High resource capture and use efficiency and prolonged growth season contribute to invasiveness of Eupatorium adenophorum

To explore the traits contributing to invasion success of Eupatorium adenophorum, a noxious invasive perennial forb throughout the subtropics in Asia, Oceania, Africa, and USA, we compared the differences in ecophysiology and phenology between the invader and native E. japonicum under eight treatment combinations of two irradiances and four nitrogen additions in a two-year shadehouse experiment. The invader had significantly higher mass-based light-saturated photosynthetic rate (P _max) than its native congener in all treatments, contributing to higher photosynthetic nitrogen-, phosphorus-, and energy-use efficiencies. The higher P _max of the invader was associated with its higher nitrogen concentrations in the photosynthetic apparatus, which resulted from higher leaf nitrogen allocation to photosynthesis. The invader had higher specific leaf area and stomatal conductance at most of the treatments, also contributing to its higher P _max. The invader was not constrained by the negative correlation between leaf lifespan and specific leaf area or P _max. Leaf lifespan and total leaf area of the invader were greater than those of the native. From November to March the native congener was leafless, whereas the invader maintained a large area of leaves with relatively high P _max. Biomass accumulated in these months accounted for more than 40 % of the total biomass of the invader. Our results indicate that both the ability to capture and utilize resources efficiently and the ability to use resources when they are unavailable to natives contribute to invasion success of E. adenophorum and emphasize the importance of exploring multiple, non-mutually exclusive mechanisms for invasions.