Biology Theses

Chytridiomycosis, caused by the etiologic agent Batrachochytrium dendrobatidis, affects the keratinocytes of the amphibian epithelium. While there have been several studies done on B. dendrobatidis both in vivo and in vitro, there is still little known about what environmental factors influence the growth of this fungus. To better understand such factors, a novel, high-throughput in vitro system was developed that utilized tissue culture plates as a submerged in vitro substrate. After analyzing B. dendrobatidis's life cycle in this new system, studies were conducted to determine the impact of pH, phosphate and nitrate concentration, and protein concentration on its growth. Results showed that B. dendrobatidis completed its life cycle in submerged tissue culture wells and that growth rates were sensitive to concentrations of protein and environmental pH. Results suggest that B. dendrobatidis can regulate its growth kinetics depending on access to environmental nutrient sources.

The blacklegged tick is the main vector for Lyme disease and Powassan virus Lineage II (Deer Tick Virus) in the United States. The objective of this study was to identify the prevalence of Powassan virus (DTV) and Lyme disease in adult and nymph blacklegged ticks collected in New Jersey (2015-2018) and Pennsylvania (2017-2018). All ticks were collected from lived trapped or hunter harvested black bears (Ursus americanus). A total of 2,713 ticks were collected, made up of four species. Only blacklegged ticks were analyzed in this study. Real-time Reverse Transcriptase Polymerase Chain Reaction (RT-PCR) was used to amplify cDNA specific to the NS5 gene of POW Lineage II, and qPCR was used to amplify the 16s-23s intergenic spacer region rDNA of Borrelia burgdorferi (Lyme disease). A minimum infection rate (MIR) of 3.52% was determined for Powassan vitus and a MIR of 19.2% for Lyme disease. The findings in this study were similar to previous studies conducted for Powassan and Lyme prevalence in Lyme endemic region.

This project examined the relationship between anthropogenic habitat disturbance and population levels in Crotalus horridus (Timber Rattlesnake). This study relied on population and habitat information collected by the Pennsylvania Fish and Boat Commission (PFBC) during a previous study known as the Timber Rattlesnake Assessment Project (TRAP). Geographic Information Science (GIS) was utilized to measure landscape features such as canopy coverage, trails, and road density through habitat utilized by Timber Rattlesnakes. Using the information from TRAP, in conjunction with GIS technology, quantitative results were produced and analyzed to construct a clear picture of how human habitat alterations affect Timber Rattlesnake populations. The results were primarily derived from two main models, (1) a linear regression with a normalize distribution and (2) a generalized linear model with a binomial distribution. An inverse relationship was found between rattlesnake populations and proximity and density of buildings at the large spatial scale. These findings suggest that anthropogenic disturbance impacts Timber Rattlesnakes negatively in the commonwealth. The weak relationships between the variables assessed may be, in part, attributable to the use of TRAP reports which were mostly based on one or two site visits and not intended to provide population estimates. Further work will be necessary to refine our models, including improved population estimates and expansion of our work to the entire commonwealth.

The northern waterthrush (Parkesia noveboracensis) experienced a drastic decline between the first and second Pennsylvania Breeding Bird Atlases despite higher sampling effort during the second atlas. Atlas data suggested a slight northward range contraction and detectable increase in elevation of occupied blocks, potentially caused by climate change. This study investigates factors that may be responsible for any detected changes in distribution in northeastern Pennsylvania (Pike, Monroe and Northampton counties). In spring of 2017 and 2018, wetland surveys were conducted to detect singing males. At each of 53 sites, point counts were conducted to characterize the avian community. Vegetative, physical, and hydrological characteristics were also recorded. Sites occupied by northern waterthrush were compared to unoccupied sites in apparently suitable habitat. Shrub height and upturned tree roots were found to be significantly different between site types as was the avian community and the herbaceous plant community. It was also found that there was a range contraction at both the northern and southern end of the NOWA range between the two atlases in the study area. These results suggest that changes in vegetation structure due to deer overbrowsing and eastern hemlock decline are contributing to the decline observed between atlases.