Table 2. Results of χ2-tests for nonsynonymous and synonymous substitutions in SWS1.
CF = 3 (774.4 non-synonymous sites: 239.6 synonymous sites) | |||||||
Observed | Expected | ||||||
Branch(es) | N | S | N | S | ω | χ2 | p value |
1. Crown odontocete + crown mysticete branches | 193.3 | 47.8 | 184.2 | 56.9 | 1.25 | 1.91 | 0.17 |
2. Odontocete stem branch | 2.1 | 4 | 4.66 | 1.44 | 0.16 | 5.95 | 0.015* |
3. Mysticete stem branch | 6.2 | 2.3 | 6.49 | 2.01 | 0.83 | 0.06 | 0.81 |
χ2-tests compared the observed versus expected numbers of nonsynonymous and synonymous substitutions for SWS1 based on a neutral model of evolution (ω = 1). All three different branch categories are expected to exhibit neutral ω values according to the “coastal” hypothesis of SWS1 evolution. CF = codon frequency model; N = nonsynonymous; S = synonymous; ω = dN/dS;
= significant p values.