Evolution of Photoperiodic Time Measurement in the Pitcher- Plant Mosquito

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9513834 Bradshaw Many organisms use the length of day to regulate their seasonal development. The pitcher-plant mosquito enters dormancy under the influence of short (Winter) daylengths and terminates or avoids dormancy under the influence of long (Summer) daylengths. This mosquito is a formerly tropical mosquito that has adapted to the climatic gradient of North America by altering its pattern of dormancy and development. In the north, or at high elevation, Winter arrives earlier and Spring arrives later than at lower latitudes or altitudes. Concomitantly, northern or alpine populations of the mosquito enter and remain in dormancy under the influence of longer days than mosquitoes for southern or lowland populations. Invasion of temperate latitudes by tropical mosquitoes requires not only the ability to withstand the harsher winter but also the ability to modify their seasonal development to coincide with progressively shorter northern growing seasons. Thus, disease-carrying mosquitoes, such as the Asian tiger mosquito, that are in the process of invading North America, must both increase their tolerance of cold and modify their seasonal program. The pitcher-plant mosquito provides established populations that have already adapted to the climate of North America from Florida to Canada. In this research, we ask how the mosquito's internal biological clock and genetic organization of that clock have enabled them to adapt to more northern and alpine seasons. Unlike many mosquitoes, the pitcher-plant mosquito does not require blood for reproduction. This trait, makes it an ideal model system for investigating how a formerly tropical mosquito has adapted to more temperate climates while not requiring the use of animal hosts for a blood source. Furthermore, this study will provide information that will increase our understanding of the evolution of photoperiodic time measurement - a process critical to a great many number of organisms.