Nitrospira communities are grouped by hierarchical clustering on the y-axis, and OTUs are grouped by phylogenetic affiliation on the x-axis. Lake names are abbreviated as in Fig. 1. Lin. IV, Nitrospira lineage IV ; Lin. II, Nitrospira lineage II; I, Nitrospira lineage I; Freq normalized frequency counts; Grp.1, group 1 lakes; Grp.2, group 2 lakes (see also Fig. 1).