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).