Differences in morphological and physiological traits between native and invasive populations of Sapium sebiferum
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1. Functional traits contribute to the success of invasive plants. These traits can reflect inherent properties or they can be new adaptations from evolutionary responses to escape from natural enemies of the introduced range. We tested the hypothesis that genetic shifts in morphological and physiological traits have occurred between native and invasive populations of Sapium sebiferum. 2. Sapium sebiferum seedlings were grown in a greenhouse using seed collected from four populations of its introduced range (US) and four from native Chinese populations that are thought to be genetic candidates of the introduced populations. We examined plant biomass production, relative growth rate (RGR), relative stem height growth rate (RHR), root : shoot ratio (RSR), total number of leaves (TLN) and leaf area (TLA), specific leaf area (SLA), leaf area ratio (LAR), net CO2 assimilation (A) and shoot specific respiration rate (RD). 3. US populations of S. sebiferum differed from Chinese populations for most plant variables. Final shoot and total biomass, as well as, RGRs of invasive (US) populations were significantly greater than those of native (Chinese) populations, although RHR and TLN per seedling did not differ between them. Root : shoot ratios (RSR) were significantly lower, while leaf traits including TLA, LAR and SLA were generally greater for invasive populations compared to native populations. Net CO 2 A was significantly higher for invasive populations than for native populations, but no significant difference in RD was found between two population types. 4. Of 13 measured plant variables, RSRs, TLA and CO 2 A were identified as traits that contributed the most to differences observed between native Chinese and invasive US populations. The suite of morphological and physiological traits functioning together may result in different growth strategies for native versus invasive populations. By virtue of these traits, invasive populations of S. sebiferum may use soil resources and light more efficiently than native populations, which may have given rise to their competitive superiority in the introduced range. 2007 The Authors.
