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

在许多哺乳动物中，孤立种群的个体大小(矮化)已经发生在衍生的物种水平上，甚至可能影响到我们的一些原始人亲属。岛状矮化的常见颅后相关性已经被记录在案，但关于头骨的形状及其许多综合组成部分如何受到影响的详细研究很少。这个项目将研究几个岛屿物种的博物馆标本，这些物种的身体尺寸比它们的祖先小，以确定头骨的大小和形状的差异。几个特有灵长类物种的头面部形态将使用多种大小和形状度量方法进行量化，包括3D几何形态计量学的方法，并与密切相关的大陆灵长类进行比较。回归分析将在适当的时候解释系统发育。此外，食肉动物中岛屿矮化的例子将提供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，这项研究将确定现存灵长类物种中与岛屿矮化相关的头面部形态的变化。其次，它将通过测试形状、大小和脑化程度的差异来确定岛屿矮小种群与大陆矮小种群之间的任何共同点。在每种情况下，零假设都将是基于先前对相关分类组的研究而预测的异速生长条件(对于给定的身体尺寸)。最后，该项目将使用目标1和目标2的发现来阐明对弗洛雷斯原始人遗骸的解释，这些遗骸显示出明显意想不到的头面部比例。在已知的岛屿矮化病例中，头骨形状的定量特征将有助于深入了解这一过程的机制，以及它对已灭绝的原始人可能产生的影响。尽管矮猛犸象和巨型啮齿动物等进化怪异现象一直引起研究人员的兴趣，但自从在印度尼西亚的弗洛雷斯岛上发现了一具小体、小脑的人类遗骸以来，它们已经崭露头角。古人类中与世隔绝的种群可能受到岛屿矮化的影响，这一说法重新引起了人们对这一奇怪的进化过程的科学兴趣。这个项目解决了许多与矮化有关的悬而未决的问题之一：头骨形状如何应对身体尺寸的显著减少，特别是在一个大脑大小对其来说如此重要的动物中？这项研究将有助于我们理解进化的基本机制，并对人类历史和当今濒危岛屿物种的保护生态产生影响。

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.