DISSERTATION RESEARCH: Key Adaptations: Morphological Specializations Creating Ecological Specialization or Ecological Generalization?

加州大学伯克利分校（University of California at Berkeley）的安东尼·巴诺斯基（Anthony Barnosky）博士和罗伯特·费拉尼克（Robert Feranec）先生获得了一笔拨款，用于研究古代哺乳动物特殊特征的进化，即所谓的关键适应，是否会导致生态专业化或泛化。要研究的形态特化是有蹄类哺乳动物的高冠牙齿的进化，这被认为是导致在新进化的草原上专门进食的关键适应。本研究分析了马、骆驼和牛科动物的形态与饮食和生境的关系。测定饮食的主要方法是分析在牙釉质中发现的稳定碳同位素值。这一饮食替代物表明哺乳动物是以草为食还是以树和灌木为食。通过确定动物出现的化石地点的数量和位置来解决栖息地占用问题。本研究的目的是分析700万年前、1万-3万年前和现代有蹄类哺乳动物三个时期的饮食和栖息地占用情况。这项研究跨越了近2000万年的哺乳动物进化，并在分析中纳入了形态、饮食和栖息地的使用。这项提议的研究将测试初步结果，该结果表明，高冠牙齿的进化使哺乳动物变得更加普遍，这与目前的假设不同。这项研究很重要，因为它揭示了近2000万年有蹄哺乳动物进化过程中20多种哺乳动物的生态学。它还提供了关于现代有蹄类哺乳动物之所以出现在特定的生态系统中，是因为它们专门用于狭义的生态位，还是因为偏好、竞争甚至偶然等原因，它们目前占据了生态系统。该研究还为同位素在哺乳动物古生物学中的应用提供了新的教学工具和研究应用。

A grant has been awarded to Dr. Anthony Barnosky and Mr. Robert Feranec at the University of California at Berkeley to study whether the evolution of specialized features in ancient mammals, so-called key adaptations, causes ecological specialization or generalization. The morphological specialization to be studied is evolution of high-crowned teeth in hoofed mammals, which has been regarded as a key adaptation that led to specialized feeding on newly evolved grasslands. This study analyzes morphology relative to diet and habitat occupation in the horse, camel, and cow families. The main method used to determine diet is analysis of stable carbon isotope values found in tooth enamel. This proxy for diet indicates whether mammals focused feeding on grasses or on trees and shrubs. Habitat occupation is resolved by determining the number and location of fossil sites in which the animals occurred. The goal of this study is to analyze the diet and habitat occupation of hoofed mammals at three time periods, older than 7 million years ago, between 10,000-30,000 years ago, and modern hoofed mammals. This research spans almost 20 million years of mammal evolution, and incorporates morphology, diet, and habitat use in the analysis. This proposed study will test preliminary results that suggest evolution of high-crowned teeth allows mammals to become more generalized, which differs from current hypotheses. The study is important because it sheds light on the ecology of more than 20 genera of mammals through nearly 20 million years of hoofed-mammal evolution. It also provides the knowledge of whether modern hoofed mammals occur in particular ecosystems because they are specialized for narrowly defined niches, or if they currently occupy the ecosystem because of reasons like preference, competition, or even chance. The study also contributes new teaching tools and research applications for the uses of isotopes to mammal paleontology.