Table 1 Four classes of observed (empirical) tree topologies with their observed frequencies, observed frequencies among trees with >75% bootstrapping support, and simulated frequencies

Class I

((((bison,wisent),yak),(taurine,zebu)),buffalo)^a

26.91%

53.57%

26.54%

Class II

((((taurine,zebu),yak),(bison,wisent)),buffalo)

12.71%

15.46%

14.35%

((((bison,wisent),(taurine,zebu)),yak),buffalo)

11.90%

15.40%

13.46%

Class III

((((bison,yak),wisent),(taurine,zebu)),buffalo)

4.70%

2.42%

3.48%

((((wisent,yak),bison),(taurine,zebu)),buffalo)

4.43%

1.60%

3.39%

((((taurine,yak),zebu),(bison,wisent)),buffalo)

2.17%

1.24%

0.98%

((((zebu,yak),taurine),(bison,wisent)),buffalo)

1.41%

0.27%

1.01%

Class IV

((((taurine,zebu),wisent),(bison,yak)),buffalo)^b

0.87%

0.39%

3.10%

((((taurine,zebu),bison),(wisent,yak)),buffalo)

0.90%

0.45%

3.10%

Others

33.99%

9.20%

30.61%