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，以及生活在脊椎动物体内的细菌群落是否可能影响新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历史和爬行动物宿主的进化历史。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是由宿主的生态（例如宿主吃什么，它们生活在哪里）或宿主的进化历史（例如它们如何与其他物种相关）构成的。 此外，该项目还将测试某些细菌群的存在是否有助于通过为宿主创造更大的机会来推动多样化/物种形成（例如帮助消化新食物，生活在新的地区）。数据将从跨越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，与多细胞生命相互作用已有近10亿年的历史。这将是第一项研究，以表征这样一个多样化的脊椎动物群体的肠道细菌群落，并提供了一个综合测试的进化脊椎动物宿主和细菌群落存在于其中。这项研究将包括来自密西西比和发展中国家巴西、埃塞俄比亚、圭亚那和墨西哥的志愿者和学生。密西西比的本科生和高中教师将获得关于识别当地两栖动物和爬行动物的实践研究经验和指导。埃塞俄比亚当地的童子军和本科生将获得宝贵的培训，这将促进他们的教育，并为他们提供有市场的技能，然后他们可以应用到他们的职业生涯作为实地生物学家。本研究旨在探讨脊椎动物内源微生物组（EM）如何影响多样化的过程，以及这些微生物群落在多大程度上影响宿主群落的组装。有鳞爬行动物（蛇，蜥蜴）提出了一个理想的系统，这样的研究，因为他们是很好的采样遗传，具有广泛的生态特征，并显示较少的分散和分裂比其他脊椎动物群体。使用高通量下一代测序，内源性细菌群落（EBC）的所有主要谱系的有鳞目除了外群爬行动物谱系的特点（α和β多样性），以获得基本信息的EM爬行动物。主要预测包括：（i）EBC在有鳞目中是遗传上保守的，（ii）只有具有适当EBC的谱系才能够利用某些生态位，（iii）某些EBC促进宿主的加速物种形成速率，（iv）EBC是可用于表征宿主生态的生态特征，并通过限制可利用的生态位空间直接影响宿主组装过程。

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.