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Articles 1 - 7 of 7
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Coexistence Of Sympatric Taxa Of Chamaecrista Section Xerocalyx: Addressing The Interplay Between Morphology And Biotic Interactions, Beatriz Baker-Méio
Coexistence Of Sympatric Taxa Of Chamaecrista Section Xerocalyx: Addressing The Interplay Between Morphology And Biotic Interactions, Beatriz Baker-Méio
Dissertations
Animal-plant interactions may prevent gene flow and promote divergent selection among closely related plants, ultimately leading to formation of new species. This may be the case for Chamaecrista sect. Xerocalyx, in which two or more of the 24 varieties often are encountered in the same area, with marked morphological and phenological differences among them. Over a broad geographical range, however, the morphological gaps among varieties disappear. Several biotic interactions contribute to the fitness of Chamaecrista species. Their flowers are pollinated by bees, and herbivores attack their leaves, flowers, fruits, and seeds. In addition, all species produce extrafloral nectar, which …
Urban Development In Costa Rica: The Direct And Indirect Impacts On Local And Regional Avian Assemblages, Jeff L. Norris
Urban Development In Costa Rica: The Direct And Indirect Impacts On Local And Regional Avian Assemblages, Jeff L. Norris
Dissertations
Urban development, the pinnacle of human land use, has drastic effects on native ecosystems and the species they contain. For the first time in recorded history there are more people living in cities than in the rural areas surrounding them. Furthermore, the global rate of urbanization continues increasing; raising serious concerns for earth's tropical regions as they harbor a disproportionate amount of the earth's species, and where the impacts of urban development on natural communities are poorly known. Therefore, for my dissertation research I investigated the impacts of urban development on avian community structure and organization at both local and …
The Effect Of Photoperiod On Regulation Of Key Components Of The Life Cycle In The Bumble Bee Bombus Impatiens L. (Hymenoptera: Apidae)., Edgar Javier Hernandez
The Effect Of Photoperiod On Regulation Of Key Components Of The Life Cycle In The Bumble Bee Bombus Impatiens L. (Hymenoptera: Apidae)., Edgar Javier Hernandez
Dissertations
This study investigates how photoperiod affects internal characteristics of colonies of the temperate bumble bee Bombus impatiens particularly; development, reproduction, and social behavior. To answer this question I used an experimental approach using commercially obtained colonies of B. impatiens kept under controlled environmental conditions, and using the exposure to photoperiod as the only variable. Eight different photoperiod treatments were evaluated over the social phase of the colony’s life cycle. Colonies exposed to photoperiods that simulate the species natural temperate photoperiod exhibited larger growth rates, higher, oviposition rates, and higher brood survival than colonies exposed to constant photoperiods. Similarly, colonies exposed …
Host-Parasite Interactions In Galapagos Seabirds, Iris Ilena Levin
Host-Parasite Interactions In Galapagos Seabirds, Iris Ilena Levin
Dissertations
Parasites exhibit a wide range of life history strategies that contribute to different dispersal abilities, host specialization, transmission modes, life-cycle complexity and population structure. Understanding dispersal rates in hosts and parasites is instrumental in defining the scale at which coevolution may be occurring. In order to better understand how and when parasites move between different hosts, I studied a seabird – Hippoboscid fly ectoparasite (and vector) – Haemosporidian parasite system in the Galapagos Islands. I began by describing the Haemosporidian parasites of Galapagos seabirds, discovering a Plasmodium species parasite in Galapagos Penguins (Sphensicus mendiculus), and a new clade of Hippoboscid-vectored …
Evolution And Biogeography Of Fire-Eye Antbirds (Genus Pyriglena): Insights From Molecules And Songs, Marcos Maldonado Coelho
Evolution And Biogeography Of Fire-Eye Antbirds (Genus Pyriglena): Insights From Molecules And Songs, Marcos Maldonado Coelho
Dissertations
The importance of climatic and geologic factors as drivers of population differentiation and speciation in the Neotropical region has long been appreciated. However, many questions remain regarding their roles underlying the processes and patterns of diversification. Studies conducted in distinct regions containing a suite of geological and ecological conditions constitute ideal scenarios to assess the role of Pleistocene climatic changes, rivers, and mountain building as historical diversification mechanisms. In chapters 1 and 2, I used an integrative approach combining molecular phylogenetics, phylogeography and population genetics to elucidate the importance of climatic and geological factors as engines of diversification. I focused …
Analysis Of The Condition-Specific Regulation Of Puf3p Activity And Puf3p-Mediated Translational Repression Of Mrna In Saccharomyces Cerevisiae, Melanie A. Miller
Analysis Of The Condition-Specific Regulation Of Puf3p Activity And Puf3p-Mediated Translational Repression Of Mrna In Saccharomyces Cerevisiae, Melanie A. Miller
Dissertations
The Puf family of proteins regulates aspects of eukaryotic development such as embryonic development, and memory formation by promoting translational repression and/or degradation of targeted mRNAs in the cytoplasm. Yeast Puf3p regulates mitochondria biogenesis and function by modulating the stabilities of nuclear-transcribed mitochondrial mRNAs in response to different carbon sources. Dextrose simulates rapid Puf3p-mediated degradation of its mRNA targets via decay complex recruitment. Ethanol, galactose, or raffinose promotes stabilization of mRNA targets, as Puf3p-mediated decay activity is severely inhibited or abolished. In this work, I have established that carbon source-induced inhibition of Puf3p activity is not due to decreased transcription …
Contribution Of The Mnr2 Protein To Magnesium Homeostasis In Saccharomyces Cerevisiae, Nilambari Prafulla Pisat
Contribution Of The Mnr2 Protein To Magnesium Homeostasis In Saccharomyces Cerevisiae, Nilambari Prafulla Pisat
Dissertations
Magnesium is an essential metal nutrient with diverse roles in biology. To maintain the optimal function of key biological processes, intracellular Mg2+ concentration is tightly regulated. Despite the importance of this process however, relatively little is known about mechanisms of Mg2+ homeostasis in eukaryotic cells. An understanding of homeostasis starts with defining the function of key transport proteins that allow the passage of Mg2+ ions across the membranes. Yeast geneticists have identified four proteins from Bakers' yeast (Saccharomyces cerevisiae) involved in regulating the accumulation of Mg2+ within the cell (Alr1 and Alr2) and within the mitochondrial compartment (Mrs2 and Lpe10). …