中性遗传分化所预期的水平。我们发现证据表明，与生长相关的性状在各大洲内部以及大陆之间均发生了适应性分化。...