Evolutionary Radiations in Paleozoic and Mesozoic Crinoids

9506568这项研究将(1)使用明确的骨骼解剖学数据来记录古生代和中生代甲壳动物的进化辐射，以及(2)通过比较甲壳动物作为一个整体的辐射与甲壳动物组成亚群的辐射来检验不同分类尺度上进化辐射之间的拟议差异。进化辐射，包括命名类群数量和形态多样性的大幅增加，是化石记录的最显著特征之一。人们普遍认为，不同分类、时间和空间尺度上的进化辐射在时间模式或潜在机制上没有显著差异。这一观点几乎没有被直接检验过。有一些迹象表明，较高分类群(支系)和嵌套在其中的较低分类群(亚支)的进化辐射之间可能存在重大差异，即亚支内的形态多样化在时间上比它们所属的较大支系的多样化更渐进。然而，这些建议是基于不太适合测试这一想法的案例研究。通过比较一个主要的无脊椎动物总科的古生代辐射，与与更大的海龙科分支同时多样化的次生海龙科枝叶的辐射，我将测试分类等级之间是否存在这样的不一致。中生代有关节的海百合的辐射将提供额外的比较。这些结果将有助于回答有关进化的层级性质以及我们从较小规模的模式预测较大规模进化模式的能力的问题。在进化辐射过程中，形态多样性或差异的变化通常是通过使用更高级分类群(主要是纲和目)的数量等指标来评估的。有许多理由质疑这些代理的充分性。这项拟议的研究将使用形态的直接量化来研究海百合的进化辐射。我将使用离散的形态特征来量化眼镜蛇的形态，并将基于物种之间的净差异来衡量形态差异。我将应用一些定量的方法，包括“分支形状”统计，来探索各种进化模型的形态预期的时间模式。这项拟议的研究将回答有关长时间进化过程中形态多样性产生的问题，并将开发一个形态数据库，供其他工作人员用来研究广泛的问题，包括系统发育关系、进化率和趋势。

Foote 9506568 This research will (1) use explicit data on skeletal anatomy to document evolutionary radiations in Paleozoic and Mesozoic crinoids, and (2) test for a proposed difference between evolutionary radiations at different taxonomic scales by comparing the radiation of crinoids as a whole to the radiations of the constituent subgroups of crinoids. Evolutionary radiations, involving substantial increases in the number of named taxa and in morphological diversity, are among the most prominent features of the fossil record. It is commonly thought that evolutionary radiations at different taxonomic, temporal, and spatial scales do not differ significantly in temporal patterns or underlying mechanisms. This perspective has scarcely been tested directly. There are some hints that there may be a major difference between the evolutionary radiations of higher taxa (clades) and the lower taxa (subclades) nested within them, namely that morphological diversification within subclades is more gradual in time than diversification of the larger clade to which they belong. However, these suggestions have been based on case studies that are not ideally suited to test this idea. By comparing the Paleozoic radiation of a major invertebrate group, the Crinoidea, to that of subsidiary crinoid clads that diversified concurrently with the larger crinoid clade, I will test for the existence of such a discordance between taxonomic ranks. The Mesozoic radiation of articulate crinoids will provide an additional comparison. The results will help to answer questions about the hierarchical nature of evolution and our ability to predict larger-scale evolutionary patterns from smaller-scale patterns. Changes in morphological diversity, or disparity, during evolutionary radiations are usually assessed by using proxies such as the number of higher taxa (mainly classes and orders). There are a number of reasons to question the adequacy of such proxies. The proposed research will use direct quantification o f morphology to study evolutionary radiations in crinoids. I will use discrete morphological characters to quantify crinoid form, and will measure morphological disparity based on the net dissimilarities among species. I will apply a number of quantitative approaches, including "clade-shape" statistics, to explore the temporal pattern of morphological expectations of various evolutionary models. The proposed research will answer questions about the generation of morphological diversity over long spans of evolutionary time, and will develop a morphological database that can be used by other workers to investigate a wide range of issues, including phylogenetic relationships, evolutionary rates, and trends.