Table 1. The results of the db-RDA analysis of PCoA scores showing (a) the effect of ecotype, stream and their interaction on bacterial community composition from the 2010 field survey and (b) the effect of ecotype, diet and their interaction of bacterial community composition from the dietary manipulation study.

	d.f.	F	P-value
(a) 2010 Survey
Abundance of bacterial OTUs (Bray–Curtis)
Ecotype	(1.32)	2.178	0.009
Stream	(3.32)	3.960	<0.001
Ecotype/stream	(3.32)	2.171	<0.001
Unweighted UniFrac distance
Ecotype	(1.32)	1.852	0.002
Stream	(3.32)	2.257	<0.001
Ecotype/stream	(3.32)	1.619	<0.001
(b) Dietary manipulation experiment
Abundance of bacterial OTUs (Bray–Curtis)
Ecotype	(1.10)	10.823	<0.001
Diet	(1.10)	2.528	0.016
Ecotype/diet	(1.10)	2.928	0.003
Unweighted UniFrac distance
Ecotype	(1.10)	3.360	<0.001
Diet	(1.10)	1.437	0.127
Ecotype/diet	(1.10)	2.010	0.013

Abbreviations: db-RDA, distance-based redundancy analysis; OTU, operational taxonomic unit; PCoA, principal coordinates analysis.