Doctoral Dissertation Improvement: The Competitive Environment of the Origination and Early Diversification of Euprimates in North America

亚利桑那州立大学博士生劳拉·斯特罗克在加里·施瓦茨博士的指导下进行了这项研究，目的是确定约5500万年前北美始新世真灵长类(最早的“真正”灵长类)起源和早期多样化的饮食竞争相互作用模式。研究了竞争相互作用的三种模式：(1)缺乏食物竞争；(2)存在强烈的食物竞争，导致非真灵长类物种的竞争性排斥；(3)存在弱的食物竞争，导致真灵长类和非真灵长类物种共存。竞争是由生态位重叠来定义的，每个假说都可以通过物种间随时间推移的食物生态位重叠的独特预测模式来区分。化石分类群的饮食生态位是使用磨牙的形态测量重建的，这些测量被发现在现存哺乳动物的比较样本中区分饮食制度。早期真灵长类动物和它们的竞争对手重建的生态位之间的分离程度，是在怀俄明州的比格伦盆地这一单一地点的一系列化石样本上进行的统计评估。就在真灵长类起源之前，然后在它们在北美境内辐射的初始阶段，对竞争环境进行了检查。观察到的食物生态位随时间重叠的模式，以及物种丰富度和气候变量，与每个竞争模型的预期模式进行了比较。通过建立真灵长类产生的食物竞争环境，通过证明饮食是否事实上是真灵长类早期进化的主要驱动力，可以直接检验真灵长类起源的长期假说。此外，在真正灵长类动物起源的时期，也出现了与今天看到的类似的气候变暖过程；因此，该项目的结果直接适用于研究全球气候变化对现代动物的影响，特别是那些濒临灭绝的动物。这项研究促进了本科生的培养，研究结果(包括方法学技术、定量数据和计算机算法)可以通过在线数据库向其他研究人员和教育工作者开放。

The goal of this research by doctoral student Laura Stroik (Arizona State University), working under the supervision of Dr. Gary Schwartz, is to determine the model of dietary competitive interaction that characterized the origination and early diversification of Eocene euprimates (earliest "true" primates) in North America, ca. 55 million years ago. Three models of competitive interaction are examined: (1) absence of dietary competition, (2) presence of strong dietary competition, resulting in the competitive exclusion of non-euprimate species, and (3) presence of weak dietary competition, resulting in the coexistence of euprimate and non-euprimate species. Competition is defined by niche overlap, and each hypothesis is distinguishable by its unique predicted pattern of dietary niche overlap among species through time. Dietary niches of fossil taxa are reconstructed using morphological measures of molar teeth that are found to discriminate dietary regimes within a comparative sample of extant mammals. The degree of separation between reconstructed niches of early euprimates and their competitors is evaluated statistically across a series of fossil samples at a single site, the Bighorn Basin in Wyoming. Competitive environments are examined just prior to the origin of euprimates and then during the initial phase of their radiation within North America. Observed patterns of dietary niche overlap over time, together with species abundance and climatic variables, are compared to the expected patterns of each competition model. Establishing the dietary competitive environment in which euprimates arose enables a direct test of the standing hypotheses of euprimate origins by demonstrating whether diet was, in fact, a primary driver of early euprimate evolution. In addition, climatic warming processes comparable to those seen today were also present during the time when true primates originated; thus, the results of this project are directly applicable to studies of the effects of global climate change on modern animals, particularly those at risk of extinction. This research promotes the training of undergraduate students, and the results of this study (including methodological techniques, quantitative data, and computer algorithms) are accessible to other researchers and educators through an online database.