Sierra willow leaf beetle overwintering genomics

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.