Date of Graduation
Davis College of Agriculture, Natural Resources and Design
Division of Forestry and Natural Resources
My study centered on a bioindicator songbird, the Louisiana Waterthrush (Parkesia motacilla), hereafter waterthrush, an organism that co-occurs in both forested and aquatic habitat across the aquatic-terrestrial interface. This enabled the opportunity to quantify demographic, spatial, and epigenetic (i.e., DNA methylation) responses in a highly forested watershed of the Central Appalachians, the areas that have undergone the most rapid transformations over the last decade from unconventional shale gas development and activities. I organized my dissertation into 4 parts (Part 1: Introduction, Part 2: Louisiana Waterthrush Demography, Part 3: Spatial Assessment of Louisiana Waterthrush Foraging, Part 4: Louisiana Waterthrush Molecular Ecology) including 6 chapters that indicate multiple biotic and abiotic factors interacted with or were altered by shale gas development resulting in atypical, negative disturbances that drove a steep decline in a waterthrush population in West Virginia.
Part 1 includes Chapter 1 and is an introduction to my dissertation. I introduce the reader to the rationale for my study, the focal species, research objectives, and the study area. I also mention some limitations to my study that can be considered in any future research endeavors.
Part 2 comprises Chapters 2–3 which are a comprehensive examination of demographic parameters over a six-year period (2009–2011, 2013–2015). In Chapter 2, I examined demographic response to shale gas development for nest abandonment, nest survival, nest productivity, a source-sink threshold, riparian habitat quality, and territory density and length. Nest productivity was lower in areas disturbed by shale gas where a source–sink threshold suggested these areas were more at risk of being sink habitat. Overall results suggest a decline in waterthrush site quality as shale gas development increased. In Chapter 3, I focused on first-year return rates (site fidelity), site fidelity factors, and apparent survival. I related natal fidelity and pairing rates to territory density, and also compared # of breeding attempts between return and non-returning females with and without territory shale gas disturbance. The study identified potential conflicts between factors that influence adult survival and site fidelity that may affect long-term population persistence.
Part 3 includes Chapters 4–5 and focuses on utilizing and accounting for spatial properties intrinsic to stream ecosystems to make informed decisions regarding waterthrush foraging. Chapter 4 was a follow-up to a waterthrush aquatic prey study at our site in 2011 that suggested shale gas development negatively affected waterthrush demography from alterations in their aquatic prey at a watershed scale. During 2013–2014, I quantified waterthrush demographic response and nest survival in relation to potential changes in its aquatic prey due to shale gas development. I utilized spatial generalized linear mixed models that accounted for both spatial and non-spatial sources of variability. I found waterthrush aquatic prey was negatively affected by shale gas development at the nest and territory level, and that there may be a disturbance threshold at which waterthrush can no longer adapt and respond negatively to changes in its aquatic prey. In Chapter 5, I used spatial stream network models (SSNMs) to explore relationships among the waterthrush, stream channel and monitoring data, and the aquatic prey of the waterthrush. I compared the spatial models to traditional regression models to see which ones performed best. We sampled aquatic prey in waterthrush territories and collected wetted perimeter stream channel and water chemistry data along a 50m fixed point stream grid that mapped the foraging substrate or stream channel where waterthrush forage. By relating foraging observations and data collected to the stream grid, I was able to develop a foraging probability index that determined what conditions or variables create or affect ideal foraging locations. Spatial models outperformed traditional regression models and made a statistical difference in whether stream covariates of interest were considered relatable to waterthrush foraging. My study also indicated waterthrush forage in areas of higher biotic stream integrity.
Lastly, Part 4 includes Chapter 6 where I examined epigenetic modifications. These are alterations to genes without changing the gene sequence and can be thought of as an evolutionary "soft" inheritance of gene expression that can either be adaptive or maladaptive for the individual. DNA methylation is one type of epigenetic modification that may vary in response to environmental stressors. We examined the association between DNA methylation and demographic characteristics in addition to potential differential methylation from shale gas development. There was differential methylation for demographic characteristics as well as for adult males between shale gas undisturbed and disturbed areas. Barium (Ba) and strontium (Sr) data were collected in 2013 feather samples where adult males had fewer methylated sites at higher concentrations of Ba and Sr, while nestlings displayed no correlation of methylation to Ba and Sr concentrations. Females displayed increased methylation with increased Ba and Sr, a trend reflected in adult female recaptures. Overall, results of our study suggest sex-specific influences of shale gas development on gene expression that may affect long-term population survival and fitness.
Frantz, Mack W., "Demographic, Spatial, And Epigenetic Response Of The Louisiana Waterthrush (Parkesia Motacilla) To Shale Gas Development" (2019). Graduate Theses, Dissertations, and Problem Reports. 3920.