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Rostö, Evelina. "Changes in alpine plant population sizes in response to climate change." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-418248.
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Alpine plants are assumed to be in particular danger as the climate changes rapidly worldwide. Specialist alpine species in Norrbotten County, northern Sweden have been surveyed over the last 20 years, providing insight to population dynamics and how the plants might respond to the changing climate. The main current threat to the species is habitat destruction as the climate changes. Variation in the number of plants among populations and years, and correlations with environmental variables were examined. Some species had increased while others had decreased over the years. No uniform relationship for all species and populations were discovered, but some of the species exhibited relationships between population size changes and temperature and precipitation. However, if the future climate in Norrbotten County changes according to the predictions, the habitats of the specialist alpine plants may be severely altered, leaving the species with no alternative places to establish and grow.
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Giles, Lynne Catherine. "Changes in activity limitations in an older population /." Title page, table of contents and abstract only, 1998. http://web4.library.adelaide.edu.au/theses/09MPM/09mpmg472.pdf.
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Stokes, T. K. "Long term changes in a laboratory insect population." Thesis, University of Strathclyde, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.371358.
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Ross, Beth E. "Assessing Changes in Waterfowl Population and Community Dynamics." DigitalCommons@USU, 2014. https://digitalcommons.usu.edu/etd/2174.
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Studying long-term ecological studies allows for a better understanding of processes driving populations and communities, and this understanding can be used to improve conservation eorts. These studies can describe how changes in the environment have led to current states of populations and communities, and indicate if the current state or trend falls within expectations based on past dynamics. Studies of long-term datasets also help ecologists predict how populations may shift with climate, water, or land-use change and determine necessary management action to maintain sustainable populations and community interactions. Serving as a \test of time," long-term monitoring can provide insight into the in uence of predation, intra- or interspecic competition, and other interactions on system dynamics. Studies need to explicitly include these drivers and sources of autocorrelation in data (e.g., spatial autocorrelation) to obtain unbiased estimates of ecological processes for guiding management. Fortunately, new statistical analyses for ecological applications are available that help ecologists make full use of the information present in long-term studies while properly accounting for sampling error and autocorrelation. In this study, I use advanced statistical methods to analyze a long-term dataset, the Waterfowl Breeding Population and Habitat Survey, and address questions about waterfowl population and community dynamics. In Chapter 2, I use multi-state occupancy models to determine how the presence of lesser and greater scaup (Aythya anis and A. marila) has changed on their breeding grounds in North America since 1955. In Chapter 3, I use a Bayesian hierarchical model to determine the drivers of the breeding scaup population in the Northwest Territories of Canada. Lastly, in Chapter 4 I incorporate more waterfowl species into the hierarchical model from Chapter 3 to determine the drivers of the pochard duck community, along with the role of species interactions. My results indicate that the occupancy of scaup has decreased in the boreal forest of Canada and increased in the prairie parklands. Additionally, scaup in the Northwest Territories are largely in uenced by density dependence and snow cover extent. Finally, the pochard community in the Northwest Territories is regulated more by environmental drivers than intra- or interspecic interactions. These results indicate that management of the species through hunting regulations likely deserves further study, as scaup likely exhibit some sort of compensation in response to hunting.
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Pappas, Nikos. "The macroeconomic impacts of projected population changes in Greece." Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=18976.
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The aim of my thesis is to explore the macroeconomic impacts of the projected demographic changes in Greece. Population of Greece is projected to age in the course of the next three decades. The thesis combines demographic projections with a multi-period economic Computable General Equilibrium (CGE) modelling framework to assess the macroeconomic impact of these future demographic trends. The size and age composition of the population in the future depends on current and future values of demographic parameters such as the fertility, mortality rates and the level of annual net migration. I use FIV-FIV demographic software in order to project population changes for 30 years. Total population and working age population changes are introduced as exogenous disturbances to the G-AMOS CGE modelling framework calibrated for the Greek economy for the year 2004. The economic impacts of a very wide range of demographic scenarios are examined. The main finding is that positive net migration is able to cancel the negative impacts of an ageing population that would otherwise occur as a result of the shrinking of the labour force. The very serious policy implication is that a viable, long-lasting migration policy should be implemented, while the importance of policies that could increase fertility should also be considered.
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Dahlan, Ahmed Said Mohammed. "Population characteristics and settlement changes in the Gaza Strip." Thesis, Durham University, 1987. http://etheses.dur.ac.uk/1172/.
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Vernooij, M. W. "Imaging of age-related brain changes a population-based approach /." [S.l.] : Rotterdam : [The Author] ; Erasmus University [Host], 2009. http://hdl.handle.net/1765/15054.
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Rezk, Ayham. "Population changes and labour market accounts in Syria, 1994-2004." Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/4136.
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Population growth in Syria 1994-2004 varied regionally, as did economic growth, and it was at the regional scale of Syrian labour market where the effects of these changes were seen. The contribution of this thesis is to empirically examine how the processes in the regional labour markets were influenced by demographic changes and varying economic opportunities. It examines these variations and determines how the regions responded to imbalances of growth in labour supply and demand. The methodology of labour market accounts distinguishes the role of demographic and economic components in each regional labour market, and identifies how far natural growth of the economically active population was absorbed by adequate employment growth in the period 1994-2004. Most regions saw substantial job shortfalls, largely due to increasing numbers of young people seeking work at a time of slow economic growth. This thesis shows the regional variations in this problem, which in some regions was highlighted by the extent to which female economic participation increased from traditionally very low levels. The combination of job shortfalls and changing economic activity rates led to an increasing labour supply imbalance, and consequently increasing unemployment or net out-migration. This research shows that the labour market accounts method can be applied to the regions of Syria. The insights gained from the analysis suggest that similar analyses may be worth pursuing in countries with similar socio-economic challenges arising from stalling economic growth when labour supply was still growing due to previously rapid demographic growth and a 'catching up' in female economic participation. These circumstances have led this thesis to introduce the supply imbalance measure to labour market accounts: presenting the data in this way highlights economic and social challenges emerging in each region. The research also highlights limitations to applying this method in a situation where the datasets present some difficulties and the populations captured by each are variable. The implications gained from this research have to be seen rather hypothetical now that Syira's population is radically changing due to ongoing conflict which began in 2011.
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Drøyvold, Wenche Brenne. "Epidemiological studies on weight change and health in a large population." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Medicine, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1461.
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Leary, Paul Niell. "The Late Cenomanian anoxic event : implications for foraminiferal evolution." Thesis, University of Plymouth, 1987. http://hdl.handle.net/10026.1/2057.
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This study lnvestigates the effect of the late Cenomanian Oceanic Anoxic Event (OAE) on the planktonic and benthonic foraminifera. On the former, the OAE was the cause of major extinctions within the population, the return to pre-OAE oxygen levels permitting recolonization of the vacated niches. On the latter, the OAE caused extinctions but resulted in a low oxygen tolerant fauna which slowly evolved into the vacated niches on the post-oAE recovery of oxygen levels. The changes in the foraminiferal populations have been integrated With changes in other marine organisms through the late Cenomanian.
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Lai, Wai-hung. "Population changes and the production and trade pattern in Hong Kong." Click to view the E-thesis via HKUTO, 1987. http://sunzi.lib.hku.hk/hkuto/record/B31975100.
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Lai, Wai-hung, and 黎偉雄. "Population changes and the production and trade pattern in Hong Kong." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1987. http://hub.hku.hk/bib/B31975100.
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Keeratipongpaiboon, Thuttai. "Population ageing : changes in household composition and economic behaviour in Thailand." Thesis, SOAS, University of London, 2012. http://eprints.soas.ac.uk/14570/.
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Thompson, I. P. "Bacterial population changes during decay of basidiomycetes : a numerical taxonomic study." Thesis, University of Essex, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.370495.
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Dewey, Jennifer K. "Evaluating Entheseal Changes from a Commingled and Fragmentary Population| Republic Groves." Thesis, Florida Atlantic University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10789480.
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The most direct way available to modern day researchers to reconstruct individual and population level behavior is to analyze markers of activity from skeletal remains (Ruff et al., 2004). An analysis of the population at the Republic Groves site (8HR4) was conducted, using the entheseal change score system, the Coimbra method, developed by Henderson et al. (2015). This study examined the implication of analyzing a commingled and fragmentary population with this methodology. Reconstructing specific behavior cannot be done with this type of approach; however, entheseal changes can be compared to specific patterns of behavior for consistency. An atlatl was found with the human remains and thus provided a suggestion of behavior for comparison. Entheses were chosen in line with a throwing motion of the atlatl and focused exclusively on the humerus, radius, and ulna. The application of the Coimbra methodology to the Republic Groves population was successful, at least in part. Overall, there was low variability of results, mostly 0, some 1, and with very few high 2 scores. The entheseal changes from Republic Groves were consistent with the throwing of an atlatl; however, this does not mean that this is the only behavior that could have generated that kind of change.
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Garnett, Anne Margaret, and n/a. "EMPLOYMENT AND POPULATION ADJUSTMENT IN RURAL AUSTRALIA." University of Canberra. School of Business & Government, 2007. http://erl.canberra.edu.au./public/adt-AUC20070802.130527.
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Rural regions in Australia have been, and continue to be, distinguished by very different population and labour market characteristics than those of more urbanised areas. Since the 1980s, rural regions have been exposed to a range of economic events and policies which has impacted on the structure and composition of the population and the labour force. These changes include trade liberalisation and globalisation, deregulation, declining numbers of agricultural establishments, advances in technology, increases in productivity and changes in the levels of public and private provision of goods and services. In addition, in recent years, serious shortages of labour, particularly skilled labour, has emerged as a major issue facing rural regions.
However, there has been little economic research into rural labour markets relative to other labour markets, particularly since the 1980s. While there has been significant public discussion and political debate in recent years on the apparent changes experienced by rural regions, evidence regarding the nature, causes and impacts of these changes has often been anecdotal. For example, there is the popular notion of the �tree change� which refers to the idea that people are leaving metropolitan areas and moving to rural areas. Concurrently, there is also the significant discussion on the �rural downturn�, which refers to the belief that rural regions are declining in term of population and employment growth. Further, the agricultural sector has continued to be cited as the likely cause for downturns in rural population and employment growth rates in rural areas. However, again, there is a lack of economic research to substantiate these claims.
The aim of this thesis is to redress the lack of economic research and to provide a comprehensive analysis of rural labour markets and population in Australia since the 1980s. Analysis focuses on the changing structure and composition of rural labour markets and the impact of population shifts on rural localities. Evidence is provided on the extent to which two decades of significant structural, technological and regulatory change have impacted on rural labour markets in Australia. This then provides a sound basis for the policy discussion in this thesis on population and labour market changes in rural Australia and the causes and implications of these changes.
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Bullock, Michael Ross. "The impact of changes in social housing provision on migration propensities." Thesis, Lancaster University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360616.
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Lee, Fung. "Climatic change and Chinese population growth dynamics over the last millennium." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39558599.
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Anderson, Kathie Ann Ryckman. "From the population bomb to the birth dearth : the stages of acceptance of public opinion about changes in population." Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2002. http://wwwlib.umi.com/cr/utexas/fullcit?p3077403.
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Duncan, John A. "Aloe Pillansii on Cornell's Kop : are population changes a result of intrinsic life history patterns or climate change?" Bachelor's thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/25928.
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Aloe pillansii populations in the biodiversity hotspot of the Succulent Karoo in Southern Africa are thought to be under threat of extinction. This study investigated the population at the type locality; Cornell's Kop in the Richtersveld, South Africa. It has been suggested that theft, animal damage and more recently climate change have caused a decline in the population by over 50% in the last decade, however very little is known about this rare species. Repeat photography and surveys were used to analyse life history patterns and dynamics of the population and thus establish what the potential threats to this keystone species actually are. Repeat photography indicates that there have been high rates of adult mortality over the last fifty years (1.8% of the population dies annually), which results in an average predicted lifespan of 39 years for the remaining adult population on Cornell's Kop. However, a recent survey reported that over 40% of the population recorded were seedlings, which weren't found in a 1995 survey, which is indicative of a recent recruitment pulse on Cornell's Kop and that conditions on the hill are still habitable for A. pillansii. Growth analyses suggest that A. pillansii has an average annual growth rate of 20 mm.yr⁻¹, which in tum means that 8 m individuals may be up to 453 years old. This long-lived strategy would require A. pillansii to only recruit infrequently, during periods of high rainfall, in order to sustain a viable population, which is consistent with findings on other large desert succulents. Seedling ages were estimated from their heights and it was found that 50% of the seedlings appear to have germinated five to ten years ago; this is consistent with rainfall records from the area which indicate that rainfall was consistently above the annual average for this same period. The findings indicate that although the adult A. pillansii population is declining, the presence of 30 seedlings suggest that the population is entering a recruitment phase after just coming out of a lengthy senescent phase. Although A. pillansii 's extensive lifespan makes it a potentially useful indicator species of climate change, the evidence presented in this study does not suggest that climate change has affected the dynamics of this population.
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Persson, Sofie. "Prevalence of Cataract changes in a Guatemala population evaluated by direct ophthalmoscopy." Thesis, Linnéuniversitetet, Institutionen för medicin och optometri (MEO), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-26786.
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Purpose: To grade cataract changes in a Guatemala population with direct ophthalmoscopy and a grading system based on the grading system used by V. Mehra and D. C. Minassian in 1988. Methods: A population from Guatemala who attended field clinics conducted by Vision For All were included in this study. The sample consisted of 352 participants, 219 women and 133 men, from 9-90 years old. Mean age of the participants was 47.9 ± 17.8 years old. Binocular VA and subjective refraction was obtained with trial lenses and a Snellen E-chart at 5 meters. A 2 mm pinhole was used monocularly with the subjective refraction and whether participants felt any improvement in VA was documented. The opacities in the red reflex in the crystalline lens were graded using a handheld direct ophthalmoscope. The grading was made in an angle of 25o nasal and at approximately 33 cm from the participant’s undilated eye. Results: The prevalence of cataract was 28.6% and 68% had some form of opacity in the red reflex. There was no statistically significant difference (p > 0.05) between the grade of lens opacities in right and left eye. Mean grade of lens opacities in right eye was 1.64 ± 1.46 and 1.63 ± 1.43 in left eye. The analysis showed a highly significant correlation between age and grade of lens opacities in right eye (y = 0.0657x -1.5106; r = 0.8; p < 0.001) and left eye (r = 0.78; p < 0.001). Lens opacities start to develop at an average age of 38.5 years in this population. There was a significant correlation between aided VA and grade of lens opacities for right eye (r = 0.52; p < 0.05) and left eye (r = 0.49; p < 0.05). 72 participants (20.5%) who had grading 3-5 in one or both eyes felt an improvement in their vision with the pinhole. Conclusions: The prevalence of cataract was 28.6% and this population had an earlier development of cataract compared to previous studies. This could be due to the UV-radiation, the temperature and nutrition and antioxidant insufficiency. Also this study showed a highly significant correlation between age and grade of lens opacities and a low, but significant, correlation between aided VA and grade of lens opacities.
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Shi, Niu 1963. "Demographic changes and genetic variation of an alfalfa (Medicago sativa L.) population." Thesis, The University of Arizona, 1991. http://hdl.handle.net/10150/277907.
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The objectives of this study were to describe demographic change in an alfalfa population and determine whether genetic changes were associated with stand loss in an alfalfa field during the year of establishment. A nondormant composite population (AZ-88NDC) was sown at 1944 seeds per square meter in Oct. 1988 at Tucson, AZ. Only 29% of the seeds sown germinated and emerged. Survivorship curve of the emerged seedling population had some characteristics of Deevey type III. Two heavy mortality periods were observed. Low temperatures might be the major cause of the first heavy stand loss. The second significant stand loss could be explained by increased density stress. Isozyme profiles were produced from 60 day survivors dug from the field, unselected greenhouse-grown AZ-88NDC (='Unsel') and 300-d progenies produced by intermating plants surviving 300 days. Significant differences were observed in overall level of population heterozygosity of 60-d and unselected populations based on fixation indices of six isozyme loci. This suggests that genetic changes may be associated with establishment of an alfalfa stand.
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Theunert, Christoph. "Approaches For Inferring Past Population Size Changes From Genome-wide Genetic Data." Doctoral thesis, Universitätsbibliothek Leipzig, 2014. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-150660.
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The history of populations or species is of fundamental importance in a variety of areas. Gaining details about demographic, cultural, climatic or political aspects of the past may provide insights that improve the understanding of how populations have evolved over time and how they may evolve in future. Different types of resources can be informative about different periods of time.
One especially important resource is genetic data, either from a single individual or a group of organisms. Environmental conditions and circumstances can directly affect the existence and success of a group of individuals. Since genetic material gets passed on from generation to generation, traces of past events can still be detected in today\'s genetic data. For many decades scientists have tried to understand the principles of how external influences can directly affect the appearance and features of populations, leading to theoretical models that can interpret modern day genetic variation in the light of past events.
Among other influencing factors like migration, natural selection etc., population size changes can have a great impact on the genetic diversity of a group of organisms. For example, in the field of conservation biology, gaining insights into how the size of a population evolves may assist in detecting past or ongoing temporal reductions of population size. This seems crucial since the reduction in size also correlates with a reduction in genetic diversity which in turn might negatively affect the evolutionary potential of a population. Using computational and population genetics methods, sequences from whole genomes can be scanned for traces of such events and therefore assist in new interpretations of historical details of populations or groups of interest.
This thesis focuses on the detection and interpretation of past population size changes. Two approaches to infer particular parameters from underlying demographic models are described. The first part of this thesis introduces two summary statistics which were designed to detect fluctuations in size from genome-wide Single Nucleotide Polymorphism (SNP) data. Demographic inferences from such data are inherently complicated due to recombination and ascertainment bias. Hence, two new statistics are introduced: allele frequency-identity by descent (AF-IBD) and allele frequency-identity by state (AF-IBS). Both make use of linkage disequilibrium information and exhibit defined relationships to the time of the underlying mathematical process. A fast and efficient Approximate Bayesian Computation framework based on AF-IBD and AF-IBS is constructed that can accurately estimate demographic parameters. These two statistics were tested for the biasing effects of hidden recombination events, ascertainment bias and phasing errors. The statistics were found to be robust to a variety of these tested biases. The inference approach was then applied to genome-wide SNP data to infer the demographic histories of two human populations: (i) Yoruba from Africa and (ii) French from Europe. Results suggest, that AF-IBD and AF-IBS are able to capture sufficient amounts of information from underlying data sets in order to accurately infer parameters of interest, such as the beginning, end and strength of periods of varying size. Additionally the results from empirical data suggest a rather stable ancestral population size with a mild recent expansion for Yoruba, whereas the French apparently experienced a rather long-lasting strong bottleneck followed by a drastic population growth.
The second part of this thesis introduces a new way of summarizing information from the site frequency spectrum. Commonly applied site frequency spectrum based inference methods make use of allele frequency information from individual segregating sites. Our newly developed method, the 2 point spectrum, summarizes allele frequency information from all possible pairs of segregating sites, thereby increasing the number of potentially informative values from the same underlying data set. These additional information are then incorporated into a Markov Chain Monte Carlo framework. This allows for a high degree of flexibility and implements an efficient method to infer population size trajectories over time. We tested the method on a variety of different simulated data sets from underlying demographic models. Furthermore, we compared the performance and accuracy of our method to already established methods like PSMC and diCal. Results indicate that this non-parametric 2 point spectrum method can accurately infer the extent and times of past population size changes and therefore correctly estimates the history of temporal size fluctuations. Furthermore, the initial results suggest that the amount of required data and the accuracy of the final results are comparable with other publicly available non-parametric methods. An easy to use command line program was implemented and will be made publicly available.
In summary, we introduced three highly sensitive summary statistics and proposed different approaches to infer parameters from demographic models of interest. Both methods provide powerful frameworks for accurate parameter inference from genome-wide genetic data. They were tested for a variety of demographic models and provide highly accurate results. They may be used in the settings as described above or incorporated into already existing inference frameworks. Nevertheless, the statistics should prove useful for new insights into populations, especially those with complex demographic histories.
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Nisa, Georgette. "The prevalenceof anterior segment and crystalline lens changes in a Nicaraguan population." Thesis, Linnéuniversitetet, Institutionen för medicin och optometri (MEO), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-54213.
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Abstract Aim: The purpose of this study was to find the prevalence of different ocular changes in the anterior segment of the eye and changes in the crystalline lens among Nicaraguan population. Method: The study was done during a journey to Nicaragua with the organization VFA and Synoptik that lasted for two weeks in March/April. There were a total of 134 participants with 71 females and 63 males. The average age of the study participants was 50 (±20) years and the age ranged from 7 to 97 years. The total sample size was collected in the three towns that we visited during the journey: Ticuantepe, Léon and Estéli. The changes were evaluated by direct ophthalmoscopy. Conjunctiva was examined by asking the patients to look into different gaze directions. Cornea and crystalline lens was examined by asking the patient to look directly at the ophthalmoscope. Results: 31% out of the participants enrolled in this study were healthy with no visible ocular changes. The remaining 69% had ocular changes with majority of them having either cataract, pterygium or pinguecula. The prevalence of cataract was 24%, pterygium 20%, pinguecula 10%. There were other minor ocular changes such as red eye in 4%, arcus senilis in 4%, ptosis in 1%, and aphakia in 1% seen in these participants. Conclusion: The UV related changes had the highest prevalence. This study like previous studies have shown that cataract was most prevalent ocular change in this population.
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Forest, Marie. "Simultaneous estimation of population size changes and splits times using importance sampling." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:8c067a3d-44d5-468a-beb5-34c5830998c4.
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The genome is a treasure trove of information about the history of an individual, his population, and his species. For as long as genomic data have been available, methods have been developed to retrieve this information and learn about population history. Over the last decade, large international genomic projects (e.g. the HapMap Project and the 1000 Genomes Project) have offered access to high quality data collected from thousands of individuals from a vast number of populations. Freely available to all, these databases offer the possibility to develop new methods to uncover the history of the peopling of the world by modern humans. Due to the complexity of the problem and the large amount of available data, all developed methods either simplify the model with strong assumptions or use an approximation; they also dramatically down-sample their data by either using fewer individuals or only portions of the genome. In this thesis, we present a novel method to jointly estimate the time of divergence of a pair of populations and their variable sizes, a previously unsolved problem. The method uses multiple regions of the genome with low recombination rate. For each region, we use an importance sampler to build a large number of possible genealogies, and from those we estimate the likelihood function of parameters of interest. By modelling the population sizes as piecewise constant within fixed time intervals, we aim to capture population size variation through time. We show via simulation studies that the method performs well in many situations, even when the model assumptions are not totally met. We apply the method to five populations from the 1000 Genomes Project, obtaining estimates of split times between European groups and among Europe, Africa and Asia. We also infer shared and non-shared bottlenecks in out-of- Africa groups, expansions following population separations, and the sizes of ancestral populations further back in time.
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Bradford, Jessica. "Examining Culex tarsalis (Diptera: Culicidae) population changes with satellite vegetation index data." Kansas State University, 2014. http://hdl.handle.net/2097/17139.
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Master of Public HealthDepartment of Diagnostic Medicine/Pathobiology
Michael W. Sanderson
A zoonotic disease is any disease or infection that is naturally transmissible from vertebrate animals to humans. Over 200 zoonoses have been described (Zoonoses and the Human-Animal-Ecosystems Interface, 2013). Many zoonotic viruses are arboviruses, viruses transmitted by an infected, blood-sucking, arthropod vector (Hunt, 2010). There are several endemic arboviruses in the United States; some foreign arboviruses, such as Rift Valley fever (RVF) virus, are potential bioterrorism agents (Dar, 2013). Arboviruses, both endemic and foreign, threaten public health (Gubler, 2002) and therefore disease surveillance, vector control and public education are all vital steps in minimizing arboviral disease impact in the United States. Mosquito-borne disease threats, such as West Nile virus and Rift Valley fever, are constant concerns in the United States and globally. Current strategies to prevent and control mosquito-borne diseases utilize vector distribution, seasonal and daylight timing, and variation in population numbers. Climate factors, such as availability of still water for development of immature mosquitoes, shade, and rainfall, are known to influence population dynamics of mosquitoes. Using 1995-2011 mosquito population surveillance data from Fort Riley, Kansas, we compared population numbers of Culex tarsalis (Diptera: Culicidae), a vector of several arboviruses including West Nile virus and potentially Rift Valley fever, to a satellite-derived index of climate, the Normalized Difference Vegetation Index (NDVI) anomaly. No correlation between the population numbers and NDVI anomaly was observed, which contrasts with results from similar analyses in other locations. These findings suggest a need for continued investigation into mosquito population dynamics in additional ecological regions of the United States to better describe the heterogeneity of environment-population relationships within and among mosquito species.
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Englama, Abwaku. "Determinants of fertility in less developed countries : a case study of Nigeria." Thesis, University of Essex, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258565.
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Wennersten, Lena. "Population-level consequences of variation." Doctoral thesis, Linnéuniversitetet, Institutionen för naturvetenskap, NV, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-32522.
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Consequences of within population variation have recently attracted an increased interest in evolutionary ecology research. Theoretical models suggest important population-level consequences, but many of these predictions still remain to be tested. These issues are important for a deepened understanding of population performances and persistence, especially in a world characterized by rapid fragmentation of natural habitats and other environmental changes. I review theoretical models of consequences from intra population genetic and phenotypic variation. I find that more variable populations are predicted to be characterized by broader resource use, reduced intraspecific competition, reduced vulnerability to environmental changes, more stable population dynamics, higher invasive potential, enhanced colonization and establishment success, larger distribution ranges, higher evolvability, higher productivity, faster population growth rate, decreased extinction risk, and higher speciation rate, compared with less variable populations. To test some of these predictions I performed experiments and compared how different degree of colour polymorphism influences predation risk and establishment success in small groups. My comparisons of predation risk in mono- and polymorphic artificial prey populations showed that the risk of being eaten by birds does not only depend on the coloration of the individual prey item itself, but also on the coloration of the other members of the group. Two experiments on establishment success in small founder groups of Tetrix subulata pygmy grasshoppers with different degree of colour morph diversity show that establishment success increases with higher degree of diversity, both under controlled conditions in outdoor enclosures and in the wild. These findings may be important for re-stocking of declining populations or re-introductions of locally extinct populations in conservation biology projects. I report on remarkably rapid evolutionary shifts in colour morph frequencies in response to the changed environmental conditions in replicated natural populations of pygmy grasshoppers in fire ravaged areas. This finding 1 illustrates the high adaptive potential in a polymorphic species, and indicates the importance of preserved within-species diversity for evolutionary rescue. Finally, I review if theoretical predictions are supported by other published empirical tests and find strong support for the predictions that more variable groups benefit from reduced vulnerability to environmental changes, reduced population fluctuations and extinction risk, larger distribution ranges, and higher colonization or establishment success. In conclusion, my thesis illustrates how within-population variation influences ecological and evolutionary performances of populations both in the short and long term. As such, it emphasizes the need for conservation of biodiversity also within populations.
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Rivers, Nicola Mary. "Seasonal changes in population structure and behaviour of the Natterer's bat (Myotis nattereri)." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.418776.
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Stanley, Zachary. "RELATIVE COMPETITIVE ABILITIES, INTERSEXUAL OVERYIELDING, AND POPULATION SEX RATIO CHANGES IN A BRYOPHYTE." UKnowledge, 2019. https://uknowledge.uky.edu/biology_etds/60.
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Unequal sex ratios are widespread in dioecious plants and understanding their cause is important to understanding fundamental aspects of their population dynamics, and yet what causes biased sex ratios in plants is still poorly understood. Competition experiments have been used in plants to predict the outcome of species interactions, but they have rarely been used to help explain sex ratio bias. This study used a response surface competition design to measure the relative competitive abilities of the sexes of the bryophyte Marchantia inflexa (a thallus liverwort of Marchantiaceae) to predict the outcome of competition before the onset of sexual reproductive structures. In bryophytes, dioecy and sex ratio bias is especially common, making them effective organisms for studying sex ratio bias. Given the frequency of female bias in bryophytes, the hypothesis was that females will show a higher competitive ability relative to males. The experiment was conducted in greenhouse conditions at several densities and proportions over the course of seven months. As individuals grew and formed clumps, identities were tracked, and growth measurements were made using photographs and computer imaging software. Both sexes grew on average 41% more with the opposite sex relative to their single-sex cultures. A model predicting future sex ratios showed coexistence between the sexes and predicted a male biased sex ratio of 3.2 males to 1 female. A trade-off was observed for males where single-sex cultures contained more asexual structures than mixed-sex cultures and the reverse for growth rate. Higher levels of asexual reproduction in males in single-sex cultures might be selected for to increase male dispersal for a higher probability of encountering females. This pattern was not found for females. The overyielding results suggest an interaction effect may exist due to niche differentiation between the sexes. In addition, the results suggest that in some dioecious plants a change in sex ratio can occur before differences in their allocation to sexual reproduction.
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Noble, Samanthia Jean. "STORM INDUCED CHANGES IN TURBIDITY, CHLOROPHYLL, AND BRACHIONUS POPULATION DYNAMICS IN ACTON LAKE." Miami University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=miami1105465428.
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Nyman, Robert H. "A study of changes in algal population density diversity and distribution and changes in physical and chemical characteristics of Lake Elsinore." CSUSB ScholarWorks, 1986. https://scholarworks.lib.csusb.edu/etd-project/372.
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McLeman, Robert Andrew. "A management strategy for potential human population movements as a result of climate change." Thesis, Hong Kong : University of Hong Kong, 1995. http://sunzi.lib.hku.hk/hkuto/record.jsp?B14040190.
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Van, Beveren Elisabeth. "Population changes in small pelagic fish of the Gulf of Lions : a bottom-up control?" Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTS040/document.
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La compréhension et la gestion des écosystèmes requièrent un maximum de connaissances sur les dynamiques de populations. Depuis 2007, la taille de la sardine (Sardina pilchardus) et de l’anchois (Engraulis encrasicolus) dans le Golfe du Lion a chuté tandis qu’au même moment, la population de sprat, qui a une faible valeur commerciale, a fortement augmenté. Les très forts enjeux économiques autour de ces espèces ont conduit au projet de recherche « EcoPelGol » dans lequel se situe cette étude portant sur les changements observés. La condition corporelle, la croissance ainsi que la structure en âge et en taille des sardines, des anchois et en partie des sprats ont été analysées sur les vingt dernières années. Alors qu’en 2005-2007, la situation semblait optimale pour les anchois et les sardines (taille et condition élevées), celle-ci s’est considérablement dégradée depuis 2008, l’anchois et la sardine étant significativement plus petits et plus maigres. De plus, une diminution de l’âge et de la croissance a été observée chez la sardine. Nous avons ensuite caractérisé les fluctuations des débarquements historiques (1865-2013) de l’anchois, de la sardine et du maquereau. La chute récente des débarquements a été mise en exergue, avec une situation inédite où la sardine est actuellement moins débarquée qu’avant les années 60, date à laquelle les débarquements ont fortement augmenté suite à un accroissement conséquent de l’effort de pêche. Bien que la majorité de la variance dans les séries de débarquements semble être engendré par les changements de l’effort de pêche, nous avons également observé une relation entre les débarquements et l’indice « Atlantic Multidecadal Oscillation » pour l’anchois et la sardine et avec le « Western Mediterranean Oscillation » pour l'anchois. Dans une troisième analyse, la pression de prédation du thon rouge sur l’anchois, la sardine et le sprat a été estimée pour voir si l’accroissement de la population du thon depuis 2007 lié à de nouvelle mesures de gestion a pu impacté les poissons petits pélagiques. Mais bien que la sardine et l’anchois soient les proies principales du thon, moins de 2% de leurs populations ont été consommés chaque année entre 2011-2013, et ce, sans sélectivité sur la taille de ces proies de la part du thon. Ainsi, le thon rouge n’a pas pu avoir un impact significatif sur la structure en taille ou les abondances des petits pélagiques. Dans le chapitre final, nous avons considéré la possible influence de pathogènes. Des analyses globales dirigées vers la détection des parasites, des bactéries et des virus ont été effectuées tout au long de l’année et ont révélées la présence ponctuelle et relativement faible de bactéries des genres Tenacibaculum et Vibrio et celle systématique de microparasites. Malgré l’impossibilité d’exclure leur pathogénicité, aucune lésion tissulaire n’a été attribuée à ces organismes, réduisant fortement la probabilité d’une épizootie. Nos travaux indiquent que les mécanismes « top-down », des pathogènes ou encore la pêche ne sont probablement pas les facteurs clés pour expliquer les changements observés chez les poissons petites pélagiques. À l'opposé, certains paramètres environnementaux ont expliqué une partie de la variabilité dans la condition corporelle des poissons et leurs débarquements. Nous concluons donc qu’un contrôle « bottom-up », et particulièrement un changement dans la quantité et/ou qualité du zooplancton, peut être la cause des phénomènes dans les populations des poissons petits pélagiques. Si cette thèse permet une avancée dans la compréhension de leur dynamique, des analyses complémentaires seront nécessaires pour confirmer notre hypothèse principale et pour estimer l’influence des autres facteurs agissant potentiellement en synergieKnowledge on population dynamics is key to the improvement of management and the understanding of ecosystem functioning. Since 2007, the size of sardine (Sardina pilchardus) and anchovy (Engraulis encrasicolus) in the Gulf of Lions (NW Mediterranean) has severely decreased, which has strongly affected the fisheries. Simultaneously, the commercially uninteresting sprat population increased remarkably. As the economic and ecological stakes are high, the EcoPelGol project of which this PhD is part was established. We first analysed the sardine, anchovy and (partially) sprat population for changes in body condition, growth and size and age structure over the last 20 years. We concluded that sardine and anchovy have had from 2008 onwards a distinctively poor body condition and size, and that sardine have also showed a concurrent decrease in age and growth. In contrast, both species were in optimal and average “health” during 2005-2007 and 1992-2004, respectively. Subsequently, historical landings of sardine, anchovy and mackerel were considered (1865-2013), of which the fluctuations were characterised and statistically related to environmental variables. The recent dramatic landings decrease was put into perspective, as for example sardine is now for the first time landed less than before the 1960s, when a big probably effort-related upsurge occurred. Despite most of the variability being explained by what looks like changes in fishing effort, a link was found between the sardine and anchovy landings and the Atlantic Multidecadal Oscillation and the anchovy landings and the Western Mediterranean Oscillation. Next, as a management associated bluefin tuna increase also happened since 2007, its predation pressure on all three small pelagic species was estimated. We concluded that although sardine and anchovy are bluefin tuna’s main prey items, less than 2% of each population (including sprat) was consumed annually during 2011-2013 and that there was no clear size selectivity. Thus, tuna could not have had a noticeable impact on the population abundance or size structure of the small pelagics. In the last chapter, an epizootic disease was considered. An all-embracing approach directed towards the all-year round detection of both general and specific parasites, bacteria and viruses revealed the mostly temporal and not necessarily high occurrence of only three groups: microparasites, Vibrio spp. (sometimes determined as Vibrio alginolyticus) and bacteria of the genus Tenacibaculum. Although we could not exclude their pathogenicity, significant tissue damage at a cellular or macroscopic level was never observed, making the disease hypothesis less likely. Thus, we considered several hypotheses and indicated that top-down control (through Bluefin tuna predation), pathogens and fisheries are unlikely to be main drivers. In contrast, some environmental parameters explained a part of the variability in fish condition and landings. After a final discussion on all probable theories we concluded that a bottom-up control, such as especially a planktonic change in quantity and/or quality, might be on the basis of the observed changes. Although this work is a great step towards the understanding of the small pelagic dynamics in the Gulf of Lions, further investigations will still be needed to confirm our main hypothesis and to estimate the potential synergetic effect of other drivers
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Guldager, Nikolina. "Effects of an Increasing Harbor Seal Population on Changes in Sites Used for Pupping." Fogler Library, University of Maine, 2001. http://www.library.umaine.edu/theses/pdf/GuldagerN2001.pdf.
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McCall, Barbara. "NONINVASIVE GENETIC SAMPLING REVELAS BLACK BEAR POPULATION DYNAMICS DRIVEN BY CHANGES IN FOOD PRODUCTIVITY." The University of Montana, 2009. http://etd.lib.umt.edu/theses/available/etd-06112009-182902/.
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I conducted research on the demography of a harvested north Idaho black bear (Ursus americanus) population to determine the underlying dynamics of changes in population abundance, to determine how much these dynamics were driven by variation in food productivity, and to evaluate how these processes could influence inferences based on mark-recapture analysis. In cooperation with Idaho Department of Fish and Game and the USDA Forest Service, I used barb-wire corrals to collect black bear DNA during 2003-2006 in the Purcell Mountains of Idaho. We analyzed these DNA samples to determine the number of uniquely identified individuals in each year, Nu. I used a combination of both genetic and mark-recapture analyses to evaluate the sources of variation in Nu over the four years and to what extent this variation was driven by changes in productivity of foods on the landscape. Specifically, I investigated deviations of Hardy-Weinberg equilibrium and genetic substructure in relation to changes in abundance, and whether variation in vital rates were a function of changing berry productivity in the study area. I found a heterozygote deficiency and detected genetic substructure indicating I sampled ≤ 4 subpopulations within the same area over the four years (a Wahlund Effect). My mark-recapture analyses suggest this pattern was probably in response to landscape changes in summer berry abundance. My results suggest important variation in population dynamics driven by changes in food productivity, which should be considered when using mark-recapture analyses to monitor population trends for black bears.
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Ward, Sarah. "Are changes in the lesser flamingo population a natural consequence of soda lake dynamics?" Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/378653/.
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McElhone, Patrick Michael. "Cerulean warbler population and habitat changes along Breeding Bird Survey routes in the central Appalachians." Morgantown, W. Va. : [West Virginia University Libraries], 2009. http://hdl.handle.net/10450/10263.
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Thesis (M.S.)--West Virginia University, 2009.Title from document title page. Document formatted into pages; contains viii, 73 p. : ill. (some col.), maps. Includes abstract. Includes bibliographical references.
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Lee, Fung, and 李峰. "Climatic change and Chinese population growth dynamics over the last millennium." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39558599.
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Swing, Rachel. "Score Changes from the WISC-R to the WISC-III in Disabled Population in Kentucky." TopSCHOLAR®, 1996. http://digitalcommons.wku.edu/theses/823.
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This study was conducted to examine the extent of score changes from the Wechsler Intelligence Scale for Children-Revised (WISC-R) to the Wechsler Intelligence Scale for Children-Third Edition (WISC-III) when administered to Learning Disabled and Mild Mental Disabled populations. Specifically, this study examined whether there are differences, or, differential score changes between these populations from one test version to the next. Score changes were obtained from 7 school districts in Western Kentucky. Recorded were scores from the WISC-R and WISC-III administrations in the areas of Verbal, Performance, and Full Scale IQ scores. The information collected about the children included date of birth, dates of testing, area of disability, gender, and race. Scores were then analyzed by a paired 1 statistic and three, two-way ANOVAs (Disability Group x WISC version). The results indicated WISC-III scores were significantly lower than WISC-R scores for both LD and MMD groups. The LD group also scored significantly higher than the MMD group across the two tests. The LD and MMD group scores changed approximately the same amount, as there was no interaction found between group and test version. Difference scores indicated that on average the total group's score changes from the WISC-R to the WISC-III were 3.67 for the Verbal Scale, 7.56 for the Performance Scale, and 5.65 for the Full Scale. Mean score changes for the LD group were 4.32 for the Verbal, 7.85 for the Performance, and 6.07 for the Full Scale. For the MMD group, the mean score changes were 2.39 for the Verbal, 8.26 for the Performance, and 5.83 for the Full Scale. Results of the present findings were discussed relative to previous findings in the literature. Implications for practice are made.
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Cherry, Bradley Alan. "Adrenal Zona Reticularis Changes Associated with Pubertal Transition in Control Versus Population-Inhibited Prairie Deermice." W&M ScholarWorks, 1995. https://scholarworks.wm.edu/etd/1539625963.
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Rook, Megan Ann. "Mortality of Diamondback Terrapins in Blue Crab Traps: Population Changes and Conservation in Southeastern Virginia." W&M ScholarWorks, 2009. https://scholarworks.wm.edu/etd/1539626881.
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Klopf, Ryan. "Community and ecosystem changes in tallgrass prairie restorations: the effects of population source and diversity." OpenSIUC, 2013. https://opensiuc.lib.siu.edu/dissertations/684.
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The overall objective of this study was to quantify the effects of dominant grass propagule source (i.e., cultivar vs. non-cultivar) and seeded diversity of propagules on community structure and ecosystem function during prairie restoration. Two field experiments, and two chronosequences were used to investigate this main objective. The two field experiments were established at the same latitude separated by 620 km (corresponding to a precipitation gradient from eastern Kansas to western Illinois), and consisted of a split plot design, with dominant grass source as the whole-plot factor (2 levels) and seeded dominance of grasses as the subplot factor (5 levels). Percent cover of each species in each treatment combination was quantified during the first five years of restoration. Total plant species richness and diversity were not adversely affected by cultivars in Kansas or Illinois. The effect of the dominant grass population source on the cover of focal grasses, planted species, and volunteer species were contingent upon location. By the fifth year of restoration, diversity and richness were greatest, and cover of volunteer species was lowest in the low grass dominance (i.e., high diversity) treatment. ANPP, as well as total, microbial, and mineralizable pools of C and N were measured to quantify ecosystem function in these two field experiments. Changes in ecosystem function in Kansas and Illinois were primarily driven by time and regional abiotic differences, not propagule source or seeded diversity. The effect of plant species diversity on ecosystem function was further investigated at a landscape scale by developing and sampling two chronosequences of high (HDC; n=20) and low diversity (LDC; n=15) prairies spanning over two decades of restoration in northwestern Illinois. In general most metrics of ecosystem function in both chronosequences moved towards levels measured in remnant prairies. While the constituent prairies of the HDC had higher species richness, diversity, and more rapidly increasing root biomass than the fields of the LDC, recovery of other important ecosystem functions including aboveground net primary productivity, total, microbial, and mineralizable soil C, and soil aggregate mean weighted diameter were achieved equally well with either high or low diversity prairie plantings.
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Saraux, Claire. "Response of penguins to environmental changes across the Southern ocean : from individuals to population trends." Strasbourg, 2011. http://www.theses.fr/2011STRA6192.
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Le changement climatique, dorénavant sans équivoque, devrait se poursuivre voire s’amplifier dans les siècles à venir, affectant profondément la composante biologique de notre planète. Il est donc nécessaire et urgent de mieux comprendre les écosystèmes et leurs réponses face au changement climatique. Au cours de cette thèse, j’ai étudié l’effet du climat dans l’Océan Austral au travers des manchots. Ceux-ci sont souvent considérés comme de bons indicateurs de leurs écosystèmes de part leur position au sommet de la chaîne trophique. Ce travail repose sur des données pluriannuelles collectées sur 3 espèces de manchots à l’aide de systèmes de suivi automatique, visant à minimiser la perturbation par rapport à la méthode habituelle des bagues alaires. Ainsi, nous montrons des effets contrastés du climat sur les différents traits d’histoire de vie chez les manchots royaux, dont la survie juvénile augmentait les années où la température de surface de la mer était élevée, au contraire de la survie adulte et du succès reproducteur. De plus, nous soulignons l’importance de l’échelle temporelle à laquelle on étudie cet effet du climat et la nécessité de l’adapter à la biologie de l’espèce. La mortalité des poussins de manchots pygmées est par exemple concentrée sur quelques semaines, indiquant que le succès reproducteur dépend chez cette espèce de conditions ponctuelles et non des moyennes saisonnières généralement utilisées. Enfin, les capacités différentes des individus à faire face à des conditions de glace variables, observées chez le manchot Adélie, montrent la nécessité de prendre en compte les différences interindividuelles en vue d’une potentielle adaptation des manchotsClimate change is now unequivocal and foreseen to continue within the next centuries, profoundly affecting the biological component of our planet. Thus, it is becoming urgently necessary to increase our understanding of ecosystems and their responses to climate change. In this thesis, we investigated the effects of climate on Southern Ocean ecosystems through the monitoring of penguins. As top-predators, penguins are often considered good indicators of their environment by integrating the effects of climate which occur lower in the food chain. Data were collected over several years on 3 penguin species (little, king and Adélie penguins) using automatic monitoring systems, that we proved to be relatively harm-free compared to the usual but deleterious flipper-banding method. We found king penguin juvenile survival to increase in years of high sea surface temperature by opposition to previous results on adult survival and breeding success, indicating contrasted effects of climate depending on life-history traits. Also, we highlighted the importance of the time-scale at which the effect of climate is investigated and the necessity of adapting it to the species biology. In little penguins, chick mortality was concentrated on some weeks, underlining the dependence of breeding success on punctual conditions instead of the mostly used mean seasonal conditions. Finally, we showed the importance of individual heterogeneity, leading for instance to differences in the ability to face various sea-ice conditions in Adélie penguins. Such inter-individual differences along with behavioural flexibility may play a role in a potential penguin adaption through phenotypic plasticity
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Meyers, Paul M. "Assessing Mourning Dove Population Declines: Changes in Nesting Dynamics and the Role of Perch Sites." DigitalCommons@USU, 1994. https://digitalcommons.usu.edu/etd/6499.
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I replicated a nesting study carried out 40 years ago in southern Utah to assess reasons for long-term population declines of mourning doves (Zenaida macroura) in the western United States. I compared current nesting patterns to similar data collected in 1952. I saw little difference in nest success and nest predation, but reproductive output and nest density decreased dramatically. The number of young fledged per pair of adults was only 64% of that estimated in 1952. A 1-2 week delay in the nesting season contributed to this decrease, but cannot explain it entirely. Nest density was about 20% of that in 1952 and total reproductive output for the study area about 12-19%. Underlying causes for these changes are uncertain, but patterns of delayed nesting, high nest abandonments, and low reproductive output are similar to those seen in stressed bird populations (e.g., food/nutrient limitation or increased toxicant levels). Finally, highest nest density occurred in a habitat type (i.e., Chalk Creek) considered unimportant for doves in 1952. Nests in Chalk Creek suffered higher predation and abandonment rates than those in irrigation ditches.
I also examined the effect of perch sites on nest density and distribution in two ways. First, I demonstrated a significant correlation between nest density and perch s:te density in riparian plots. Second, I erected artificial perch sites in the second year of the study and recorded changes in nest densities. For the year of the study only, nest density was higher in the experimental plots, but the difference was not statistically significant. From the levels recorded the previous year, however, nest densities increased in the experimental plots and decreased in the control plots. This difference was statistically significant, suggesting that mourning doves use the presence of perch sites as cues for habitat selection. Finally, in comparing the presence of other avian species, I found significantly more blackbirds (Aqelaius phoenicus and Euphaqus cyanocephalus) and western meadowlarks (Sturnella neglecta) in experimental plots than in control plots.
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Bacigalupe, Rodrigo. "Population genomic analysis of bacterial pathogen niche adaptation." Thesis, University of Edinburgh, 2018. http://hdl.handle.net/1842/31266.
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Globally disseminated bacterial pathogens frequently cause epidemics that are of major importance in public health. Of particular significance is the capacity for some of these bacteria to switch into a new environment leading to the emergence of pathogenic clones. Understanding the evolution and epidemiology of such pathogens is essential for designing rational ways for prevention, diagnosis and treatment of the diseases they cause. Whole-genome sequencing of multiple isolates facilitating comparative genomics and phylogenomic analyses provides high-resolution insights, which are revolutionizing our understanding of infectious diseases. In this thesis, a range of population genomic analyses are employed to study the molecular mechanisms and the evolutionary dynamics of bacterial pathogen niche adaptation, specifically between humans, animals and the environment. A large-scale population genomic approach was used to provide a global perspective of the host-switching events that have defined the evolution of Staphylococcus aureus in the context of its host-species. To investigate the genetic basis of host-adaptation, we performed genome-wide association analysis, revealing an array of accessory genes linked to S. aureus host-specificity. In addition, positive selection analysis identified biological pathways encoded in the core genome that are under diversifying selection in different host-species, suggesting a role in host-adaptation. These findings provide a high-resolution view of the evolutionary landscape of a model multi-host pathogen and its capacity to undergo changes in host ecology by genetic adaptation. To further explore S. aureus host-adaptive evolution, we examined the population dynamics of this pathogen after a simulated host-switch event. S. aureus strains of human origin were used to infect the mammary glands of sheep, and bacteria were passaged in multiple animals to simulate onward transmission events. Comparative genomics of passaged isolates allowed us to characterize the genetic changes acquired during the early stages of evolution in a novel host-species. Co-infection experiments using progenitor and passaged strains indicated that accumulated mutations contributed to enhanced fitness, indicating adaptation. Within-host population genomic analysis revealed the existence of population bottlenecks associated with transmission and establishment of infection in new hosts. Computational simulations of evolving genomes under regular bottlenecks supported that the fitness gain of beneficial mutations is high enough to overcome genetic drift and sweep through the population. Overall, these data provide new information relating to the critical early events associated with adaptation to novel host-species. Finally, population genomics was used to study the total diversity of Legionella longbeachae from patient and environmental sources and to investigate the epidemiology of a L. longbeachae outbreak in Scotland. We analysed the genomes of isolates from a cluster of legionellosis cases linked to commercial growing media in Scotland and of non-outbreak-associated strains from this and other countries. Extensive genetic diversity across the L. longbeachae species was identified, associated with intraspecies and interspecies gene flow, and a wide geographic distribution of closely related genotypes. Of note, a highly diverse pool of L. longbeachae genotypes within compost samples that precluded the genetic establishment of an infection source was observed. These data represent a view of the genomic diversity of this pathogen that will inform strategies for investigating future outbreaks. Overall, our findings demonstrate the application of population genomics to understand the molecular mechanisms and the evolutionary dynamics of bacterial adaptation to different ecological niches, and provide new insights relevant to other major bacterial pathogens with the capacity to spread between environments.
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Tringali, Michael D. "Genetic changes in natural populations caused by the release of cultured fishes." [Tampa, Fla.] : University of South Florida, 2003. http://purl.fcla.edu/fcla/etd/SFE0000153.
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Tringali, Michael Dominic. "Genetic Changes in Natural Populations Caused by the Release of Cultured Fishes." Scholar Commons, 2003. https://scholarcommons.usf.edu/etd/1495.
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Genetic changes likely occur in wild fish populations as a consequence of interactions with cultured fish, but to what extent do those changes threaten the maintenance of natural genetic diversity and population viability? Following a review and categorization of numerous processes suspected of being agents of post-release genetic change in recipient wild populations (Chapter 1), I focus on risks relating to the magnitude and duration of releases -- but with a twist. That is, I assume that the mean fitness of released, cultured individuals does not differ from that of the recipient natural population. Throughout, attention is devoted to potential post-release changes in inbreeding (NeI) and variance (NeV) effective population sizes -- indicators of expected rates of population-level change in inbreeding and drift variance, respectively. The reductive effect that large-scale releases exert on NeI in recipient populations can be significant. The effect is shown to be a threshold process (Chapter 2) and thus suggestive of an approach for determining risk-adverse stocking (or release) rates. This approach is utilized in Chapter 3, which describes genetic recommendations for an incipient marine stocking program. Several discordant contemporary NeI models are examined mathematically and by computer simulation (Chapter 4). I show that certain published results pertaining to the effect of multiple paternity on NeI are erroneous; a general model is described which accounts for inbreeding and relatedness in and among parents. That model is utilized in an empirical study of gene correlation in a hatchery cohort (Chapter 5). Propagation-related causes of reductions in NeI are also investigated in this cohort. Finally, extending mutational meltdown theory to accommodate fluctuating population sizes and recessive selective effects, I show that when large reductions in NeV occur (such as those that accompany admixtures of cultured and wild fish), the expected time to population inviability is significantly reduced (Chapter 6). Although a more comprehensive theoretical approach is needed, a precautionary inference may be drawn -- aquaculture-induced reductions in Ne, even though they may be transient, can lead to adverse genetic impacts. Avoidance of Ne-reductions cannot be accomplished, in a practical sense, without considering the stocking or release rates of cultured fish.
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Shaw, Chester Worth Jr. "Human responses to past climate, environment, and population in two Mogollon areas of New Mexico." Diss., The University of Arizona, 1993. http://hdl.handle.net/10150/186167.
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Climate-sensitive tree ring chronologies and modern climate data are used to produce prehistoric estimates of summer drought for the Mimbres and Pinelawn-Reserve areas in New Mexico. The nature of these estimates are evaluated using tenets of the Anasazi behavioral model. It is concluded that many of the behavioral processes associated with prehistoric populations on the southern Colorado Plateaus can be seen operating within the two Mogollon areas selected for study. As they have on the plateaus, processes in past human behavior can be linked to three factors: prehistoric efforts to intensify agricultural production, fluctuations in population group size, and increases (or decreases) in summer drought.
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Maciulevičienė, Edita. "Changes in the position of Kaunas city middle-aged population regarding their leisure time physical activity." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130522_082355-83549.
Full textAbstract:
In European countries, people, whatever the socio-economic group or nationality they belong to, men or women, the young or the elderly without distinction, should be guaranteed the right to health as well as its promotion and support measures (Javtokas, 2009). Personal health promotion reflects the general idea stating that in order to enhance health it is necessary to change the way of life (Tones, Tilford, 1994; Donev et al., 2007).
In this era of radical modernity related to the increased personal anxiety and uncertainty, there appear new alternative ways to enhance a person’s health: taking a variety of medications, trying different diets, engaging in traditional and non-traditional forms and ways of physical education (Cavill et al., 2006). In turn, physical education specialists and health educators bring out the importance of exercise encouraging a person to understand the social value and significance of their health promotion and physical development (Schneider and Becker, 2005; Netz et al., 2005). It is widely recognized that a major health risk factor associated with a person’s lifestyle, is low physical activity, the importance of which for human health has been shown in numerous scientific studies. They have emphasized the positive interface between active leisure time physical activity and a range of health indicators (Kalėdienė et al., 1999; Domarkienė, 2000; Borodulin, 2006; Kallings, 2008; Klumbienė, 2008, Gill et al., 2010; Weiler et al., 2010). The... [to full text]Visuotinai pripažįstama, kad esminis sveikatos rizikos veiksnys, susijęs su asmens gyvensena, yra mažas fizinis aktyvumas, kurio svarba žmogaus sveikatai yra įrodyta daugelyje mokslinių studijų. Jose pabrėžiama pozityvi aktyvios fizinės veiklos laisvalaikiu sąsaja su įvairiais sveikatos rodikliais (Kalėdienė ir kt., 1999; Domarkienė, 2000; Borodulin, 2006; Kallings, 2008; Klumbienė, 2008; Gill et al., 2010; Weiler et al., 2010). Nekelia abejonių faktas, kad dažnai deklaruojama sveikatos stiprinimo idėja yra tiesiogiai susijusi su gyvensenos ypatumais, kuriuos lemia tiek atskiro individo požiūris į savo sveikatą, tiek įvairūs išoriniai veiksniai, visų pirma gyvenimo sąlygos. Savaime suprantama, daugiausia dėmesio stiprinant žmonių sveikatą turėtų būti skiriama įvairiose sveikatos ugdymo (sveikatinimo) programose. Šių programų pagrindinis tikslas turėtų būti asmens elgesio keitimas panaudojant žiniasklaidos ir individualaus poveikio priemones (Van der Bij et al., 2002; Rise, 2004; Roux et al., 2008). Reiškiama nuomonė, kad supažindinus gyventojus su aktyvaus gyvenimo būdo principais, propaguojant ir skatinant pastovų jų realizavimą, tobulinant fizinę parengtį, pagerėtų ir žmonių gyvenimo kokybė (Aхвердова, Maгин, 2002; Taylor et al., 2002; Netz et al., 2005; Kallings, 2008; Miller, Miller, 2010). Kita vertus, kada kalbama apie fizinį aktyvumą laisvalaikiu kaip apie asmens visapusiškos gerovės sąlygą bei ligų profilaktikos veiksnį labiau akcentuojama jo reikšmė vaikystės ir... [toliau žr. visą tekstą]