Signalling Theory - Costly Signalling and Fisherian Diploid Dynamics

Costly Signalling and Fisherian Diploid Dynamics

The effort to discover how costs can constrain an "honest" correlation between public signals and private qualities within signallers is built on strategic models of signalling games, with many simplifying assumptions. These models are most often applied to sexually selected signalling in diploid animals, but they rarely incorporate an important feature of diploid sexual reproduction that was pointed out by Ronald Fisher in the early 20th century: if there are "preference genes" correlated with choosiness in females as well as "signal genes" correlated with display traits in males, choosier females should tend to mate with showier males. Over generations, showier sons should also carry genes associated with choosier daughters and choosier daughters should also carry genes associated with showier sons. This correlation could introduce an evolutionary dynamic known as a Fisherian runaway. Russell Lande explored this with quantitative genetic models and his work inspired a very active line of research in the quantitative genetic framework. These analyses revealed that Fisherian diploid dynamics are very sensitive to signalling and search costs. Recent models have begun to bridge the gap between the costly-signalling and Fisherian-runaway traditions by developing modelling frameworks that incorporate both simultaneously. These models recognize that if fitness depends on both survival and reproduction, having sexy sons and choosy daughters (in the stereotypical model) can be adaptive, increasing fitness just as much as having healthy sons and daughters.