Table 1. Mantel statistics between metavariable dissimilarity matrices.

	β-diversity	resource use distribution	resource use diversity	DOC mass transfer	glucose mass transfer	community composition
flow heterogeneity	.81* P = .007	.38 P = .22	.48 P = .046	.55 P = .018	.94* P = .000	.52 P = .07
beta diversity		.61 P = .011	.83* P = .008	.73 P = .010	.86* P = .004	.50 P = .06
resource use distribution	.55 P = .038		.51 P = .017	.21 P = .23	.29 P = .18	.23 P = .31
resource use diversity	.85* P = .007	.40 P = .09		.54 P = .07	.59 P = .024	.16 P = .26
DOC mass transfer	.57 P = .05	.01 P = .37	.37 P = .12		.67* P = .007	.68* P = .000
glucose mass transfer	.50 P = .047	−.21 P = .75	.45 P = .09	.53 P = .07		.47 P = .10
community composition	.15 P = .33	.04 P = 41	−.12 P = .64	.55* P = .001	−06 P = 49

Lower diagonal gives partial Mantel statistics (controlling for flow heterogeneity). Significant values are in bold and marked with an asterisk when significant at P<0.05 after Bonferroni-correction. Used dissimilarity matrices: HET (flow heterogeneity), BETA (beta diversity), DOCUSE (resource use distribution), DOCDIV (resource use diversity), DOCMT (DOC mass transfer), GLCMT (glucose mass transfer). See Methods and Table S3 for details of computation.