Date of Award

Spring 1-1-2013

Document Type


Degree Name

Doctor of Philosophy (PhD)


Ecology & Evolutionary Biology

First Advisor

Jeffry B. Mitton

Second Advisor

Rob Knight

Third Advisor

Andrew Martin

Fourth Advisor

Robert P. Guralnick

Fifth Advisor

Patrik Nosil


A major tenet of evolutionary biology is that the fitness of an individual is determined by its genetics and its interactions with the environment. Yet microbial ecology has taught us that the microbes with which animals live in close association also constitute an important component of the animal’s phenotype, playing necessary roles in their development, nutrition, and immunity; thus, they too can affect animal fitness and their interactions with the environment. Consequently, a better understanding of both of these factors is essential, and has significant implications for the conservation of natural systems. My dissertation research examines these two factors and thus lies at the interface of evolutionary genetics and microbial ecology by investigating the consequences of hybridization among three catostomid fish species and analyzing the factors affecting the diversity of their associated microbes. Two of these species are native to the Upper Colorado River Basin, and an introduced third species has spread throughout the ranges of the two native fish.

Although it is well known that non-native fish introductions often cause the decline of native species, the effects of subsequent hybridization on the potential survival of the native species are often challenging to quantify. To meet this challenge, I surveyed the genetic composition of hybrid individuals among all three species across a wide geographic range and found that the bulk of hybridization occurs between the introduced sucker and one of the native species and that this process is slowly destroying the genetic integrity of the native suckers. Moreover, the range of hybrid types found was related to the amount of phylogenetic distance and overlap of biogeographic history among species.

Second, I investigated the diversity of microbes associated with the gastrointestinal tracts and epidermal mucus of these catostomids and my findings indicate that while host diet and possibly host phylogeny play a role in shaping their gut microbial communities, the environment plays a larger role than these factors in shaping their skin microbiota. Collectively, this dissertation highlights how evolutionary history can determine the potential for hybridization between species and interacts with the environment to influence host-microbe relationships.