Fridley Jason, Griffin-Nolan Robert J, Bensaddek Lamine, Decocq Guillaume, Hikosaka Kouki, Kichey Thomas, LeVonne Julie, Mishio Masako
Department of Biology, Syracuse University, Syracuse, New York, USA.
Department of Biological Sciences, Clemson University, Clemson, South Carolina, USA.
Ecology. 2025 Jun;106(6):e70129. doi: 10.1002/ecy.70129.
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.
本地适应性在入侵植物中很常见，但对于入侵植物“本土”和“异域”分布区之间功能性状的变化是否有助于它们在与本地物种的竞争中取得成功，目前尚无定论。基于天敌释放的理论表明，入侵者应该将有限的资源从基于营养的防御中重新分配，转向具有高生长潜力的方向。然而，关于本土与异域性状变化的实证研究通常只针对单一入侵者进行，且未考虑不同地区的环境差异可能如何影响叶片性状组合。我们在法国、日本和美国测量了27种入侵物种在其本土和异域分布区的9种与防御相关的叶片性状，并将它们与本土共生物种在其本土和异域分布区的相同性状分布进行了比较。我们的研究总共包括在森林树冠下采样的21种木本植物，以及在田野和路边采样的23种草本植物。这些性状包括有毒的叶片生物碱和氰苷；结构属性，包括细胞壁质量和纤维含量；碳（C）、氮（N）、C:N和总蛋白含量；以及比叶面积。我们发现定性（生物碱）和定量（纤维、细胞壁、氮含量）防御性状都有显著的总体变化，特别是在那些被认为对食草动物更明显的木本植物中。然而，性状变化的方向在不同地区并不一致。相反，在9个性状中的7个中，入侵者的性状均值向接受群落中本土物种的均值偏移，这可能反映了不同地区之间的环境差异，而不是从防御到生长的分配变化。我们认为这种“融入当地人”的模式，即由于环境变化，入侵者的性状变化与本土性状组合的区域差异相匹配，是入侵物种适应性进化研究的一个合理的零模型。尽管“融入当地人”的模式与天敌释放引起的功能性状变化并非相互排斥，但我们涉及多个物种和栖息地的研究表明，环境梯度超越了由不同食草动物群落驱动的性状变化。
