Fig. 4.

Predicted effects of protandry on the evolution of adaptive death. Alternative means to increasing fitness are living longer and increasing personal fitness by continued reproduction (top), or dying and increasing inclusive fitness through consumer sacrifice (bottom). Protandry (where self-fertilizing organisms produce first sperm and then eggs, such that reproduction ceases upon self-sperm depletion) leads to early cessation of reproduction, thus creating conditions that favor natural selection of altruistic death. C. elegans can also reproduce by mating with males, and this extends the reproductive period, but males are very rare in wild populations (Frezal and Felix, 2015). In terms of Hamilton's rule rB > C where r is the relatedness, B is the benefit to the recipient, and C is the cost to the donor (Hamilton, 1964), protandry results in a smaller reduction in C when B is increased.