Zelditch Miriam Leah, Bookstein Fred L, Lundrigan Barbara L
Museum of Paleontology, University of Michigan, Ann Arbor, MI, 48109, USA.
Center for Human Growth and Development, University of Michigan, Ann Arbor, MI, 48109, USA.
Evolution. 1992 Aug;46(4):1164-1180. doi: 10.1111/j.1558-5646.1992.tb00626.x.
Because development is epigenetic, diverse aspects of morphology are integrated during ontogeny. Using the method of thin-plate splines, and the decomposition of these splines by their principal warps, we examine the ontogeny of integrated features of skull growth of the cotton rat, Sigmodon fulviventer as observed in landmark locations in the ventral view. Postnatal growth of the skull in Sigmodon is not adequately described by the familiar contrast between relatively rapid facial elongation and slow, precocial growth of the cranial base. No developmental units corresponding to "facial skull" and "cranial base" emerge from analysis of geometric shape change. Rather, skull growth is both more integrated and more complex, exhibiting both skull-wide integration and locally individualized regions. Like skull shape, integration has an ontogeny; different regions of the skull can be partitioned into developmentally individualized parts in different ways at different ages. The effective count of individualized parts decreases substantially before weaning occurs, suggesting that the integration required by the functionally demanding activity of chewing gradually develops before the functional transition occurs. Our description of skull growth and integration does not depend upon arbitrary a priori choices about what to measure; rather, we base our decomposition of the whole into parts upon results of the data analysis. Our approach complicates the study of heterochrony, but, because it expresses the spatiotemporal organization of ontogeny, it enables the study of heterotopy.
由于发育是表观遗传的，形态学的各个方面在个体发育过程中相互整合。我们使用薄板样条法，并通过其主弯曲对这些样条进行分解，来研究棉鼠（Sigmodon fulviventer）颅骨生长综合特征的个体发育情况，这些特征是从腹侧视图中的地标位置观察到的。棉鼠颅骨的出生后生长不能通过相对快速的面部伸长与颅底缓慢、早熟生长之间常见的对比来充分描述。从几何形状变化分析中没有出现与“面颅骨”和“颅底”相对应的发育单元。相反，颅骨生长更加综合且更复杂，既表现出全颅骨范围的整合，也有局部个体化区域。与颅骨形状一样，整合也有个体发育过程；颅骨的不同区域在不同年龄可以以不同方式被划分为发育上个体化的部分。在断奶前，个体化部分的有效数量大幅减少，这表明咀嚼这一功能需求活动所需的整合在功能转变发生之前就逐渐发展起来了。我们对颅骨生长和整合的描述并不依赖于关于测量内容的任意先验选择；相反，我们将整体分解为部分是基于数据分析的结果。我们的方法使异时性研究变得复杂，但是，由于它表达了个体发育的时空组织，所以它能够进行异位性研究。
