In the Sierra Nevada mountain ranges, like many high altitude environments, snow cover is extremely variable from year to year. Many high altitude animals survive through winter underneath snow that buffers them from extremes of temperature. Many unique and ecologically important animals live in mountainous environments, making it vital to understand and predict impacts of annual differences in snow cover on their population abundances, but as yet we have limited understanding of how snow impacts survival and reproduction of insects and other animals. This project proposes to study physiological and genetic responses to variation in snow cover in a high altitude beetle in the laboratory and the natural environment to understand how snow alters reproductive success during the winter and subsequent summer. This work will develop a partnership between UC-Berkeley and two Primarily Undergraduate Institutions. Undergraduates at the Primarily Undergraduate Institutions will work with researchers from Berkeley, and Berkeley PhD students will supervise undergraduates from a wide variety of backgrounds and experiences. Thus both groups of students will be exposed to the culture of different educational institutions and will have access to professional contacts outside their usual network. A curriculum module developed from the project for K-12 students will be used to contribute towards their understanding of challenges that organisms face in snowy climates, and this module will be distributed to K-12 teachers through a UC Berkeley-based website.
For high altitude animals, summer is a time of energy gain, while energy conservation is key during winter because resources are scarce and animals rely on energy stores. To resist winter cold, high altitude insects use energy stores to synthesize metabolically expensive cryoprotectants. This may generate a trade-off between cold hardiness and energy conservation. Snow buffers thermal fluctuations, decreasing cold mortality and need for cold hardiness. However, since temperatures are greater beneath snow than in a snow-free, exposed habitat, there may be increased overall energy demand associated with living under snow. Due to the energetic trade-off, inter-annual fluctuations in winter snowpack and air temperature will alter selective pressures on overwintering organisms, and may significantly affect growth and reproduction in summer. The central hypothesis is that variation in snow cover alters selective pressures on cold hardiness and energy conservation, influencing physiological performance of overwintering individuals and genetic composition of survivors. The investigators further hypothesize that cold hardiness trades off against future reproduction by depleting winter energy reserves due to energetic costs of cold hardiness. The research will: 1) Measure how variation in snow alters selective gradients on winter-relevant genetic variation in a high altitude beetle, and isolate causal drivers of winter selective gradients. 2) Gain a predictive and quantitative understanding of how cold and energy stressors interact to shape physiological performance during winter and the subsequent summer. 3) Uncover mechanisms underlying interactions between cold and energy stress by asking how single or combined stressors alter reaction norms for energy reserves and cryoprotectants.
