Invasive Chromolaena odorata has similar size but higher phenolic concentration than native conspecifics

Background: Chromolaena odorata, a perennial shrub, is native to tropical America and invasive in Asia. In Asia it interferes with agriculture, forestry, and stockbreeding, and threatens biodiversity. Hypothesis: Invasive populations of C. odorata have adapted rapidly to new local environments, and this adaptation is at least partly responsible for their success. They show a cline with climatic conditions absent in the natives. And they have evolved increased competitive ability and decreased defensive ability (the EICA hypothesis) by growing to be larger than they had been in their native range. Locations: Tlayacapan, Morelos, Mexico and Menglun, Mengla, Yunnan, China. Methods: Conduct two common garden experiments. Plant seedlings of 13 native and 13 invasive C. odorata populations in the garden in Mexico, and plant seedlings of eight native and eight invasive populations in another garden in China. In the garden in Mexico, compare native and invasive C. odorata populations. After 8 months, compare several of their functional traits, and after 2 months, compare their leaf phenolic contents and their stem phenolic contents. Results: Genetic differentiation in response to variation in mean annual temperature and precipitation occurred in invasive populations but was not significant in native populations. Inconsistent with the EICA hypothesis, invasive C. odorata were of similar size or even smaller than natives. Total phenolics in leaves and stems of invasives were higher than in natives.