DISSERTATION RESEARCH: Phylogenetic Persistence of Modularity of the Rodent Skull

复杂形态结构的发育结构(DA)导致性状作为完整的单位或独立的模块发展。挥之不去的问题是DA是否影响通常伴随着生物多样性的形态特征的差异，以及DA本身是否进化。这项研究的目的是通过将DA与一大群有强大系统发育史可用的生物进行比较来解决这些问题。发现更密切相关、形态截然不同的物种共享共同的DA，这将证明其持久性。在本研究中，将对一组生态和形态不同的啮齿动物Sigmodontinae进行广泛采样，比较颅颌复合体的DA，以确定DA是否在多样化的情况下持续存在。这些比较将基于对DA的量化分析，DA是通过性状之间的统计协方差揭示的。这些协方差的结构提供了一组DA的估计。这种协方差结构将在不同物种之间进行对比，使用一种方法将它们与根据发育机制假说推导出的模型进行比较。如果一个谱系内的所有物种都符合相同的模型，这将被视为DA持续存在的证据。这些广泛的比较分析将基于成人标本的样本。通过比较不同发育阶段的标本样本来检验发育信息持续到成体阶段的假说。在这些分析中将使用一种新的方法来比较通过开发产生或消除变化的过程的影响。

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.