Results
All life-history traits were influenced by both food ration and dopamine treatments (Table 2). Most of them responded in the same direction to a change in food ration for both control and dopamine treatments. Specifically, somatic growth rate increased with higher food ration, whereas age at maturation, offspring dry mass and offspring longevity decreased (Fig. 2, Table 3). For dry mass at maturation there was a strong interaction between food ration and dopamine treatment (Table 2). While dry mass at maturation decreased with increasing food ration in the control treatment, the opposite pattern was observed in the dopamine treatment (Fig. 2C, Table 3).
The steepness of the food ration reaction norms depended on dopamine treatment for somatic growth rate and offspring dry mass (Table 2). Specifically, dopamine exposure increased somatic growth rate, but this was more pronounced at high food ration (Table 3), causing the reaction norm to be steeper for the dopamine exposed group compared to the control (Fig. 2A). For offspring dry mass, treatment had no effect at high food ration, whereas exposure to dopamine reduced offspring dry mass at restricted food ration (Table 3). Thus, for this trait, the reaction norm was steepest for the control group (Fig. 2D). In contrast, exposure to dopamine lowered age at maturation to an equal extent across food rations (Fig. 2B, Table 2). Similarly, the effect of dopamine treatment on offspring longevity did not depend on the maternal food ration (Table 2). Rather, exposure to dopamine increased offspring longevity across food rations (Fig. 2E).