Which mechanisms promote success in phylogenetically novel invasive species?

Background/Question/Methods Invasive species pose a substantial threat to biodiversity and create a series of economic and ecological problems. While the mechanisms of invasion, specifically herbivore escape and resistance to competition, and characteristics of native environments have both been studied, they have typically been studied separately. Phylogenetic novelty of introduced species, relative to the native community, allows us to look at both traits of the invasive species and the characteristics of the biotic community. In some study systems, more phylogenetically novel species have been shown to be more invasive; however, we do not know what mechanisms drive this pattern. We used fifteen species at Tyson Research Center to test for two mechanisms that might drive a benefit of novelty: herbivory escape and competitive ability. Species were categorized as novel (having no congener present in the native community) and not novel (with a congener present in the native community) and either highly invasive or noninvasive.

Results/Conclusions Invasiveness and novelty both affected species performance: novel, highly invasive species are larger than less novel highly invasive species. However, novel noninvasive species are smaller than less novel noninvasive species, which suggests that there are costs, as well as benefits, to being novel. Species differed in their response to competition and herbivory removals: some species showed herbivore escape and/or competitor resistance. There is evidence that the novel species experience greater herbivory escape and have greater competitive ability than less novel species, suggesting that these two mechanisms might drive a benefit for more novel species. There was also some evidence for the presence of water-soluble allelochemicals in the leaf tissue of several species, potentially driving the greater competitive ability of more novel species.