Plant traits are often a useful tool to describe and examine the composition of plant communities. In particular, traits can be used to address the question of what determines the success of introduced species in a novel habitat. Several hypotheses (e.g., the pre-adaptation hypothesis, or more generally, environmental filtering) suggest that plants with traits similar to the native community might be more successful due to shared characteristics that allow those species to tolerate or thrive in a given environment. Conversely, introduced plants may be more successful if they are dissimilar to the native community, increasing the chance that they can exploit an empty niche (e.g., Darwin’s naturalization hypothesis; limiting similarity). I surveyed riparian plant communities along 53 small streams in the Upper Hudson Watershed (NY, USA) to identify the native and introduced plant species present in those communities. Using information on 19 quantitative plant traits obtained from the TRY-DB plant traits database, I examined the trait diversity and composition of these riparian communities and the native and introduced components of those communities.
Introduced and native plant species in riparian communities differ significantly in their average trait values across 19 quantitative plant traits. This difference is maintained within comparisons limited to particular growth forms and lifespans (e.g., annual introduced plants differ from annual native plants; woody introduced plants differ from woody native plants). Therefore, trait differences between the two groups do not appear to be driven substantially by any differences in the proportion of species from various plant functional groups within the native and introduced components of the community. This suggests that introduced species in these riparian plant communities may be successful in that environment due to their ability to exploit unused niches in the novel environment.