Dissertation Research: Endogenic Microbial Community Structure and its Influence on Community Assembly and Speciation in Squamate Reptiles

该项目的目标是了解物种群落的结构，以及脊椎动物体内的细菌群落是否可能影响新的脊椎动物物种的进化。该项目采用了一种新的方法来研究这些问题，方法是探索爬行动物肠道中发现的细菌的进化史和爬行动物宿主的进化史。通过利用新技术，该项目将揭示生活在脊椎动物体内的细菌群落在多大程度上由宿主的生态(例如宿主吃什么，它们生活在哪里)或宿主的进化史(例如它们与其他物种的关系)构成。此外，该项目将测试某些细菌群的存在是否通过为宿主创造更大的机会(例如，帮助消化新食物、生活在新地区)来帮助推动多样化/物种形成。数据将从横跨五个国家和三大洲的各种爬行动物中收集。细菌是最古老的生命形式之一，近10亿年来一直与多细胞生命相互作用。这将是第一次对如此多样化的脊椎动物群体的肠道细菌群落进行表征的研究，并对脊椎动物宿主及其内部存在的细菌群落的进化进行综合测试。这项研究将包括来自密西西比州以及巴西、埃塞俄比亚、圭亚那和墨西哥等发展中国家的志愿者和学生。密西西比州的本科生和高中教师将获得识别当地两栖动物和爬行动物的实践研究经验和指导。埃塞俄比亚的当地童子军和本科生将获得宝贵的培训，这些培训将促进他们的教育，并为他们提供可销售的技能，然后他们可以将其应用于田间生物学家的职业生涯。本研究旨在探讨脊椎动物内源微生物群(EM)如何影响多样性的过程，以及这些微生物群落在多大程度上影响宿主群落的组装。鳞状爬行动物(蛇、蜥蜴)是进行此类研究的理想系统，因为它们具有良好的系统发育样本，具有广泛的生态特征，与其他脊椎动物相比，分散和碎片化程度较低。利用高通量下一代测序技术，除爬行动物外群外，所有鳞目主要谱系的内源性细菌群落(EBCs)将被表征(α和β多样性)，以获得爬行动物EM的基本信息。主要预测包括：(I)EBCs在鳞片体内是系统发育保守的，(Ii)只有拥有适当EBC的谱系才能利用某些生态位，(Iii)某些EBCs促进宿主物种形成的速度，(Iv)EBCs是可用于描述宿主生态特征的生态特征，并通过限制可开发的生态位空间直接影响宿主的组装过程。

The goal of the project is to understand how communities of species are structured and whether bacterial communities living inside vertebrates might influence how new vertebrate species evolve. The project employs a novel approach to investigating these questions by exploring the evolutionary histories of both the bacteria found in the gut of reptiles and the evolutionary history of the reptile hosts. By utilizing novel technologies the project will reveal the extent to which bacterial communities living inside vertebrates are structured by the ecology of the host (e.g. what the host eats, where they live) or the evolutionary histories of the host (e.g. how they are related to other species). Additionally, this project will test whether the presence of certain bacterial groups helps drive diversification/speciation by creating greater opportunity for the host (e.g. help with digesting new foods, live in new areas). Data will be collected from a wide range of reptiles spanning five countries and three continents. Bacteria are some of the oldest forms of life and have interacted with multicellular life for nearly a billion years. This will be the first study to characterize the gut bacterial communities of such a diverse vertebrate group, and provide a synthetic test of evolution in vertebrate hosts and the bacterial communities existing inside them. The study will incorporate volunteers and students from Mississippi and the developing nations of Brazil, Ethiopia, Guyana and Mexico. Undergraduate students and high school teachers in Mississippi will get hands-on research experience and instruction on identifying local amphibians and reptiles. Local scouts and undergraduates in Ethiopia will gain valuable training that will advance their education and provide them with marketable skills they can then apply to their careers as field biologists. This study aims to explore how the vertebrate endogenic microbiome (EM) influences the process of diversification and to what extent these microbial communities affect assembly of host communities. Squamate reptiles (snakes, lizards) present an ideal system for such study as they are well sampled phylogenetically, possess a wide range of ecological traits, and show less dispersal and fragmentation than other vertebrate groups. Using high-throughput next generation sequencing, endogenic bacterial communities (EBCs) for all major lineages of Squamata in addition to outgroup reptilian lineages will be characterized (alpha and beta diversity) to obtain fundamental information on the EM of Reptilia. Key predictions include: (i) EBCs are phylogenetically conserved within Squamata, (ii) only lineages that possess the appropriate EBC will be able to exploit certain niches, (iii) certain EBCs facilitate accelerated speciation rates of the host, (iv) EBCs are ecological traits that can be used to characterize host ecology and directly influence the host assembly process by limiting exploitable niche space.