Degree

Doctor of Philosophy (PhD)

Department

Biological Sciences

Document Type

Dissertation

Abstract

My dissertation provides critical insights on the pattern and process of evolution in front-end and back-end dietary adaptations of mammals. I found that the position of the rodent masseter muscle, a complex front-end adaptation that improves the efficiency of mechanical digestion, has convergently evolved numerous times, suggesting that selective pressure for this adaptation has been strong. For back-end adaptations, I found gut bacterial taxa that likely aid in chemical digestion of food have predictable associations with host diet across host species in natural environments. To detect patterns in gut microbial community structure that are related to host factors such as taxonomy and diet, it is critical to consider where microbes are being sampled from in the gut and this differs by species and individual depending on gut architecture. In rodents, gut bacterial community structure was most distinguishable by host taxonomy in the cecum, a fermentation chamber that facilitates interactions with microbes. In animals with simple guts (i.e., lacking a fermentation chamber) such as shrews, gut bacterial communities are more distinguishable by host taxonomy in the small intestine compared to the colon. Recognition that the location microbial communities are sampled from in the gastrointestinal tract affects the detection of associations with host factors (e.g., diet, phylogeny, geography) is important because almost all sampling of gut microbial communities used in comparative studies rely on fecal and colon specimens, a practice that likely obscures some of the mechanisms underlying how microbial communities facilitate host dietary habits.

Date

7-21-2021

Committee Chair

Esselstyn, Jacob

DOI

10.31390/gradschool_dissertations.5624

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