Table 2.
Sexual dimorphism in the stickleback brain
| Males | Females | SSD | |||
|---|---|---|---|---|---|
| Trait | Mean ± SD; range | corrMean | Mean ± SD; range | corrMean | |
| Bulbus olfactorius (mm3) | 0.105 ± 0.025; 0.054–0.168 | 0.101 | 0.107 ± 0.025; 0.039–0.195 | 0.105 | 3.4 %b |
| Telencephalon (mm3) | 1.062 ± 0.184; 0.554–1.579 | 1.025 | 0.940 ± 0.167; 0.549–1.573 | 0.942 | 8.9 %a |
| Tectum opticum (mm3) | 3.712 ± 0.486; 2.381–5.007 | 3.619 | 3.604 ± 0.469; 2.643–5.025 | 3.616 | <0.1 % |
| Cerebellum (mm3) | 1.017 ± 0.174; 0.626–1.590 | 0.986 | 0.944 ± 0.148; 0.654–1.370 | 0.948 | 4 %a |
| Hypothalamus (mm3) | 1.287 ± 0.187; 0.806–1.776 | 1.251 | 1.207 ± 0.161; 0.825–1.637 | 1.215 | 3 %a |
| Total brain (mm3) | 4.542 ± 0.195; 4.006–4.929 | 4.588 | 4.492 ± 0.190; 4.108–4.968 | 4.441 | 3.3 %a, b |
| Standard length (mm) | 40.70 ± 2.66; 35.11–46.72 | -- | 42.95 ± 3.07; 36.62–51.82 | -- | -- |
Raw means (Mean) ± Standard Deviations (SD) and range are shown first, and corrected means (corrMean) second. Corrected means are back-transformed Least Squares means from the General Linear Mixed Models (GLMMs) ran on lg-transformed variables. Percentage of difference between sexes (SSD) are calculated as [(higher value – lower value) / lower value]*100] using corrected means for brain regions and raw means for standard length. adenotes a significant sex difference, bdenotes a significant sex × treatment interaction (see Results). Standard length is added for illustrative purposes, it was a covariate in the GLMMs