Biology Theses and Dissertations
Permanent URI for this collectionhttp://hdl.handle.net/1903/2749
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Item REFINING METAGENETIC ENVIRONMENTAL DNA TECHNIQUES FOR SENSITIVE BEE COMMUNITY MONITORING(2023) Avalos, Grace; Richardson, Rodney T; Marine-Estuarine-Environmental Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Molecular taxonomic detection is now widespread across the sciences, because of advances in direct PCR, improved marker selection, and increases in sequencing throughput. Facilitated by these advances in sequencing, methodological sensitivity of sample identification has improved substantially. Metagenetic techniques to infer what species are present in a sample by sequencing unknown samples and comparing them to known references has the potential to advance our understanding of biodiversity. Metagenetic analysis of environmental DNA (eDNA) represents a novel, non-lethal method for characterizing floral-associated arthropod communities. Diverse arthropod assemblages interact with flowers, and floral surfaces have been shown to harbor arthropod DNA. We performed metagenetic sequencing on eDNA isolated from flower samples and honey bee-collected pollen samples using multiple markers and compared the frequency and taxonomic breadth of eDNA detections across these genetic markers and substrate types. Understanding which markers and substrates are most effective for eDNA characterization of floral-associated arthropod communities will guide future research and enable low-risk detection of threatened or endangered arthropods.Item BIOLOGICAL CONNECTIVITY OF WETLAND AND STREAM HABITATS ON THE DELMARVA PENINSULA USING AQUATIC MACROINVERTEBRATES(2019) Couch, Brock Thomas; Lamp, William O; Behavior, Ecology, Evolution and Systematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Biological connectivity is the connection of habitats through the movement of organisms that need to utilize said habitats to maintain their life history. Macroinvertebrate communities in freshwater can create biological connectivity by dispersing between temporary and permanent water sources. For this study, I collected and analyzed seasonal and temporal macroinvertebrate data to understand macroinvertebrate communities in six Delmarva Bays and four surrounding streams and identify potential overlapping genera between habitats. Environmental data was also collected to understand seasonal and temporal similarities and differences between Delmarva Bays and streams. For environmental data, Delmarva Bays and streams were most similar during the winter sampling period and become progressively dissimilar until summer sampling periods. For macroinvertebrate data, there were seventeen overlapping taxa that were found within predator and collector-gather feeding guilds. From this data, I can conclude that there is a potential for isolated wetlands and streams to have a biological connection.Item ANALYSIS OF MACROINVERTEBRATE COMMUNITIES IN SEASONAL WETLANDS THROUGH TIME, ACROSS SPACE, AND USING SPECIES TRAITS(2016) Spadafora, Elanor; Lamp, William O; Behavior, Ecology, Evolution and Systematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Restoration of natural wetlands may be informed by macroinvertebrate community composition. Macroinvertebrate communities of wetlands are influenced by environmental characteristics such as vegetation, soil, hydrology, land use, and isolation. This dissertation explores multiple approaches to the assessment of wetland macroinvertebrate community composition, and demonstrates how these approaches can provide complementary insights into the community ecology of aquatic macroinvertebrates. Specifically, this work focuses on macroinvertebrates of Delmarva Bays, isolated seasonal wetlands found on Maryland’s eastern shore. A comparison of macroinvertebrate community change over a nine years in a restored wetland complex indicated that the macroinvertebrate community of a rehabilitated wetlands more rapidly approximated the community of a reference site than did a newly created wetland. The recovery of a natural macroinvertebrate community in the rehabilitated wetland indicated that wetland rehabilitation should be prioritized over wetland creation and long-term monitoring may be needed to evaluate restoration success. This study also indicated that characteristics of wetland vegetation reflected community composition. The connection between wetland vegetation and macroinvertebrate community composition led to a regional assessment of predaceous diving beetle (Coleoptera: Dytiscidae) community composition in 20 seasonal wetlands, half with and half without sphagnum moss (Sphagnum spp.). Species-level identifications indicated that wetlands with sphagnum support unique and diverse assemblages of beetles. These patterns suggest that sphagnum wetlands provide habitat that supports biodiversity on the Delmarva Peninsula. To compare traits of co-occurring beetles, mandible morphology and temporal and spatial variation were measured between three species of predaceous diving beetles. Based on mandible architecture, all species may consume similarly sized prey, but prey characteristics likely differ in terms of piercing force required for successful capture and consumption. Therefore, different assemblages of aquatic beetles may have different effects on macroinvertebrate community structure. Integrating community-level and species-level data strengthens the association between individual organisms and their ecological role. Effective restoration of imperiled wetlands benefits from this integration, as it informs the management practices that both preserve biodiversity and promote ecosystem services.Item THE ATTACK DYNAMICS AND ECOSYSTEM CONSEQUENCES OF STEM BORER HERBIVORY ON SITKA WILLOW AT MOUNT ST. HELENS(2014) Che-Castaldo, Christian; Fagan, William F; Behavior, Ecology, Evolution and Systematics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Variation in plant quality across space and time is considered a driving force behind the heterogeneous distribution of herbivorous insects on their host plants. At the same time, herbivory itself can mediate ecosystem processes that can cause feedbacks directly affecting plant quality. Here I examine both of these processes in a primary successional system to ask how insect herbivory can shape successional outcomes. I performed a three year observational study to determine which host plant factors - stress, vigor, and sex - were associated with insect herbivory by the poplar willow weevil (Cryptorynchus lapathi) on Sitka willow (Salix sitchensis), a dioecious pioneer shrub recolonizing Mount St. Helens after the 1980 eruption. I found that weevils prefer or perform best on vigorously growing willows that are seasonally water stressed. This result highlights the need to integrate hypotheses regarding insect response to stress and vigor into a single phenologically based framework focusing on nutrient mobilization to early insect herbivore life stages. I performed a field experiment involving leaf litter from stems attacked and not by weevils to determine whether weevils mediate nutrient cycling by altering willow leaf litter quality or resources available in its root environment. I found that although weevils do not consume leaves directly, stem herbivory is associated with a large reduction in leaf phosphorus, which in turn decelerates phosphorus cycling on Mount St. Helens. Lastly, I performed observational and experimental studies to show that the large female bias seen in willow on Mount St. Helens is not caused by weevil herbivory or other late acting ecological factors, but likely result from biased seed sex ratios. Taken together, these results suggest that weevil herbivory is retarding willow colonization in upland areas on Mount St. Helens, possibly allowing for alternative successional trajectories.Item Patterns of song and preference variation in Laupala cerasina and their evolutionary implications(2010) Grace, Jaime Leigh; Shaw, Kerry L; Biology; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Closely related species often differ conspicuously in secondary sexual characters, many of which may be shaped by sexual selection. Changes in these characters may directly influence speciation, since females use them to assess males and to choose a mate. I investigate the hypothesis that in closely related populations, divergence in preference for sexually selected characters may promote sexual isolation through assortative mating. Ultimately, if reproductive isolation is complete, this process of divergent sexual selection through preference divergence may result in the formation of new species. I have investigated the relationship between divergence in the pulse rate of male song and female preference for pulse rates in a group of Hawaiian crickets, Laupala cerasina. Within a population, males sing at a characteristic pulse rate, but males from different populations sing with significantly different pulse rates. The degree of population divergence is almost an order of magnitude less than that which distinguishes closely related species of Laupala. Using phonotaxis trials, I found that females show acoustic preferences for males whose pulse rates fall nearest to the population mean. Across populations, male pulse rates and female preferences are significantly correlated, suggesting that they are coevolving. I have demonstrated that females discriminate among songs whose pulse rates vary within the range of pulse rates found among neighboring populations. Furthermore, in choice trials, females prefer the songs of males from the same population to those from neighboring populations. These females also exhibit significant assortative mating based on their acoustic preferences. Divergence in female acoustic preference among populations thus provides a mechanism for generating and maintaining biodiversity through divergence in sexually selected characters used in mate choice.