The gopher tortoise is a keystone species that creates networks of underground burrows that are home to an additional 350 species, where 60 are vertebrates. Vertebrates have been shown to differ between habitat types and seasonally, but limited information is known about vertebrate associates in our region. This study was one of the first to investigate this in our region of south Florida. This study was designed to investigate factors that may affect the presence of vertebrates at gopher tortoise burrows. Camera data was collected to determine vertebrate presence and if specific vertebrate groups elicit a territorial response from the tortoise, while habitat vegetation surveys and weather data were collected to evaluate seasonality. Statistical analysis showed variation in vertebrate presence both seasonally and by habitat type. Few territorial interactions were observed overall. This study acts as a starting point to increase our understanding of local tortoise populations. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2021. / FAU Electronic Theses and Dissertations Collection

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 119-132).

No description available.

The need for new antibiotics has been highlighted recently with the increasing pace of emergence of drug resistant pathogens (MRSA, XDR-TB, etc.). Modification of existing antibiotics with the additions of side chains or other chemical groups and genomics based drug targeting have been the preferred method of drug development at the corporate level in recent years. These approaches have yielded few viable antibiotics and natural products are once again becoming an area of interest for drug discovery. We examined the antimicrobial "Red Soils" of the Hashemite Kingdom of Jordan that have historically been used to prevent infection and cure rashes by the native peoples. Antimicrobial producing bacteria were present in these soils and found to be the reason for their antibiotic activity. After isolation, these bacteria were found to excrete their antimicrobials into the liquid culture media which we could then attempt to isolate for further study. Adsorbent resins were employed to capture the antimicrobial compounds and then elute them in a more concentrated solution. As part of a drug discovery program, we sought a way to quickly characterize other soils for potential antibiotic producing bacteria. The community level physiologic profile was examined to determine if this approach would allow for a rapid categorizing of soils based on their probability of containing antimicrobial producing microorganisms. This method proved to have a high level of variability that could not be overcome even after mixing using a commercial blender. The role of these antimicrobial producing bacteria within their natural microbial community has largely been confined to microbe-plant interactions. The role of antimicrobial-producing microorganisms in driving the diversity of their community has not been a focus of considerable study. The potential of an antimicrobial-producing bacterium to act as a driver of diversity was examined using an artificial microbial community based in a sand microcosm. The changes in the microbial assemblage indicate that antimicrobial-producing bacteria may act in an allelopathic manner rather than in a predatory role. / Ph. D.

Determining the molecular basis of heritable variation in complex, quantitative ecologically important traits will provide insight into the proximate mechanisms driving phenotypic and ecological variation, and the molecular evolutionary history of these traits. Furthermore, if the study organism is a “keystone species” whose presence or absence shapes ecological communities, then we extend our understanding of the effects of molecular variation to the level of communities. I examined the molecular basis of variation in 32 ecologically important traits in the freshwater pond keystone species Daphnia pulex, and identified thousands of candidate genes for which variation may affect not just Daphnia phenotypes, but the structure of communities. I extended the basic results to address two questions: what genes are associated with the offspring size-number trade-off in Daphnia; and can we identify candidate “keystone gene networks” for which variation may have a particularly strong influence on eco-evolutionary dynamics of limnetic communities? I found that different genes, with different biological functions, are associated with the trade-off in subsequent broods, and propose a model linking evolutionary frameworks to molecular biological functions. Next I found that quantitative genetic variation in keystone traits appears to co-vary with the selection regimes to which Daphnia is subject, and identified two candidate gene networks that may underpin this genetic variation. Not only do these results provide a host of molecular hypotheses to be tested as Daphnia matures as a model genomic organism, but they also suggest models that link molecular research with broader themes in ecology, evolution, and behavior. / text

The modifications animals make to their environments can be critical to species diversity. Red squirrels (Tamiasciurus hudsonicus) create large piles of conifer cone debris (middens) and are hypothesized to function as a keystone species due to positive associations between middens and other vertebrate species. We assessed vegetation and landscape structure at middens with a resident red squirrel for varying consistencies over the prior 5 years and surveyed mammals and birds at the community and population level. After accounting for vegetation and landscape characteristics, red squirrel-created resources positively influenced species richness of medium and large mammals and ground foraging birds, abundance of deer mice (Peromyscus maniculatus) and ground foraging birds, and activity of cliff chipmunks (Tamias dorsalis). Increased knowledge of the interaction strength of the red squirrel with its environment may be used to inform decisions in forest management and restoration and offer insight on the conservation value of larderhoarding mammals.

Removing just one species from an ecosystem can have radical results. Tony Sinclair's grand-scale biodviersity knockout experiment sets out to determine why.

abstract: As much as 40% of the world's human population relies on rivers which originate on the Qinghai-Tibetan Plateau (QTP) (Xu et al. 2009, Immerzeel et al. 2010). However, the high alpine grasslands where these rivers emanate are at a crossroads. Fed by seasonal monsoon rains and glacial runoff, these rivers' frequent flooding contributes to massive losses of life and property downstream (Varis et al. 2012). Additionally, upstream grasslands, which regulate the flow of these rivers, are considered to be deteriorating (Harris 2010). This thesis examines the regional vulnerability of these rivers and highlights the impacts of several policy responses, finding that both climate change and grassland degradation pose significant challenges to Asia's water security. Additionally, I suggest that many of the responses elicited by policy makers to meet these challenges have failed. One of these policies has been the poisoning of a small, endemic, burrowing mammal and keystone species, the plateau pika (Ochotona curzoniae) (Smith and Foggin 1999). Contrary to their putative classification as a pest (Fan et al. 1999), I show that the plateau pika is instead an ecosystem engineer that actively increases the infiltration rate of water on the QTP with concomitant benefits to both local ecosystems and downstream hydrological processes. / Dissertation/Thesis / M.S. Biology 2012

Beavers have been described as a “keystone species” and “ecosystem engineers”, and in this dual role have great potential to physically modify their environment through tree-felling, foraging and construction activities. The resultant change in habitat heterogeneity can affect the flora and fauna that share the habitat with them. There has been recent interest in reintroducing the Eurasian beaver to the United Kingdom after an absence of over 400 years. To date, no research (aside from this thesis) has focussed on beaver ecology and behaviour in Scotland. This study has investigated the ecological effects of a small number of beavers in two enclosed but semi-natural Scottish sites at Bamff in Perthshire. The research conducted over a three-year period, with particular emphasis on the effects of tree-felling, foraging and construction activities. Trees were felled for both dietary and construction purposes, with felling rates being influenced by habitat availability, quality and the degree of habitat modification required. Highest rates were evident during the initial colonisation period of marginal sites (c. >300 trees / beaver / calendar year), and lowest rates in later years of occupation of more optimal sites (c. 55 – 70 trees / beaver / calendar year). Preferences were generally for willow and aspen trees, with conifers almost entirely avoided, and smaller trees preferred over larger ones. Proximity of trees to waterbodies was also an important factor, with nearer trees favoured, and generally most felling occurred within 50 m of water. Such behaviour followed the principles of optimal central place foraging. These preferences were less predictable however when intense construction activity was undertaken, with larger trees preferred and generic preferences for deciduous trees apparently invalid. In such cases, close proximity to the construction site was of prime importance. Increased cover of herbaceous plant species was observed in beaver-created canopy gaps in riparian woodland, whilst macrophyte diversity within waterbodies increased slightly in areas of herbaceous grazing. The diversity of terrestrial ground invertebrates was highest in areas of heavy tree-felling, and invertebrate richness and abundance was greatest in areas of herbaceous grazing under an intact tree-canopy. Furthermore, the abundance, diversity and richness of macroinvertebrate communities were increased by beaver-generated woody debris in ponds and streams. Overall, 30% of all macroinvertebrate species collected were found only in beaver-affected areas, due to the refugia and food supply provided by beaver dams, caches and lodges, as well as hydrological effects of these structures. These results are discussed with reference to future plans to return the beaver to Scotland. The habitat usage and modification of riparian ecosystems in northern Britain is likely to be similar to that found in this study, and the results are believed to be relevant, applicable and transferable to many areas of Scotland.

<p>The minimum ecologically viable population size (MEVP) of a species describes the minimum size at which the species itself or another species in the same ecosystem goes extinct as a result of the loss of inter-specific interactions. The MEVP shows a good potential for use as a tool for exploring the mechanisms behind species extinctions, but presently only a small amount of research has been done that takes advantage of this. In this study the MEVP is used to investigate what properties of species can be used as good indicators of ecological importance. 100 large computer generated food webs were created with an assembly model and the reduction in density that was necessary to induce an extinction event in the web was subsequently determined for each species within the webs. This change in density was then correlated with 28 different properties, measured for each species. The results show that properties that measure how well connected a species is, as well as measures of the species role as a prey item in the web are the ones with the greatest potential to find species with high MEVP. Further, the results put emphasis on the importance of regarding the web as a whole when working with species extinctions, while also highlighting the usefulness of the MEVP concept.</p>