Table 2 Likelihood ratio tests using various models to determine the selective pressures on the cetacean Hr gene

Dataset I: 17 sequences (16 terrestrial mammals plus the ancestral cetacean sequence)

A. All branches with the same ω

ω = 0.27908

−24914.624502

34

B. Branch a (ancestral to cetacean) with ω₂, other branches with ω₁

ω₁ = 0.27502, ω₂ = 0.40432

−24912.059374

35

A vs B

5.130256

0.024

C. Branch a with ω₂ = 1, other branches with ω₁

ω₁ = 0.27427, ω₂ = 1

−24925.508371

34

B vs C

26.89799

2.14E-07

Dataset II: 19 sequences (16 terrestrial mammals plus two baleen whales and the ancestral sequence of toothed whales)

D. All branches with the same ω

ω = 0.28065

−25530.203259

38

E. Branch b (ancestral to toothed whale) with ω₂, other branches with ω₁

ω₁ = 0.27911, ω₂ = 0.48639

−25528.780477

39

D vs E

2.845564

0.092

F. Branch b with ω₂ = 1, other branches with ω₁

ω₁ = 0.27890, ω₂ = 1

−25530.928574

38

E vs F

4.296194

0.038

Dataset III: 22 sequences (16 terrestrial mammals plus five toothed whales and the ancestral sequence of baleen whales)

G. All branches with the same ω

ω = 0.28417

−26239.723434

44

H. Branch c (ancestral to baleen whale) with ω₂, other branches with ω₁

ω₁ = 0.28182, ω₂ = 0.62531

−26236.569206

45

H vs G

6.308456

0.012

I. Branch c with ω₂ = 1, other branches with ω₁

ω₁ = 0.28170, ω₂ = 1

−26237.557075

44

H vs I

1.975738

0.160