Effects of spatial subsidies and canopy cover on pond communities and multiple life stages in amphibians

Title from PDF of title page (University of Missouri--Columbia, viewed on October 26, 2012).The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file.Dissertation advisor: Dr. Raymond D. SemlitschIncludes bibliographical references.Vita.Ph. D. University of Missouri-Columbia 2012."July 2012"Spatial subsidies are resources that move from one ecosystem to another. In aquatic systems, canopy cover determines both light availability and subsidy input in the form of senescing leaves. This phenomenon has been well studied in streams, and general patterns of ecosystem production, community structure, and the reciprocal export of animals have been discovered. I was interested in whether these patterns also occurred in ponds. I examined these patterns using experimental pond mesocosms and supported the results using an observational study of natural ponds. For the pond mesocosm experiment, I placed mesocosms along a canopy cover gradient and manipulated spatial subsidy input. I found a shift from net heterotrophy in closed canopy mesocosms to a balance between heterotrophy and autotrophy in open canopy mesocosms. The macroinvertebrate community structure responded to both canopy cover and subsidy input in mesocosms. The biomass of collectors (detritivores) was highest in mesocosms with litter input and increased with canopy cover, a pattern also present in natural ponds. Finally, I found that litter input increased the reciprocal export of amphibian biomass compared to no input. Amphibian biomass also decreased with increases in primary productivity. This research highlights the importance of spatial subsidies that connect different ecosystem types. Conserving these ecosystem connections will help maintain biodiversity and ecosystem function.Includes bibliographical reference

Effects of Leaf Diversity on Tannin Concentration and Water Quality

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Effects of Leaf Tannin Concentration on Aquatic Beetle Colonization

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Effects of Freshwater Microorganisms on the Degradation of Tannins

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Effects of Leaf Litter on Amphibian Oviposition Site Selection

Rebekah Magee is a graduate student in the School of Biological Sciences at Louisiana Tech University. Julia E. Earl is an Assistant Professor in the School of Biological Sciences at Louisiana Tech University. The abstract for this presentation can be downloaded by clicking on the blue download button

Amphibian Oviposition Site Selection Preferences in Response to Leaf Litter Chemical Characteristics

Rebekah Magee and Julia E. Earl are a part of the School of Biological Sciences at Louisiana Tech Universit

The Effects of Leaf Tannin Concentration on Water Quality

Ian Lovemore, Joseph Phillips, and Julia E. Earl are a part of the School of Biological Sciences at Louisiana Tech University

The effects of leaf litter type on the growth and development of gray treefrog tadpoles

Abstract only availableForestry practices are implemented worldwide to manage tree populations and harvest resources. Forestry practices involve the thinning and/or intentional planting of trees which influences canopy cover and litter species. Leaf litter from different species play a role in pond ecosystems as a source of nutrients, refugia from predators, and a food source. When certain litter species are eliminated from or added to pond ecosystems, it can have diverse effects on ecosystem processes and pond communities, including amphibians, which are declining worldwide. To test the effects of litter species on ecosystem processes, water quality, and tadpole growth and development, we set up mesocosm tanks with five litter species: red oak, white oak, sugar maple, white pine, and prairie cordgrass. Phyto- and zooplankton inoculum and 40 gray treefrog hatchlings were added to each tank. A diel oxygen technique was used to measure community metabolism and primary productivity. We measured pH, dissolved oxygen, and temperature throughout the study. Size and time to metamorphosis of gray treefrogs will be measured as indicators of fitness. Preliminary results indicate differences among treatments in water quality and ecosystem processes. Water in tanks with pine and red oak had a higher pH than sugar maple and white oak, while tanks with grass were intermediate. The sugar maple and white oak treatment were consistently lower in dissolved oxygen than all other treatments. Grass and red oak had higher levels of primary productivity and community metabolism than sugar maple and white oak, with pine being intermediate in both. Differences in primary productivity could be related to concentrations of nutrients in the litter, the rate of litter decomposition, or both. Future data on decomposition and nutrients could determine which of these are more important. Preliminary observations reveal that tadpoles are smaller in white oak than in other treatments, possibly from lower primary productivity. These results indicate that forestry practices could influence water quality and ecosystem processes.NSF Undergraduate Mentoring in Environmental Biolog

Assessing the Current Status and Distribution of Crawfish Frogs in Louisiana

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Resident Skin-specific γδ T Cells Provide Local, Nonredundant Regulation of Cutaneous Inflammation

The function of the intraepithelial lymphocyte (IEL) network of T cell receptor (TCR) γδ+ (Vγ5+) dendritic epidermal T cells (DETC) was evaluated by examining several mouse strains genetically deficient in γδ T cells (δ−/− mice), and in δ−/− mice reconstituted with DETC or with different γδ cell subpopulations. NOD.δ−/− and FVB.δ−/− mice spontaneously developed localized, chronic dermatitis, whereas interestingly, the commonly used C57BL/6.δ−/− strain did not. Genetic analyses indicated a single autosomal recessive gene controlled the dermatitis susceptibility of NOD.δ−/− mice. Furthermore, allergic and irritant contact dermatitis reactions were exaggerated in FVB.δ−/−, but not in C57BL/6.δ−/− mice. Neither spontaneous nor augmented irritant dermatitis was observed in FVB.β−/− δ−/− mice lacking all T cells, indicating that αβ T cell–mediated inflammation is the target for γδ-mediated down-regulation. Reconstitution studies demonstrated that both spontaneous and augmented irritant dermatitis in FVB.δ−/− mice were down-regulated by Vγ5+ DETC, but not by epidermal T cells expressing other γδ TCRs. This study demonstrates that functional impairment at an epithelial interface can be specifically attributed to absence of the local TCR-γδ+ IEL subset and suggests that systemic inflammatory reactions may more generally be subject to substantial regulation by local IELs