Table 3. COI-16S dataset: AMOVA.

Source of variation	d.f.	SSD	Var. comp.	% var	Fixation indices	P-value
A - Group 1 (BMC, OSM, MOL, CCE, SAL, OTT, ORI, MAR, CPA, MAD, IPI, CPC, ELB, SVC, MON, MLZ, PAC, OGN, VEN); Group 2 (EP, AG, XI)
Among groups	1	52.953	1.221	39.61	0.396	<0.001
Among populations within groups	20	104.776	0.370	12.00	0.199	<0.001
Within populations	201	299.754	1.491	48.38	0.516	<0.001
B - Group 1 (BMC, OSM, MOL, CCE, SAL, OTT, ORI, MAR, CPA, MAD, IPI, CPC, SVC, MON, MLZ, PAC, OGN, ELB); Group 2 (EP, AG, XI); Group 3 (VEN)
Among groups	2	80.326	0.971	35.56	0.356	<0.001
Among populations within groups	19	77.403	0.268	9.80	0.152	<0.001
Within populations	201	299.754	1.491	54.64	0.454	<0.001
C - Group 1,western Mediterranean (BMC, OSM, MOL, CCE, SAL, OTT, ORI, MAR, CPA, MAD, IPI, CPC, SVC, MON, MLZ, ELB); Group 2, eastern Mediterranean (PAC, OGN, VEN, EP, AG, XI)
Among groups	1	17.491	0.096	4.48	0.045	>0.05
Among populations within groups	20	140.238	0.558	26	0.272	<0.001
Within populations	201	299.754	1.491	69.62	0.305	<0.001
D - Group 1, western Mediterranean (BMC, OSM, MOL, CCE, SAL, OTT, ORI, MAR, CPA, MAD, IPI, CPC, SVC, MON, MLZ, ELB); Group 2, eastern Mediterranean, (PAC, OGN, EP, AG, XI); Group 3, Adriatic Sea (VEN)
Among groups	1	53.206	0.376	16.44	0.164	<0.01
Among populations within groups	19	104.524	0.421	18.39	0.220	<0.001
Within populations	201	299.574	1.491	65.17	0.348	<0.001

Results of the analysis of molecular variance (AMOVA). Groups were defined a posteriori (A, B) according to the geographic trend emerged from pairwise Φ_ST values, or a priori (C, D) according to biogeographic criteria. d.f.: degrees of freedom; SSD: sum of squared deviations; var. comp.: variance component; % var: percentage of variation.