Format: ORAL

Montserrat Vil1,2, Javier Galn-Daz3, Ingrid M Parker4, Enrique G de la Riva5

1 Doñana Biological Station (EBD-CSIC), Sevilla, Spain 2 Department of Plant Biology and Ecology, University of Sevilla, Sevilla, Spain 3 Department of Pharmacology, Complutense University of Madrid, Madrid, Spain 4 Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, USA 5 Department of Biodiversity and Environmental Management, University of León, León, Spain

Many plant species of European origin have been introduced to North America. Many of these introduced species are highly competitive, and have displaced endemic native plant species. However, in most invaded communities, non-native species co-occur with some native species. We investigated the role of non-native plant species in the functional assembly of putative donor and recipient communities by conducting coordinated floristic surveys and analysis of plant traits related to competitive ability in California and Spanish grasslands. While in Spain, all species were native, in California, half species were non-native. All non-native species found in California grasslands were native in Spain. Many non-native species were more abundant in the Californian invaded grasslands than in the communities of their putative Spanish native range. Invaded California grasslands were more similar in species composition to Spanish grasslands than some Spanish grasslands were among themselves. In California, non-native species had more resource acquisitive traits than co-occurring native species. In Spain, species that invaded California were also more acquisitive than species not known to be invasive somewhere. However, trait differences were not as large as in the introduced range of California indicating that they might have increased their competitive ability. This might also reflect preadaptation of the entire species pool to the management practices that have taken place in Europe for millennia. Trait differences between native and non-native species were also dependent on environmental conditions indicating that niche differentiation are subject to the influence of abiotic and biotic filters encountered in the new region of introduction. Our results show that differences between co-occurring native and non-native species are context dependent and that a correct interpretation of filtering processes in community assembly requires a biogeographical perspective.