Innate and evolutionarily increased advantages of invasive over native under ambient and doubled atmospheric CO concentrations

Both innate and evolutionarily increased ecophysiological advantages can contribute to vigorous growth, and eventually to invasiveness of alien plants. Little effort has been made to explore the roles of innate factors of alien plants in invasiveness and the effects of CO enrichment on alien plant invasions. To address these problems, we compared invasive , its native conspecific, and a native congener () under ambient and doubled atmospheric CO concentrations. Native from Mexico grew slower than invasive but faster than native under both CO concentrations. The faster growth rate of invasive was associated with higher photosynthetic capacity and leaf area ratio. For invasive , the higher photosynthetic capacity was associated with higher nitrogen (N) allocation to photosynthesis, which was related to lower leaf mass per area; the higher leaf area ratio was due to lower leaf mass per area and higher leaf mass fraction. Tradeoff between N allocations to photosynthesis versus defenses was found. CO enrichment significantly increased relative growth rate and biomass accumulation by increasing actual photosynthetic rate for all studied materials. However, the relative increase in growth was not significantly different among them. CO enrichment did not influence N allocation to photosynthesis, but increased N allocation to cell walls. The reduced leaf N content decreased N content in photosynthesis, explaining the down-regulation of photosynthetic capacity under prolonged elevated CO concentration. Our results indicate that both innate and evolutionary advantages in growth and related ecophysiological traits contribute to invasiveness of invasive , and CO enrichment may not aggravate ’s invasion in the future.