Data from: Adaptive and non-adaptive evolution of trait means and genetic trait correlations for herbivory resistance and performance in an invasive plant

The EICA-hypothesis predicts that invading plants adapt to their novel environment by evolving increased performance and reduced resistance in response to the release from natural enemies, and assumes a resource allocation tradeoff among both trait groups as mechanistic basis of this evolutionary change. Using the plant Silene latifolia as a study system, we tested these predictions by investigating whether 1) invasive populations evolved lower resistance and higher performance, 2) this evolutionary change is indeed adaptive, and 3) there is a negative genetic correlation among performance and resistance (i.e. a tradeoff) in native and introduced individuals. We sampled eight native and eight invasive populations and determined their population co-ancestry based on neutral SSR-markers. We performed controlled crossings to produce five sib-groups per population and exposed them to increased and reduced levels of enemy attack in a full-factorial experiment to estimate performance and resistance. With these data, we performed trait-by-trait comparisons between ranges with ‘animal models’ that account for population co-ancestry to quantify the amount of variance in traits explained by non-adaptive vs. adaptive evolution. Moreover, we tested for genetic correlations among performance and resistance traits within sib-groups. We found significant reductions in resistance and increases in performance in invasive versus native populations, which could largely be attributed to adaptive evolution. While we detected a non-significant trend towards negative genetic performance × resistance correlations in native populations, invasive populations exhibited both significant and non-significant positive correlations. In summary, these results do not support a shift of performance and resistance trait values along a tradeoff line in response to enemy release, as predicted EICA. They rather suggest that the independent evolution of both traits is not constrained by a tradeoff, and that various selective agents (including resource availability) interact in shaping both traits and in weakening negative genetic correlations in the invaded habitat.

EICA假说（EICA-hypothesis）预测，入侵植物会通过演化提升适合度并降低防御能力，以响应天敌逃逸带来的选择压力，并将两类性状间的资源分配权衡（resource allocation tradeoff）作为这一演化改变的机制基础。本研究以麦瓶草（Silene latifolia）为研究系统，从三个维度检验上述预测：1）入侵种群是否演化出更低的防御能力与更高的适合度；2）这一演化改变是否确实具有适应性；3）本地种群与引入种群的适合度与防御能力之间是否存在负遗传相关（即权衡关系）。我们共采集了8个本地种群与8个入侵种群的样本，并基于中性简单序列重复标记（neutral SSR-markers）解析其种群共祖关系。我们通过控制性杂交技术构建了每个种群的5个全同胞家系（sib-groups），并采用完全因子实验设计设置天敌攻击水平升高与降低的两组处理，以估算植物的适合度与防御能力。基于上述实验数据，我们采用纳入种群共祖关系的动物模型（animal models）开展跨分布区的性状比较，以量化非适应性演化与适应性演化分别解释的性状变异贡献率。此外，我们还检验了全同胞家系内适合度与防御性状间的遗传相关关系。研究结果表明：相较于本地种群，入侵种群的防御能力显著降低、适合度显著提升，这一差异在很大程度上可归因于适应性演化。我们在本地种群中仅检测到适合度与防御能力间负向遗传相关的非显著趋势，而入侵种群则呈现出显著与非显著的正向遗传相关。综上，本研究结果并不支持EICA假说所预测的、响应天敌逃逸的适合度与防御性状沿权衡轴发生位移的结论。相反，本研究结果表明两类性状的独立演化并未受权衡关系约束，且多种选择因子（包括资源可获得性）共同参与塑造两类性状，并弱化了入侵生境中的负遗传相关。