Principal coordinate analyses (PCoA) showing the similarity of bacterial (A,B) and fungal (C,D) OTUs incubated under varying isoprene mixing ratios. Soil samples were collected beneath a high isoprene emitting evergreen tree species (Populus tremuloides; A,C) and non-isoprene emitting conifer tree species (Pinus contorta; B,D). Results from ANOSIM are set in figures and the legend.