Theses and Dissertations from UMD
Permanent URI for this communityhttp://hdl.handle.net/1903/2
New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM
More information is available at Theses and Dissertations at University of Maryland Libraries.
Browse
3 results
Search Results
Item INFORMING CONSERVATION OF THREATENED BAT SPECIES USING GENOMICS AND ACOUSTICS(2022) Nagel, Juliet Joy; Nelson, David; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Bats are vital to healthy ecosystems, providing billions of dollars of services in the form of forest and crop pest control. Unfortunately, North American bat populations have faced novel pressures during the past decade that may threaten their persistence. First, several species of tree-roosting bats (primarily hoary [Lasiurus cinereus], eastern red [L. borealis], and silver-haired [Lasionycteris noctivagans] bats) are experiencing large numbers of fatalities at industrial wind-energy facilities. Second, several species of cave-dependent bats have experienced large-scale mortality as the result of infection by a fungal pathogen that causes white-nose syndrome (WNS). As bats are generally long-lived and have low reproductive rates, such increases in mortality can cause significant population declines from which they may be unable to recover. Basic questions about population trends, size and structure remain largely unanswered for these species because of challenges in applying traditional wildlife monitoring approaches to bats. This lack of understanding impedes conservation and management efforts. In my dissertation, I use genomic and acoustic survey techniques to investigate questions related to the threats that wind-energy development and WNS are posing to bat species in North America. In my first chapter, I evaluate range-wide population structure and effective population size (Ne) for hoary, eastern red, and silver-haired bats. Using genotyping-by-sequencing (GBS), I genotyped single-nucleotide polymorphism (SNP) data from 173 hoary, 113 eastern red, and 89 silver-haired bats from multiple locations spread across their geographic distributions. Hoary bats and eastern red bats showed no geographic structure in genetic diversity, whereas silver-haired bats displayed longitudinal population variation. Coalescent modeling suggested that eastern red bats have the largest evolutionary Ne, followed by hoary bats, then silver-haired bats. In my second chapter, I used GBS to assess the population structure of two federally endangered cave bat species: Indiana bats (Myotis sodalis) and gray bats (M. grisescens). Using tissue samples from 45 Indiana bats and 47 gray bats spread across their ranges, I showed that Indiana bats display no geographic genetic structure, whereas gray bats exhibit east–west population variation across the Mississippi River Valley. In my final chapter, I used acoustic surveys across the State of Maryland to investigate bat community changes in the decade following the arrival of WNS. From 2010 through 2019, I conducted annual mobile acoustic routes each summer, for a total of 344 completed routes resulting in 426 hours of recordings and 24,375 identified bat passes. I detected massive (> 92%) declines of little brown bats (M. lucifugus), northern long-eared bats (M. septentrionalis), eastern small-footed bats (M. leibii), and tricolored bats (Perimyotis subflavus), with no evidence of recovery in recent years. Trends in hoary bats and eastern red bats were non-significant during this period. Bat community composition varied among Maryland’s physiographic regions, with eastern red bats comprising a larger percentage in the east. Species composition across the state likely reflects the impact of several factors, including mortality from WNS and wind-energy development, and perhaps reduced interspecific competition. Overall, my results illustrate the unique insights, but also distinct limitations, that genomic and acoustic data can provide regarding the conservation of bats in North America.Item The relationship between maternal speech clarity and infant language outcomes(2011) McColgan, Kerry; Ratner, Nan B; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Mothers' use of infant-directed speech (IDS) may assist infants in decoding language input. IDS is characterized by exaggerated prosodic features (Fernald, 1989), shorter mean length of utterance (Cooper, 1997; Bernstein Ratner, 1996), repetition (Bernstein Ratner, 1996), and more highly clarified acoustic qualities (Bernstein Ratner, 1984; Malsheen, 1980) in comparison to speech directed to adults. However, it is not yet known to what extent such measures of maternal input have long-term impacts on language development. This thesis seeks to test the overarching hypothesis that children who receive more clarified speech input during the prelinguistic stage may be expected to have better language skills at an earlier age than children who receive poorer quality input.Item Distributed Source Localization and Tracking Algorithms for Ad-hoc Acoustic Sensor Networks(2006-05-05) Pham, Tien; Papadopoulos, Haralabos C; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)In this dissertation, we construct an algorithmic framework for systematic tracking of moving sources in large-scale sensor networks. The tracking algorithms we developed generate the estimates of the tracking locations from fusion of space-time data by first fusing the data in space and subsequently by fusing the data in time. Fusion in space is performed by fusing current sensed data that is sufficiently high-quality from the sensor nodes to produce the current source location estimate. These location estimates are indexed as they become available and subsequently fused iteratively in time to produce tracking estimates. Both fusion in space and fusion in time are performed distributively over the ad-hoc sensor network by exploiting distributed algorithms of computation of averages. The distributed tracking algorithms are locally constructed at each participating sensor node exploiting only locally available sensor observations and local available network connectivity information. These algorithms we developed are also resource efficient, scalable, fault-tolerant and can readily adapt to local changes in network topologies. We present methods for optimizing and characterizing the performance of the algorithms as a function of the quality of the sensor measurements, the source dynamics, the sensor density and the network connectivity.