Facultative Endothermy in Pythons: Insight into the Evolution of Endothermy

蟒蛇的兼性恒温动物：对恒温动物进化的洞察戴尔·德纳尔亚利桑那州立大学恒温动物提供了很大的自由，使其免受变幻莫测的环境的影响，但同时也付出了相当大的能量代价。尽管各种模型（包括体温调节模型、有氧能力模型和生殖模型）都“解释”了有效恒温动物的优势，但很少有实证研究进行。此外，提供有限吸热能力选择优势的初始驱动力不仅未经检验，而且很少被提出的模型解释。繁殖模式的独特之处在于为吸热能力的逐步发展提供了选择优势。虽然在这方面是新颖的，但生殖模式也仍未经检验。这并不奇怪，对恒温动物进化模型的实证测试是罕见的，因为很少有现存的生物体提供机会来评估有限恒温动物的选择优势。然而，这个项目将利用蟒蛇独特的产卵特征，所有物种都产卵，但只有一些物种进化出有限的兼性恒温动物。这项研究将采用一系列实验。首先，将对蟒蛇的吸热能力进行比较评估，以评估不同物种特征（如系统发育关系、体型、气候）对吸热能力的影响。其次，研究人员将构建人工变吸热蛇模型，以验证吸热能力的逐步增加导致胚胎热环境的逐步控制的假设。最后，卵将在不同的热环境中孵育，以评估胚胎环境的热调节对后代质量的影响。综上所述，这些实验将为恒温动物进化的生殖模式提供难得的经验检验。除了其强大的科学价值外，该项目还具有更广泛的影响，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。这个项目的本质将向学生强调使用生理学方法对进化模型进行实证检验的重要性。此外，这项研究的广泛影响将通过媒体报道、纪录片和在实验室网站上创建公共宣传组件，从学术界扩展到公众。

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.