Local adaptation is common in invasive plants, but there is no consensus as to whether shifts in functional traits between invader "home" and "away" ranges contribute to their success in competition with native species. Theory based on enemy release suggests that invaders should reallocate limiting resources away from nutritive-based defenses and toward high growth potential. However, empirical studies of home-away trait shifts are typically conducted on a single invader and fail to consider how environmental differences across regions may impact leaf trait syndromes. We measured nine defense-related leaf traits for 27 invasive species across their home and away ranges in France, Japan, and the United States, and compared them to distributions of those same traits for co-occurring native species in both their home and away ranges. Our study included a total of 21 woody species sampled under forest canopies, and 23 herbaceous species sampled in fields and roadsides. Traits included toxic leaf alkaloids and cyanogenic glycosides; structural attributes including cell wall mass and fiber content; carbon (C), nitrogen (N), C:N, and total protein content; and specific leaf area. We found significant overall shifts in both qualitative (alkaloids) and quantitative (fiber, cell wall, N content) defense traits, particularly in woody species that are hypothesized to be more apparent to herbivores. However, the direction of trait shifts was not consistent across regions. Rather, for seven of nine traits, trait means of invaders shifted toward the means of native species in the recipient communities, likely reflecting environmental differences among regions rather than a shift in allocation from defense to growth. We suggest this "join the locals" pattern, whereby trait shifts in invaders match regional differences in native trait syndromes due to environmental variation, is a reasonable null model for studies of adaptive evolution in invasive species. Although the "join the locals" pattern is not mutually exclusive with shifts in functional traits caused by enemy release, our study involving multiple species and habitats suggests environmental gradients override trait shifts driven by varying herbivore communities.

Keywords: alkaloids; biological invasions; enemy release; evolution of increased competitive ability; glycosides; growth‐defense theory; plant traits; shifting defense theory.

© 2025 The Author(s). Ecology published by Wiley Periodicals LLC on behalf of The Ecological Society of America.

本地适应在入侵植物中很常见，但目前没有一致的看法认为入侵者在其“原生”和“非原生”范围内的功能特征变化是否有助于其与本土物种的竞争成功。基于敌害释放的理论表明，入侵者应该重新分配限制资源，减少以营养为基础的防御，并增加高生长潜力。然而，关于原生-非原生性状转变的实际研究通常仅针对单一入侵物种进行，并且未能考虑跨地区环境差异如何影响叶片特征综合征。我们测量了27种入侵物种在法国、日本和美国原生及非原生范围内的九个与防御相关的叶片特性，并将其与这些同一特性的本土共存物种在其原生及非原生范围的分布进行了比较。我们的研究总共包括21种木本植物（在森林冠层下取样）和23种草本植物（在田野和路边取样）。这些特征包括有毒叶生物碱和氰苷；结构属性，如细胞壁质量和纤维含量；碳(C)、氮(N)、C:N比以及总蛋白含量；以及特定叶片面积。我们发现，在定性(生物碱)和定量(纤维、细胞壁、N含量)防御特性方面都存在显著的整体转变，尤其是在假定更受食草动物关注的木本物种中特别明显。然而，特征变化的方向在不同地区并不一致。事实上，对于九个特性中的七个，入侵者的平均值倾向于向当地本土物种的均值靠拢，这可能反映了区域间的环境差异而非防御到生长资源分配的变化。我们建议这种“融入当地人”的模式（即由于环境变异导致入侵者性状转变与原生地本地特征综合征相匹配），是研究外来物种适应性进化的一个合理的零假设模型。尽管“融入当地人”这一模式并不排除由敌害释放引发的功能性状变化，但本项涉及多个物种和栖息地的研究表明，环境梯度在很大程度上超越了由不同食草动物群落驱动的性状转变。

关键词：生物碱；生物入侵；敌害释放；竞争能力增强进化；糖苷；生长-防御理论；植物特征；防御转移理论。

© 2025 The Author(s). Ecology published by Wiley Periodicals LLC on behalf of The Ecological Society of America.