Abstract：
Exotic plant invaders pose a serious threat to native plants. However, despite showing inferior competitive ability and decreased performance, native species often subsist in invaded communities. The decline of native populations is hypothesized to be halted and eventually reversed if adaptive evolutionary changes can keep up with the environmental stress induced by invaders, that is, when population extinction is prevented by evolutionary rescue (ER). Nevertheless, evidence for the role of ER in postinvasion persistence of native flora remains scarce. Here, I explored the population density of a native forb, Veronica chamaedrys, and evaluated the changes in the shade-responsive traits of its populations distributed along the invasion chronosequence of an exotic transformer, Heracleum mantegazzianum, which was replicated in five areas. I found a U-shaped population trajectory that paralleled the evolution of plasticity to shade. Whereas V. chamaedrys genotypes from intact, more open sites exhibited a shade-tolerance strategy (pronounced leaf area/mass ratio), reduced light availability at the invaded sites selected for a shade-avoidance strategy (greater internode elongation). Field experiments subsequently confirmed that the shifts in shade-response strategies were adaptive and secured postinvasion population persistence, as indicated by further modeling. Alternative ecological mechanisms (habitat improvement or arrival of immigrants) were less likely explanations than ER for the observed population rebound, although the contribution of maternal effects cannot be dismissed. These results suggest that V. chamaedrys survived because of adaptive evolutionary changes operating on the same timescale as the invasion-induced stress, but the generality of ER for postinvasion persistence of native plants remains unknown.
摘要：
外来植物入侵者对本地植物构成严重威胁。然而,尽管显示出较差的竞争力和下降的表现，本地物种通常在入侵的社区中生存。如果适应性进化变化能够跟上入侵者引起的环境压力，则假设本地种群的下降会停止并最终逆转。也就是说,当进化拯救(ER)防止种群灭绝时。然而，关于ER在本地菌群入侵后持续存在中的作用的证据仍然很少。这里,我探索了本地forb的人口密度，VeronicaChamaedrys,并评估了其种群的阴影响应特征的变化，这些特征沿着外来变压器的入侵时间序列分布，Mantegazzianum，在五个领域复制。我发现了一个U形的种群轨迹，与可塑性到阴影的演变平行。而V.chamaedrys基因型来自完整的，更开放的地点表现出耐荫性策略(明显的叶面积/质量比)，在选择避荫策略的入侵地点减少了光的可用性（更大的节间伸长率）。田间试验随后证实，遮荫反应策略的变化是适应性的，并且是入侵后种群持久性的。如进一步建模所示。替代生态机制（栖息地改善或移民的到来）对观察到的人口反弹的解释要比ER少。尽管不能忽视产妇效应的贡献。这些结果表明，由于适应性进化变化在与入侵引起的压力相同的时间尺度上运行，因此V.chamaedrys得以幸存。但是ER对本地植物入侵后持久性的一般性仍然未知。
