Trait spaces of non-native plants at community level in the Canary Islands

Non-native plants, introduced through anthropogenic vectors, are causing changes at local up to global scales, altering species communities and entire ecosystems, modifying the structure of landscapes and even the functioning of biogeochemical cycles. Ultimately, however, changes induced by non-native plants occur locally at the level of species communities. With ongoing developments towards open-access information about species at increasingly fine spatial scales, the data and tools to better understand the consequences of vegetation changes caused by non-natives are available. Further, islands that commonly have less saturated ecosystems and unoccupied ecological niches with depauperate trophic cascades are particularly susceptible to the establishment of non-native plants and their potential impacts, respectively. Steep environmental gradients, unique plant communities with high percentages of endemism and a long history of human settlement alongside which hundreds of non-native species became established make the Canary Islands a suitable testing ground for invasion ecology. We aim at explaining divergence and overlap of native and non-native trait spaces within and between vegetation communities in this oceanic archipelago in order to assess the functional consequences of plant introductions for communities and ecosystems.

As a profound basis, we compiled a revised flora of the Canary Islands using local and global taxonomic databases combined with recent publications. Plant traits derived from comprehensive open-access sources and additional literature. At community level, we separated native and non-native species and their associated traits.

The analysis revealed strong differences in trait space divergence of non-native vs. native species within different vegetation communities. Surprisingly, certain traits such as woodiness of non-native species do not correlate with the role of this trait in plant communities previously dominated by native species. The inferences we can draw from our results differ from the conclusions made at the level of entire ecosystems, which underlines the relevance of investigating traits at community level.

We encourage implementing further studies at vegetation community level, to understand the direct changes caused by non-native species, build reliable explanatory models, enable targeted conservation measures and ultimately better understand patterns of biodiversity in the Anthropocene.