Table 2.

Multiple stepwise regression model results for dominant bacterial and fungal phyla (and classes for Proteobacteria) that significantly correlated with a secondary metabolites. Soil origin was also included as an explanatory variable to discern metabolite versus soil effects. Raw abundances were centered log-ratio transformed prior to analysis. Type-1 error rates given are FDR-corrected

				Full model statistics
Microbial Phylum	Explanatory variable	T	p-value	F-statistic	Adj. R2	p-value
Bacteria
Betaproteobacteria	Intercept	67.3	< 0.01	13.07	0.19	< 0.01
	Soil(Corvallis)	−2.84	< 0.01
	salicylic acid	−2.67	< 0.01
Deltaproteobacteria	Intercept	17.99	< 0.01	21.99	0.38	< 0.01
	Soil(Corvallis)	−7.33	< 0.01
	catechin	1.74	0.09
	phenolics	−2.17	0.03
Acidobacteria	Intercept	70.39	< 0.01	51.94	0.6	< 0.01
	Soil(Corvallis)	−10.26	< 0.01
	saliyclic acid	−1.49	0.14
	populin	2.66	< 0.01
Actinobacteria	Intercept	45.92	< 0.01	25.79	0.42	< 0.01
	Soil(Corvallis)	8.48	< 0.01
	tremuloidin	2.25	0.03
	populin	−1.85	0.07
Verrucomicrobia	Intercept	62.91	< 0.01	22.79	0.39	< 0.01
	Soil(Corvallis)	−5.68	< 0.01
	salicylic acid	−2.56	0.01
	populin	2.29	0.02
Bacteroidetes	Intercept	36.34	< 0.01	10.82	0.22	< 0.01
	Soil(Corvallis)	−3.49	< 0.01
	salicylic acid	−1.82	0.07
	populin	2.51	0.01
Chloroflexi	Intercept	48.68	< 0.01	41.9	0.45	< 0.01
	Soil(Corvallis)	−8.98	< 0.01
	salicylic acid	2.15	0.03
Gemmatimonadetes	Intercept	45.06	< 0.01	7.65	0.12	< 0.01
	salicylic acid	−2.79	< 0.01
	populin	2.75	< 0.01
Firmicutes	Intercept	7.93	< 0.01	3	0.08	0.02
	tremuloidin	2.93	< 0.01
	catechin	2.24	0.03
	populin	−1.53	0.13
	phenolics	−2.11	0.04
Fungi
Mortierellomycota	Intercept	24.9	< 0.01	5.96	0.09	< 0.01
	tremuloidin	−2.42	0.02
	populin	2.41	0.02

Explanatory variables deemed statistically significant are bold