Contrasting exotics native and introduced range trait combination: a test to the trait preservation hypothesis

Background/Question/Methods Searching for a set of traits that predict the success of exotic plants after their introduction has been a major topic on invasive biology. To date, all the screening systems generated from this search are based on the important assumption that exotics will express the same traits in both its native and introduced range. However, phenotypic adjustment to new environments and/or genetic change may invalidate this approach. To assess the validly of this approach we compared three key plant physiological traits (specific leaf area, maximum possible canopy height and individual seed weight) from 365 exotic species between their native and exotic range. Additionally, using a larger dataset (1351 species) traits of co-occurring native and exotics were compared to assess if key traits of exotics significantly differ from native species. Results/Conclusions We found that neither individual traits nor the trait composition of exotics differed between its native and introduced range; we believe that this results give support the trait preservation assumption. This conclusion was also supported by the results form phylogenetic ANCOVA's, which verified that the observed trends did not appear to be influenced by phylogenetic bias within each data set. Comparisons of co-occurring native and exotics showed exotics having 9% higher SLA, 13% Hmax and 49% smaller SWT. Comparisons of the trait composition and ecological distances pointed out significant differences between plant groups. These results provide empirical evidence on the conservation of characteristics of exotics when introduced to a novel range; and support the idea that invasions could be explained by the colonisation of species with novel or extreme traits.