Table 3. Skewness, neutrality index (NI) and direction of selection (DoS) statistics for GC content and codon usage.
| Species | GC content | Codon usage | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Mean allele frequency of GC alleles | Skewness | p-valuea | NI | DoS | p-valueb | Mean frequency of Pref alleles | Skewness | p-valuea | NI | DoS | p-valueb | |
| Sorghum bicolor | 0.576 | -0.351 | <10E-16 | 0.834 | 0.043 | 7.50E-07 | 0.535 | -0.164 | 5.45E-06 | 0.94 | 0.02 | 0.256 |
| Pennisetum glaucum | 0.562 | -0.294 | <10E-16 | 0.963 | 0.009 | 0.007 | 0.534 | -0.158 | <10E-16 | 0.87 | 0.03 | 3.72E-15 |
| Triticum monococcum | 0.547 | -0.222 | 1.81E-05 | 0.728 | 0.078 | 8.70E-11 | 0.550 | -0.236 | 1.16E-05 | 0.71 | 0.08 | 3.84E-11 |
| Musa acuminata | 0.570 | -0.343 | <10E-16 | 0.827 | 0.047 | <10E-16 | 0.570 | -0.344 | <10E-16 | 0.83 | 0.05 | 7.01E-15 |
| Elaeis guineensis | 0.540 | -0.201 | <10E-16 | 0.819 | 0.050 | 3.30E-09 | 0.535 | -0.170 | 3.06E-13 | 0.82 | 0.05 | 1.79E-08 |
| Dioscorea abyssinica | 0.554 | -0.277 | <10E-16 | 0.856 | 0.037 | 0.035 | 0.549 | -0.252 | <10E-16 | 0.87 | 0.03 | 0.112 |
| Coffea canephora | 0.450 | 0.234 | <10E-16 | 0.913 | 0.022 | 3.13E-05 | 0.458 | 0.199 | <10E-16 | 0.92 | 0.02 | 5.47E-04 |
| Solanum pimpinellifolium | 0.534 | -0.152 | 0.019 | 1.132 | -0.031 | 0.051 | 0.539 | -0.174 | 0.016 | 0.73 | 0.08 | 1.04E-06 |
| Olea europaea | 0.509 | -0.047 | 0.001 | 0.884 | 0.031 | 0.003 | 0.510 | -0.051 | 0.001 | 0.89 | 0.03 | 0.017 |
| Theobroma cacao | 0.515 | -0.071 | 4.66E-04 | 0.838 | 0.044 | 7.14E-14 | 0.510 | -0.045 | 0.053 | 0.88 | 0.03 | 5.38E-06 |
| Vitis vinifera | 0.550 | -0.229 | <10E-16 | 0.737 | 0.075 | <10E-16 | 0.538 | -0.172 | <10E-16 | 0.66 | 0.10 | 3.80E-88 |
a Null hypothesis: skewness = 0
b Null hypothesis: NI = 1 / DoS = 0 (equivalent test done on the same contingency table).