Doctoral Dissertation Improvement: Extant Island Dwarf Mammals as Models for Insular Dwarfing in Pleistocene Hominids

在许多哺乳动物中，孤立种群的身体尺寸在物种水平上的衍生性缩小（侏儒化）已经发生，甚至可能影响到我们的一些人科亲戚。 岛状侏儒症常见的颅后相关因素已经被记录在案，但很少有详细的研究如何影响头骨的形状及其许多综合组成部分。 该项目将检查几个岛屿物种的博物馆标本，这些物种与其祖先相比体型缩小，以描述头骨大小和形状的差异。几种特有灵长类动物的颅面形态将使用多种尺寸和形状指标进行量化，包括3D几何形态测量学方法，并与密切相关的大陆灵长类动物进行比较。 适当时，回归分析将解释遗传学。 此外，一个食肉动物的岛屿矮化的例子将提供一个非灵长类动物的比较案例。这些物种间比较的目的有三个。 首先，这项研究将确定与现存灵长类物种样本中岛屿侏儒相关的颅面形态变化。 其次，它将通过测试形状、大小和脑化程度的差异，确定岛屿侏儒种群与大陆侏儒种群之间的任何共性。 在每种情况下，零假设将是基于所讨论的分类组的先前研究的异速生长预测条件（对于给定的体型）。 最后，该项目将利用目标1和目标2的发现，阐明对弗洛雷斯人科动物遗骸的解释，这些遗骸显示出明显出乎意料的颅面比例。 在已知的岛屿侏儒化案例中，头骨形状的定量特征将有助于深入了解这一过程的机制及其对已灭绝的原始人谱系成员的可能影响。尽管侏儒猛犸象和巨型啮齿动物等进化上的古怪现象一直令研究人员感兴趣，但它们最近已经变得突出，因为一个小型身体的遗骸，在印度尼西亚的弗洛雷斯岛上发现了一个小脑袋的人类。 一个与世隔绝的古人类群体可能经历了岛屿侏儒化的说法，重新引起了科学界对这一奇怪的进化过程的兴趣。 这个项目解决了与侏儒相关的许多未解答的问题之一：头骨形状如何对身体尺寸的显着减少做出反应，特别是在大脑尺寸可能如此重要的动物中？ 这项研究将有助于我们了解进化的基本机制，对人类历史和当今濒危岛屿物种的保护生态学具有影响。

Derived, species-level reduction in body size (dwarfing) of isolated populations has occurred in many mammals and may have even affected some of our hominid relatives. Common postcranial correlates of island dwarfing have been documented, yet there are few detailed studies of how the form of the skull and its many integrated components are affected. This project will examine museum specimens of several island species that have reduced body size compared to their ancestors in order to characterize differences in size and shape of the skull. Craniofacial morphology of several endemic primate species will be quantified using multiple size and shape metrics, including methods from 3D geometric morphometrics, and compared to closely-related mainland primates. Regression analyses will account for phylogeny when appropriate. In addition, an example of island dwarfing in carnivores will provide a non-primate comparative case. The aims of these interspecies comparisons are threefold. First, the study will define the changes in craniofacial form associated with island dwarfing in a sample of extant primate species. Second, it will identify any commonalities among the island dwarf populations relative to their mainland counterparts by testing for differences in shape, size, and degree of encephalization. The null hypothesis in each case will be the allometrically-predicted condition (for a given body size) based on previous studies of the taxonomic group in question. Finally, the project will use the findings of aims 1 and 2 to shed light on the interpretation of the Flores hominid remains exhibiting apparently unexpected craniofacial proportions. The quantitative characterization of skull shape in known cases of island dwarfing will lend needed insight into the mechanisms of this process and its possible effects on an extinct member of the hominid lineage.Although evolutionary oddities such as dwarf mammoths and giant rodents have always interested researchers, they have recently risen to prominence since the remains of a small-bodied, small-brained human were recovered on the island of Flores in Indonesia. The suggestion that an isolated population of the ancient humans may have been subject to island dwarfing has renewed scientific interest in this curious evolutionary process. This project addresses one of the many unanswered questions related to dwarfing: How does skull shape respond to a significant reduction in body size, particularly in an animal for which brain size is presumably so important? This research will contribute to our understanding of basic mechanisms of evolution, with implications for human history and for the conservation ecology of endangered island species today.