Vole disturbances and plant community diversity in a productive hay meadow

It is recognized that disturbances by fossorial small mammals are important factors determining plant community diversity, especially in grasslands. However, although information about the effects of disturbances by fossorial small mammals on species richness are starting to accumulate, we know little about the impact of these disturbances on the functional and phylogenetic facets of plant community diversity in grasslands. In a study site located in the French Jura Mountains, we compared taxonomic, functional and phylogenetic diversity of plant communities in areas highly disturbed by montane water vole (Arvicola terrestris) with areas lowly disturbed by this small mammal. In accordance with previous studies, we found that species richness was higher in highly disturbed communities. Indeed, competitive species unable to withstand disturbances were less abundant in disturbed communities, allowing species less adapted to competition for light to survive. Because these species have different trait values in comparison to strong competitors, functional richness was also higher in highly disturbed communities. Results were similar for phylogenetic richness, maybe due to the fact that the used metric was not independent from species richness. Although species composition differed between highly and lowly disturbed communities, functional composition was very similar. Thereby, the studied disturbances were probably not strong enough to affect plant community functioning. Rao functional diversity and functional evenness were not different between both community types. Interestingly, phylogenetic evenness was lower in highly disturbed areas, supporting the idea that disturbances might select for disturbance tolerance traits that are phylogenetically conserved. Though correlational, our results suggest that water vole disturbances may modify multiple facets of plant community diversity, while ecosystem functioning is maintained across disturbance levels. Further research is needed to understand causal mechanisms in this system and the ecological repercussions of small mammal disturbances more broadly.