Figure 2.
A unified theory for the evolution and phenotypic expression of alternative mating tactics (AMTs). Past theory has focused on two approaches comprising alternative strategies and the conditional strategy. Alternative strategies imply a genetic polymorphism in a population that give rise to genetically determined AMTs such as fight versus sneak. Negative frequency-dependent selection is required for evolutionary stability and the strategies/tactics are expected to have equal fitness. A conditional strategy implies a genetically monomorphic decision gene that is condition-dependent such as fight when large versus sneak when small. Negative frequency-dependent selection is not required for evolutionary stability, and the tactics are expected to have unequal fitness. Conditional alternative strategies incorporate quantitative genetic theory, and combine genetic and environmental effects on tactic phenotypic expression. Regardless of whether the condition-dependent decision gene shows genetic variation within a population, it is expected to be influenced by polymorphic, modifier loci via epistasis (fightA/sneakA versus fightB/sneakB, where the A and B denote different genotypes) as well as by biotic and abiotic environmental factors, leading to genotype-by-environment interactions (G × E). G × Es reflect variation in reaction norms and tactic switch points within populations. Temporal variation in the environment will lead to a shifting fitness landscape, which will change the relative fitness of the tactics. Equal fitness is not expected at any given time period.