Dissertation Research: Integrative Study of the Evolution of Squamate Limb Reduction

陆生脊椎动物（四足动物）肢体减少是一种普遍现象。一些谱系减少了四肢的总长度，或者完全失去了四肢，而另一些则只是减少了骨头的总数（两栖动物只有四根手指，鸟类只有三根）。尽管四肢减少在四足动物中很常见，但这种现象背后的进化和发育机制尚不清楚。本研究将采取综合的方法来了解澳大利亚半蜥肢体减少的形态学、分子和功能方面。半爪虫是研究肢体减少的理想模式生物，因为它在几个密切相关的物种属中具有手指结构的梯度（从5个手指和脚趾到2个手指和脚趾）。本研究旨在比较不同种类的半人猿的骨骼发育模式，追踪肢体模式基因表达的变化，并记录伴随肢体减少的功能变化。肢体减少通常涉及一个常见的手指丧失顺序，对半足动物发育的研究将为其他四足动物群体的肢体减少提供见解。该项目还将阐明特定基因在胚胎肢体模式中的进化作用。

PI: Crompton 9801134 Limb reduction in terrestrial vertebrates (tetrapods) is a common phenomenon. Some lineages reduce the total size of their limbs or lose them altogether, while others simply reduce the total number of bones (amphibians have only four fingers and birds have only three). Despite the common occurrence of limb reduction in tetrapods, the evolutionary and developmental mechanisms underlying this phenomenon are poorly understood. This study will take an integrative approach to understanding the morphological, molecular, and functional aspects of limb reduction through the Australian lizard Hemiergis. Hemiergis is an ideal model organism for limb reduction studies because it features a gradient of digit configurations (from 5 fingers and toes to 2 fingers and toes) within a genus of several closely related species. This investigation endeavors to compare patterns of skeletal development in different species of Hemiergis, trace changes in the expression of limb patterning genes, and document the functional changes that accompany limb reduction. Limb reduction typically involves a common order of digit loss, and studies of Hemiergis development will provide insight into cases of limb reduction in other tetrapod groups. This project will also elucidate the evolutionary role of specific genes in patterrdng the embryonic limb.