Table 1.

Summary of MHC class I variants, genetic divergence and codon-based Z tests for selection in the three Japanese Rana species

Species	No. of variants (total)	No. of variants (per individual)	Total no. of segregating sitesa		Range of divergence within individual		Mean distance (nucleotide, amino acid)			Z tests for selection for α1 and α2 domains combined (Z statistic)
			Nucleotide	Amino acid	Nucleotide	Amino acid	α1	α2	α3	Neutrality	Purifying	Positive
R. japonica	10	2–5	136	78	0.012–0.115	0.031–0.212	0.064, 0.135	0.080, 0.155	0.024, 0.045	4.199*	−4.204 n.s.	4.219**
R. ornativentris	28	3–5	192	94	0.063–0.104	0.108–0.173	0.067, 0.158	0.067, 0.122	0.035, 0.048	3.446*	−3.422 n.s.	3.372*
R. t. tagoi	22	2–5	167	83	0.050–0.101	0.100–0.169	0.081, 0.149	0.081, 0.152	0.036, 0.060	3.808**	−3.808 n.s.	3.920**

*p < 0.01, **p < 0.0001, n.s.: p > 0.05

^aExcludes insertions or deletions