Evolution of Photoperiodic Time Measurement and the Circadian Clock in Animals: Perspectives from the Pitcher-Plant Mosquito, Wyeomyia smithii

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Evolution of Photoperiodic Time Measurement and the Circadian Clock in Animals: Perspectives from the Pitcher-Plant Mosquito, Wyeomyia smithiiWilliam E. BradshawUniversity of Oregon EugeneEvolution of life cycles that are compatible with the changing seasons is a major feature of temperate organisms. No life cycle in a temperate zone like North America can be complete without the ability to exploit the favorable season, the ability to mitigate or avoid the unfavorable season, and the ability to switch from one lifestyle to the other on a timely basis. The most prominent switching mechanism used by temperate plants and animals to anticipate and prepare for the changing seasons is the length of day or photoperiod. Evolution of photoperiodic response is a major feature of the geographic dispersal of invading species and, as prior funding to this lab by NSF has recently shown, adaptation to rapid climate change. This research examines the physiological and genetic processes within and between populations that ultimately constitute the basis for the diversity of seasonal adaptations observed over a continental scale at temperate latitudes. The main objective of this work is to test whether there is a necessary, causal connection between the "daily" (circadian) clock controlling daily activities and the "seasonal" (photoperiodic) timer controlling seasonal activities. Daily activities include sleep-wakefulness patterns and hunger cycles in humans; disruption of the circadian clock is responsible for "jet lag." Seasonal cycles include migration in birds, hibernation in mammals, and dormancy and reproduction in a wide array of animals under natural conditions. The genetic basis of daily clocks is fairly well understood, but little is known about the genetic basis of the seasonal timer, let alone how the two processes relate to each other. The work in this proposal will test for the genetic flexibility of the connection between the daily and the seasonal timer by employing a set of artificial selection experiments. Knowledge of the potential interaction between these two timing mechanisms is fundamental to understanding how temperate organisms expand their ranges, time events as diverse as dormancy and reproduction, and cope with climate change. North America is undergoing a period of unprecedented climate change that is imposing strong natural selection for altering the timing of seasonal activities. The experiments to be run will show whether and how modification of the seasonal timer affects the daily clock and vice versa. Understanding the genetics underlying seasonal adaptation will assist in evaluating the survival of important agricultural crops, the spread of vector-borne diseases, the impact of agricultural pests, and the composition of natural biotic communities. This research lends itself well to undergraduate participation, not just as research assistants, but also as young investigators pursuing related but independent projects. Recent undergraduate students from this lab have continued on to graduate or medical school, to careers as teachers, applied biologists, lawyers, journalists, and to other professions not related to science. Regardless of their future endeavors, these students constitute an informed citizenry, more aware of basic research, its importance, and its implications. This research will continue a strong tradition and commitment to undergraduate research participation and training by this laboratory.