Electronic Thesis and Dissertation Repository

Degree

Master of Science

Program

Biology

Supervisor

Dr. B.J. Sinclair

Abstract

To understand the potential effects of climate change on the sub-alpine willow leaf beetle, the cold tolerance strategy and mechanisms involved in cold tolerance were investigated for all life stages. Microhabitat choice and microclimate temperatures within each microhabitat were related to median lethal temperature for each life stage. Summer active and quiescent adults are freeze tolerant, eggs and pupae are freeze avoidant and all larval stages are chill susceptible. Quiescent adults accumulated the highest concentration of glycerol (~24 mM) and haemolymph osmolality (875 mOsm). Haemolymph from pupae had angular crystals suggestive of antifreeze agent activity, but this was absent in the haemolymph of other life stages. Quiescent adults must move to a thermally buffered microhabitat in the soil to survive the winter in the Sierra Nevada Mountains in California. Low temperatures beyond the limits of the cold tolerance of the willow leaf beetle occur often at the mid-willow, but the quiescent adults are protected from these cold exposures in the soil beneath the willow. Overall, the willow leaf beetle uses both behavioural avoidance strategies and physiological mechanisms to survive cold exposures in its habitat.


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