archives@tulane.edu / Although interspecific competition and relevant coexistence mechanisms are core concepts in ecology and evolution, most such research has focused on two-species interactions. Lacking is important information on how and when interspecific competition operates in more complex species assemblages. This dissertation examined interspecific competition and coexistence mechanisms between a focal species, the American redstart (Setophaga ruticilla, Parulidae) and its potential competitors in multiple communities. Using a theoretical framework that builds on the well documented population ecology of redstarts, combined with interspecific dietary overlaps, I demonstrate ongoing interspecific competition. I found that species generally both overlap highly in diet and exhibit small, but consistent, differences consistent with their foraging behavioral differences. Although some competitive interactions were mediated by direct aggressive interactions, this research also highlighted diffuse competition as more important than previously recognized. My findings also differed from systems that have shown similar patterns insofar as high dietary overlaps persisted during times of resource scarcity, were driven by overlaps on low value prey taxa, and did not involve exclusive use of any resources by different competitors. All of these factors increase the potential negative demographic effects of interspecific competition, some of which have been documented in these bird species. A long history of competition studies in these warblers has shown large differences in foraging behavior among species, assumed to be what allows coexistence. However, it is not clear how and if differences in foraging behavior correspond to differences in resource use. I confirmed that locally coexisting study species differed almost completely in foraging behavior, particularly in microhabitat use. Likewise, using a variety of arthropod sampling methods, I found that microhabitats differed greatly in their available prey. Combining the large differences in foraging behavior with available prey significantly predicted the small dietary differences, although it did a poor job of explaining the already limited variation in diet. Overall, I found mixed support for behavioral niche partitioning, leading me to examine alternative mechanisms of coexistence. Contrary to past work focused on interspecific interactions, I found that population level forces dominate in determining local distributions, with birds of the same species being more evenly distributed due to intraspecific territoriality. This pattern led to higher local (point count scale) species richness, and greater community covariance than predicted. This intraspecific territoriality and repulsion is proposed as as a novel coexistence mechanism. / 1 / Cody M. Kent

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references. Also available on the Internet.

Thesis (M.S.)--University of Missouri-Columbia, 2003. / Typescript. Includes bibliographical references. Also available on the Internet.

Thesis--Auburn University, 2009. / Abstract. Vita. Includes bibliographic records (p.23-29).

Thesis (M.S.)--Brigham Young University. Dept. of Biology, 2007. / Includes bibliographical references (p. 18-22).

Climate change is expected to have a profound impact on freshwater fish communities, especially at higher latitudes. In this study I investigated potential effects of climate change on the niche structure of Eurasian perch (Perca fluviatilis) by looking at their diet across a latitudinal gradient and at varying light climate. Dietary niche width of Eurasian perch did not differ significantly between boreal and temperate latitudes. Additionally, no significant difference in the prevalence of specialist individuals was found along the latitudinal gradient and water transparency levels. Habitat was the main factor that significantly affected niche width and level of specialization with both being significantly higher in the littoral habitat. Taken together my results suggest that climate change might indirectly affect niche patterns by altering fish densities through changes in productivity resulting in niche and specialization variation among habitats.

Kritische Knochendefekte stellen heutzutage ein ungelöstes Problem in der klinischen Praxis dar, da die verfügbaren prothetischen Optionen oft die mechanische Anpassung an das Gewebe nicht gewährleisten oder zu wichtigen immunologischen und Implantat-bedingten Komplikationen führen. In diesem Kontext ermöglichen Tissue Engineering-Ansätze neue Strategien, um in vitro Zell-Material Interaktionen zu untersuchen und so die Implantatmaterialien zu optimieren. In dieser Arbeit habe ich Zell-Material Interaktionen eines neuen Kollagen-basierten Scaffolds untersucht, das langfristig als Trägerstruktur für eine zellbasierte Therapie für kritische Knochendefekte entwickelt werden soll. Im Rahmen der Dissertation konnte ich belegen, dass die Kollagen-basierten makroporöse Mikrocarrier für die Zellvermehrung humaner mesenchymaler Stammzellen (MSC) und deren osteogene Differenzierung unter GMP Bedingungen verwendet werden können. Außerdem habe ich die die Kokultur von hämatopoietischen Stammzellen des Knochenmarks und multiplen Myelomzellen funktionell charakterisiert. Ich konnte erstmals Kulturbedingungen etablieren, die die Langzeitkultur ohne die Verwendung von Zytokinen ermöglicht. Mittels dieser Kokultur konnte ich ein Knochenmarknischen-Modell etablieren und die Untersuchung der Expression von zentralen Signalkaskaden der Homöostase dieser Nische untersuchen. Ich konnte die Expression von zwei verschiedenen Isoformen von Osteopontin nachweisen, die in Tiermodellen nicht gefunden werden. Diese Isoformen des Osteopontins habe ich kloniert und die rekombinanten Isoformen exprimiert und ihre Rollen in der Homöostase der Knochenmarknische untersucht. Critical size bone defects represent nowadays an unresolved problem in the clinical practice, where the available prosthetic options often lack adequate mechanical matching to the host tissue or lead to important immunological and implant-related complications. In this context, Tissue Engineering approaches promise more effective strategies to study cell-material interactions in vitro and consequently optimize implant materials. In this work, I investigated the cell-scaffold interactions of a new collagen-based scaffold for a putative cell-based therapy for critical size defects to be developed. In the context of this thesis, I could demonstrate that the collagen-based macroporous microcarriers could be employed for the expansion and osteogenic differentiation of human mesenchymal stromal cells (MSCs) under GMP-compliant conditions. Moreover, I functionally characterized the co-culture of bone marrow hematopoietic stem cells and multiple myeloma cells. I was for the first time able to establish culture conditions allowing their long-term culture in absence of externally supplemented cytokines. Using this co-culture, I was able to establish a bone marrow niche model to investigate the expression of key signaling pathways involved in the niche´s homeostasis. I was able to demonstrate the expression of two different isoforms of Osteopontin, that could not previously be detected in animal models. Finally, I cloned these Osteopontin isoforms, expressed recombinant versions of the isoforms, and investigated their roles in the homeostasis of the bone marrow niche. / Kritische Knochendefekte stellen heutzutage ein ungelöstes Problem in der klinischen Praxis dar, da die verfügbaren prothetischen Optionen oft die mechanische Anpassung an das Gewebe nicht gewährleisten oder zu wichtigen immunologischen und Implantat-bedingten Komplikationen führen. In diesem Kontext ermöglichen Tissue Engineering-Ansätze neue Strategien, um in vitro Zell-Material Interaktionen zu untersuchen und so die Implantatmaterialien zu optimieren. In dieser Arbeit habe ich Zell-Material Interaktionen eines neuen Kollagen-basierten Scaffolds untersucht, das langfristig als Trägerstruktur für eine zellbasierte Therapie für kritische Knochendefekte entwickelt werden soll. Im Rahmen der Dissertation konnte ich belegen, dass die Kollagen-basierten makroporöse Mikrocarrier für die Zellvermehrung humaner mesenchymaler Stammzellen (MSC) und deren osteogene Differenzierung unter GMP Bedingungen verwendet werden können. Außerdem habe ich die die Kokultur von hämatopoietischen Stammzellen des Knochenmarks und multiplen Myelomzellen funktionell charakterisiert. Ich konnte erstmals Kulturbedingungen etablieren, die die Langzeitkultur ohne die Verwendung von Zytokinen ermöglicht. Mittels dieser Kokultur konnte ich ein Knochenmarknischen-Modell etablieren und die Untersuchung der Expression von zentralen Signalkaskaden der Homöostase dieser Nische untersuchen. Ich konnte die Expression von zwei verschiedenen Isoformen von Osteopontin nachweisen, die in Tiermodellen nicht gefunden werden. Diese Isoformen des Osteopontins habe ich kloniert und die rekombinanten Isoformen exprimiert und ihre Rollen in der Homöostase der Knochenmarknische untersucht.

No description available.

The early Pliocene age Gray Fossil Site (GFS) was relatively recently found, with much still to be discovered and examined, and represents one of only a few sites of its age in eastern North America. It has been noted that the diverse faunal remains found at GFS are unique compared to what have been found at other fossil sites in North America from the same time period. Studying mammalian community structures at fossil sites can provide an abundance of information about the past environment and species adaptations to it, such as niche occupation of species, resource partitioning, and interactions between organisms and their environment. The main questions being asked in this study are: 1) what is the mammal community structure like at GFS?, and 2) how does the community structure at GFS compare to other contemporaneous sites? While studies of the fauna and flora have helped us to understand the ecosystem at GFS, detailed study of the mammal community will help us better understand this unique site. It is expected that the community structure and niche occupation of the mammals at GFS will be different from other contemporaneous sites, dominated by mammals adapted for life in the warm oak, hickory forest present at the site. A taxon-free approach to analysis will be used so that environments not sharing the same taxa or of different ages can be compared to one another. Each mammal species from GFS (48 total) and five well-known contemporaneous sites are categorized by body size, locomotor mode, and dietary preference to characterize the niches occupied by each species. Categorizations for each species will come from published works and measurements / ecomorphological analysis of specimens. Preliminary results show that GFS is different from other sites in that there are more brachyodont and tree dwelling/climbing adapted species present, and there are fewer running species present. The initial findings are likely associated with the site being a closed, forested ecosystem, compared to the more open environments of the other sites. Moving forward, descriptions pertaining to specifically how GFS and its mammal community structure compare to the niche occupation of similar species at other sites will be discussed. This project will also examine what more this analysis can reveal about the ecosystem at GFS, particularly how the herbivorous mammals can provide greater insight into what environmental conditions were like, including what vegetation was predominant at GFS.

Eastern wild turkeys (Meleagris gallapavo silvestris) were extirpated from most of the Mississippi Alluvial Valley (MAV) by 1980 by overharvest and habitat loss. Federal programs have restored areas of the MAV to hardwood forest, potentially warranting restoring wild turkeys to the MAV. As part of a pilot restoration study, I gathered data on resource use and nest sites from July 2010–August 2011. I observed intraspecific niche specialization and spatial niche separation between genders. Spatiotemporal variation in resource availability and intraspecific competition appear to be factors influencing intraspecific niche specialization. Mature hardwood forest was primary habitat selected by translocated wild turkeys. Hardwood regeneration areas were primary habitat selected by hens for nesting. Visual obstruction from 0.0 m–0.5 m was important in selecting fine-scale nest sites. Hardwood regeneration areas have dual value for restoring wild turkeys to the MAV: future mature hardwood areas; and potential nest sites.