Evolutionary Radiations in Paleozoic and Mesozoic Crinoids

脚9506568 这项研究将（1）使用骨骼解剖学的明确数据来记录古生代和中生代海百合的进化辐射，以及（2）通过比较海百合作为一个整体的辐射和海百合的组成亚群的辐射来测试不同分类尺度下进化辐射之间的差异。 进化辐射，包括命名类群数量和形态多样性的大幅增加，是化石记录中最突出的特征之一。 人们普遍认为，在不同的分类，时间和空间尺度的进化辐射没有显着不同的时间模式或潜在的机制。 这一观点几乎没有得到直接的检验。 有一些迹象表明，可能有一个更高的类群（分支）和较低的类群（亚支）嵌套在它们的进化辐射之间的重大差异，即亚支内的形态多样性是更渐进的时间比他们所属的较大的分支的多样化。 然而，这些建议是基于案例研究，并不适合测试这一想法。 通过比较古生代辐射的一个主要的无脊椎动物群，海百合总科，附属海百合分支，多样化的同时与较大的海百合分支，我将测试存在这样一个不一致的分类等级之间。 中生代有关节的海百合的辐射将提供一个额外的比较。 这些结果将有助于回答有关进化的等级性质以及我们从较小规模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通过使用诸如高等分类群（主要是纲和目）的数量等替代物来评估。 有许多理由质疑这种代理人的适当性。 拟议中的研究将使用形态学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海百合的形式，并将衡量形态差异的基础上，物种之间的净差异。 我将应用一些定量的方法，包括“分支形状”的统计，探索各种进化模型的形态预期的时间模式。 拟议的研究将回答有关在长时间的进化过程中形态多样性的产生的问题，并将开发一个形态数据库，可供其他工作人员用于调查广泛的问题，包括系统发育关系，进化速率和趋势。

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.