Theses and Dissertations from UMD

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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.

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Author: search.filters.author.Lepping, Miles

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    Ground-dwelling beetles as bioindicators in transgenic corn
    (2009) Lepping, Miles; Shrewsbury, Paula M; Dively, Galen P; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Ecological risk assessment for transgenic crops requires identification of appropriate biological indicator organisms for use in laboratory and field biomonitoring studies. Ground-dwelling predatory beetles in the families Carabidae and Staphylinidae comprise a diverse and abundant group of nontarget organisms in field corn systems where rootworm-resistant transgenic varieties are deployed. First, the utility of two sampling methods (pitfall trapping and suction-based litter extraction) was assessed for estimating ground beetle (Coleoptera: Carabidae) population parameters in Maryland cornfields. Sampling bias was established for pitfall trapping, confirming the limitations of this semi-quantitative method for capturing a representative portion of the epigeal community. Litter extraction data conformed to predictions for abundance in relation to trophic identity, body size and biomass. Litter extraction identified smaller bodied carabid omnivores and carnivores as numerically dominant over larger bodied species that have received focus in risk assessment studies. A small-bodied carabid, Elaphropus xanthopus (Dejean), was identified as the dominant carnivore, and therefore selected for nontarget exposure and toxicity studies. Second, in choice and no-choice experiments, corn pollen was identified as a realistic, direct exposure pathway to transgenic proteins for E. xanthopus. Third, organism-level exposure to Cry34Ab1 rootworm-resistant protein was demonstrated for E. xanthopus in the laboratory and field during corn pollen shed. Field studies also revealed contamination across transgenic and non-transgenic test plots, indicating experimental design must account for the movement of study organisms and/or transgenic plant tissues. Finally, a toxicity study examined the effects of dietary exposure to rootworm-resistant Cry34/35Ab1 corn pollen for two beetle species, a carabid, E. xanthopus, and a staphylinid, Strigota ambigua (Erichson). Transgenic pollen exposure did not affect longevity or sub-lethal behaviors for either species. Small-bodied, predatory ground beetles are recommended as candidate bioindicator organisms in risk assessment studies designed to optimize field monitoring, exposure detection, and bioassay for transgenic pesticides.
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    THE INFLUENCE OF THERMAL ENVIRONMENT ON DEVELOPMENT AND VULNERABILITY TO PREDATION OF THE AZALEA LACE BUG, STEPHANITIS PYRIOIDES (HETEROPTERA: TINGIDAE)
    (2004-01-09) Lepping, Miles; Shrewsbury, Paula M; Raupp, Mike J; Denno, Robert F; Entomology
    Differential thermal environments were examined for their influence on performance traits of a key ornamental pest, the azalea lace bug, Stephanitis pyrioides, in the presence and absence of a generalist predator, the green lacewing, Chrysoperla carnea. In laboratory studies, duration of development increased for nymphal instars of S. pyrioides as temperature decreased, producing significant developmental lags in cooler environments. Predation trials identified early nymphal stages as more susceptible to predation than older, dispersal-capable stages, specifically in warmer environments. Additionally, morphological characteristics attained at adulthood combined with behavioral defenses may mediate the reduction in consumption of later S. pyrioides stages by piercing-sucking arthropods such as C. carnea. Field studies confirmed development and life-stage vulnerability findings from the laboratory, however, differential thermal environments created by shading did not generally influence predation. In urban landscapes, S. pyrioides may attain a degree of enemy-free space by occupying a thermal refuge in sunny, exposed habitats.