Ricciardi and Ward Comment on Parker et al SCIENCE 2006

TECHNICALCOMMENTmeta-analyses on the exclusive effects of verte-brate and invertebrate herbivores, respectively,thesameresultwasobtainedasforthecombineddata set.Comment on ‘‘Opposing Effects ofThis finding supports the view that variationin an invader_s success and impact is, at least inNative and Exotic Herbivores onpart, explained by the invaded community_spre-vious experiencewithfunctionallysimilarspeciesPlant Invasions’’ (10). Factors proposed to explain the variation inthe success of exotic species include the numberAnthony Ricciardi* and Jessica M. Ward of introduced propagules (e.g., seeds, eggs, andindividuals), reproductive capacity, environmen-Parker et al. (Reports, 10 March 2006, p. 1459) showed that native herbivores suppress exotic plants tal tolerance limits, previous disturbance in themore than native plants. Further analysis reveals that the effect of native herbivores is reduced on recipient community, and release from naturalexotic plant species that are closely related to native species in the invaded region. Exotic plants enemies (11–13). To date, few studies have ex-may share traits with native congeners that confer similar resistance to resident herbivores. amined invasion success as a function of thephylogenetic relationship between the intro-hrough a meta-analysis of published ex- analysis revealed that the negative effects of duced species and members of the recipientperimental data, Parker et al.(1)dem- native herbivores are ...