DISSERTATION RESEARCH: Macroevolutionary drivers of digit reduction in fossil horses

论文研究：化石马趾数减少的宏观进化驱动因素

基本信息

批准号：
1701656
负责人：
Stephanie E Pierce
金额：
$ 1.6万
依托单位：
Harvard University
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2017
资助国家：
美国
起止时间：
2017-06-01 至 2019-05-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1701656&HistoricalAwards=false
关键词：
DISSERTATION RESEARCH Macroevolutionary drivers digit

项目摘要

This study uses the rich fossil record of the horse family, combined with information about changing habitats and anatomy in horse evolution, to test the causes and consequences of digit reduction. Domestic horses and their relatives (zebras and donkeys) are large, grazing animals with slender limbs that end in a single digit (the hoof). The evolution of today?s horses is traditionally explained as simple ongoing adaptation to grasslands: as grasslands gradually took over from forests, the early dog-sized, three-toed horses evolved into large, single-toed grazers. Their teeth also became longer to deal with abrasive grass, while their digits reduced so they could run faster or more efficiently across open spaces. However, this textbook explanation is oversimplified and remains largely untested. This study will shed light on a significant evolutionary transition that culminated in one of humans? most culturally and economically important species. Results will be featured in the Harvard Museum of Natural History (HMNH), whose fossil horse exhibit currently shows the oversimplified pattern of evolution. They will also be shared via lectures designed to engage with members of the public, as well as teacher education events at the HMNH that will bring this project into the classroom. A variety of hypotheses have been proposed for the selective pressures driving digit reduction in the horse lineage: speed for predator escape, economy of movement over open grasslands with scarce resources, and compensation for increasing body size. However, none have been explicitly tested with modern methods. By integrating information on fossil occurrences, trait change, phylogenetic relationships, ecology, and environment, this project aims to directly test potential evolutionary causes of digit reduction in horses. Specifically, this research will use ecological and phylogenetic comparative methods to assess the following questions: 1) Did tridactyl and monodactyl horses overlap in space and time or did they occupy separate niches? 2) Are changes in digit morphology, body mass, tooth height, or habitat correlated across the horse phylogeny? 3) Do changes in digit morphology or environment influence speciation and extinction rates in the fossil record? The results of this project will provide quantitative support (or lack thereof) for the cause of digit reduction in fossil horses, filling in a key gap in our understanding of why this major evolutionary transition happened.

这项研究利用马科丰富的化石记录，结合马进化过程中栖息地和解剖结构变化的信息，来测试手指减少的原因和后果。家养马及其近亲（斑马和驴）是大型食草动物，四肢细长，末端只有一个数字（蹄）。今天马的进化传统上被解释为对草原的简单持续适应：随着草原逐渐取代森林，早期狗大小的三趾马进化成大型单趾食草动物。它们的牙齿也变得更长，以应对磨蚀性的草，而它们的手指则减少了，这样它们就可以在开放空间中跑得更快或更有效。然而，这个教科书的解释过于简单化，并且在很大程度上尚未经过检验。这项研究将揭示一个重大的进化转变，该转变在人类中达到顶峰？最具有文化和经济重要性的物种。结果将在哈佛自然历史博物馆 (HMNH) 展出，该博物馆的马化石展览目前展示了过于简单化的进化模式。它们还将通过旨在与公众互动的讲座以及 HMNH 的教师教育活动来分享，这些活动将把这个项目带入课堂。对于导致马谱系数量减少的选择压力，人们提出了多种假设：捕食者逃跑的速度、在资源稀缺的开放草原上的经济性运动以及对体型增加的补偿。然而，没有一个经过现代方法的明确测试。通过整合化石出现、性状变化、系统发育关系、生态和环境等信息，该项目旨在直接测试马趾减少的潜在进化原因。具体来说，本研究将使用生态学和系统发育比较方法来评估以下问题：1）三趾马和单趾马在空间和时间上是否重叠，或者它们占据不同的生态位？ 2) 手指形态、体重、牙齿高度或栖息地的变化是否与马的系统发育相关？ 3）手指形态或环境的变化是否会影响化石记录中的物种形成和灭绝率？该项目的结果将为化石马趾数减少的原因提供定量支持（或缺乏定量支持），填补我们理解这一重大进化转变发生原因的关键空白。