Table 2.

Measures of MHC-I diversity (segregating nucleotide (S _nt) and amino acid sites (S _aa) and average nucleotide diversity (π)) of exon 3 alleles in Icelandic black-tailed godwits (Limosa limosa islandica), red-billed gulls (Larus scopulinus), and red knots (Calidris canutus). All analyses were carried out on 21 putatively classical alleles per species. Estimates of non-synonymous (d _N) and synonymous (d _S) substitution rates, plus the d _N/d _S ratio, were calculated separately for the peptide-binding residues (PBR) and non-PBR (the PBR here were defined as 12 sites in exon 3, see Fig. 3 for details)

α2	d N ± SE	d S ± SE	d N/d S	S nt	S aa	π
Black-tailed godwit
PBR	0.340 ± 0.113	0.344 ± 0.172	0.988	8	9	0.268
Non-PBR	0.047 ± 0.011	0.093 ± 0.030	0.505	10	22	0.042
Red-billed gull
PBR	0.236 ± 0.108	0.179 ± 0.118	1.318	5	7	0.191
Non-PBR	0.037 ± 0.010	0.057 ± 0.020	0.649	7	17	0.028
Red knot
PBR	0.428 ± 0.170	0.271 ± 0.132	1.579	7	7	0.320
Non-PBR	0.072 ± 0.013	0.145 ± 0.032	0.497	19	35	0.055