Doctor of Philosophy / Division of Biology / Brett K. Sandercock / Gastrointestinal microbiota play a vital role in maintaining organismal health, through facilitating nutrient uptake, detoxification and interactions with the immune system. Shorebirds vary widely in life-history characteristics, such as habitat, migration and breeding system, but the dynamics of their gut microbial communities are unknown. In my dissertation, I investigated composition and dynamics of gut microbiota in migratory shorebirds from embryos to 10 day old chicks, and determined environment and host-related factors affecting gut microbial communities of adults. First, I tested whether precocial chicks from three species of arctic-breeding shorebirds acquire gut microbiota before or after hatching using next-generation sequencing. In addition, I documented the dynamics of gut microbial establishment. I showed that gut microbiota were absent in shorebird embryos before hatching, but that stable gut communities established within the first three days after hatching. In addition, gut microbiota of young shorebird chicks were more similar to the environmental microbiome than later in life, suggesting that the environment is a likely source for microbial recruitment. After reaching adulthood, shorebirds migrate long distances, potentially exposing them to a wide range of microorganisms. Host phylogeny and environmental factors have both been identified as drivers of gut microbiota composition in birds in previous studies. The second part of my project aimed to compare the relative importance of host and environmental factors that underlie variation in gut microbiota composition in eight species of migratory shorebirds sampled across the North American Arctic. I found that sampling site was the main driver of variation in gut microbiota of Arctic-breeding shorebirds, and that site-related variation in gut microbiota of shorebirds was a result of differences in core bacterial taxa that occurred in more than half of the analyzed samples. A relatively large influence of local environment on gut microbiota composition of chicks and adults lead to the question: how does site affect pathogen prevalence in shorebirds? Migratory behavior has been hypothesized to have evolved as a response to variation in climatic conditions and food availability, to avoid predation, and to reduce risk of exposure to pathogens. The migratory escape hypothesis predicts avoidance of high disease prevalence areas through migration, and has been proposed as one of the main reasons that many bird species migrate to the Arctic for breeding. To test the migratory escape hypothesis in shorebirds, I screened for prevalence of seven known avian pathogens in shorebirds at different stages of migration. I did not detect the majority of pathogens we tested for, with the exception of Campylobacter jejuni and C. coli. Prevalence of C. jejuni in shorebirds was linked to sampling sites but not shorebird species. My dissertation is the first comprehensive study to broadly characterize the gut microbiota in shorebirds. Overall, local environment emerged as an important factor in shaping microbiota composition in Arctic-breeding shorebirds throughout my dissertation research. The role of local environment in shaping gut microbiota invites future investigations of the interactions among shorebirds and the microorganisms present in their environment, as well as the functions gut microbiota perform within their shorebird hosts.

Little is known about the tick populations found within the central Appalachian/southwestern region of Virginia. The main focus of this research was to better assess local tick communities in the central Appalachian-Southwestern region of Virginia, which was addressed by determining species diversity, habitat associations, seasonal phenology, pathogen prevalence, and ecological factors that influences tick presence and abundance. A field study was conducted from June 2019 - November 2020 across 8 counties and 3 habitat types. Forested habitats exhibited greater tick species diversity than pasture and urban habitats. Each tick species was observed to be associated with particular habitats. The presence of B. burgdorferi sensu stricto (causative agent of Lyme disease), the human variant of A. phagocytophilum (causative agent of human granulocytic anaplasmosis), and Powassan virus (the causative agent of Powassan encephalitis) were detected in collected field specimens, suggesting a significant threat to public health. The detection of Powassan virus RNA in local Ixodes scapularis ticks is the first evidence of this viral pathogen within the region. The overwintering abilities of ticks, whose populations are expanding or becoming more invasive, including Haemaphysalis longicornis, Amblyomma americanum, and Amblyomma maculatum, were examined through a combination of laboratory and field experiments. Amblyomma americanum and H. longicornis nymphal ticks had a lower supercooling temperature than adult ticks, suggesting their potential to overwinter better; A. maculatum nymphs had similar average supercooling temperatures as the other two species at nymphal stage. Via a field experiment, A. americanum, H. longicornis, and A. maculatum were subjected to natural elements of a Virginian winter in a two-factor design investigating elevation and potential insulation coverage. Elevation and insulation coverage were found to have no significant impact on the overwintering survival of H. longicornis and A. americanum. However, the life-stage of the tick was determined to be a significant factor that dictated the survival of ticks of these species. Overwintering survival of Amblyomma maculatum nymphs was influenced by insulation (proxied by leaf litter); which may be attributed to this tick's preference of drier climate. Low overwintering survival suggests that a tick may not be able to establish a permanent population within the area. / Master of Science in Life Sciences / Ticks can transmit many pathogens, bacteria or viruses that cause disease, to both humans and animals. Diseases associated with ticks can include Lyme disease, Human Anaplasmosis, Ehrlichiosis, Rocky Mountain spotted fever, as well as viral illnesses. The pathogens that cause these diseases are vectored by specific tick species. Currently, there are no published reports of tick species present within the central Appalachian/southwestern region of Virginia. A study to determine local tick populations presence and the factors influencing their maintenance in the environment was conducted. Additionally, field collected specimens were screened to assess pathogen prevalence within the region. I confirm the presence of Borrelia burgdorferi sensu stricto (causative agent for Lyme disease), Anaplasma phagocytophilum (causative agent for Human Granulocytic Anaplasmosis), and Powassan virus within Ixodes scapularis, commonly referred to as black-legged ticks. Habitat (forest, urban, pasture) was a significant influencing factor on the presence of I. scapularis, Amblyomma americanum, and Haemaphysalis longicornis (e.g., the latter species was predominantly found in pasture habitats). Secondly, I investigated how well three sympatric tick species would overwinter within the region. Survival of a tick is heavily dependent upon their ability to withstand desiccation, obtain a blood meal from a host, mate, and reproduce. Certain ticks may be limited to certain regions based on elevation, temperature, and relative humidity. I investigated the influence of elevation and insulation coverage (presence of leaves vs. no leaves) on A. americanum (Lone star tick), H. longicornis (Asian longhorned tick), and A. maculatum (Gulf Coast tick). Elevation and insulation coverage had no significant impact on the overwintering survival of the Lone star and Asian longhorned ticks. Tick survival was mainly dictated by what life-stage they were in; Lone star ticks survived better as adult than at other life stages. Asian longhorned ticks survived better as nymphs than larva and adults. Insulation coverage influenced the overwintering survival of the Gulf Coast tick. These ticks survived better with no leaves, which may be associated with their preference of drier climates.

Due to recent declines regarding pollinators, The Swedish Civil Contingencies Agency launched a project investigating possible biological threats towards wild bumblebees. This led to an extensive collection of bumblebees from areas in southern Sweden during the summer of 2018. The purpose of this project was to investigate the prevalence of ten bumblebee pathogens and see if there were any difference in prevalence in areas with and areas without commercial bumblebees. This study also aimed to investigate if the prevalence of the pathogens tended to fluctuate during the season. Of the collected bumblebees (Bombus spp) the ones from the late summer season were analyzed in this project, and data from the already analyzed samples from the early summer season was used. To screen the bumblebees for the pathogens a laboratory process was followed with dissections – homogenization – DNA and RNA extractions – conversion of RNA to cDNA and lastly real-time quantitative PCR. The results showed significant differences between areas with and without commercial bumblebees for some pathogens, but the results were only consistent between early and late season for Apicystis bombi and Black queen cell virus. Apicystis bombi had a higher prevalence (2,0 and 3,0 for late and early season) in areas with commercial bumblebees. Black queen cell virus had a higher prevalence (1,3 and 1,6 for late and early season) in areas without commercial bumblebees. For the seasonal fluctuation a significant difference between early and late season could be seen for the pathogens – Crithidia bombi, Apicystis bombi, Locustacarus buchneri and Sphaerularia bombi.