Alternative Mating Tactics and Evolutionarily Stable Strategies

Abstract

Difficulties with applying Evolutionarily. Stable Strategy (ESS) methodology and terminology to alternative mating behaviors (in which some males in local populations adopt strikingly different, often non-competitive, behavioral patterns) are reviewed. Definitions for “tactic” (behavioral phenotype) and “strategy” (evolved set of rules for expressing tactics) are given. Inconsistent and incorrect applications of “mixed,” “pure,” and “conditional” ESSs are discussed. Cases of condition-dependent alternative mating tactics are reviewed. Because most alternative behaviors are condition dependent, neither their population-wide nor individual fitness contributions are expected to equal the fitness contributions of “primary” tactics. Individuals should, however, switch tactics at “equal fitness points.” A particular conditional tactic will persist when its maintenance cost (genetic or physiological) is less than its fitness contribution. In only exceptional cases are the fitness contributions of tactics expected to be equal: 1) genetic polymorphisms, 2) stochastic “mixed” ESSs, 3) frequency-dependent choice and, 4) arbitrary assessment. Although alternative tactics may occur in cases of genetic polymorphism or genetic equipotence, most mating tactics probably occur when continuous heritable variation in underlying conditional strategy exists. Selection for genetically influenced “roles” (genetic background) may also uncover apparent heritability.