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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
211

Using drilled-undrilled shell damage analysis to estimate crushing predation frequencies in modern marine gastropod assemblages

Stafford, Emily S. 06 1900 (has links)
Predation is a frequently studied subject, but estimating crushing predation in mollusk communities is challenging. Shells record successful attacks, but it is not always possible to identify attacks on an individual basis. Repair scar frequency is a common proxy for crushing mortality, but shell repair does not directly measure mortality, so results are ambiguous. Borrowing a technique from Vermeij (1982), crushing mortality frequencies were estimated in a recent shell assemblage. Because crushing damage can be confused with taphonomy, a taphonomic baseline was established: the cause of death of drilled shells is known, so additional damage is postmortem. The frequencies of several damage types were tallied for drilled shells to estimate a taphonomic baseline for the assemblage. The same frequencies were calculated for undrilled shells (cause of death unknown). In many cases, undrilled shells had significantly higher frequencies than drilled shells. The differences in damage frequencies likely are caused by crushing predation.
212

Factors Affecting the Fragmentation of Peptide Ions: Metal Cationization and Fragmentation Timescale

Kmiec, Kevin 2012 August 1900 (has links)
The factors affecting peptide fragmentation have been extensively studied in the literature in order to better predict the fragment ion spectra of peptides and proteins. While there are countless influences to consider, metal cation binding in the gas-phase is particularly interesting. Herein, a comparison of fragmentation patterns of a model peptide series with various charge carriers (H+, Li+, Na+, K+, and Cu+) will assist in determining the location of the preferred binding site of the metal cation and in assessing differences in the fragmentation pattern as a result of this binding site. An interesting observation from these studies reveals abundant x-type fragment ions occurring from the fragmentation of alkali-metal cationized peptides. As these fragment ions have been observed in previous studies by others but not addressed, the factors affecting the formation of these x-type fragment ions are explored. Additionally, a home-built 193-nm photodissociation tandem time-of-flight mass spectrometer is utilized to study how peptide fragmentation kinetics affect the fragmentation pattern observed. Initially, the fragmentation timescales of various peptides are investigated. Results indicate that longer fragmentation timescales (~10 microseconds) result in an increased number of identified peaks with internal and ammonia loss fragment ions being the most common in comparison to 'prompt' fragmentation timescales (~1 microsecond). Furthermore, b-type fragment ion formation is also favored at longer timescales for the arginine containing peptides investigated. The fragmentation pattern of several proline containing peptides is examined by collision-induced dissociation and 193-nm photodissociation. Unique fragment ions are observed with each occurring at a proline residue. Few differences are detected between CID and 193-nm photodissociation spectra, indicating that the proline residues direct fragmentation rather than the dissociation method. In an effort to improve the performance of the photodissociation tandem TOF instrument, the addition of a second source and a dual-stage reflectron are incorporated. The modifications result in improved mass range, signal-to-noise, and increased fragment ion collection efficiencies. High quality mass spectra are acquired across a range of mass-to-charge ratios from ~600 to 1900. Furthermore, the modifications continue to allow investigation of various fragmentation timescales with the addition of an additional timeframe of ~3 microseconds.
213

Population fragmentation in the Murray Hardyhead Craterocephalus fluviatilis McCulloch, 1912 (Teleostei: Atherinidae) : ecology, genetics and osmoregulation.

Wedderburn, Scotte Douglas January 2009 (has links)
Population fragmentation is a common symptom of the decline of species, including freshwater fishes. It occurs naturally, but has also proliferated in response to human interventions that increase the prevalence and intensity of isolating barriers and events. In regulated rivers, for example, fish are affected by the loss of connectivity between habitats that is associated with hydrological changes. The process has evolutionary consequences by limiting gene flow, reducing genetic diversity and rendering the isolates vulnerable to local environmental changes. Comparative studies of related species may help to elucidate the causes and consequences of fragmentation. For example, they may identify habitat features that influence the spatial separation of congeneric species. An opportunity for such a study arises with small fishes (Atherinidae) in the intensively-regulated River Murray, southeastern Australia. Whereas the unspecked hardyhead Craterocephalus stercusmuscarum fulvus is widespread and abundant, the Murray hardyhead C. fluviatilis has a patchy distribution and is listed as 'endangered‘ by the International Union for Conservation of Nature and 'vulnerable‘ under the Australian Environment Protection and Biodiversity Conservation Act 1999. These two species rarely cohabit, implying that they could be separated by particular habitat characteristics. In the past, several species of Craterocephalus, including C. fluviatilis and the Darling River hardyhead C. amniculus, have been regarded as C. eyresii sensu lato. The taxonomic separation of C. s. fulvus has been confirmed, but some doubt remains about the relationship of C. fluviatilis and C. amniculus. This issue needs resolution to ensure that appropriate targets are set for conservation. This study is a comparative investigation of the aforementioned species. It was designed (1) to identify the habitat characteristics that influence the distribution and abundance of C. fluviatilis and, given that salinity emerged as a key factor, (2) to explore the biological implications of salinity through a comparative study of osmoregulation in C. fluviatilis and C. s. fulvus, (3) to determine whether the osmoregulatory responses of population isolates of C. fluviatilis differ at varying salinities, and (4) to evaluate the genetic population structure of C. fluviatilis, confirm its taxonomic separation from C. amniculus and identify genetic 'management units‘ for conservation. Field sampling showed that C. fluviatilis is confined mainly to saline waters (0.4-20‰), whereas C. s. fulvus is absent from salinities >7‰. Comparisons were made of osmoregulation in these two taxa over a salinity range of 0.03-85‰, with additional reference to the small-mouth hardyhead Atherinosoma microstoma, a related estuarine species that tolerates salinities >94‰. The three species all are euryhaline, although the osmoregulatory ability of C. s. fulvus falters above about 35‰ salinity. C. fluviatilis is a better osmoregulator than A. microstoma at salinities <1‰, but both species tolerate hypersaline conditions (85‰). Osmoregulation was compared in C. fluviatilis from two isolated populations in different salinity regimes (Wyngate: 0.4-1.5‰, Disher Creek: c. 1.0-45‰) to determine whether they show related phenotypic differences. Fish from both populations remained healthy at salinities from 5-65‰. The Disher Creek population maintained a significantly lower blood osmotic concentration than the Wyngate population at salinities ≤1‰, suggesting that there is a physiological difference between them. The genetic population structure of C. fluviatilis and its taxonomic distinction from C. amniculus were investigated using complementary allozyme and mtDNA markers. This confirmed that C. fluviatilis is genetically distinct from its sister taxon, C. amniculus. It also identified several genetically-defined 'management units‘ as a framework for future conservation. Further, it revealed that C. fluviatilis in habitats downstream of Lock 1 on the Murray (274 km from the river mouth) displays a genetic signature indicating introgression with C. amniculus. Clearly, these findings have implications for the conservation of C. fluviatilis. For example, isolates can be prioritised for protection, and re-introduction programs can be modified accordingly. The findings may be applied to other freshwater fish, especially populations of closely-related species subject to salinisation or other stressors, and they may also contribute toward understanding of the factors and processes underlying rarity and fragmentation. It is clear that salinity can be a significant factor in population fragmentation, and that closelyrelated species with similar ranges may be segregated by differences in osmoregulatory ability. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1363300 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2009
214

Conservation genetics of the koala (Phascolarctos cinereus) in Queensland and Northeast New South Wales

Kristen Lee Unknown Date (has links)
The koala (Phascolarctos cinereus) is an iconic Australian marsupial that is the sole extant representative of the Family Phascolarctidae and forms part of the mammalian fauna in four Australian States and one Territory. There has been a significant decline in the range and distribution of the koala since European settlement, with habitat loss and its associated threats, including vehicle strikes, dog attacks and disease, continuing to reduce population numbers. Koalas provide the tourism industry and the Australian economy with revenue up to $1 billion per annum with 80 zoos and wildlife parks around the country displaying koalas. Koalas were introduced to a number of islands in southern Australia the early 20th century, in an attempt to ‘save’ them from near extinction due to habitat loss, hunting and disease. While populations on Queensland islands remain stable and require no management intervention, introduced populations on southern Australian islands show extremely low levels of genetic diversity yet have grown substantially and require constant monitoring and management to overcome overabundance and starvation associated with defoliation of food trees. The only known extant, naturally occurring, island population of koalas is on North Stradbroke Island in Southeast Queensland’s Moreton Bay. Infection with bacteria of the Family Chlamydiacae is at high prevalence in most koala populations but the resulting diseases are generally of low prevalence in koalas in Southeast Queensland and New South Wales. The role of the koala retrovirus (KoRV) in relation to infectious diseases is not fully understood, but it has been identified from all northern koala populations and the majority of southern koala populations though, like chlamydial infection, it is not usually associated with high disease prevalence. The major histocompatability complex (MHC) is a gene family in mammals that is vital for its role in disease resistance and so may play a role in disease susceptibility in koalas. This study provided detailed information about the genetic diversity and population structuring of the mainland koala population in Southeast Queensland, which is amongst the most threatened of koala populations because of anthropogenic disturbance. Microsatellite genotyping of 512 samples and mitochondrial DNA sequencing of a subset of 77 samples collected from sick, injured and dead koalas showed that in Southeast Queensland koalas had high microsatellite diversity (12.8 alleles/locus, He = 0.81) and at least 16 mitochondrial haplotypes. Population genetic analysis revealed six genetically differentiated clusters consistent with the existence of biogeographic and anthropogenic barriers like rivers and highways. The Koala Coast, an area in Southeast Queensland that provides habitat for one of the most significant natural koala populations in Australia was found to be genetically distinct from adjacent areas; the rapid decline of this population means it meets the criteria for classification as “Endangered Wildlife” under Queensland’s Nature Conservation Act 1992. Climatic patterns of warming and cooling that produced the disappearance and reappearance of rainforests is likely to have affected long term koala distribution in coastal eastern Australia – expansion into drier forests when they were available and restriction to refugia during times of rainforest dominance. The koala population in Northeast New South Wales, which has conventionally been classified as a different subspecies to the koalas in Southeast Queensland, has colonised an extensive part of the area since the destruction of the “Big Scrub” rainforest. This forest occupied about 75,000 ha before European settlement and would almost certainly have represented a natural barrier to the movement of koalas as it was unsuitable habitat due to its lack of suitable food trees. Population structuring analysis identified two major genetic clusters in the region, the northernmost of which was less differentiated from koalas sampled on the Gold Coast in Southeast Queensland than the southernmost cluster. The southern cluster, largely found around the city of Lismore, had significantly lower diversity than the northern cluster, consistent with a southward radiating colonisation pathway. Ninety-six percent (96%) of koalas in Northeast New South Wales shared the same mitochondrial DNA haplotype, which was the most common haplotype in Southeast Queensland. There was, therefore, little evidence to support the subspecies delineation of coastal koalas in Southeast Queensland and Northeast New South Wales. From a comparison between wild, mainland populations and two captive koala colonies in Southeast Queensland, genetic diversity in 106 captive koalas was found to be similar to the local wild populations (Dreamworld 9.2 alleles/locus, He = 0.75, Currumbin Wildlife Sanctuary 10.2 alleles/locus, He = 0.80). Microsatellite alleles in captive koalas were, in general, representative of the local wild populations and of similar frequencies, but the captive koalas possessed mitochondrial DNA haplotypes that were not found in the local wild koalas. Some of the original founders of the captive populations were not from Southeast Queensland so these different mitochondrial haplotypes are likely remnants of the koala genotypes at the original founders’ locations. The preservation of habitat and reduction of consequential threats to the koala’s long term survival in the wild are the most fundamental aspects of koala conservation in this region. However, the successful preservation of high genetic diversity at neutral loci in the captive colonies studied indicates that ex situ measures incorporating a captive breeding program could potentially be used as reservoirs for important genetic material should such an approach become necessary in the context of the drastic and accelerating decline towards local extinction of key Southeast Queensland koala populations. Urgent action would be essential to obtain a representative sample of current genetic diversity (both genomic and mitochondrial), given the drastic rate of decline. Island populations of organisms are expected to show reduced genetic diversity compared to their mainland counterparts because of factors such as founder effects and the increased susceptibility of small populations to the effects of genetic drift. A comparison of genetic diversity was made between the naturally occurring North Stradbroke Island koala population in Southeast Queensland and the introduced populations on St Bees, Brampton, Newry and Rabbit Islands in central Queensland with the mainland populations. As expected, the island populations had lower genetic diversity than mainland populations, however, the introduced St Bees Island population had higher mean number of alleles and expected heterozygosity (5.7 alleles/locus, He = 0.67) than the naturally occurring population on North Stradbroke Island (3.7 alleles/locus, He = 0.55). Anecdotal evidence suggests that the koala populations on Brampton, Newry and Rabbit Islands off the central Queensland coast were established by the unauthorised transfer of koalas from St Bees Island. Mitochondrial DNA haplotype analysis supports this claim however, the most likely explanations for the presence of at least four microsatellite alleles in the Brampton, Newry and Rabbit Island populations that were not found in St Bees Island koalas are that either there were additional introductions from elsewhere or that koalas were already present on these islands prior to the transfers from St Bees Island. A study on the prevalence of chlamydial and retroviral infection in captive and wild koalas showed that 100% of koalas in this study had retroviral and chlamydial infection in at least one tested swab site. None of the captive animals showed clinical signs of disease despite the high prevalence of infection. Signs of disease were evident in some wild koalas, which, in some cases, was the reason for their admission to Moggill Koala Hospital for treatment. In an attempt to understand the immunological mechanisms underlying the apparent disease resistance of koalas which usually limits latent infection progressing to clinical disease states, the MHC genes of koalas were investigated. Low variation at MHC loci is thought to increase susceptibility to infectious diseases because fewer foreign antigens are recognised. The first class II sequences identified from koalas are presented here and showed variation. Variation was also detected at exon 3 of class I, with evidence for at least three class I loci. The koala is a unique Australian marsupial that makes a nationally significant contribution to the Australian economy annually. The results of this study have important conservation and management implications for koala populations in Southeast Queensland and Northeast New South Wales - particularly declining populations in Southeast Queensland - as well as being informative on other aspects of the species’ biology and for mammalian conservation genetics, generally.
215

Functional Approaches to the Development of Koala Sperm Cryopreservation Techniques

Yeng Zee Unknown Date (has links)
The primary objective of the studies described in this thesis was to improve the cryopreservation success of koala spermatozoa for the purpose of establishing a genome resource bank for this species. A defining feature of the studies in this thesis was the implementation of an organelle-specific approach to better understand the causes of koala sperm cryo-injury. The functional attributes of spermatozoa, such as mitochondrial function, plasma membrane fluidity, membrane lipid asymmetry and DNA integrity were assessed as an indication of cryo-injury. Sperm mitochondrial function and plasma membrane integrity were examined by cryomicroscopy using the fluorescent probes JC-1 and propidium iodide (PI) respectively in a dual staining technique. Cooling and re-warming koala spermatozoa were more detrimental to mitochondrial function than to plasma membrane integrity. Mitochondrial membrane potential (MMP) was suppressed by freezing and thawing treatments; after thawing, MMP declined significantly during rewarming (from 5ºC to 35ºC). The distribution of GM1 ganglioside was examined using fluorescent-labelled cholera toxin B. No significant redistribution of GM1 was observed after chilling or cryotreatment. The externalisation of phosphatidylserine (PS) was examined using fluorescent-labelled annexin V. There was no significant increase in translocation of PS after chilling or cryopreservation. These observations imply that cryotreatment had little effect on plasma membrane lipid asymmetry. Koala spermatozoa were incubated in a range of anisotonic media to investigate whether nuclear swelling was caused by osmotic flux during the cryopreservation process. Although the most hypotonic solution tested (64 mOsm/kg) induced the highest incidence of nuclear relaxation (mean ± SEM; 12 ± 3%), this was not as severe as that previously documented following cryopreservation. Chromatin relaxation is a phenomenon observed in koala spermatozoa, where the sperm nucleus expands due to the result of structural changes in the natural conformation of the sperm DNA/protamine complex. DNA fragmentation was not a primary cause of cryopreservation-induced sperm chromatin relaxation, although in situ nick translation of putative DNA breaks indicated that these increased as the sperm head became progressively more relaxed. Using a Sperm Chromatin Dispersion test (SCDt) specifically developed and validated for koala spermatozoa, a continuum of nuclear morphotypes was observed, ranging from no apparent DNA fragmentation to spermatozoa with highly dispersed and degraded chromatin. A double comet assay was also developed to investigate DNA fragmentation in the koala spermatozoa. Conducted under neutral followed by alkaline conditions, this assay was able to differentiate between single- (SSB) and double-stranded (DSB) DNA damage in an effort to refine the interpretation of DNA damage in mature koala spermatozoa; the majority of the koala spermatozoa had nuclei with DNA abasic-like residues. The ubiquity of these residues suggested that constitutive alkali-labile sites are part of the structural configuration of the koala sperm nucleus. Spermatozoa with “true” DNA fragmentation exhibited a continuum of comet morphologies, ranging from a more severe form of alkaline-susceptible DNA, to nuclei that exhibited both SSB and DSB. Swelling of koala sperm chromatin following cryopreservation has largely been attributed to the absence of inter-molecular disulphide cross-linkages in the marsupial sperm nucleus. Fish spermatozoa also lack disulphide bonds within their chromatin, but nevertheless, have been successfully cryopreserved. To examine the hypothesis that the cryoprotectants used for fish sperm cryopreservation will confer a similar degree of protection on koala spermatozoa, various concentrations of five cryoprotectants (dimethyl sulphoxide, methanol, propylene glycol, ethylene glycol and dimethylacetamide) were evaluated. Each treatment was compared against an established koala sperm cryopreservation protocol that uses 14% glycerol. Dimethylacetamide at a concentration of 12.5% (v/v) was found to be comparable to glycerol in the successful cryopreservation of koala spermatozoa although high inter-male variability was observed. However, when the new protocol was subsequently validated for a larger population of captive koalas (n = 22), glycerol emerged the better cryoprotectant with respect to all sperm viability parameters assessed except for that of the incidence of chromatin relaxation, which was not affected by the cryoprotectant. Significant difference was also observed in the post-thaw survival of spermatozoa from different animals, which was independent of pre-freeze semen quality. Based on post-thaw semen viability parameters, the koalas could be divided into two distinct groups, where one group had significantly higher sperm viability compared to the other group, regardless of cryoprotectant used. Positive correlation between motility and MMP was observed before and after cryopreservation. However, cryopreservation significantly reduced the dependency between these variables (P < 0.001), suggesting that cryopreservation reduced the dependency between mitochondrial function and motility.
216

The effects of deforestation and forest fragmentation on a central Amazonian frog community

Tocher, Mandy Darlene January 1996 (has links)
An investigation into the effects of deforestation and habitat fragmentation on a central Amazonian frog community was carried out on the Biological Dynamics of Forest Fragments Project, (BDFFP) based in Manaus, Amazonas, Brazil. Three aspects of deforestation were investigated: the effects of fragmentation and reserve size, the influence of matrix habitat and the effects offorest edge on frogs in 10- hectare isolates. Very few frogs species were lost from fragments (regardless of size) following fragmentation and isolation for 7-10 years. Instead, frog species richness increased, with an average increase in 10 species per fragment. The increase in species was brought about by an increase in matrix associated species, some of which were present in the absence of their preferred breeding habitat. Different frog species had varied responses to fragmentation. The abundance of Eleutherodactylus fenestratus, a terrestrial breeder, increased significantly as fragment size decreased, and its abundance was significantly higher in both large and small fragments than in continuous forest. Colostethus stepheni, a semi-terrestrial breeder, was less abundant in fragments than continuous forest. Finally, Eleutherodactylus zimmermanae and Osteocephalus sp.A did not differ significantly in abundance among fragments, or between fragments and continuous forest. Multiple regression analysis indicated that variation in litter depth and canopy cover may explain the observed increase in E. fenestratus abundance in small fragments. Breeding success of pool breeders attracted to artificial pools was variable, but there was no evidence of reduced breeding success in fragments relative to primary forest. Overall, fragmentation appeared to affect the frog community less severely than other taxonomic groups. Species richness in tropical forest remnants showed a tendency to increase as a result of fragmentation, and only one of four species exhibited lowered abundance in fragments. The effects of fragmentation and subsequent small isolated populations of frog species in fragments was alleviated somewhat by the ability of central Amazonian frogs to utilise matrix habitat. Litter frogs, wallow breeders and upland forest pool breeders all displayed an ability to permeate, and in most cases become residents of matrix habitat. Both matrix with a history of cut and burn and matrix which was only cut supported a similar frog community. Thus, for central Amazonian frogs isolates were not truly isolated due to the ability of frogs to utilise matrix habitat. Litter frogs in 10- hectare isolates displayed an independence from edge related abiotic and biotic gradients. This independence was true for frog species richness, abundance and composition. Consequently, forest fragments are in effect larger for frogs than for other taxa who are constrained by edge effects to exist only within the core of large fragments. Colostethus stepheni was one species found to be negatively affected by habitat fragmentation. Abundance of Colostethus stepheni was significantly lower in fragments and matrix habitat compared to primary continuous forest. This species was also found to be sensitive to edge, with higher abundances recorded as distance from the edge increased. The community level approach adopted in this study, as opposed to intensive investigation of single species, may well have overlooked other' sensitive' species which show more subtle responses to habitat fragmentation than that of Colostethus stepheni. The ability to use matrix and the relative independence from edge related phenomena accounts for the resilience of central Amazonian frogs in a disturbed and fragmented landscape. However, with respect to matrix habitat, forest surveyed in this study has not been repeatedly cut or cut and burnt (with the exception of pasture-land where the frog community is depauperate). In other areas of the Amazon, away from the experimental plots of the BDFFP, matrix habitat is destroyed more frequently. More work is needed to determine the ability of central Amazonian frogs to utilise matrix habitat which is disturbed more frequently.
217

Spallation reactions of plutonium-240 with helium ions and plutonium-242 with deuterons

Eads, Donald L. January 1959 (has links)
Thesis (Master's)--University of California, Berkeley, 1959. / Includes bibliographical references (p. 32-34).
218

Genetické markery pro sledování posttransplantačního chimerismu / Genetic markers for monitoring post-transplant chimerism

Řehounková, Michaela January 2017 (has links)
Charles University in Prague Faculty of Pharmacy in Hradec Králové Department of Biochemical Sciences Candidate: Bc. Michaela Řehounková Supervisor: doc. PharmDr. Martin Beránek, Ph.D. Title of diploma thesis: Genetic markers for monitoring post-transplant chimerism The aims of the thesis: Data processing of patients, who underwent allogenic hematopoietic stem cell transplantation in a period from 2010 to 2014 in University Hospital Hradec Kralove and whose state of chimerism was monitored at the Section of Molecular Biology at the Institute of Clinical Biochemistry and Diagnostics. Consequently, analysis of the possible relationship between selected clinical parameters and used genetic markers for chimerism quantification was carried out after the processing of acquired data. Finally, the possible influence of treatment success and mortality by chosen clinical parameters was evaluated. Methods: Analysis of short tandem repeat loci, which uses genetic variability between donor and recipient of transplanted graft, was employed for quantification of post- transplant chimerism. DNA of donor and recipient was isolated by QIAmp DNA Blood Mini Kit (QIAGEN, Germany), amplified by AmpFlSTR Identifier Kit (Applied Biosystems, USA) and separated by capillary electrophoresis (analyzer ABI 3130-4, Applied...
219

DYNAMIC ADAPTATION OF BANDWIDTH GRANULARITY FOR MULTIPATH ROUTING IN ELASTIC OPTICAL OFDM-BASED NETWORKS

Al-Tarawneh, Luae Abdul Fatah Barakat 01 May 2016 (has links)
In this research, we consider the impact of spectrum fragmentation in optical single-/multi-path routing transmission on the efficiency of the elastic optical networks. O-OFDM multicarrier transmission is a promising technique that makes it possible to choose just an adequate portion of available spectrum to satisfy the requested capacity. This involves focusing on the work to reduce the fragmentation effects by dynamically updating and controlling the minimum bandwidth allocation granularity. that serves the light path requests over multipath networks. We adopt linear and nonlinear dynamic mechanisms, which are denoted as LDAɡ and NLDAɡ that are proportional to the optical link/path bandwidth fragmentation status. Simulation results show that the minimum bandwidth granularity dynamic adaptation based on the optical path fragmentation status offers improved performance over fixed minimum bandwidth allocation granularity with respect to the bandwidth blocking probability, the throughput, the network bandwidth utilization and the number of path splitting.
220

Metapopulation viability of swamp rabbits (Sylvilagus aquaticus) in southern Illinois

Robinson, Christopher 01 August 2013 (has links)
Swamp rabbits (Sylvilagus aquaticus) in southern Illinois exist as a metapopulation due to loss and fragmentation of the bottomland hardwood forests in which they live, making their persistence in the state uncertain. I ran a spatially-explicit population viability analysis (PVA) on the metapopulation, using a habitat suitability map I created and life history parameters drawn from the literature. I varied parameters related to reproduction, survival, catastrophes, dispersal, and carrying capacity from 50 to 150% of the initial value of each parameter to compare their effects on extinction risk. I modified the map to test the effects of potential habitat loss, fragmentation, and the addition of dispersal corridors on the swamp rabbit metapopulation in southern Illinois. Under baseline conditions, the model suggested about a 20% chance of quasi-extinction (90% metapopulation decline) in 25 years. Changes in fecundity values and the effects of catastrophic flooding had the greatest effect on the risk of extinction, causing quasi-extinction probabilities to range from 0 to 100% and 0 to 87%, respectively. In contrast, changing dispersal values yielded the least impact on the risk of extinction (18-24%), and all other parameters had moderate impacts on the model. Removing groups of the largest habitat patches increased the risk of extinction, whereas removing groups of the smallest habitat patches decreased the risk of extinction, suggesting that small patches could act as population sinks with a negative impact on swamp rabbit persistence. Decreasing patch fragmentation per se reduced the risk of extinction slightly. The addition of dispersal corridors made no significant impact on the probability of extinction. My findings indicate that more research estimating fecundity and the effect of catastrophic floods on swamp rabbits in Illinois is required to more accurately predict swamp rabbit persistence in the state. I also suggest that managers should work to decrease the effect of flooding on the population by improving upland habitat, or decrease fragmentation by increasing the area of bottomland hardwood forests around existing habitat patches. Lastly, I suggest managers focus on preventing further habitat fragmentation into small patches, which will mitigate the creation of potential sink populations and will enable current populations to persist.

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