Evol Ecol Res 10: 1157-1172 (2008)     Full PDF if your library subscribes.

Evolution of polyphenism: the role of density and relative body size in morph determination

Joe Y. Wakano1,4 and Howard H. Whiteman2,3,4

1Department of Biological Sciences, The University of Tokyo, Tokyo, Japan,  2Department of Biological Sciences, Murray State University, Murray, Kentucky, USA,  3Rocky Mountain Biological Laboratory, Crested Butte, Colorado, USA and  4Center of Excellence in Ecosystem Studies, Hancock Biological Station, Murray, Kentucky, USA

Correspondence: J.Y. Wakano, Meiji Institute for Advanced Study of Mathematical Sciences, 1-1-1 Higashi Mita, Tama-ku, Kawasaki, Kanagawa 214-8571, Japan.
e-mail: joe@math.meiji.ac.jp


Questions: Why and how do relative body size and density influence the expression of polyphenism?

Background: Facultative paedomorphosis in salamanders is a polyphenism. There are two alternative adult phenotypes: paedomorph (remains in the aquatic environment and matures within the larval form) and metamorph (transforms and matures in the terrestrial environment).

Mathematical methods: Evolutionary game model; evolutionary stability and convergence stability analysis justified by population genetics.

Key assumptions: The fitness of each morph is determined by density, relative body size, and the frequencies of phenotypes. Individual body size is environmentally determined. Each strategy is given by the probability of becoming paedomorphic as a function of body size.

Conclusions: Large animals become paedomorphic when density is low, small animals become paedomorphic when density is high, and the frequency of paedomorphosis is minimized when density is intermediate. These results are consistent with current empirical studies, and make testable predictions for future research on this and other polyphenisms.

Keywords: conditional strategy, evolutionary game model, facultative paedomorphosis, phenotypic plasticity, polymorphism, polyphenism.

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