Most features of animals of interest to evolutionary biologists involve complex traits: Sets or systems of interrelated aspects of the animal. For example composed of a system of interrelated bones. Most complex traits are influenced by the environment in which they develop (called phenotypic plasticity); thus for example the development of the human hand may be influenced by the nutritional history of the individual. Despite the importance of such complex traits, little is known quantitatively of how natural selection acts on complex traits in wild populations, or of consequences of phenotypic plasticity for selection on such traits. The proposed research will study natural selection and phenotypic plasticity of one complex trait: The wing pigmentation pattern of the butterfly, Pieris occidentalis. Using a series of field experiments in wild populations, the research will: (1) measure natural selection on different aspects of wing pigment pattern, and how such selections may vary seasonally; (2) determine whether selection is the result of the effects of pigment pattern on body temperature regulation or on camouflage from potential predators; and (3) measure the selective consequences of phenotypic plasticity in wing pigment pattern. These experiments will provide the first detailed case study of the mechanisms and seasonal variation in natural selection for a complex, phenotypically-plastic trait.
