Emerging infectious diseases (EIDs) in vulnerable populations are a proposed cause of reduced global biodiversity due to local and regional extinctions. Chytridiomycosis, a fungal disease caused by Batrachochytrium dendrobatidis (Bd), is affecting amphibian populations worldwide.

Chapter 1 of this thesis reports using lab-raised larval tiger salamanders (Ambystoma tigrinum nebulosum), collected as eggs, to test if Bd infects them. Bd infects metamorphosed tiger salamanders; however, it is currently unknown if larvae can be infected by Bd. Adult frogs tend to host Bd on ventral surfaces and hind legs while tadpoles host Bd in keratinized mouthparts. No research has considered differences in infection between life stages of salamanders. It was hypothesized that Bd can colonize larvae in the same manner as metamorphosed animals. Larval salamanders were inoculated to test if Bd concentrations differ among body regions in larvae compared to metamorphosed salamanders. Larvae can carry Bd with the concentration of Bd varying between body region.

Chapter 2 report using native tiger salamanders (Ambystoma tigrinum nebulosum), from northern Arizona and Bd as a study system to test if Bd is native or introduced to Arizona. It was hypothesized that Bd is not endemic to Arizona, but is introduced. There are multiple hypotheses regarding potential routes Bd may have traveled through Arizona and into Mexico. These hypotheses were tested using the Kaibab Plateau in Coconino County, Arizona, as a study site. The plateau is isolated from surrounding areas by the Grand Canyon to the south and the Vermillion Cliffs to the north serving as major biogeographical barriers. It is hypothesized that tiger salamanders are not dispersing into or out of the Kaibab Plateau due to geological restrictions. Bd, therefore, should not be present on salamanders on the Kaibab Plateau due to geological restriction. Tiger salamanders in stock tanks located on the Kaibab as well as preserved museum specimens housed in the Arizona State University Natural History Collection were sampled. The results indicate that Bd occurs at low levels on Kaibab Plateau tiger salamanders.

Batrachochytrium dendrobatidis (Bd), the amphibian chytrid fungus causing chytridiomycosis, is the cause of massive amphibian die-offs. As with any host-pathogen relationship, it is paramount to understand the growth and reproduction of the pathogen that causes an infectious disease outbreak. The life-cycle of the pathogen, Bd, is strongly influenced by temperature; however, previous research has focused on Bd isolated from limited geographic ranges, and may not be representative of Bd on a global scale. My research examines the relationship between Bd and temperature on the global level to determine the actual thermal maximum of Bd. Six isolates of Bd, from three continents, were incubated at a temperature within the thermal range (21°C) and a temperature higher than the optimal thermal range (27°C). Temperature affected the growth and zoosporangium size of all six isolates of Bd. All six isolates had proliferative growth at 21°C, but at 27°C the amount and quality of growth varied per isolate. My results demonstrate that each Bd isolate has a different response to temperature, and the thermal maximum for growth varies with each isolate. Further understanding of the difference in isolate response to temperature can lead to a better understanding of Bd pathogen dynamics, as well as allow us the ability to identify susceptible hosts and environments before an outbreak.