DISSERTATION RESEARCH: The Paradox of Flying Insects at High Altitude

环境梯度是生活在地球上不可避免的后果，海拔梯度是最极端的例子之一。例如，从内华达山脉的底部到达纳山的顶峰（3979米，约塞米蒂公园，CA）的距离只有60英里。然而，平均气温下降了大约24摄氏度——相当于穿越了3700多英里的纬度。气温的变化伴随着空气密度下降37%，资源、紫外线照射、湿度和捕食者的急剧变化。高海拔条件具有挑战性；在中等海拔高度以上，物种多样性急剧减少，这并不奇怪。飞虫在高海拔地区可能会受到特别的挑战，因为它们的飞行能力会受到低温和稀薄空气的影响。本研究探讨了海拔梯度对昆虫生理和进化的影响。为了实现这一目标，将从加利福尼亚州约塞米蒂公园的一系列海拔高度收集果蝇，以确定：1)温度和空气密度对发育、适应和飞行能力的直接和交互影响；2)“有益适应”和“局部适应”对该物种在广泛海拔范围内的成功的相对贡献；3)由于染色体倒位的存在，尽管存在广泛的基因流，但局部适应是否沿着海拔梯度进化维持。这项研究将有助于更好地了解空气密度和温度如何相互影响昆虫的运动和适应，并有可能促进开发更准确的模型来预测环境变化的影响。此外，这将有助于阐明自然选择与基因沿环境梯度流动之间的拮抗关系。

Environmental gradients are an inescapable consequence of living on earth, with altitudinal gradients being one of the most extreme examples. For instance, the distance from the base of the Sierra Nevada to the peak of Mount Dana (3,979 m, Yosemite Park, CA) is a mere 60 miles. Yet, the average temperature drops approximately 24 degree Celsius - the equivalent of traversing over 3,700 miles in latitude. These changes in air temperature are accompanied by a 37% decrease in air density and dramatic changes in resources, ultraviolet exposure, humidity, and predators. High altitude conditions are challenging; and not surprisingly, species diversity decreases precipitously above moderate altitudes. Flying insects may be particularly challenged at altitude because their ability to fly will be compromised by both cold temperatures and thin air. This research investigates how altitudinal gradients impact insect physiology and evolution. To accomplish this goal, the fruit fly, Drosophila pseudoobscura will be collected from a range of altitudes in Yosemite Park, CA to determine: 1) the direct and interactive effects of temperature and air density on development, fitness, and flight ability, 2) the relative contributions of "beneficial acclimation" and "localized adaptation" to this species' success across a wide range of altitudes, and 3) whether local adaptations are evolutionarily maintained along the altitudinal gradient despite extensive gene flow due to the presence of chromosomal inversions. This research will promote a better understanding of how air density and temperature interactively affect insect locomotion and fitness, potentially facilitating the development of more accurate models to predict the impacts of environmental change. In addition, it will help clarify the antagonistic relationship between natural selection and gene flow along environmental gradients.