The Evolution of Conspecific Acceptance Thresholds

Abstract

The differential treatment of conspecifics (e.g., kin recognition) has three components. (1) The production component refers to the nature of the cues used by an individual (actor) to discriminate among classes of conspecifics (recipients) differing in their effects on the actor's fitness. (2) The perception component refers both to the internal template against which the actor matches these cues and to the matching algorithm that allows classification of a recipient (Sherman and Holmes 1985). I introduce a third component, (3) the action component, which refers to the determinants of an action taken by an actor that has calculated a particular degree of similarity between its internal template and a recipient's phenotype. I attempt to provide a theory of the action component of conspecific discrimination. In particular, I examine the factors that determine the optimal or evolutionarily stable acceptance threshold, that is, the level of dissimilarity between the actor's template and the recipient's phenotype below which recipients are accepted and above which recipients are rejected. Analyses of six different classes of recognition contexts show how the optimal or evolutionarily stable acceptance threshold is a function of the relative frequencies of interaction with the different classes of recipients, of the fitness consequences of accepting or rejecting different classes of recipients, and of the ways in which the latter fitness consequences combine. I discuss diverse behavioral phenomena that are elucidated by these models and suggest ways in which these models may be further tested.