Table 2.
Linear mixed‐effect model (LME) analyses of factors predicting changes in swimming endurance and in the duration of breeding ornamentation (blue eye colour) of three‐spined sticklebacks. In both cases, the full models included season of experiment (Winter or Spring), photoperiod treatment (ambient or delayed) and sex (male or female) as fixed effects, compensatory growth rate (partitioned into between‐group effects due to diet treatment, and within‐group effects due to remaining individual variation) as a covariate, and tank as a random effect, plus 2‐way interactions. Non‐significant variables were dropped from the final models. Note that for swimming endurance a positive estimate indicates an increase in endurance over the breeding season, while for breeding ornamentation it indicates a longer period of blue eye coloration in the second than in the first breeding season. The parentheses represent the reference coding of the categorical variable
| Analysis | Final model | Estimate ± SE | F | d.f. | P |
|---|---|---|---|---|---|
| Swimming endurance | Intercept | −0·037 ± 0·010 | |||
| Season (Winter) | 0·047 ± 0·010 | 20·50 | 1, 15·68 | <0·001 | |
| Photoperiod (Ambient) | −0·021 ± 0·010 | 4·94 | 1, 16·60 | 0·041 | |
| Between‐group effect of growth | −0·148 ± 0·062 | 5·59 | 1, 15·86 | 0·031 | |
| Within‐group effect of growth | −0·829 ± 0·143 | 26·56 | 1, 93·44 | <0·001 | |
| Season (Winter) × within‐group effect of growth | 0·626 ± 0·200 | 9·75 | 1, 93·61 | 0·002 | |
| Breeding ornamentation | Intercept | 0·488 ± 0·060 | |||
| Season (Winter) | −0·606 ± 0·082 | 54·74 | 1, 19·01 | <0·001 | |
| Sex (Male) | −0·321 ± 0·081 | 15·88 | 1, 76·63 | <0·001 | |
| Between‐group effect of growth | −8·174 ± 0·558 | 188·16 | 1, 31·90 | <0·001 | |
| Within‐group effect of growth | −1·561 ± 0·545 | 8·22 | 1, 76·56 | 0·005 | |
| Season (Winter) × between‐group effect of growth | 5·956 ± 0·636 | 87·76 | 1, 28·25 | <0·001 | |
| Sex (Male) × between‐group effect of growth | 1·256 ± 0·542 | 5·37 | 1, 76·26 | 0·023 |