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.

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    Investigation of Bilingual Disadvantage in Verb and Noun Retrieval in Mandarin-English Bilinguals
    (2017) Li, Ran; Faroqi-Shah, Yasmeen; Hearing and Speech Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The bilingual literature has shown a bilingual disadvantage in spoken language compared to monolinguals. This study first investigated how highly proficient Mandarin-English bilinguals retrieved verbs and nouns compared to monolingual English speakers in a picture-naming task. In order to explain why bilinguals are disadvantaged than monolinguals in language processing, this study examined if it was due to the frequency effect, which was predicted by the “weaker-links”, or if it was due to the translatability effect, as predicted by the cross language interference. Results captured a bilingual effect, a word category effect, and a smaller bilingual disadvantage for verbs than for nouns in lexical retrieval. The bilingual disadvantage could be explained by the “weaker-links” hypothesis, rather than the cross language interference. But the smaller bilingual verb disadvantage could be partially explained by the cross language interference hypothesis. Clinical implications and future research directions were discussed.
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    Evaluating Competition between the Non-native Slug Arion subfuscus and the Native Slug Philomycus carolinianus
    (2010) Paustian, Megan Elisabeth; Barbosa, Pedro; Behavior, Ecology, Evolution and Systematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The degree to which invasive species have altered the demography, ranges, and microhabitat occupation of native species is poorly known. Yet, the competition-mediated decline of native populations, in concert with other factors such as habitat degradation, can place native species at risk of extirpation. Understanding whether competition between native and non-native species can take place under ordinary environmental conditions can allow us to extrapolate whether native species are likely to have experienced harm in the past and/or if they are likely to do so in the future. The native slug Philomycus carolinianus is likely to compete for resources with the aggressive non-native slug Arion subfuscus in central Maryland forests. In order to establish whether competition occurs between these two species, I tested for the following criteria: the existence of competitive displacement in the field, overlap in the use of limited resources (shelter and food), a decline in the fitness of P. carolinianus in the presence of A. subfuscus, and the action of competition mechanisms (interference and exploitation) between them. Field surveys showed that displacement between A. subfuscus and P. carolinianus does not apparently occur within mixed natural populations. Resource use of the two slugs overlapped, with part of the diet (i.e. fungus) and a large proportion of the microhabitats occupied (i.e. coarse woody debris) in common. A lab experiment established that low natural levels of food (fungus) can limit the fitness of each slug species, while shelter (coarse woody debris) was not limiting. When sharing a low-resource lab cage with either A. subfuscus or conspecifics, P. carolinianus experienced a similar decline in fitness, suggesting that exploitative resource competition was no greater between heterospecifics than between conspecifics. No evidence of heterospecific interference (competition independent of resource levels) was found. Given the limited support for the criteria of competition, A. subfuscus was not shown to be an immediate threat to the persistence of P. carolinianus.