Table 4. Identification of species-specific PSS by likelihood analysis in MHC class II DRB exon 2 amino-acid sequences of N. albiventris.

PSS	Mean ω	Pb (ω>1)	Distance to ABS
9	4.561±0.496	1.000**	0
11	4.561±0.496	1.000**	0
12	4.490±0.693	0.982*	0
13	4.556±0.514	0.999**	0
16	3.908±1.434	0.836	2
18	4.353±0.950	0.948	4
28	4.464±0.740	0.976*	0
34	3.633±1.604	0.768	4
37	4.552±0.526	0.998**	0
47	3.460±1.677	0.724	0
57	4.561±0.496	1.000**	0
60	3.733±1.530	0.793	1
61	4.512±0.643	0.988*	1
63	4.462±0.747	0.975*	0
66	4.334±0.970	0.944	0
67	4.524±0.604	0.991**	0
70	4.560±0.493	1.000**	0
71	4.561±0.496	1.000**	0
74	4.561±0.496	1.000**	0
76	3.581±1.650	0.755	2
77	4.529±0.592	0.992**	1
78	4.559±0.503	1.000**	0
86	4.561±0.496	1.000**	0
88	3.646±1.731	0.778	0
92	4.545±0.549	0.996**	2

Abbreviations: ABS, antigen-binding sites; Distance to ABS, amino acids to nearest human ABS of the HLA-DR1 β-chain (Brown et al., 1993); Mean ω (±s.e.), ratio of non-synonymous and synonymous substitutions at PSS and its probability (P_b (ω>1)) using a cutoff posterior probability of 95% PSS, positively selected sites, numbers indicate the amino-acid positions in the β1-domain.

^**α⩽0.01, ^*α⩽0.05.