Doctoral Dissertation Improvement: Dental Microstructure and Growth in the Cebidae

牙齿在进食方面显然很重要，对于发现有关灭绝物种的关键生态信息至关重要，包括我们自己的史前祖先。它们还嵌入了与环境有关的法医信息。牙齿以类似于树轮生长的周期性、递增的方式生长，因此保存了它们自身形成的永久记录。它们沿着一个时间表发展，该时间表与断奶等事件相适应，与非母体食物资源的性质相协调，甚至与个体在发展自己特定物种的社会角色时的成熟相协调。正在进行的研究旨在从几个灵长类动物的牙齿中描绘出这种类型的信息，但主要的差距仍然存在。这个项目是第一个专注于新大陆灵长类动物牙齿显微解剖和生长的项目，特别是卷尾猴、松鼠猴、罗望子和绒猴。例如，这项工作解决了具有广泛意义的新问题，尚不清楚季节性饮食波动是否会影响给定物种的总体身体生长率。这样的信息很难获得，即使在监测野生动物的时候也是如此。然而，这项研究的方法可以揭示偶然的瘦肉期，就像许多雨林物种在旱季发生的那样，是否会影响牙齿的生长速度，这反映了整体身体的生长。作为另一个例子，尽管在特定的社会和交配制度下生活时，雄性灵长类动物的犬齿比雌性灵长类动物的牙齿大是很常见的，但我们对犬齿大小差异是如何发展的了解很少，这意味着我们对性别二型性的普遍现象的理解相当不完整。在更广泛的脉络中，该领域的大多数研究都集中在广泛调查灵长类或更高分类水平的家族之间的差异。因此，我们对物种和属水平上的牙齿生长及其模式，或者在适应性辐射下的牙齿生长及其模式知之甚少。通过对鸭嘴兽灵长类的几个物种和属的研究，这项研究有望填补其中的一些空白。在分类上，这一组呈现出几个优势。它们可以说是现存灵长类动物中规模最大、最多样化的群体，但它们在很大程度上也被忽视了，取而代之的是它们的东半球近亲，如猕猴、狒狒和猿类。这项研究选择的动物是一个很好的起点，因为它们的饮食多样化，有些物种的饮食表现出季节性的变化。我的试点工作还显示，一些雄性头鲸表现出不同于东半球猴子模型的犬类生长模式，这表明白颈猴可能更适合重建犬类和高等灵长类动物社会制度的早期进化。这个项目是为了帮助研究生培养。正在使用的一些技术是新的，一旦得到证实，将使有各种兴趣的研究人员能够更好地利用博物馆收藏品，包括化石，允许在不切割牙齿以暴露其内部结构的情况下获得显微解剖信息。将开发的图像数据库将在网上公开提供。总而言之，这项研究将为我们对灵长类多样性和进化的理解增添一个新的方面。

Teeth are obviously important in feeding and vital to discovering crucial ecological information about extinct species, including our own prehistoric ancestors. They also embed environmentally related forensic information. Teeth grow in a periodic, incremental manner similar to the way tree rings grow, and thus preserve a permanent record of their own formation. They develop along a time schedule that is coordinated adaptatively with events like weaning, with the nature of non-maternal food resources, and even the maturation of an individual as he/she develops their own species-specific social roles. Ongoing research aims to delineate this type of information from teeth among several primate groups, but major gaps remain. This project is the first to focus on dental microanatomy and growth in New World primates, specifically the capuchins, squirrel monkeys, tamarins, and marmosets. As an example where this work addresses new issues of wide significance, it is not known if seasonal dietary fluctuations impact overall bodily growth rates of a given species. Such information is hard to come by, even when monitoring animals in the wild. However, the approach of this study can reveal if incidental lean periods, as occurs during the dry season for many rain forest species, influences growth rates of teeth, which mirrors overall body growth. As another instance, although it is common for male primates to have larger canine teeth than females when living under certain social and mating systems, we understand little about how canine tooth size differences develop, meaning our understanding of the pervasive phenomenon of sexual dimorphism is rather incomplete. In a more general vein, most research in this field has concentrated on broadly surveying differences among families of primates, or higher taxonomic levels. Thus we know little about dental growth and its patterns at the species and genus level, or within an adaptive radiation. By focusing on several species and genera of the platyrrhine primates this study promises to fill some of these gaps. Taxonomically, this group presents several advantages. They are arguably the largest and most diverse group of living primates but they have also been largely ignored in favor of their Old World cousins, such as macaques, baboons and apes. The animals chosen for this study (Family Cebidae) are a good place to start because they are dietetically diverse, with some species showing seasonal shifts in their diet. My pilot work has also revealed that some male cebids exhibit a pattern of canine growth that differs from Old World monkey models, suggesting that the platyrrhine monkeys may be more pertinent to reconstructing the early evolution of canines and social systems in higher primates. This project is to assist graduate student training. Some of the techniques that are being employed are new and, once proven, will enable researchers with various interests to take greater advantage of museum collections, including fossils, by allowing microanatomical information to be obtained without cutting teeth apart to expose their internal structure. The image databases that will be developed will be made publicly available on the web. All in all, the research will add a new aspect to our understanding of primate diversity and evolution.