Table 2.

Comparison among different features associated to the groups of taxa whose abundances were positively or not significantly correlated [No correl] with the number of sequences of their parent class: number of sequences, OTUs, proportion (%) of the “dominant” OTUs [>0.1% of the pooled sequences] within each class contained by each group, average taxonomic diversity (Shannon Index), and mean phylogenetic distance [MPD].

		Sequence number	Number of OTUs	% “dominant”	Diversity	MPD
Actinobacteria	Positive	39163	40	36	1.5	0.39
	No correl	26601	347	64	2.6	0.60
Betaproteobacteria	Positive	9435	15	44	1.0	0.38
	No correl	4172	134	56	2.6	0.41
Alphaproteobacteria	Positive	3324	9	33	0.3	0.28
	No correl	2007	70	67	2.2	0.37
Gammaproteobacteria	Positive	48	2	0	0.01	0.01
	No correl	473	43	0	1.7	0.58
Flavobacteria	Positive	2377	16	33	0.5	0.12
	No correl	2126	49	67	1.8	0.50
Sphingobacteria	Positive	1435	4	25	0.1	0.03
	No correl	1363	32	75	1.6	0.70

For this analysis, we used the full (non-rarefied) OTU table. Values in bold indicate significantly different diversity (Shannon) or MPD values (p < 0.05) between the groups within a given class. Within Gammaproteobacteria, all taxa were classified as “moderately abundant” (< 0.1% of the pooled sequences).