PS 76-167
Environmental preferences rather than evolutionary relatedness predicts species invasiveness in the British flora
Darwin’s naturalization hypothesis predicts that invasive species should perform better in their novel range in the absence of close relatives in the native flora due to reduced competition. Alternatively, closely related invaders may be better preadapted to the novel environment due to shared evolutionary history. Evidence from a recent and rapidly growing literature of taxonomic and phylogenetic-based studies, however, remains equivocal and have been argued to be due to scale-dependency in phylogenetic patterns. Here, we classified naturalized aliens into invasive and non-invasives based on their ecological impact and spread in the British landscape, and test Darwin’s naturalization hypothesis at two different spatial scales using a fossil-dated molecular phylogenetic tree of the British native and alien flora (> 1,600 species) as well as extensive, fine-scale survey data from the 1998 Countryside Survey. Finally, using a model averaging approach, we test the relative importance of phylogenetic relatedness and various ecological traits such as life form, clonality and Ellenberg indicator scores, in influencing species invasiveness.
Results/Conclusions
At both landscape and local scales, invasive species were neither significantly more nor less related to the native flora than their non-invasive alien counterparts. Species invasiveness was instead correlated with higher soil fertility and moisture preference, but not other life history traits such as life form and size. While we do not dismiss the role of native species composition on the invasibility of local communities, anthropogenic drivers such as eutrophication, urbanization or land use changes that alter habitat-level attributes more likely have had greater influence on the spread of invasive species in Britain than biotic interactions with the native flora. Phylogenetic relatedness alone may not be a silver bullet to predicting species invasiveness, especially in highly modified landscapes, and combined phylogenetic and trait-based approaches may be more useful in such cases.