Alternative Reproductive Tactics

One of the big questions in evolutionary biology is why there is variation within a species – why individuals don’t converge on a “best” type. Alternative tactics (variation in any combination of behavioral and physical traits that result in distinct types within a species) provide a model system for studying phenotypic variation. Alternative tactics represent an extreme example of variation among individuals with very similar ecological roles.


Alternative reproductive tactics (ARTs) are discrete mating types within one sex of the same species which are influenced by sexual selection. Alternate morphs utilize life history tradeoffs to maximize their reproductive fitness in different ways. ARTs lead to rapid speciation; when one strategy is lost from a population, rapid phenotypic evolution can occur in the remaining morphs (Corl et al., 2010).


Species in nearly every taxa have evolved ARTs. Two alternative strategies are by far the most common scenario (reviewed in Oliveira et al., 2008), however mating systems with three morphs (Rock-Paper-Scissors) have also evolved repeatedly (reviewed in Friedman and Sinervo, 2016; Sinervo and Calsbeek, 2006). Remarkably, a single species with five co-existing male morphs is known, the Para molly (Poecilia parae). This 5-player system is unique in its complexity, Rock-Paper-Scissors-Lizard-Spock. We are working to understand the mechanisms underlying its stability.

Fish, from RPS-lizard-spock

Corl, A., Davis, A.R., Kuchta, S.R., Sinervo, B., 2010. Selective loss of polymorphic mating types is associated with rapid phenotypic evolution during morphic speciation. PNAS 107, 4254–4259. doi:10.1073/pnas.0909480107

Friedman, D., Sinervo, B., 2016. Evolutionary Games in Natural, Social and Virtual Worlds. Oxford University Press, New York, NY.

Lindholm, A.K., Brooks, R., Breden, F., 2004. Extreme polymorphism in a Y-linked sexually selected trait. Heredity 92, 156–162. doi:10.1038/sj.hdy.6800386

Sinervo, B., Calsbeek, R., 2006. The developmental, physiological, neural, and genetical causes and consequences of frequency-dependent selection in the wild. Annual Review of Ecology. doi:10.1146/annurev.ecolsys.37.091305.110128