UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

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 given thesis/dissertation in DRUM.

More information is available at Theses and Dissertations at University of Maryland Libraries.

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Subject: search.filters.subject.Generalist Predators

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    The role of relative abundance and identity in the effectiveness of generalist predators as biocontrol agents of Pieris rapae L. (Lepidoptera: Pieridae)
    (2006-12-11) Moreno, Carlo Rene; Barbosa, Pedro; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The importance of generalist arthropod predator assemblages in suppressing pests has recently received more attention. However, few studies have investigated the impacts of assemblage structure on pest mortality. This study assessed the influence of relative abundance and taxonomic identity among an assemblage of generalist predators in collards, (Brassica oleracea var. acephala), on the mortality of Pieris rapae. In field surveys and laboratory assays, I determined that Coleomegilla maculata was the numerically dominant while Coccinella septempunctata and Podisus maculiventris were numerically subdominant predators of P. rapae larvae. Experimental mesocosms were used to determine whether numerically dominant predators alone, regardless of taxonomic identity, imposed greater P. rapae larval mortality than when in an assemblage. As numerically dominant species, only C. septempunctata imposed greater P. rapae larval mortality alone than when in an assemblage. This research highlights the importance of considering both relative abundance and identity in studies involving predator assemblages and biocontrol.
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    The Influence of Predator Species Richness on Prey Mortality: Implications to Conservation Biological Control.
    (2006-12-04) Lewins, Scott Asher; Barbosa, Pedro; Entomology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Understanding how changes in biodiversity affect the function of agroecosystems is paramount to conservation biological control. The Species Assemblage Control Hypothesis predicts increasing species richness of predator assemblages can increase the assemblages' ability to suppress pests. I hypothesized that an increase in species richness of a predator assemblage leads to an increase in prey mortality and predator species identity can alter the relationship. An assemblage of predators identified from an assessment of a collard agroecosystem was evaluated to find that only some predators fed on larval Pieris rapae, they did not differ in their per capita consumption, and some intraguild predation occurred. In testing the hypotheses I found a significant relationship between predator species richness and prey mortality; however, predator species identity altered the relationship. These findings highlight the importance in understanding predator assemblages before conservation decisions that effectively suppress pests can be made.