Functional trait similarity of native and invasive herb species in subtropical China: environment-specific differences are the key

The attempt to identify traits associated with plant invasions has revealed ambiguous results to date. Accounting for environmental and temporal variation in multispecies trait comparisons of native and invasive species might help explain such inconsistency.

The relative importance of light and nutrient availability was tested in a greenhouse experiment on trait expression and variation of 15 native and 15 invasive herb species from Southeast China. In addition, N uptake of a subset of these species and its temporal pattern were assessed by means of a 15N tracer experiment.

A predominant lack of significant differences between the two status groups indicated strong overall trait similarities, thus supporting the ‘join-the-local’ hypothesis. However, at high light levels, the invasive species displayed significantly higher trait relative growth rates, whereas the native species had a higher tissue quality as displayed in a higher dry matter content of shoots and leaves. The invasion success of the invasive species could neither be explained by a general higher N uptake nor by a distinction in temporal N uptake strategy between native and invasive species.

Despite comparable fundamental niches of the species, increased growth rates under beneficial light conditions may provide a head start advantage for invasive species compared to native ones. The present study confirms the assumption of an opportunistic strategy for invasive species and emphasizes the need to assess trait variation between native and invasive species in different environmental contexts.