Erigeron canadensis L. and Native Plants Exhibit a Stronger Community‐Weighted Trait Similarity in Less Invaded Areas but Display a Higher Community‐Weighted Trait Dissimilarity in Highly Invaded Areas

The existence of invasive alien plants (IAP) and native plants in the same environment, subjected to analogous selection pressures, renders the functional differences between IAP and native plants a key factor in determining the success of IAP invasion. This study aimed to propose a methodology for the measurement of the community‐weighted trait difference between IAP and native plants by calculating the community‐weighted trait difference index. A case study was conducted to determine the community‐weighted trait difference between the notorious IAP Erigeron canadensis L. and native plants in the middle and lower reaches of the Yangtze River in China. This study was conducted using cross‐site comparisons. The degree of invasion of E. canadensis was evaluated using its relative abundance in the invaded communities (including less invaded areas (the relative abundance < 50%) and highly invaded areas (the relative abundance ≥ 50%)). As the degree of invasion increased, the community invasibility and invasion intensity of E. canadensis increased. E. canadensis and native plants exhibited a higher community‐weighted trait similarity in less invaded areas. The higher community‐weighted trait similarity between E. canadensis and native plants can enable the realisation of E. canadensis 's fast colonisation in a new habitat via pre‐adaptation in the early stages of the invasion. E. canadensis and native plants displayed a higher community‐weighted trait dissimilarity in highly invaded areas. The higher community‐weighted trait dissimilarity between E. canadensis and native plants can facilitate the successful invasion of E. canadensis in a new habitat via stronger competitive advantage compared to native plants in the late stages of the invasion. Thus, E. canadensis and native plants exhibit a stronger community‐weighted trait similarity in less invaded areas but display a higher community‐weighted trait dissimilarity in highly invaded areas.