Table 1.

Likelihood Ratio Tests of selective pressures on Atp8 gene in molluscs.

Models	ω (Ka/Ks)	Comparisons	p value (LRT)
Data set I: 18 Atp8 sequences (17 nonbivalve molluscs plus the ancestral sequence of all bivalves)
A. All branches have the same ω	ω = 0.07	B vs. A	0.021
B. Ancestral branch of all bivalves has ω2 and other branches have ω1	ω1 = 0.07, ω2 = 0.71
Data set II: 30 Atp8 sequences (29 nonmarine bivalve molluscs plus the ancestral sequence of all marine bivalves)
C. All branches have the same ω	ω = 0.09	D vs. C	0.037
D. Ancestral branch of all marine bivalves has ω2 and other branches have ω1	ω1 = 0.09, ω2 = 0.24
Data set III: 41 Atp8 sequences (29 nonmarine bivalve molluscs plus 12 marine bivalves)
E. Ancestral branch of all marine bivalves and branches connecting 12 marine bivalves have ω2, whereas other branches have ω1	ω1 = 0.09, ω2 = 0.20	F vs. E	0.145
F. Ancestral branch of all marine bivalves has ω3, branches connecting 12 marine bivalves have ω2, and other branches have ω1	ω1 = 0.09, ω2 = 0.24, ω3 = 0.14

Significant P values (<0.05) are indicated in bold.