August 2003
Blackwell Publishing Ltd.
Parasites mediate plant invasions Ever since Charles Darwin proposed the 'naturalization hypothesis', scientists have attempted to understand the factors that allow non-native organisms to establish and flourish.Non-native plants and animals often become invasive and cause major economic and aesthetic losses. In a new study soon to appear in Ecology Letters, Anurag Agrawal and Peter Kotanen (University of Toronto) present the most rigorous test of the hypothesis that parasites (insect herbivores) are less effective in attacking non-native plants compared to native plants. In a field experiment with 30 locally occurring species, non-native plants typically received equal or greater levels of attack than native plants. This result is in striking contrast to recent surveys, which reported 'enemy release' or lower diversities of parasites on organisms in the new habitat, compared to the native habitat. Thus, concordant with Darwin's idea, invasive plants may be more likely to establish only if they lack close relatives in the new habitat. |