Central Concepts

The chapter defines and discusses some of the central concepts in biological game theory. Strategies, which are rules for choosing actions as a function of state, play a pivotal role. It is explained how the theory operates at the level of strategies rather than attempting to follow the details of the underlying genetics that code for them. This is referred to as 'the phenotypic gambit', which is discussed and illustrated. The concept of the invasion fitness of a mutant strategy in a population that adopts another resident strategy is also central. This performance measure is used to give a necessary condition for evolutionary stability, formulated as the Nash equilibrium condition. It is explained how this stability condition can be reformulated in terms of simpler fitness proxies such as the mean lifetime number of offspring or the net rate of energy gain.