Biological invasions increasingly reshape ecosystems, yet the mechanisms linking climate, plant functional traits, herbivore communities, and the occurrence of invasive alien plant species (IAPS) across environments remain poorly resolved. We used region-wide IAPS occurrence data, combined with measurements of herbivore communities and plant functional traits, to investigate how these drivers jointly structure the relative IAPS frequency across two climatically contrasting regions in the mountainous landscapes of western Sichuan, China. We quantified direct and indirect pathways connecting climate, plant traits, and herbivore assemblages to invasion outcomes. Herbivore abundance and richness exhibited strong but site-dependent associations with the relative IAPS frequency, with negative effects emerging in the humid region but not in the drier valley. In contrast, functional traits—particularly leaf thickness and the C:N—showed consistent positive associations with IAPS occurrence across sites. Elevation and precipitation further reorganized these relationships: several trait and herbivore effects reversed direction across gradients, indicating that the roles of plant traits and herbivores shift from limiting to facilitating invasion depending on climatic context. Path analyses confirmed that climate shaped the relative IAPS frequency primarily through its effects on plant trait axes and herbivore communities, and that the influence of herbivore richness on invasion was opposite in the two regions. Our findings demonstrate that plant invasions are governed by climate-mediated trait–trophic interactions rather than single-factor effects, and that invasion processes are fundamentally context-dependent. These insights highlight the need to incorporate coordinated plant–trait and biotic interactions into invasion forecasting across increasingly heterogeneous and changing environments.

摘要： 生物入侵加剧正重塑生态系统。目前，我们仍不清楚气候、入侵植物功能性状、以及相应的植食性昆虫如何影响外来入侵植物的发生规律。本研究通过系统调查，基于区域尺度的外来入侵植物数据，结合对植食性昆虫群落和入侵植物功能性状的测定结果，探讨了在中国西部山区两个气候差异显著的区域内，这些驱动因素如何共同决定外来入侵植物相对发生频率；并量化了气候、植物性状和植食性昆虫组合与入侵结果相联系的直接和间接路径。研究发现，植食性昆虫的多度和丰富度与外来入侵植物相对发生频率显著相关，但具有生境依赖性：在湿润地区呈现负相关，而在较干旱的河谷地区相关性不显著。相比之下，植物功能性状（特别是叶片厚度和碳氮比）在不同生境下与IAPS的发生均呈现一致的正相关。海拔和降水进一步也起到了一定的作用：部分性状和植食性昆虫的作用随着环境梯度可能发生逆转，这些结果潜在表明植物性状和植食性昆虫的作用会随着气候背景的不同，从限制入侵转变为促进入侵。结构方程模型结果表明，气候主要通过影响植物性状组成和植食性昆虫群落来影响外来入侵植物相对发生频率，且植食性昆虫丰富度对入侵的影响在两个研究区域内作用不同。总之，研究结果表明，植物入侵可能受气候介导的“性状-营养级”互作所主导，而非单一因素效应，且入侵过程本质上具有强烈的环境依赖性。这些发现强调，在日益异质化和不断变化的环境中预测生物入侵时，需要纳入协同的植物性状与生物群落间互作等因素，以全面揭示生物入侵的潜在机制。