Results

Taxonomic richness

Environment (represented by the first two PCA axes) was predominant in explaining variation in taxonomic richness in all organism groups (Fig. 2). It varied between 10.6 and 52.2%, and was statistically significant in almost all organism groups except for phototrophic and heterotrophic microeukaryotes. The effect of relative spatial position (closeness centrality) was also relevant for some taxa varying between 1.9 and 9.3% explained variation. It was the highest and statistically significant in rotifers (9.3%, F(1,50)=9.08, p=0.004) and crustaceans (1.9%, F(1,50)=3.94, p=0.047), while only marginally significant in prokaryotes (2.8%, F(1,50)=3.05, p=0.091) and dipterans (3.4%, F(1,50)=3.30, p=0.068; Table S3 and S4, Supporting Information). The relationship between taxonomic richness and centrality (with the environment partialled out) was positive in all these groups (Fig. S3, Supporting information).