Vertebrates have diverse reproductive cycles spanning continua from brief to prolonged breeding seasons, and from precisely timed to opportunistic reproductive periods. Variations in the timing of gonadal maturation and onset of breeding require that individuals of a population or species adjust secretion of reproductive hormones in response to environmental signals. Dr. Wingfield proposes to develop a mathematical model to describe the type of breeding cycle for a given population. Of particular interest are the degrees of constancy and contingency within a particular breeding cycle. The more constancy within a cycle (e.g. the environment is in a state conducive to breeding most of the time), then less environmental information is required to regulate secretion of reproductive hormones and thus optimize breeding. As contingency in the cycle increases (e.g. the environment shows major changes in suitability for breeding within a year), more environmental cues are required to time onset of breeding. The PI has chosen several avian species, with varying degrees of constancy and contingency in their reproductive cycles, as tests of this model. The responses of each species to environmental signals known to influence reproductive function (e.g. annual change in daylength, temperature, availability of food) will be tested. Their effects on gonadal development, and secretion of reproductive hormones will be measured. Ultimately, the effects of these environmental cues on gene expression for hormones within the brain, that act as a link between the environmental and internal processes, will also be determined. The proposed research is designed to explore the possibility of a unifying theory that can be used to predict how all vertebrates (and perhaps all organisms) integrate signals from the environment in order to optimize reproduction. It may also be possible to use this model for processes other than reproduction (e.g. migration, growth etc.) The research will provide new insight into the mechanisms by which environmental signals are transduced into internal processes (such as hormone secretion) that regulate reproductive function. This may have considerable impact on our knowledge of reproduction in general, and could provide a firm base for approaching problems of how to breed and protect endangered species and populations.
