Species Level Processes and the Evolutionary Dynamics of Agnostid Trilobites

[804955] smith提出了对中寒武纪Ptychagnostidae（三叶虫，无知虫门）的种水平分析，以检验该分支中物种的微观进化属性与宏观进化模式之间的假设。具体来说，我的目标是测量表型变异性，并根据文献、博物馆和野外收藏记录所有种类的Ptychagnostidae的地理和地层范围。这些属性在确定物种后代数量方面的作用将在使用Westrop等人（1996）的进化图构建的系统发育和分类群的地层发生的背景下进行评估。目前正在建立一个基于文献的数据库，但表型变异性的可靠测量需要博物馆收藏的大量标本样本，并辅以额外的实地收集。该项目将建立在对中寒武纪Ptychagnostidae的广泛研究基础上，并将具体解决以下假设：1)物种的表型变异水平以及物种的地理和地层范围与物种产生的后代数量相关；2)Ptychagnostidae物种在形态空间中的分布应该是恒定的，以避免竞争，同时最大限度地减少进化分化。对这些假说的评价，对于理解寒武纪海洋无脊椎动物辐射时期和地球历史其他时期Ptychagnostidae的进化动态、进化速度和进化模式具有重要意义。

9804955SmithI propose a species-level analysis of Middle Cambrian Ptychagnostidae (Trilobita, Agnostida) in order to test hypotheses relating microevolutionary attributes of species to macroevolutionary pattern within this clade. Specifically, I aim to measure phenotypic variability and document the geographic and stratigraphic ranges of all species of Ptychagnostidae based on literature, museum, and field collections. The role of these attributes in determining the number of descendants of a species will be assessed in the context of a phylogeny constructed using the cladogram of Westrop et al. (1996) and the stratigraphic occurrence of taxa. A literature-based database is currently being constructed, yet robust measures of phenotypic variability require large samples of specimens available in museum collections and supplemented by additional field collections. The proposed project will build upon extensive prior research on Middle Cambrian Ptychagnostidae and will specifically address the hypotheses that: 1) levels of phenotypic variability and the geographic and stratigraphic range of a species are correlated with the number of descendants produced by a species, and 2) the distribution of species of Ptychagnostidae within a morphospace should be constant in order to avoid competition while minimizing evolutionary differentiation. The evaluation of these hypotheses has great significance for understanding both the evolutionary dynamics of the Ptychagnostidae and the tempo and mode of evolution during the Cambrian radiation of marine invertebrates and during other intervals of Earth history.