Parent-Offspring Conflict and Life-History Consequences in Herbivorous Insects

Abstract

We develop an evolutionarily stable strategy theory of parent-offspring conflict in insect herbivores for the case in which offspring can choose to leave host plants on which they have been deposited by their mother. We find that a fundamental parent-offspring conflict in larval leaving rates occurs because individual larvae are more related to themselves than to their siblings whereas mothers are equally related to each of their offspring. Several patterns emerge: (1) The optimal probability of movement from the mother's perspective, P*(mom), is always greater than or equal to the optimal probability of movement from the offspring's perspective, P*(off), (2) a consequence of this difference in optimal probabilities of movement is that the mother's fitness for a given clutch is always greater for P*(mom) than P*(off), (3) as the payoff for leaving a plant decreases, (i) the optimal movement rates decrease and (ii) clutches become smaller, (4) as relatedness increases, optimal movement probabilities increase and this causes an increase in optimal clutches, and (5) the clutch size that maximizes the mother's lifetime fitness will frequently diverge from that which the mother would produce were the offspring to move at her optimal rate (i.e., P*(mom)).