Dissertation Research: The Evolutionary Significance of Environmental Sex Determination

本研究旨在确定影响爬行动物温度依赖性性别决定（TSD）适应性的因素，并评估环境条件对TSD爬行动物自然种群的影响。本文将研究孵化温度对两种龟（普通鳄龟，Chelydra serpentina和多刺软壳龟，Trionyx spiniferus）幼龟生长和行为的影响。这些性状中的一种或两种与孵育温度和后代性别的相关性将为TSD的适应性意义提供第一个具体证据。目前的气候温度对彩龟（Chrysemys picta）孵化性别比的影响也将被测量。该项目将提供关于当地夏季气温的典型波动如何影响TSD自然种群结构的急需基线信息。此外，为了研究预测的全球变暖对TSD物种的影响，将研究遗传变异对性别比例对孵化温度的响应。如果没有这种遗传变异，如果当地气温变化足够迅速，导致性别比严重偏斜，患有TSD的物种可能会灭绝。综合这些研究结果将有助于阐明创伤后应激障碍的进化意义。

The proposed research is designed to identify factors that account for the adaptive significance of temperature-dependent sex determination (TSD) in reptiles and to assess the impact of environmental conditions on natural populations of reptiles with TSD. The influence of incubation temperature on growth and behavior of juveniles of two species of turtles (common snapping turtles, Chelydra serpentina and spiny softshell turtles, Trionyx spiniferus) will be examined. Correlation of one or both of these traits with incubation temperature and offspring sex would provide the first concrete evidence for the adaptive significance of TSD. The effects of current climatic temperatures on hatchling sex ratios of painted turtles (Chrysemys picta) also will be measured. This project will provide much-needed baseline information on how typical fluctuations in local summer temperatures influence the structure of natural populations with TSD. Additionally, to investigate implications of the predicted global warming on species with TSD, genetic variation, in response of sex ratios to incubation temperature will be examined. Without such genetic variation, species with TSD may be susceptible to extinction if local temperatures change sufficiently and rapidly to greatly skew the sex ratio. The synthesis of the results of these studies will elucidate the evolutionary significance of TSD.