Evaluation of the allelopathic effects of leachate from an invasive species (Wedelia triobata) on its own growth and performance and those of a native congener (W. chinensis).
Allelochemicals released by exotic plants can affect neighboring plants. In this study, we examined the effects of leachate extracted from shoots of an invasive clonal plant (Wedelia trilobata) on its own growth and performance, and that of its native congener (W. chinensis). Leachate from W. trilobata was prepared at concentrations of 0, 50, 75, and 100% and was applied to both Wedelia species (which were grown in mono and mixed culture). We monitored the effects of the leachate on plant growth, physiological traits, and relative competition intensity (RCI) in each species. Leachate concentration significantly affected the majority of growth and physiological traits in both species. Higher leachate concentrations significantly increased most traits of W. trilobata under mono and mixed culture. In contrast, many growth and physiological parameters in W. chinensis were significantly reduced in response to higher concentrations of leachate. Growth and physiological traits were higher in W. trilobata than W. chinensis at higher leachate concentrations in both mono and mixed culture. In W. trilobata, RCI significantly increased with increasing leachate concentration. However, RCI in W. chinensis remained consistently low in response to higher leachate concentrations. Overall, the addition of leachate from invasive W. trilobata had a strong allelopathic effect on native W. chinensis under mono and mixed culture. Conversely, growth and competitive ability in W. trilobata was enhanced in response to the leachate. Thus, allelochemicals from W. trilobata promote its own performance while simultaneously suppressing that of a native congener, which has likely contributed to its invasion success.