Figure 2.
(a) The optimal allocation of competitive effort by each sister to maximize inclusive fitness, i.e. numerical solutions of 
for all possible b (dominance) and p (paternity certainty). The red surface represents x* (optimal competitive effort by older sister) and green surface denotes y* (optimal competitive effort by younger sister). (b) The inclusive fitness of S1 and S2 for all (x*, y*). The red surface denotes ϕS1 (x*, y*) and the green surface denotes ϕS2 (x*, y*). The older sister always has higher fitness, because she needs to exert less competitive effort, for all values where b < 1. (c) The optimal allocation of competitive effort by each female cousin to maximize inclusive fitness, i.e. numerical solutions of 
The red surface represents x* (optimal competitive effort by older female cousin) and green surface y* (optimal competitive effort by younger female cousin). (d) The inclusive fitness of C1 and C2 for all (x*, y*). The red surface denotes ϕC1 (x*, y*) and the green surface ϕC2 (x*, y*).