Ecology and Evolutionary Biology Commons^™

Sources Of Variability In Agronomic Weed Seed Predation: Time, Space, Habitat, And Hyperpredation, Sonja K. Birthisel

Electronic Theses and Dissertations

Weed seed predation is an ecosystem service that benefits farmers by decreasing seedbank inputs, thereby reducing weed pressure in subsequent growing seasons. Seed predation can be considerable, but is highly variable. Sources of variability may include time, space, habitat, and trophic interactions such as hyperpredation. Two experiments were conducted to measure the impacts of these sources of variability on weed seed predation rates in Maine mixed vegetable agroecosystems.

Chapter One of this thesis describes a series of landscape-level field experiments conducted to quantify the effects of time, space, and habitat on seed predation rates. Seed assays, with and without vertebrate …

A Glyptosaurine Lizard From The Eocene (Late Uintan) Of San Diego, California, And Implications For Glyptosaurine Evolution And Biogeography, David Moscato

Electronic Theses and Dissertations

Glyptosaurinae is an extinct subfamily of lizards of the family Anguidae. Glyptosaurine lizards are known exclusively from the Paleogene of North America and Eurasia, reaching their peak of diversity and distribution in the Eocene. In North America these lizards are largely restricted to the intermontane basins along the Rocky Mountain range, with only sparse, indeterminately-identified skeletal elements known from outside of this region. Glyptosaurine lizards are split into two tribes: the monophyletic Glyptosaurini and paraphyletic “Melanosaurini”. Within Glyptosaurini, the most common and widespread genus is Glyptosaurus. In this study I describe a new specimen assignable to G. sylvestris, …

Cause And Impacts Of The Early Season Collapse Of Lilium Grayi (Gray’S Lily), On Roan Mountain, Tn/Nc, Russell J. Ingram

Electronic Theses and Dissertations

A population of the rare Southern Appalachian endemic species Lilium grayi, (Gray’s lily) Roan Mountain, TN/NC was monitored for 2 years to determine the cause and impact of an early season collapse. High concentrations of the Lilium spp. host-specific fungal phytopathogen, Pseudocercosporella inconspicua (G. Winter) U. Braun were associated with 19/20 symptomatic and 0/30 asymptomatic plants. Strength of the association between pathogen and disease and the replication of disease symptoms in 4/4 healthy hosts showed that P. inconspicua was the causal agent of the disease referred to as lily leaf spot. Disease had a severe impact on the population …

Host Use And Geographic Variation In Fall Webworms (Hyphantria Cunea), Katrina J. Loewy

Electronic Theses and Dissertations

Host use in herbivores is determined by a variety of ecological drivers, including bottom-up and top-down selective pressures such as host abundance, host plant quality, and parasitism pressure. If the relative importance and strength of interactions among these selective conditions change over an herbivore’s geographic range, local patterns of host use should change in response, evident in differing diet breadths. The fall webworm (Hyphantria cunea) is a widespread, polyphagous moth with two color morphs, red and black-headed. In the eastern United States, fall webworms feed on dozens of plant species and previous research demonstrated that host plant abundance …

Effects Of Dissolved Nutrient Ratios And Concentrations On Litter-Associated Microbial Activity In Streamside Channels, Timothy Burns

Electronic Theses and Dissertations

Heterotrophic consumers, such as microorganisms and invertebrates, play a fundamental role in the flow of carbon and energy in streams. The effects of dissolved nutrient concentrations, and especially ratios, on litter—associated microorganisms and decomposition rates of detritus are poorly understood. This study addressed the responses of heterotrophic microbes to a wide range of concentrations and ratios of dissolved inorganic nitrogen (N) and phosphorus (P) in streamside channels simulating headwater streams. Two main questions were: (1) do microbial parameters and litter decomposition rates peak at a dissolved N:P ratio that approaches the nutrient ratio of microbial biomass, and (2) does microbial …

Impact Of Macroconsumers On Leaf Breakdown And Detritivores In Wet And Dry Wetlands On A Southeastern Us Coastal Plain Floodplain, Bryanna Libby

Electronic Theses and Dissertations

Interactions among macroconsumers (predators and large omnivores) and detritus breakdown are poorly understood on river floodplains. I evaluated the impact of macroconsumers on leaf breakdown, macroinvertebrate abundance and biomass, and fungal biomass on the Great Pee Dee River floodplain using exclosures in 6 wetlands. Sweetgum (Liquidambar styraciflua) leaves were held in mesh bags and in leaf packs. After 301 days, breakdown rates (k) were low in all treatments (k < 0.003 day-1) and did not significantly differ. Fungal biomass also did not significantly differ between treatments nor did overall macroinvertebrate abundance or biomass. Collector-gatherer invertebrates were significantly more abundant in treatments open to macroconsumers in mesh bags (P<0.001). Shredders had significantly higher biomass in packs held in exclosures closed to macroconsumers (P=0.048). Lack of rain limited stream-floodplain connectivity so a second, shorter study was done in one flooded wetland. After 98 days, pre-conditioned leaves in mesh bags open to macroconsumers had significantly higher breakdown rates (k = 0.0078 day-1) than those closed to macroconsumers (k = 0.0058 day-1; P= 0.050). Fungal biomass did not significantly differ between treatments. Total macroinvertebrate abundance (but not biomass) was higher in mesh bags open to macroconsumers (P=0.014). Scrapers and predators were significantly more abundant in mesh bags opens to macroconsumers (P=0.001 and P=0.004, respectively) than those closed to macroconsumers. These results indicated macroconsumers had a larger impact on litter breakdown in wet floodplain wetlands than in dry ones.

Differences In Habitat At Two Spatial Scales Fail To Predict Differing Occurrences Of Three Species Of Wintering Ammodramus Sparrows In South Carolina Salt Marshes, Kimberly A. Trinkle

Electronic Theses and Dissertations

Salt marshes have low levels of vertebrate diversity yet extremely high rates of endemism. Two of these endemic species are the Saltmarsh (Ammodramus caudacutus) and Seaside Sparrow (A. maritima); the closely related Nelson's sparrow (A. nelsoni) winters exclusively on salt marshes. A previous winter study found that individual sparrows of all three species were highly faithful to specific banding sites, and that the relative abundances of the three species differed by site. I hypothesized that the reason sparrow assemblages varied among sites was that the three species' winter habitat requirements were different. All three species winter in salt marshes, but …

Ecological Effects And Genetic Diversity Of The Invading Rhizocephalan Parasite Loxothylacus Panopaei In The Flatback Mud Crab Eurypanopeus Depressus, Kathryn A. O'Shaughnessy

Electronic Theses and Dissertations

The rhizocephalan barnacle Loxothylacus panopaei (Gissler, 1884) is a parasite of xanthid crabs. Infection results in parasitic castration and anecdysis of the host. Loxothylacus panopaei is invasive to the US Atlantic coast. The parasite's range was expanded by introduction of infected crabs to Chesapeake Bay in the mid-1960s, and now extends from Long Island Sound, New York to Cape Canaveral, Florida. Monthly flatback mud crab (Eurypanopeus depressus Smith, 1869) collections over 13 months (January 2012-January 2013) at three South Carolina locations found an overall parasite prevalence of 24.2% (391 of 1,615), and provided the first reports of L. panopaei at …

Sagebrush Ecosystem Characterization, Monitoring, And Forecasting With Remote Sensing: Quantifying Future Climate And Wildlife Habitat Change, Collin G. Homer

Electronic Theses and Dissertations

Sagebrush (Artemisia spp.) ecosystems constitute the largest single North American shrub ecosystem and provide vital ecological, hydrological, biological, agricultural, and recreational ecosystem services. Disturbances continue to alter this ecosystem, with climate change possibly representing the greatest future disturbance risk. Improved ways to characterize and monitor gradual change in this ecosystem are vital to its future management. A new remote sensing sagebrush characterization approach was developed in Wyoming which integrates three scales of remote sensing to derive four primary continuous field components (bare ground, herbaceousness, litter, and shrub), and four secondary components (sagebrush, big sagebrush, Wyoming sagebrush, and shrub …

Variation In Population Densities Of The Florida Scrub Lizard (Sceloporus Woodi) Between Managed Sand Pine Scrub And Longleaf Pine Stands In The Ocala National Forest, Matthew D. Kaunert

Electronic Theses and Dissertations

Population-level response to habitat fragmentation is central to applied species management and conservation. Managed landscapes are often subject to increased fragmentation and, consequently, may force once connected populations to function as metapopulations. Studies investigating metapopulations occurring over patchy, managed landscapes are of increasing importance as fragmentation is a known cause of biodiversity loss. In June-September 2012, populations of the rare, endemic Florida scrub lizard (Sceloporus woodi) were sampled across the Ocala National Forest (ONF) to compare abundance and density across two management types. In the ONF, sand-pine scrub is clearcut and rollerchopped whereas longleaf pine is managed via …