Table 3.
Statistical tests for both the comparison between the sexes and the comparison among genotypes
| Term | Base model | Δdeviance | d.f. | P | |
|---|---|---|---|---|---|
| Comparison between the sexes | Distance × sex × size | Distance + sex + size + distance × sex + distance × size + sex × size | 1.0756 | 1 | 0.2997 |
| Sex × size | Distance + sex + size + distance × sex + distance × size | 0.2151 | 1 | 0.6428 | |
| Distance × sex | Distance + sex + size + distance × size | 1.0556 | 1 | 0.3042 | |
| Distance × size | Distance + sex + size | 1.6034 | 1 | 0.2054 | |
| Size | Distance + sex | 7.4035 | 1 | 0.00651 | |
| Ssex | Distance + size | 7.6285 | 1 | 0.005745 | |
| Distance | Sex + size | 5.0022 | 1 | 0.02531 | |
| Comparison among genotypes | Distance × sex × size† | Distance + sex + size + distance × sex + distance × size + sex × size | 10.735 | 1 | 0.0011 |
| Distance × sex | Distance + sex + size + distance × size + sex × size | 0.8148 | 1 | 0.3667 | |
| Distance × size | Distance + sex + size + sex × size | 15.188 | 1 | <0.0001 | |
| Sex × size | Distance + sex + size + distance × size | 5.5102 | 1 | 0.0189 |
We performed a model reduction by starting with a full model containing all fixed effects and all interaction terms among the fixed effects, and removed one term at a time until we were left with the simplest model. To determine whether or not a term was significant, we computed the change in deviance (∆deviance) when we compared the statistical fit of the base model with the statistical fit of the base model and the term. If the change in deviance was significant based on a χ2 test, we left the term in. These models also included the effect of genotype and individual identification number nested within genotype as random intercepts, and the interaction between distance, genotype and individual nested within genotype as a random slope. Terms in bold are the highest order terms included in the final statistical model. If the interaction term was significant, all the main effects of that interaction term were also included. For example, in the ‘Comparison among genotypes’, the sex × size interaction is significant, so we retained the interaction term as well as sex and size by themselves.
†Differences between statistical models with and without the term were significant, However, the coefficient for the term was not significantly different from 0.