Plant Community Assembly in Invaded Recipient Californian Grasslands and Putative Donor Grasslands in Spain

Rubén Bernardo-Madrid,María Leiva,Montserrat Vilà,Javier Galán Díaz,Enrique De La Riva,Ingrid Parker

doi:10.3390/d12050193

Abstract

The introduction of exotic species to new regions offers opportunities to test fundamental questions in ecology, such as the context-dependency of community structure and assembly. Annual grasslands provide a model system of a major unidirectional introduction of plant species from Europe to North America. We compared the community structure of grasslands in two Mediterranean regions by surveying plots in Spain and in California with similar environmental and management conditions. All species found in Spanish grasslands were native to Spain, and over half of them (74 of 139 species) are known to have colonized California. In contrast, in California, over half of the species (52 of 95 species) were exotic species, all of them native to Spain. Nineteen species were found in multiple plots in both regions (i.e., shared species). The abundance of shared species in California was either similar to (13 species) or greater than (6 species) in Spain. In California, plants considered pests were more likely than non-pest species to have higher abundance. Co-occurring shared species tended to maintain their relative abundance in native and introduced communities, which indicates that pools of exotic species might assemble similarly at home and away. These findings provide interesting insights into community assembly in novel ecosystems. They also highlight an example of startling global and local floristic homogenization.

Highlights

The introduction and invasion of exotic species across new regions is causing biotic homogenization of species assemblages at different spatial scales [1,2,3,4]
All species we found in Spanish grasslands, and all exotic species we found in California, were native to Spain [33,34]
In California, we found 43 native species and 52 exotic species, all of which are native to Spain

Summary

Introduction

The introduction and invasion of exotic species across new regions is causing biotic homogenization of species assemblages at different spatial scales [1,2,3,4]. Many exotic species co-occur in habitats outside their native regions [5,6]. Because patterns may arise from local differences in species richness and diversity, these comparisons need to consider the entire plant community, not just one focal species [9]. Biogeographical comparisons of exotic plant species in their native and recipient communities are important and gaining interest [8,9,10,11]. A general assumption is that exotic species are more abundant

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Results

Conclusion