Date of Graduation

5-2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Environmental Dynamics (PhD)

Degree Level

Graduate

Department

Environmental Dynamics

Advisor/Mentor

Ungar, Peter S.

Committee Member

Delezene, Lucas K.

Second Committee Member

Avenant, Nico

Third Committee Member

Suarez, Celina A.

Keywords

diet; evolution; habitat; muroid; paleoecology; rodent; South Africa

Abstract

Dental microwear texture analysis (DMTA) of fossil fauna has become a valuable tool for dietary inference and paleoenvironment reconstruction. Most of this work has utilized larger taxa with larger home ranges. These studies may result in broader-scale habitat inferences that could mask the details of complex mosaic habitats. Rodent DMTA offers an opportunity to work at finer spatial scales because most species have smaller home ranges. Rodents are also keystone species within their ecosystems, abundant, ubiquitous, and found in many fossil deposits. These attributes make them excellent proxies for environmental reconstructions. However, the application of DMTA to rodents remains relatively new. Furthermore, many rodent species are dietary generalists, and individuals available for study in museum collections lack detail on feeding behavior, which makes it difficult to develop strong dietary associations with microwear patterns. The same holds for limited environmental metadata associated with such samples.

This dissertation sought to explore the efficacy of rodent DMTA as a proxy for fine-scale paleoenvironment reconstruction and to establish a baseline of extant incisor and molar textures with detailed metadata associations to aid in future comparisons to fossil taxa. The biomonitoring project at Kolomela Mine, located within South Africa’s Northern Cape, provided an ideal opportunity with which to conduct this research. Stomach content analyses conducted on 214 muroid specimens caught within the Kolomela properties examined diets by species, location, and month. These analyses indicated that the Kolomela rodent community mainly consumed grass seed despite the presence of other foodstuff within stomachs.

A confocal profiler scanned high resolution casts to provide microwear textures for 198 incisors and 175 molars, from which SSFA and ISO parameter data were derived. Statistical tests explored the effects of diet, taxon, and habitat attributes on the central tendencies of these parameters, as well as effects by tooth form. Incisor microwear textures seemed to possess a stronger environmental signal than that of molars, with analyses indicating significant variation by species, macrohabitat, microhabitat, burrowing behavior, soil, and land cover classification. These results suggested that while soil characteristics had a strong influence on parameter central tendencies, incisor microwear textures seem to result from complex interactions with habitat characteristics.

Molar microwear did not parse the considered dietary categories, likely because all individuals had diets dominated by grass seed that swamped any diet signal reflecting the food elements of each group. Significant variation in parameter central tendencies by both species and burrowing behavior were believed to be the result of differing molar topography between Gerbillinae and Murinae specimens. Analyses also separated molar microwear from different dust levels, which indicated that perhaps an environmental signal can be parsed, at least when diets are homogeneous and controlled for. Finally, molar and incisor microwear textures were significantly different from one another, presumably due to a) different roles in food acquisition and process, b) different rates in gross wear and surface turnover, and c) different degrees of interaction with exogenous grit and the outside environment. These results suggest that both tooth types should be considered in future paleoenvironment reconstructions.

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