DISSERTATION RESEARCH: Morphological Diversification of Anostomimorph and Curimatimorph Fishes

非技术摘要：论文研究：无口型和奇口型鱼类的形态多样性：为什么生物多样性在生命之树中分布不均匀？ 一些物种群体进化出了非凡的解剖变异，而其他群体包含许多外观和行为相似的物种。为了开始了解不平等多样化的一般现象是如何以及为什么会发生的，本研究将调查如何以及为什么与食人鱼和河豚有关的南美鱼类的特定谱系进化出比其近亲谱系更大的解剖学多样性。这个案例研究是罕见和有价值的，因为它近似于一个自然控制实验。由于这两组鱼类包含相同数量的物种，共享一个最近的共同祖先（因此同时开始独立进化），并在整个热带南美洲生活在一起，它们的差异不能用净物种形成率，年龄或环境影响的差异来解释。 去除这些因素后，至少有两种可能解释所观察到的多样性差异。这些差异可能是由于随机进化，或者只有更多样化的群体才共享的解剖学或生态学的内在特征可能促进新形态的进化。 该研究计划将通过以下方式调查这两种选择：1）使用详细的解剖学研究来重建这些鱼类的系谱关系或“生命树”，2）从一系列广泛的X射线图像中测量这些物种之间的解剖差异，3）进行一种新的分析，将解剖差异和生命树的测量与计算机模拟进化相结合。这项分析将检验，像观察到的那样不同的差异是否可能是随机进化的。 如果分析拒绝随机进化的假设，那么很可能是内在的差异驱使一个群体极大地多样化，而另一个群体则没有。 如果第二种选择得到支持，该项目将确定最有可能催化更多样化群体中新事物进化的解剖学和生态学特征。未来的研究可以测试其他生物群体中相似特性的进化是否普遍促进了生物多样性的发生和维持。从广义上讲，这项研究将有助于揭示为什么生物多样性在所有生物的生命树中不是均匀分布的。为该项目开发的方法可用于研究各种其他生物，并将通过互联网免费提供。该项目还将促进国际合作，研究一组重要的热带鱼，这些热带鱼在整个南美洲都是有价值的食物，因其观赏之美而在世界各地受到珍视，作为世界上物种最丰富的淡水鱼类区系的一部分，它们发挥着重要的生态作用。 目前和潜在的合作包括新物种的发现和描述，在美国和南美洲建立自然历史收藏，以及保护生物学。这项工作的成果还通过一系列展览和公开介绍，推动了与学生和博物馆参观者就生物多样性进行持续对话。

Non-technical abstract: Dissertation Research: Morphological diversification of anostomimorph and curimatimorph fishes.Why is biodiversity distributed unequally across the tree-of-life? Some groups of species have evolved extraordinary anatomical variation while other groups contain many species that look and act similar. To begin to understand how and why the general phenomenon of unequal diversification occurs, this research will investigate how and why a specific lineage of South American fishes related to piranhas and tetras evolved an anatomical diversity very much greater than that of the lineage of its closest relatives. This case study is rare and valuable because it approximates a naturally controlled experiment. Because the two groups of fishes contain equal numbers of species, share a recent common ancestor (and therefore began to evolve independently at the same time) and live together throughout tropical South America, the differences in their diversities cannot be explained by differences in net speciation rate, age, or environmental effects. The removal of these factors leaves at least two potential explanations of the observed differences in diversity. The differences may be due to random evolution, or an intrinsic feature of anatomy or ecology shared only by the more diverse group may promote the evolution of new morphologies. This research program will investigate these two alternatives by 1) using a detailed anatomical study to reconstruct the genealogical relationships, or "trees-of-life" for these fishes, 2) measuring the anatomical differences between these species from an extensive series of x-ray images and 3) performing a novel analysis that combines the measurements of anatomical differences and trees-of-life with computer simulations of evolution. This analysis will test whether diversities as different as those observed could have evolved randomly. If the analysis were to reject the hypothesis of random evolution, then it would be likely that an intrinsic difference drove one group to diversify greatly while the other did not. If the second alternative is supported, this project will identify the anatomical and ecological features most likely to have catalyzed the evolution of novelties in the more diverse group. Future studies can then test whether the evolution of similar properties in other groups of organisms generally promotes the genesis and maintenance of biodiversity.In a broad sense, this study will help reveal why biodiversity is not distributed equally across the tree-of-life for all organisms. The methods developed for use in this project are transferable to studies of a wide variety of other organisms and will be made freely available via the Internet. This project will also promote international collaboration on the study of an important group of tropical fishes valued as food throughout South America, prized for their ornamental beauty worldwide and that serve important ecological roles as part of the most species-rich freshwater fish fauna in the world. Current and potential collaborations include work on the discovery and description of new species, the building of natural history collections in the United States and in South America, and conservation biology. Results from this work also fuel a continuing dialogue about biodiversity with students and museum visitors through a series of exhibits and public presentations.