Ecological niche and species traits: key drivers of regional plant invader assemblages

Linking species traits to niche properties is fundamental to understand the spatial structure of invasive species assemblages and the invasion process itself. Using information on 74 invasive species in Spain, the aims of this paper are to (1) test whether invasive plant species assemblages follow a nested pattern at the regional scale, (2) inspect the relationship between range size and niche properties (position and breadth) of invasive species to test whether the nested pattern is a product of species niche overlap; and finally (3) examine how species traits of invaders are related to their niche properties. We show that regional invasive plant species assemblages in Spain are organized in nested subsets. Invasive species with restricted range occur in areas invaded by widespread invaders. By relating nestedness metrics to species’ niche properties from multivariate analyses, we found that these restricted invaders are less tolerant of broad climatic and landscape conditions than widespread invaders. Finally, regarding the association between niche properties and species traits, we found that species with large environmental niche breadth commonly exhibit non N-fixing strategy, short-life span, and clonal growth, while those with niche position in anthropogenic coastal areas were perennial and clonal species of unintentional and agricultural origin. Using an integrative approach linking the regional spatial structure of invasive plant assemblages, species niche properties and species traits, we were able to understand the potential causes of invasive species distribution in Spain. The approach developed in this research could be easily applied to other areas to disentangle the mechanisms driving invasive species distributions.