COS 120-10
Evolution by an invader abroad leads to strong costs when returned home
Some invasive plant species appear to evolve greater size and/or competitive ability in their non-native ranges. This suggests that greater size and competitive ability may be selected for and thus evolve in the new ranges of many exotic plants. However, whether this greater competitive ability is general, e.g. transferrable back to the native range, or context-specific to the range in which the evolution occurred is not known. The Evolution of Increased Competitive Ability hypothesis poses that if the introduced plants have escaped their specialized herbivores there may be a selection for increased competitive ability at the cost of defense.
In a common garden experiment we tested the performance of giant goldenrod (Solidago gigantea) grown from seeds collected from six populations in the native North American and six populations in the non-native European ranges. In a greenhouse experiment, we also tested whether the competitive ability of 15 native and invasive populations differed when matched against 11 common native North American competitors.
Results/Conclusions
In our common garden experiment we found that plants from both ranges produced more biomass, grew taller and developed more rhizomes when grown in the non-native range. But in the native range the same populations were smaller and produced less rhizomes. For example in the case of the biomass production the effect of origin (F1, 10=0.369, P=0.557) was not significant, but the destination continent (F1, 2=36.078, P=0.027), and their interaction (F1, 943=71.16, P<0.0001) was highly significant. There was no difference among populations (χ2=0.0064, P=0.9364) in the magnitude of herbivory in Europe, but in North America herbivory was significantly higher (χ2=6.1289, P<0.005) on North American than on European populations.
In the greenhouse experiment S. gigantea populations from both ranges equally inhibited the growth of North American native species (F1, 28=0.894, P=0.353). There was no significant difference in the performance of the 15 invasive and native populations when grew together with 11 common competitors (F1, 27.97=1.089, P=0.306).
Our results suggest a rapid and biogeographically-based response in S. gigantea plants abroad, but a response that was environmentally and context dependent and that came at a strong cost to performance when reintroduced to the native range.
Acknowledgements The research leading to these results has received funding from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme (FP7/2007-2013) under REA grant agreement number 300639.