Leaf construction cost, nutrient concentration, and net CO2 assimilation of native and invasive species in Hawaii

The effects of biological invasions are most evident in isolated oceanic is lands such as the Hawaiian Archipelago, where invasive plant species are ra pidly changing the composition and function of plant communities. In this s tudy, we compared the specific leaf area (SLA), leaf tissue construction co st (CC), leaf nutrient concentration, and net CO2 assimilation (A) of 83 po pulations of 34 native and 30 invasive species spanning elevation and subst rate age gradients on Mauna Loa volcano in the island of Hawaii. In this co mplex environmental matrix, where annual precipitation is higher than 1500 mm, we predicted that invasive species, as a group, will have leaf traits, such as higher SLA and A and lower leaf CC, which may result in more effici ent capture of limiting resources (use more resources at a lower carbon cos t) than native species. Overall, invasive species had higher SLA and A, and lower CC than native species, consistent with our prediction. SLA and foli ar N and P were 22.5%, 30.5%, and 37.5% higher, respectively, in invasive s pecies compared to native ones. Light-saturated photosynthesis was higher f or invasive species (9.59 mu mol m(-2) s(-1)) than for native species (7.31 mu mol m(-2) s(-1)), and the difference was larger when A was expressed on a mass basis. Leaf construction costs, on the other hand, were lower for t he invasive species (1.33 equivalents of glucose g(-1)) than for native spe cies (1.37). This difference was larger when CC was expressed on an area ba sis. The trends in the above traits were maintained when groups of ecologic ally equivalent native and invasive species (i.e., sharing similar life his tory traits and growing in the same habitat) were compared.:Foliar N and P were significantly higher in invasive species across all growth forms. High er N may partially explain the higher A of invasive species. Despite relati vely high N, the photosynthetic nitrogen use efficiency of invasive species was 15% higher than that of native species. These results suggest that inv asive species may not only use resources more efficiently than native speci es, but may potentially demonstrate higher growth rates, consistent with th eir rapid spread in isolated oceanic islands.