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Wildlife disease surveillance and pathogen detection are fundamental for conservation, population sustainability, and public health. Detection of pathogens in snakes is often overlooked despite their essential roles as both predators and prey within their communities. Ophidiomycosis (formerly referred to as Snake Fungal Disease, SFD), an emergent disease on the North American landscape caused by the fungus Ophidiomyces ophiodiicola , poses a threat to snake population health and stability. We tested 657 individual snakes representing 58 species in 31 states from 56 military bases in the continental US and Puerto Rico for O . ophiodiicola . Ophidiomyces ophiodiicola DNA was detected in samples from 113 snakes for a prevalence of 17.2% (95% CI: 14.4–20.3%), representing 25 species from 19 states/territories, including the first reports of the pathogen in snakes in Idaho, Oklahoma, and Puerto Rico. Most animals were ophidiomycosis negative (n = 462), with Ophidiomyces detected by qPCR (n = 64), possible ophidiomycosis (n = 82), and apparent ophidiomycosis (n = 49) occurring less frequently. Adults had 2.38 times greater odds than juveniles of being diagnosed with ophidiomycosis. Snakes from Georgia, Massachusetts, Pennsylvania, and Virginia all had greater odds of ophidiomycosis diagnosis, while snakes from Idaho were less likely to be diagnosed with ophidiomycosis. The results of this survey indicate that this pathogen is endemic in the eastern US and identified new sites that could represent emergence or improved detection of endemic sites. The direct mortality of snakes with ophidiomycosis is unknown from this study, but the presence of numerous individuals with clinical disease warrants further investigation and possible conservation action.

The chytrid fungus Batrachochytrium dendrobatidis (Bd) has been devastating amphibians globally. Two general scenarios have been proposed for the nature and spread of this pathogen: Bd is an epidemic, spreading as a wave and wiping out individuals, populations, and species in its path; and Bd is endemic, widespread throughout many geographic regions on every continent except Antarctica. To explore these hypotheses, we conducted a transcontinental transect of United States Department of Defense (DoD) installations along U.S. Highway 66 from California to central Illinois, and continuing eastward to the Atlantic Seaboard along U.S. Interstate 64 (in sum from Marine Corps Base Camp Pendleton in California to Naval Air Station Oceana in Virginia). We addressed the following questions: 1) Does Bd occur in amphibian populations on protected DoD environments? 2) Is there a temporal pattern to the presence of Bd? 3) Is there a spatial pattern to the presence of Bd? and 4) In these limited human-traffic areas, is Bd acting as an epidemic (i.e., with evidence of recent introduction and/or die-offs due to chytridiomycosis), or as an endemic (present without clinical signs of disease)? Bd was detected on 13 of the 15 bases sampled. Samples from 30 amphibian species were collected (10% of known United States' species); half (15) tested Bd positive. There was a strong temporal (seasonal) component; in total, 78.5% of all positive samples came in the first (spring/early-summer) sampling period. There was also a strong spatial component—the eleven temperate DoD installations had higher prevalences of Bd infection (20.8%) than the four arid (<60 mm annual precipitation) bases (8.5%). These data support the conclusion that Bd is now widespread, and promote the idea that Bd can today be considered endemic across much of North America, extending from coast-to-coast, with the exception of remote pockets of naïve populations.

The Timber Rattlesnake (Crotalus horridus) occurs in discontinuous populations throughout the eastern and central United States. The species exhibits high levels of polymorphism in morphological traits, especially in coloration and pattern. Previous studies recognized either distinct northern and southern subspecies or three regional morphs (northern, southern, and western), but conflicting data sets and limited geographic sampling o f previous studies have left the relationships among those regional variants unclear. In this study, univariate and multivariate statistics, together with a geographic information system, were used to analyze geographic variation in 36 morphological characters recorded from 2,420 specimens of C. horridus across its range.Sexual dimorphism was strong in ventral and subcaudal scales, and weak to moderate in band length and band spacing. Univariate analyses detected substantial geographic variation in all meristic characters. Scutellation exhibited a general northsouth pattern of variation, and most scale counts averaged higher in southern regions. Pattern characters differentiated the northeastern, central-eastern, and north-central regions from the southern and western regions. Coloration displayed a pattern of strong clinal variation among three broad areas consisting of the combined northeastern, centraleastern, and southern Appalachian regions, the northwestern regions, and the southern Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. regions. Morphometric characters exhibited a general north-south pattern of geographic variation, with larger head and body sizes in southern regions. Principal component analysis indicated that band length was the most important variable for characterizing geographic variation. The northeastern regions remained moderately distinct in all multivariate cluster analyses. The northwestern regions appeared very distinct in most cluster analyses for females. However, the clusters in all models showed extensive geographic overlap. Percentage maps of clusters revealed two north-south patterns of clinal variation among the northeastern, northwestern, and southern regions. The discordant patterns of variation among individual characters, the overlapping patterns of coloration, and the extensive overlap among the multivariate clusters collectively indicate that zones of intergradation among subpopulations of C.horridus are much broader than previously thought. Furthermore, the general patterns of geographic variation are strongly clinal and support the conclusion that C. horridus is a single widespread, polymorphic species.Reproduced with permission o f the copyright owner. Further reproduction prohibited without permission. V This dissertation is dedicated to my mother, Barbara Allsteadt, for her unconditional love and support.Reproduced with permission of the copyright owner. Further reproduction prohibited without permission.

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