Invasive Eupatorium adenophorum has ecophysiological advantages over native congeners but similar responses to CO(2) enrichment.
Both global change and biological invasions threaten biodiversity worldwide. However, their interactions and related mechanisms are still not well elucidated. To elucidate potential traits contributing to invasiveness and whether ongoing increase in CO(2) aggravates invasions, noxious invasive Eupatorium adenophorum and native E. japonicum and E. chinensis were compared under ambient and doubled atmospheric CO(2) concentrations in terms of growth, biomass allocation, morphology, and physiology. The invader had consistently higher leaf mass fraction and specific leaf area than the natives, contributing to a higher leaf area ratio, and therefore to faster growth and invasiveness. The higher leaf mass fraction of the invader was associated with lower total root mass fraction. The invader allocated a higher fraction of leaf nitrogen (N) to photosynthesis, contributing to higher area-based N content in photosynthetic apparatus, photosynthetic rate, nitrogen- and water-use efficiencies, and invasiveness. CO(2) enrichment increased growth of all studied plants by increasing actual photosynthesis, although it decreased photosynthetic capacities due to decreased area-based leaf and photosynthetic N contents. Responses of the invasive and native plants to elevated CO(2) were not significantly different, indicating that the ongoing increase in CO(2) may not exacerbate biological invasions, inconsistent with the prevailing results in references. The difference may be associated with the fact that almost all previous studies compared phylogenetically unrelated invasive and native plants. More comparative studies of sympatric, related invasive and native plants are needed to elucidate whether CO(2) enrichment facilitates invasions.