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

Arizona State University, Scottsdale AZ

Investigators

Abstract

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.