Phylogenetic Analysis of Murid Skull Shape Ontogeny

动物的许多特征，如头骨形状，在其一生中都会发生变化。然而，头骨形状的比较研究，包括那些试图推断群体间进化关系的研究，以及那些研究头骨形状进化变化的研究，通常只调查成年人。提出的研究将分析颅骨形式的发育变化，以确定这些变化是否提供了有关选定啮齿动物之间进化关系的信息，并解剖颅骨发育的进化变化。量化形状变化方法的最新进展已经产生了有前途的技术，将应用于这一分析。薄板样条的方法，我建议使用的方法，有一个独特的优势，它提供了一种方法来识别一系列独立的形状特征，这些特征在头骨上有特定的位置和空间范围。在这个项目的第一阶段，我将比较三个属的鼠，Sigmodon和Peromyscus。这些属之间的关系没有争议。我将比较：1)每个物种不同年龄颅骨形状的变化；2)不同物种各年龄阶段的平均颅骨形状；3)颅骨形状及其转换的种内变异性。这一阶段的研究将探讨几个方法学问题，如编码形状字符的发展转换的方法。研究的第二阶段将使用这些方法来分析Sigmodon物种之间的关系，并描述头骨生长的进化变化。

Many features of an animal, such as its skull shape, change throughout its life. Yet, comparative studies of skull shape, including those that seek to infer evolutionary relationships among groups, and those that examine evolutionary changes in skull form, commonly survey only adults. The proposed research will analyze developmental changes in skull form to determine whether these transformations provide information about evolutionary relationships among selected rodents, and to dissect evolutionary changes in skull development. Recent advances in methods for quantifying shape change have yielded promising techniques that will be applied in this analysis. The method of thin-plate splines, the method that I propose to use, has a unique advantage in that it gives a way to identify a series of independent shape characters that have specific location and spatial extent on the skull. In the first stage of this project, I will compare three genera of murid rodent Mus, Sigmodon and Peromyscus. Relationships among these genera are not controversial. I will compare: 1) transformations in skull shape from age to age in each species; 2) average skull shape at each age across species; and 3) intraspecific variability of skull shapes and their transformations. This phase of the research will explore several methodological issues, such as methods for coding developmental transformations of shape characters. The second stage of the research will use these methods to analyze relationships among Sigmodon species, and to describe evolutionary modifications of skull growth.