Fig. 5

Matrix of incidence of nectar microbial communities in the 20 Linaria vulgaris populations located across an urbanization gradient in the vicinity of Leuven, Belgium. Rows are populations and columns are OTUs. The populations have been color coded to represent the degree of impervious surfaces within 500 m radius of each population, as in Fig. 7. The matrix was sorted according to ‘binmatnest’ algorithm as implemented in the R package ‘bipartite’. The presence of yeast communities is indicated in blue, while presence of bacterial communities is indicated in red. The communities showed significant nestedness (T = 16.81, p < 0.01, NODF = 42.19, p < 0.01), and their nestedness rank was correlated with impervious surface index (Spearman-ρ = 0.49, p = 0.02), which implies that nectar urban microbial communities are a subset of nectar rural microbial communities