From Native Habitats to Invasion Frontiers: Understanding Spatial Niches of Invasive Plants Through Functional Traits

ABSTRACT Aim Functional traits that affect plant performance and adaptation strategies are critical for shaping the distribution of invasive plants under global change. However, quantitative assessments of functional traits on spatial niche predictions are still lacking. In this study, we aimed to understand how functional traits alter the distribution of invasive plants across native and introduced ranges. Location Eastern USA (66‐106W, 24‐47N); Eastern China (104‐125E, 18‐43N). Taxon Spartina alterniflora Loisel. Methods We developed a new integrated framework using structural equations and ecological niche models to determine the causal relationships among plant functional traits in the field, presence distribution data, and environmental variables. This framework was used to predict the latitudinal distribution and spatial dynamics of Spartina alterniflora Loisel across its native (USA) and introduced (China) ranges. Results We found that functional traits were variable and remarkably altered the distribution of S. alterniflora , especially in mid‐ and low‐latitudes of China. Furthermore, leaf, vegetative, and sexual reproductive traits had different effects on the distribution of S. alterniflora , with approximately −2% to 15% and 10% to 40% of the distribution areas influenced by functional traits in the native and introduced ranges, respectively. Notably, sexual reproductive traits affected plant distribution more than leaf and vegetative traits. Additionally, hump‐shaped relationships were observed between habitat suitability and most of the functional traits, thus demonstrating that moderately suitable areas had better plant performance. Main Conclusions These findings suggest that plant functional traits influence the prediction of species distribution and thus need to be accounted for when performing niche modelling of invasive species. Furthermore, we suggest that global change may threaten the habitat in the native range but will improve the spatial niche of species in the introduced range. This study highlights the focus areas for conservation and prevention efforts.