SG: Collaborative Research: The evolution of extreme phenotypic convergence across fish lineages in the hyper-diverse lower Congo River

刚果河下游是地球上最极端的淡水栖息地之一，拥有地球上最大的激流急流和最深的水下峡谷。这些急流，漩涡和峡谷是一系列非凡的鱼类的家园，其中许多鱼的外观引人注目，并表现出许多适应湍流，高能量沃茨生活的能力。在这种极端的栖息地，进化有时会产生独立衍生但非常相似的特征。例如，在下刚果的许多远亲鱼已经独立地失去了身体颜色，眼睛减少或缺失，并且具有相似的细长身体形状和改变的感觉特征。这些不寻常的特征是如何以及何时进化的？这些引人注目的趋同（当相似的性状独立进化时）的例子强烈表明了一个共同的选择签名，可能是对河流本身非凡的水文条件的回应。该研究项目将研究下刚果鱼类区系趋同的系统发育和形态学基础，以解决有关促进极端环境适应和多样化机制的基本问题。这些分析将为了解不同鱼类谱系中肢体是如何减少或丢失的提供新的见解，然后可以更广泛地应用于其他脊椎动物。 来自少数民族服务，主要是本科院校的美国本科生将接受热带实地研究，分子系统学和非洲生物多样性的广泛培训。研究结果将纳入研究生和本科生课程，研究结果将通过科学探索视频和项目网站更广泛地传播。 其他数据将存放在在线、开放获取的储存库中。本研究调查了一个新发现的系统复杂的原位表型收敛的成员之间的遗传多样性鱼类谱系。两个主要的数据集将被生成和整合：1）基于超保守元件的系统发育框架，以确定分支内分歧的拓扑结构和时间框架;以及2）利用一系列量化和可视化技术，包括三维计算机断层扫描（3DCT）重建、组织学、扫描电子显微镜（SEM），和多变量形态测量方法。使用这些数据集，该研究将调查这些表型出现的速度，分支内和分支之间收敛的形态学对应，以及多个性状是否协同进化。通过对这一无与伦比的自然实验进行深入的、基础性的系统发育、解剖学和形态测量学分析，该研究可能会改变对趋同表型在深系统发育时间内反复进化的各种机制的理解。这项研究也将产生一个广泛有用的资源，为未来的比较研究与类似的收敛系统（如Astyanax洞穴鱼类），并将建立基础，确定这些表型的基因组基础。

The lower Congo River is one of the most extreme freshwater habitats on Earth, with some of the planet's largest whitewater rapids and deepest underwater canyons. These rapids, eddies and canyons are home to an extraordinary array of fishes, many of which are striking in appearance and exhibit numerous adaptations to life in turbulent, high-energy waters. In such extreme habitats, evolution sometimes produces independently derived yet remarkably similar traits. For example, many distantly related fishes in the lower Congo have independently lost body coloration, have reduced or absent eyes, and share similar elongate body shapes and modified sensory features. How and when did these unusual features evolve? These striking examples of convergence (when similar traits evolve independently) strongly suggest a shared signature of selection, likely in response to the extraordinary hydrology of the river itself. This research project will examine the phylogenetic and morphological basis of convergence in the lower Congo fish fauna to address fundamental questions about the mechanisms that promote adaptation and diversification in extreme environments. These analyses will provide new insights into how limbs are reduced or lost in diverse fish lineages that can then be applied more broadly to other vertebrates. U.S. undergraduate students from a minority-serving, principally undergraduate institution will receive broad training in tropical field studies, molecular systematics, and African biodiversity more generally. Findings from the study will be incorporated within both graduate and undergraduate courses, and results will be disseminated more broadly by a Science Explorations video and project website. Other data will be deposited in online, open-access repositories. This study investigates a newly discovered system of complex in situ phenotypic convergence among members of phylogenetically diverse fish lineages. Two major datasets will be generated and integrated: 1) a phylogenetic framework based on ultra-conserved elements to determine the topology and temporal framework of within-clade divergences; and 2) a detailed morphological characterization of within-group convergence utilizing a range of quantification and visualization techniques, including 3-dimensional computed tomography (3D CT) reconstruction, histology, scanning electron microscopy (SEM), and multivariate morphometric approaches. Using these datasets, the study will investigate how rapidly these phenotypes arose, morphological correspondence of convergence within and between clades, and whether multiple traits evolved in concert. By conducting in-depth, foundational phylogenetic, anatomical, and morphometric analyses of this unparalleled natural experiment, the study will potentially transform understanding of the variety of mechanisms by which convergent phenotypes have repeatedly evolved across deep phylogenetic time. This research will also generate a broadly useful resource for future comparative studies with similar convergent systems (e.g. Astyanax cavefishes) and will establish the foundation for determining the genomic basis of these phenotypes.