A new perspective on trait differences between native and invasive exotic plants

Authors: Leffler, Alan; James, Jeremy; Monaco, Thomas; Sheley, Roger

Submitted to: Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/6/2013
Publication Date: 2/20/2014
Citation: Leffler, A.J., James, J.J., Monaco, T.A., Sheley, R.L. 2014. A new perspective on trait differences between native and invasive exotic plants. Ecology. 95(2):298-305.

Interpretive Summary: Functional differences between native and exotic species are often presumed to be one factor responsible for plant invasion. Accordingly, invasion occurs when a niche is vacated and an exotic species enters the community that is able to exploit available resources. Differences in trait values between native and exotic invasive species may or may not be large, depending on the specific context of the comparison and the distinction necessary to trigger invasion is unknown. We used a meta-analysis approach to determine the magnitude of difference between native and exotic invasive species for various traits examined in previous studies. We suggest that ecologically meaningful differences in trait values between a native and exotic invasive species are greater than differences between co-occurring natives. We identified significant differences between native and exotic invasive species but the effect size was not significanlty greater than the effect size between native species. Consequently, these differences may not be important for invasion at the broadest scale. Our analysis indicates that traits may be most useful in predicting invasion in certain environments only (i.e., trait by environment interactions), that ecologists are not necessarily measuring the correct traits (regeneration traits are poorly represented in the data set), or other mechanisms of invasion more important.

Technical Abstract: Functional differences between native and exotic species are often presumed to be one factor responsible for plant invasion. Accordingly, invasion occurs when a niche is vacated and an exotic species enters the community that is able to exploit available resources. Differences in trait values between native and exotic invasive species may or may not be large, depending on the specific context of the comparison and the distinction necessary to trigger invasion is unknown. We used a meta-analysis approach to determine the magnitude of difference between native and exotic invasive species for various traits examined in previous studies. We suggest that ecologically meaningful differences in trait values between a native and exotic invasive species are greater than differences between co-occurring natives. We identified significant differences between native and exotic invasive species but the effect size was not significantly greater than the effect size between native species. Consequently, these differences may not be important for invasion at the broadest scale. Our analysis indicates that traits may be most useful in predicting invasion in certain environments only (i.e., trait by environment interactions), that ecologists are not necessarily measuring the correct traits (regeneration traits are poorly represented in the data set), or other mechanisms of invasion more important.