Long-term Sabbatical

The evolution of performance curves in seasonal environments

PI(s): George Gilchrist (College of William and Mary)
Start Date: 1-Aug-2008
End Date: 30-Jun-2009
Keywords: climate change, natural selection, thermal biology, physiology, evolutionary genetics

Climate change directly alters seasonal patterns of temperature, resulting in observable changes in the distribution and timing of seasonal populations. As populations shift their activity to cooler periods of the year or migrate to cooler climates, they also experience reduced day length. For many species, specific conditions are required for successful mating and reproduction. For example, many butterfly species require long days and temperatures of 25 to 35ÂșC in order to reproduce; under short days or when temperatures vary outside of that window, reproductive activity ceases, resulting in reduced population growth rate and population size. It is this reduction in demographic potency, rather than the ability to survive extreme conditions, that causes the greatest fitness loss during thermal stress. Temperature-related reduction in population size and growth rate can also limit the potency of natural selection. Thus, the evolution of thermal niche dimensions may be influenced by demographic constraints. Changes in the amount of time an organism experiences under permissive light and temperature conditions will impose selection to alter thermal sensitivity. My proposed research will model demographic limitations on natural selection arising from time constraints imposed by daily and seasonal variation in temperature and photoperiod. This work builds on my earlier models exploring the evolution of thermal sensitivity in a variable environment (Gilchrist 1995; Gilchrist 2000). These models are a synthesis of physiological modeling and evolutionary genetics to explore how the physical environment structures the fundamental thermal niche in a changing world.

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