Exploring changes in the invasion pattern of alien flora in Catalonia (NE of Spain) from large datasets

Abstract

Plant invasions are characterized by their dynamism, but they are generally described at a precise time step due to the dearth of datasets on species distribution across time. In this paper we employed specific alien plant databases to assess the factors associated with recent changes in plant invasion patterns in Catalonia from two perspectives, site and species. We gathered records of neophyte plant species per 10-km UTM cell from two spatially coincident large-scale datasets collected in 1989 and 2012. We estimated the richness increase of species per UTM cell and the range size increase of each species (i.e. the number of occupied UTM cells) between these dates. We then evaluated the association of richness increase with geographic, climatic and landscape factors, and that of range size increase with species traits and the characteristics of the introduction event. We found 401 species, 291 recorded up to 1989 and 110 afterwards. Richness increase was concentrated in new hotspots compared to those observed in 1989, suggesting that patterns of susceptibility to plant invasion have changed in recent decades. Climatic factors were the most important in determining the large-scale pattern of alien species, with the highest values of species richness increase in warmest and rainiest areas. Range size increase of each alien species was mostly explained by the historical range size, the introduction pathway, namely unintentional introductions and the interaction between habitat and the minimum residence time. These factors were more influential than species traits in the recent spread of alien plant species across the region.