Locomotor Ontogeny in Microcebus Murinus, Petaurus Breviceps and Monodelphis Domestica: The Influence of Very Small Body Size on the Evolution of Primate Quadrupedal Locomotion

这项研究通过考察非常小的体型对灵长类运动适应进化的影响，为灵长类起源的研究带来了新的视角。现存的灵长类动物表现出各种各样的专门运动行为，但大多数都包括四足动物在他们的运动剧目。 灵长类动物使用的四足行走形式在哺乳动物中是不寻常的，并且被认为是最早的灵长类动物从其哺乳动物祖先中分化出来时的进化创新。目前的共识认为，灵长类动物的四足特征是一种生物力学复合体，通过在小而不稳定的树枝上提供平衡机制，使早期灵长类动物能够独家获得树木“细分支生态位”中可用的资源。在灵长类动物四足动物进化研究中经常被忽视的一个重要问题是身体大小与基底的相互作用（例如，分支）大小。 显然，不能假设小型和大型灵长类动物的“细分支生态位”所带来的运动挑战是相同的。如果不考虑身体大小相对于基底大小的关系，我们就无法理解灵长类动物四足行走的进化。 最近关于灵长类祖先体型的争论包括认为灵长类祖先可能比现存最小的灵长类（鼠狐猴）小得多，可能只有10- 15克，但很少有研究考虑到100克或更小的体型对灵长类四足动物的影响。本研究将以灵长类动物的运动发育为手段，探讨微小体型对灵长类动物运动进化的影响。 四足运动的各种基板将比较之间和婴儿和成年鼠狐猴（Microcebus murinus）结合在两个小身体的有袋动物，树栖糖滑翔机（Petaurus breviceps），和陆地灰色短尾负鼠（Monodelphis arctica）的运动发育的研究。 姿势稳定的婴儿将被用于测试关于减小的体型和基质类型对四足运动的影响的假设。 此外，从最年轻的婴儿期到成年期的形态和运动的发育过渡将被用来测试关于身体形状对四足动物的生物力学影响的假设。非常小的身体尺寸对灵长类四足动物的影响，以及在“细分支生态位”的背景下，在灵长类动物或有袋动物中仍然很大程度上未被探索。 这项研究将是第一个联合收割机的发展分析，从非常小的身体尺寸的角度检查灵长类动物四足运动，第一个解决运动发展的Microcebus，Petaurus，Monodelphis从生态和进化的角度。这项研究将加强UT奥斯汀的本科教育，因为糖滑翔机和鼠狐猴将被安置在一个观察室里，供学生收集人类学和生物学课程的行为数据。将加强对博士后助理和参与该项目的学生的研究培训。 结果将被纳入一个教育电子实验室模块，原始数据将提供给其他研究人员。 德州大学奥斯汀分校、西南国家灵长类动物研究中心和杜克大学之间的合作将得到加强。

This study brings a new perspective to the study of primate origins by examining the influence of very small body size on the evolution of primate locomotor adaptations. Living primates exhibit a diverse array of specialized locomotor behaviors, but most include quadrupedalism in their locomotor repertoire. The form of quadrupedal walking used by primates is unusual among mammals, and is thought to have arisen as an evolutionary innovation when the earliest primates diverged from their mammalian ancestor. Current consensus states that primate quadrupedal features are a biomechanical complex that gave early primates exclusive access to resources available in an arboreal "fine branch niche," by providing mechanisms for balance on small and unstable branches. One important issue often overlooked in research on the evolution of primate quadrupedalism is the interaction of body size with substrate (e.g., branch) size. Clearly, the locomotor challenges presented by the "fine branch niche" cannot be assumed to be the same for small and large primates. We cannot understand the evolution of primate quadrupedal locomotion without considering body size relative to substrate size. Recent debate on primate ancestral size includes the view that ancestral primates may have been much smaller than the smallest living primates (mouse lemurs), perhaps as small as 10-15g, yet few studies have considered the effects of body sizes of 100g or less on primate quadrupedalism. This study will use locomotor growth and development as a means to investigate the influence of very small body size on primate locomotor evolution. Quadrupedal movement on a variety of substrates will be compared between and within infant and adult mouse lemurs (Microcebus murinus) in conjunction with a study of locomotor development in two small-bodied marsupials, the arboreal sugar glider (Petaurus breviceps) , and the terrestrial gray short-tailed opossum (Monodelphis domestica). Posturally stable infants will be used to test hypotheses regarding the effects of reduced body size and substrate type on quadrupedal movement. In addition, developmental transitions in morphology and locomotion from youngest infancy to adulthood will be used to test hypotheses about the biomechanical effects of body shape on quadrupedalism. The influence of very small body size on primate quadrupedalism and in the context of the "fine branch niche" remains largely unexplored in either primates or marsupials. This study will be the first to combine developmental analysis with an examination of primate quadrupedal locomotion from the perspective of very small body size, and the first to address locomotor development in Microcebus, Petaurus, and Monodelphis from an ecological and evolutionary perspective. This study will enhance undergraduate education at UT Austin, as the sugar gliders and mouse lemurs will be housed in an observation room utilized by students collecting behavioral data for anthropology and biology courses. Research training will be enhanced for a postdoctoral associate and students participating in the project. Results will be incorporated into an educational electronic lab module, and raw data will be made available to other researchers. Collaboration between UT Austin, Southwest National Primate Research Center, and Duke University will be strengthened.