Table 2.

Reproductive payoff matrices. For comparing alternative actions, arrows point from smaller to larger payoffs (indicating the expected direction of selection). (a) Generic version; our central assumption is that unilateral desertion yields a higher payoff for the deserting partner (both male and female) than biparental care (a behaviour we never observed in our population), i.e. b > a and B > A. (b–e) Four specific scenarios for the different relationships between the payoffs when caring alone (c for males, C for females) and when both parents desert (d for males, D for females).