Collections > Electronic Theses and Dissertations > Adaptation to Climate and Climate Change in Rocky Mountain Butterflies: Morphology, Physiology, and Behavior
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Understanding the relative contributions of evolution, plasticity and behavior for local adaptation to climate, and for adaptive responses to recent climate change, is a major challenge for global change biologists. My dissertation explores these issues for Colias butterflies along an elevation gradient. Adults use thermoregulatory behaviors to achieve optimal body temperatures. Past studies show local adaptation in fixed morphological differences in ventral hind-wing melanin and thoracic setal length and a degree of developmental plasticity associated with melanin. My dissertation makes four major contributions. First, reciprocal-transplant and common-garden experiments documented differences in thermal sensitivity for flight initiation between high (C. meadii) and lower (C. eriphyle) elevation species. C. meadii initiated flight at lower body temperatures than C. eriphyle. This result was contrary to expectations that behavior will hinder evolution in fixed physiological differences along climatic gradients. Second, laboratory experiments showed that high-elevation adults had higher survival after heat-shock relative to lower-elevation. In contrast, there were no significant differences in upper thermal limits for eggs from different elevations suggesting the lack of movement did not lead to the evolution of fixed physiological differences in this life stage. Third, I used historic collections of a high-elevation C. meadii to quantify changes over the past 60 years. While mean temperatures during the adult flight have increased significantly, both hind-wing melanin and setal length have also increased. I suggest that this due in part to developmental plasticity; cooler pupal temperature was associated with increased melanin. I propose that this is non-adaptive because pupal temperatures are poor predictors of adult temperatures. Fourth, I quantified seasonal changes in wing melanin for two populations of C. eriphyle. Seasonal change in wing melanin was associated with increases in pupal temperature. In contrast to C. meadii, pupal temperatures were a good predictor of adult flight season temperature for C. eriphyle. Collectively, my results suggest that behavior does not reduce the importance of physiology and morphology in local adaptation to climate, and that potential for adaptive plasticity in high-elevation ectotherms may be strongly limited by variability and unpredictability in seasonal climate.