Table 2. COI 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, M, N, S, B, K)
Among groups	1	67.784	0.747	36.89	0.369	<0.001
Among populations within groups	24	57.689	0.119	5.90	0.093	<0.001
Within populations	246	284.823	1.158	57.21	0.428	<0.001
B - Group 1 (BMC, OSM, MOL, CCE, SAL, OTT, ORI, MAR, CPA, MAD, IPI, CPC, ELB, SVC, MON, MLZ, PAC, OGN); Group 2 (EP, AG, XI, M, N, S, B, K); Group 3 (VEN)
Among groups	2	85.947	0.703	36.67	0.367	<0.001
Among populations within groups	23	39.526	0.056	2.91	0.046	<0.01
Within populations	246	284.823	1.158	60.41	0.396	<0.001
C - Group 1, western Mediterranean (BMC, OSM, MOL, CCE, SAL, OTT, ORI, MAR, CPA, MAD, IPI, CPC, ELB, SVC, MON, MLZ); Group 2, eastern Mediterranean (PAC, OGN, VEN, EP, AG, XI, M, N, S, B, K)
Among groups	1	19.047	0.116	7.27	0.073	<0.05
Among populations within groups	24	106.427	0.318	19.98	0.215	<0.001
Within populations	246	284.823	1.158	72.75	0.272	<0.001
D - Group 1, western Mediterranean (BMC, OSM, MOL, CCE, SAL, OTT, ORI, MAR, CPA, MAD, IPI, CPC, ELB, SVC, MON, MLZ); Group 2, eastern Mediterranean, (PAC, OGN, EP, AG, XI,M, N, S, B, K); Group 3, Adriatic Sea (VEN)
Among groups	2	54.484	0.353	20.69	0.207	<0.001
Among populations within groups	23	70.990	0.193	11.34	0.143	<0.001
Within populations	246	284.823	1.158	67.96	0.320	<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.