DISSERTATION RESEARCH: Morphological Diversification of Anostomimorph and Curimatimorph Fishes

非技术性摘要：论文研究：动口型和弧型鱼类的形态多样化。为什么生物多样性在生命树上分布不均？一些物种进化出了非同寻常的解剖变异，而另一些物种则包含了许多外表和行为相似的物种。为了开始理解不平等多样化的普遍现象是如何以及为什么会发生的，这项研究将调查与食人鱼和金枪鱼相关的南美鱼类的特定谱系如何以及为什么进化出比其近亲谱系的解剖多样性大得多的解剖多样性。这个案例研究是罕见和有价值的，因为它接近于一个自然对照实验。由于这两类鱼包含相同数量的物种，共享一个共同的祖先(因此同时开始独立进化)，并生活在整个热带南美洲，因此它们多样性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。除去这些因素，对观察到的多样性差异至少有两种可能的解释。这些差异可能是由于随机进化，或者只有更多样化的群体共享的解剖学或生态学的内在特征可能会促进新形态的进化。这项研究计划将通过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)从广泛的一系列X射线图像测量这些物种之间的解剖差异，以及3)执行一项新的分析，将解剖差异和生命树的测量与进化的计算机模拟相结合，来研究这两种选择。这项分析将测试与观察到的差异一样的多样性是否可能是随机进化的。如果分析否定了随机进化的假设，那么很可能是内在的差异驱使一组人大量多样化，而另一组人则没有。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的新奇事物进化的解剖和生态特征。未来的研究可以测试其他生物群体中类似属性的进化是否通常会促进生物多样性的产生和维持。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上不是平均分布的。为该项目开发的方法可转移到对各种其他生物的研究中，并将通过互联网免费提供。该项目还将促进国际合作，研究南美洲一组重要的热带鱼类，作为世界上物种最丰富的淡水鱼动物群的一部分，这些热带鱼类在全世界因其观赏美景而受到珍视，并发挥着重要的生态作用。目前和潜在的合作包括发现和描述新物种的工作，在美国和南美洲建立自然历史收藏，以及保护生物学。这项工作的结果还通过一系列展览和公开展示，推动了与学生和博物馆参观者关于生物多样性的持续对话。

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.