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（Evolution of Increased Competitive Ability Hypothesis）提出，入侵植物因逃离自然天敌，可通过进化提升自身生长表现并降低抗性以适应新环境，并假定两类性状间存在资源分配权衡，作为该演化改变的机制基础。本研究以白玉草（Silene latifolia）为研究系统，通过以下三个方向验证该假说的预测：1）入侵种群是否进化出更低的天敌抗性与更高的生长表现；2）该演化改变是否确实为适应性演化；3）本土与引入种群的生长表现与抗性之间是否存在负遗传相关（即性状权衡）。我们共采集8个本土种群与8个入侵种群，并基于中性SSR标记（Simple Sequence Repeat）解析种群的共同祖先关系。我们开展控制性杂交实验，为每个种群构建5个半同胞家系（sib-group），并通过全因子实验设置天敌侵染水平升高与降低的处理，以此估算生长表现与天敌抗性。基于上述实验数据，我们采用考虑种群共同祖先关系的“动物模型（animal model）”开展跨分布区的逐性状比较，以量化非适应性演化与适应性演化分别解释的性状变异量。此外，我们还检测了半同胞家系内生长表现与抗性性状间的遗传相关。研究发现，相较于本土种群，入侵种群的天敌抗性显著降低、生长表现显著提升，且该差异在很大程度上可归因于适应性演化。尽管在本土种群中仅检测到生长表现与抗性呈负遗传相关的非显著趋势，但入侵种群则表现出显著与非显著并存的正相关关系。综上，本研究结果并不支持EICA假说所预测的：入侵植物在逃离天敌后，其生长表现与抗性性状值会沿性状权衡轴发生协同变化。相反，研究结果表明两类性状的独立演化并未受性状权衡的约束，且多种选择因子（包括资源可获得性）共同作用于两类性状的塑造，并弱化了入侵生境中的负遗传相关。