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

亚利桑那州立大学的博士生Laura Stroik在Gary Schwartz博士的指导下进行了这项研究，目的是确定饮食竞争相互作用的模型，该模型描述了大约5500万年前北美始新世原始灵长类动物（最早的“真正的”灵长类动物）的起源和早期多样化。研究了三种竞争相互作用模式：(1)缺乏饮食竞争；(2)存在强烈的饮食竞争，导致非灵长类物种的竞争排斥；(3)存在弱的饮食竞争，导致灵长类物种和非灵长类物种共存。竞争是由生态位重叠来定义的，每一种假设都是通过其独特的预测物种间饮食生态位重叠的模式来区分的。利用臼齿的形态学测量重建了化石分类群的饮食位，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。在怀俄明州的比格霍恩河盆地，通过对单一地点的一系列化石样本进行统计，评估了早期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。竞争环境是在原始灵长类动物起源之前和它们在北美辐射的初始阶段进行研究的。观察到的饮食生态位随时间重叠的模式，连同物种丰度和气候变量，与每个竞争模型的预期模式进行了比较。建立原始灵长类动物产生的饮食竞争环境，通过证明饮食是否实际上是早期原始灵长类动物进化的主要驱动力，可以直接测试原始灵长类动物起源的长期假设。此外，与今天所见的气候变暖过程相当的气候变暖过程也出现在真正的灵长类动物起源的时期；因此，该项目的结果可直接应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。本研究促进了本科生的培养，本研究的结果（包括方法技术、定量数据和计算机算法）可通过在线数据库供其他研究人员和教育工作者访问。

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.