SG/RUI: 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，拥有地球上一些最大的激流急流和最深的水下峡谷。这些急流、漩涡和峡谷是各种非同寻常的鱼类的家园，其中许多鱼类的外表引人注目，并展示了许多适应动荡、高能量水域生活的能力。在这种极端的栖息地中，进化有时会产生独立衍生但非常相似的特征。例如，刚果下游的许多远亲鱼类已经独立地失去了身体颜色，眼睛减少或消失，有着相似的细长身体形状和改良的感官特征。这些不同寻常的特征是如何以及何时演变的？这些惊人的汇聚例子(当相似的特征独立进化时)强烈地表明了共同的选择签名，可能是对河流本身非凡的水文的回应。这项研究项目将研究刚果下部鱼类动物群汇聚的系统发育和形态基础，以解决有关促进极端环境中适应和多样化的机制的基本问题。这些分析将为肢体如何在不同的鱼类谱系中减少或丧失提供新的见解，然后可以更广泛地应用于其他脊椎动物。来自少数族裔服务机构的美国本科生将接受热带实地研究、分子分类学和更广泛的非洲生物多样性方面的广泛培训。这项研究的结果将纳入研究生和本科课程，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。这项研究调查了新发现的一个复杂的、原位的和表型趋同的系统，这些系统发生在系统发育不同的鱼类谱系的成员之间。将生成并整合两个主要数据集：1)基于超保守元素的系统发育框架，以确定支系内分歧的拓扑和时间框架；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(3D CT)重建、组织学、扫描电子显微镜(SEM)和多变量形态计量学方法，详细描述组内趋同的形态特征。使用这些数据集，这项研究将调查这些表型出现的速度，分支内部和分支之间趋同的形态对应，以及多种性状是否一致进化。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、解剖学和形态计量学分析，这项研究可能会改变对收敛表型在深层系统发生时间内反复进化的各种机制的理解。这项研究还将产生一个广泛有用的资源，用于今后与类似汇聚系统的比较研究(例如，海豚)，并将为确定这些表型的基因组基础奠定基础。

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.