Facultative Endothermy in Pythons: Insight into the Evolution of Endothermy

蟒蛇的兼性吸热：洞察吸热的进化Dale DeNardo亚利桑那州立大学吸热提供了远离变幻莫测的环境的实质自由，但也付出了相当大的能量成本。虽然包括体温调节模型、有氧能力模型和生殖模型在内的各种模型都“解释”了有效吸热的优势，但很少有实证研究。此外，提供有限吸热能力的选择优势的初始驱动力不仅没有得到检验，而且很少被所提出的模型解释。生殖模型在为吸热能力的逐步发展提供选择性优势方面是独一无二的。虽然在这方面是新奇的，但生殖模式也仍未得到检验。对吸热进化模型的经验测试很少，这并不令人惊讶，因为很少有现存的生物提供机会来评估有限吸热的选择优势。然而，这个项目将利用蟒蛇独特的产卵特性，所有物种都会孵化它们的卵，但只有一些物种进化出了有限的兼性吸温。这项研究将采用实验相结合的方法。首先，将对蟒蛇的吸热能力进行比较评估，以评估各种物种特征(例如，系统发育关系、身体大小、气候)对吸热能力的影响。其次，研究人员将构建人工可变吸热蛇模型，以检验吸热能力逐步增加导致胚胎热环境逐步控制的假设。最后，卵子将在不同的温度环境中孵化，以评估胚胎环境的温度调节对后代质量的影响。总而言之，这些实验将为吸热进化的生殖模型提供一个难得的经验检验。除了它强大的科学价值之外，这个项目还有更广泛的影响，因为它将提供一个特殊的教育机会，需要研究生和本科生研究人员的直接参与。这个项目的性质将向学生强调使用生理学方法对进化模型进行经验性测试的重要性。此外，这项研究的更广泛影响将通过媒体报道、纪录片和创建实验室网站的公共宣传部分，从学术界延伸到普通公众。

Facultative endothermy in pythons: insight into the evolution of endothermyDale DeNardoArizona State UniversityEndothermy provides substantial freedom from the vagaries of the environment, but comes at considerable energetic costs. While the advantages of effective endothermy have been "explained" by various models, including the thermoregulatory model, the aerobic capacity model, and the reproductive model, very few empirical studies have been conducted. Furthermore, the initial driving forces that provided selective advantages of limited endothermic ability are not only untested but also are rarely explained by the proposed models. The reproductive model is unique in providing selective advantages to a stepwise progression in endothermic ability. While novel in this respect, the reproductive model also remains untested. It is not surprising that empirical tests of the models for the evolution of endothermy are rare since few extant organisms provide an opportunity to assess the selective advantages of limited endothermy. However, this project will capitalize on the unique egg brooding characteristics of pythons, where all species brood their eggs, but only some species have evolved limited facultative endothermy. This study will use a combination of experiments. First, a comparative assessment of endothermic capability among pythons will be conducted in order to evaluate the effect that various species traits (e.g., phylogenetic relationships, body size, climate) have on endothermic capability. Second, the investigators will construct artificial variably-endothermic snake models to test the hypothesis that stepwise increments in endothermic capability lead to stepwise control of the embryonic thermal environment. Lastly, eggs will be incubated at various thermal environments to assess the impact that thermal regulation of the embryonic environment has on offspring quality. Combined, these experiments will provide a rare empirical test of the reproductive model for the evolution of endothermy.Beyond its strong scientific merit, this project has a broader impact in that it will provide an exceptional educational opportunity in requiring the direct participation of both graduate and undergraduate researchers. The nature of this project will emphasize to students the importance of using physiological approaches to empirically test evolutionary models. Additionally, the broader impact of this study will extend beyond academia into the general public through media coverage, documentaries, and the creation of a public outreach component to the laboratory's web site.