DISSERTATION RESEARCH: Phylogenetic Persistence of Modularity of the Rodent Skull

复杂形态结构的发育结构（DA）导致性状作为整体或独立的模块发展。一直存在的问题是DA是否会影响经常伴随生物体多样化的形态特征的分化，以及DA本身是否会进化。本研究的目的是通过比较一个强大的系统发育是可用的大组生物的DA来解决这些问题。如果发现关系更密切、形态上不同的物种共享一个共同的DA，就会证明它的持久性。在本研究中，颅下颌骨复合体的DA将在生态和形态多样化的啮齿动物Sigmodontinae中进行广泛的抽样比较，以确定DA是否在多样化的情况下持续存在。比较将基于DA的定量分析，即性状间统计协方差所揭示的DA。这些协方差的结构提供了一个组的DA的估计。这种协方差结构将在物种之间进行对比，使用一种方法将它们与从发育机制假设中推断出来的模型进行比较。如果一个谱系中的所有物种都符合相同的模式，这将被视为进化持续存在的证据。这些广泛的比较分析将以成年标本的样本为基础。发育信息持续到成年阶段的假设将通过比较不同发育阶段的标本样本来验证。在这些分析中将采用一种新的方法来比较通过开发产生或消除变异的过程的影响。

The developmental architecture (DA) of complex morphological structures causes traits to develop as integrated units or independent modules. Persistent questions are whether DA influences the divergence of morphological features that often accompanies organismal diversification, and whether DA itself evolves. The aim of this research is to address such issues by comparing DA over a large group of organisms for which a robust phylogeny is available. Finding that more closely related, morphologically distinct species share a common DA would argue for its persistence. For the present study, the DA of the craniomandibular complex will be compared across an extensively sampled group of ecologically and morphologically diverse rodents, the Sigmodontinae, to determine whether DA persists despite diversification. The comparisons will be based on a quantitative analysis of DA, being DA revealed by statistical covariances among traits. The structure of those covariances provides an estimate of a group's DA. Such covariance structures will be contrasted across species, using an approach that compares them to models deduced from hypotheses of developmental mechanisms. Should all species within a lineage fit the same model, that will be taken as evidence for the persistence of DA. These broadly comparative analyses will be based on samples of adult specimens. The hypothesis that developmental information persists until the adult stage will be tested by comparing samples of specimens on different developmental stages. A novel approach will be employed in these analyses to compare the effects of processes that generate or eliminate variation through development.