Linking the functional traits of Australian acacia species to their geographic distribution and invasion status

Among the characteristics of alien plant species that are likely to infuence invasion success, those that capture variation in relation to distribution and environmental requirements in their native range are of special interest. Similarly, traits such as maximum height, specifc leaf area (SLA) and seed dry mass, related respectively to vegetative growth, resource use strategy, and reproductive effort and dispersal ability, have been found to vary with invasiveness. Australian Acacia species ('wattles') present an exceptional natural experiment for identifying traits linked with invasiveness, while applying the source-area framework and controlling for the environmental conditions within the native range. We combine large-scale data sets of the distribution and functional traits of wattles with high-resolution climate surfaces to re-examine the effect of range size, environmental niche breadths and functional traits in determining invasion status (not introduced, casual, naturalized, or invasive) in wattles. We extracted occurrence records of 1036 wattle species (96% of all species in the genus) in Australia from the Atlas of Living Australia. For each species, we calculated the range size through the minimum convex polygon, and environmental niche breadths by matching occurrence records with WorldClim long-term average climate conditions. We extracted trait values from AusTraits and gap-flled when certain values were not known. We compared the obtained values, grouping wattle species by their introduction (not introduced vs introduced species) and invasion statuses, and calculated functional hypervolumes for each of the groups and overlaps between pairs of them. We found the performance of introduced wattle species to be profoundly infuenced by their historical environment; species with broader distributions and climate niche breadths in their native range were more likely to become invasive. Trait strategies for wattles that enhance invasion consisted of maximizing plant height to promote competitive ability, displaying medium-to-high SLA values for enhanced photosynthetic activity and relative growth rate, and intermediate values of seed mass for successful establishment and suffcient seed output and dispersal.