The effects of behavioral plasticity and leadership on the predictions of optimal skew models

Abstract

Skew models predict how reproduction or resources produced by the group are divided between dominant and subordinate group members. These include transactional models, in which one group member may allocate some group productivity to another to prevent group dissolution and tug-of-war inefficiency models, in which group members compete for access to resources at a cost to group productivity. Although skew models involve a transactional or competitive interaction among group members, most existing models do not allow individuals to respond to new information about the strategy of their group mate. Here, I expand transactional and tug-of-war models to allow one individual (the follower) to respond plastically to a fixed strategy of its partner (the leader). I solve for the Stackelberg equilibrium conditions for each model. For the transactional model, leadership results in a greater share of group productivity to the leader compared with models that do not include leadership. When the follower’s information about the leader’s strategy is perfect, the equilibrium division of productivity does not vary with relatedness, in contrast to the predictions of previous skew models, and the effects of ecological variables may change. In the tug-of-war model, leadership influences equilibrium investment in competition only if relatedness is greater than zero. Dominant leaders receive a larger share of group productivity, but group productivity declines and grouping is mutually beneficial over a smaller parameter range than in the absence of leadership. Subordinate leaders receive a smaller share of group productivity, but benefit from overall higher group productivity. Key wor ds: commitment, cooperative breeding, evolutionar y game theory, skew models. [Behav Ecol]