No description available.

Study of the genetic relationships and evolutionary histories of pupfish populations (Cyprinodontidae: Cyprinodon spp.) from the remnant aquatic habitats of Death Valley was approached by exploring the genetic structure and divergence within and among populations using mitochondrial and nuclear DNA markers. The findings of these studies illustrate the influences of population size and isolation time in the divergence of small, fragmented populations largely via genetic drift. The information revealed in this study has implications for assessing priorities in the conservation of the unique evolutionary heritage among populations of the Death Valley pupfishes. A new retrotransposable element family was identified and characterized. This family of genetic elements was uncovered during a search of the pupfish genome for transposable elements to be used as molecular markers for population analyses. The description of this element family, named "Swimmer 1" (SW1), provides new insights into the evolution of long interspersed nuclear elements (LINEs) in vertebrates. Therefore, a full characterization of the SW1 element family was undertaken in the Japanese medaka (Oryzias latipes) as well as in the pupfish genome. The Japanese medaka is a model organism widely used for genetic and developmental biology studies. / Ph. D.

Barriers to fish movement can cause aquatic habitat fragmentation by reducing the amount of available habitat. The primary goal of my research was to investigate applications of population genetic analysis tools as indicators of barrier effects on brook trout populations in fragmented subwatersheds. In chapter1, I tested the hypothesis that brook trout population genetic differentiation (FST) above and below barriers will differ in relation to barrier height and gradient. I also tested the hypothesis that average gene diversity per locus (H) and the numbers of alleles (A) differed between samples below and above each barrier. There was no significant difference in average number of alleles (A) or average gene diversity per locus (H) between the above- and below-barrier samples, but linear regression identified a statistically significant relationship between barrier height and FST values. Unrooted neighbor-joining consensus trees of Cavalli-Sforza and Edwards (1967) chord distances provided evidence of genetic differentiation between samples of resident brook trout above and below natural barriers. Additionally, average total allelic diversity (A), average gene diversity per locus (H), average number of private alleles per locus per sample, and total alleles per sample differed between Level III Ecoregions. In chapter 2 I tested the hypothesis that the presence of a barrier, total habitat potentially isolated above a barrier (km), road density, and percent forest cover within a subwatershed (USGS 6th-level Hydrologic Units) were significant habitat fragmentation factors affecting the effective population size (Ne) of brook trout in the Blue Ridge Level III Ecoregion. Multivariable linear regression indicated that total habitat above the barrier (km) and road density were significant variables retained in the model to predict Ne. In chapter 3, the objective of the study was to infer relationships between barriers and family structure in brook trout populations. Maximum likelihood analysis of pairwise kinship relationships between above- and below-barrier individuals indicated the presence of parent-offspring relationships between above- and below-barrier individuals at six sites in the Blue Ridge Level III Ecoregion and five sites in the Northern Lakes and Forests Level III Ecoregion, which indicated movement of individuals between the above- and below-barrier locations. / Ph. D.

Gilthead seabream (Sparus aurata) is one of the most important species of intensively reared fish in the Mediterranean region. Its short history of domestication, along with the need to develop markets, new products and efficiency in the production process, has resulted in an increased interest in the potential genetic improvement of this species. Little work has so far been directed at establishing the procedures for selective breeding in gilthead seabream at a commercial level, although genetic parameters calculated in other studies have indicated that there is a large potential for improvement in certain traits. Selective breeding of commercial gilthead seabream populations is constrained by aspects of the biology that complicate the production of genetic groups and the maintenance of same-age offspring populations. The aim of this thesis was to develop a protocol for the selective breeding of gilthead seabream, specifically to serve a commercial hatchery and on-growing unit in Cyprus, where the fieldwork was carried out. The hatchery broodstock was monitored over a three-year period to identify the rate of sex reversal in introduced fish and to quantify the sex ratio of the stock over time. The analysis of the egg production records was used to evaluate the success of photoperiod manipulation in each group. Size variation in the larval and juvenile stages is a common problem in the rearing of gilthead seabream, leading to cannibalism and labour-intensive sorting operations. Studies on larval populations, from first feeding through to metamorphosis, indicated the origin of size variation was the differences in early feeding ability. The size advantages could be maintained throughout the larval period. During the juvenile stage of the farm production system, a method to standardise the size sorting of populations by grading was developed in order to counter environmental effects of separating groups of fish. Using this method, grading would be suitable to form the first stage of a selection programme for growth rate. The potential gain of selection for growth rate during the on-growing stage was very high, using a simulated criterion and previous estimates of heritability. Other possible quality traits for selection were also examined and quantified in the hatchery populations. Existing and specifically developed microsatellite markers were used for the assignment of offspring to parents from mass spawning of the hatchery broodstock. The effective population size of single spawning events were found to be low and determined by a high variation in contribution to mass spawning. Contribution was found to be significantly linked to body size, which led to the formation of a replacement policy for the broodstock to maximise spawning performance. Survival of individual families through the larval period was also examined. Based on the results of the experimental work, a two-stage selection programme was designed, along with the presentation of specific procedures for each stage of the production system. This project makes recommendations on various strategies that can increase the effective population size within a selection programme and these are discussed as part of the genetic management of hatchery populations. Significant progress has also been made in the use of genetic markers in monitoring the rate of inbreeding and contribution of individual broodfish, which are considered essential in this species.

This is a demographic study of Nigeria between 1952-1982. Relationships between population growth and economic development are described in detail. Comparisons are made of demographic growth in Nigeria with other developing countries, particularly those in Africa. Population pressure, the condition of the rural areas, and some internal and external population problems are discussed in length. The government's position and the public view on population control and family planning programs are also examined. Current programs of family limitation are discussed and evaluated. The study concludes with recommendations for solutions. Emphasis is placed on the need for immediate recognition and action. Various solutions, particularly education, are evaluated.

Master of Science / Department of Statistics / Paul I. Nelson / Capture-Recaputre (CR) experiments stemmed from the study of wildlife and are widely used in areas such as ecology, epidemiology, evaluation of census undercounts, and software testing, to estimate population size, survival rate, and other population parameters. The basic idea of the design is to use “overlapping” information contained in multiple samples from the population. In this report, we focus on the simplest form of Capture-Recapture experiments, namely, a two-sample Capture-Recapture design, which is conventionally called the “Petersen Method.” We study and compare the performance of three methods of constructing confidence intervals for the population size based on a Capture-Recapture design, asymptotic normality estimation, Chapman estimation, and “inverting a chi-square test” estimation, in terms of coverage rate and mean interval width. Simulation studies are carried out and analyzed using R and SAS. It turns out that the “inverting a chi-square test” estimation is better than the other two methods. A possible solution to the “zero recapture” problem is put forward. We find that if population size is at least a few thousand, two-sample CR estimation provides reasonable estimates of the population size.

The earned income differ across municipalities in Sweden, where Stockholm is the location with the highest average earned income. One can ask whether this is depending on higher educational attainment, the disparity in population size and house prices. This paper aims to explain which parameter affects the income disparities between large and small cites. Using data from Statistics Sweden between the years 1991-2017. The above-mentioned topics are used in the three statistical models; Ordinary Least Squares, Pooled OLS, and Fixed-Effects. From this analyze, this paper can conclude that human capital is essential to explain earned income disparities. The discussion part includes limitations of the dataset and its consequences depending on geographical choice. Another exciting explanation of earned income differences is mentioned in the discussion, namely happiness level in each region.

<p>This thesis attempts to improve our understanding of the role of population size for the process of speciation. First, the effect of population size on speciation is studied using several meta-analyses of published laboratory experiments. Second, the effect of population size on behaviour is studied using a laboratory population of the blowfly <i>Lucilia sericata</i>. Third, the effect of population size on morphological and genetic variation is studied using wings and microsatellites from wild populations of <i>L. illustris</i> as well as experimentally bottlenecked populations of <i>L. sericata</i>. The meta-analyses showed that the result of many previous laboratory experiments on sympatric and parapatric speciation may have been biased by too small population sizes. Reduced interbreeding was less likely to develop in small populations where the selection against hybridisation often seemed to have been opposed by inbreeding depression or loss of genetic variation. In allopatric speciation experiments, no general consistent effect of population size was observed. There was no support for speciation through founder events. In fact, significant assortative mating was only found in vicariance experiments where derived populations was tested against each other. Population size influenced reproductive behaviour in <i>L. sericata</i>. There was a positive effect of increasing number of males on egg-laying but only as long as the female was in the company of at least one other female. Female mate choice and a positive effect of number of eggs on larval survival are suggested to be the underlying factors. No historic bottlenecks could be detected in the fly populations, but strong genetic indications suggest a fine grained genetic population structure of wild <i>Lucilia</i> flies. Bottlenecks had unpredictable effects on wing morphology as well as on genetic variation and fitness in a laboratory stock of <i>L. sericata</i>. Thus a bottlenecked population will not necessarily have a higher chance of evolving morphological novelties than one which has not undergone a bottleneck. However, among many bottlenecked populations there is a good chance that in at least one of them the conditions will be conducive to morphological change and evolution. In this statistical sense, thus, strong population fluctuations may enhance the probability of speciation events.</p>

<p>Although the practice of releasing fish into the wild is common in the management and conservation of fish populations, the success of release programmes and the potential harmful genetic and ecological effects that may follow are rarely considered. This thesis focuses on genetic and ecological consequences of fish releases, exemplified by supportive breeding of brown trout (<i>Salmo trutta</i>) and translocation of European eel (<i>Anguilla anguilla</i>). Specific questions addressed include: What is the relative performance of hatchery produced fish released to support wild populations, and do released hatchery fish contribute to the natural productivity? What is the variation in reproductive success in the wild, and how does it affect the genetic consequences of a supportive breeding programme? Is there a spatial genetic structure in the European eel that must be considered in the management of this rapidly declining species?</p><p>Experiments conducted under natural and near-natural conditions in the River Dalälven, Sweden, suggest that hatchery produced trout can reproduce in the wild. In fact, when the pronounced variation between individual breeders was accounted for, there were no detectable differences between hatchery produced and wild born trout in reproductive success or offspring survival. These results were supported by molecular genetic data suggesting a pronounced gene flow from hatchery to wild trout in the river. Hatchery reared trout were, however, found to exhibit reduced survival rates immediately following release into the wild, an effect that was most likely due to phenotypic responses to the hatchery environment during ontogeny and a lack of experience of the wild.</p><p>In sharp contrast to recently published studies, the present genetic analyses of European eels sampled across the whole distribution range suggest no spatial genetic structure but a subtle temporal genetic heterogeneity within sampled locations. These results emphasise the need to consider temporal replication when assessing population structure of marine species.</p><p>The results obtained have general implications for the management and conservation of fish populations. First, supportive breeding of threatened salmonid populations might be successful, not only for boosting the census size and thereby reducing the short-term probability of extinction, but also for reducing the risks of inbreeding depression and loss of adaptive potential in future generations. However, the results also highlight the need to restore the natural productivity of a population under supportive breeding to avoid a potential reduction in fitness due to hatchery selection. Further, the lack of a detectable spatial genetic structure in the European eel suggests that the management strategy of translocating juvenile eels from locations were they are overabundant to other suitable freshwater habitats does not necessarily have to include genetic considerations with respect to the geographical origin of the translocated eels.</p>

This thesis attempts to improve our understanding of the role of population size for the process of speciation. First, the effect of population size on speciation is studied using several meta-analyses of published laboratory experiments. Second, the effect of population size on behaviour is studied using a laboratory population of the blowfly Lucilia sericata. Third, the effect of population size on morphological and genetic variation is studied using wings and microsatellites from wild populations of L. illustris as well as experimentally bottlenecked populations of L. sericata. The meta-analyses showed that the result of many previous laboratory experiments on sympatric and parapatric speciation may have been biased by too small population sizes. Reduced interbreeding was less likely to develop in small populations where the selection against hybridisation often seemed to have been opposed by inbreeding depression or loss of genetic variation. In allopatric speciation experiments, no general consistent effect of population size was observed. There was no support for speciation through founder events. In fact, significant assortative mating was only found in vicariance experiments where derived populations was tested against each other. Population size influenced reproductive behaviour in L. sericata. There was a positive effect of increasing number of males on egg-laying but only as long as the female was in the company of at least one other female. Female mate choice and a positive effect of number of eggs on larval survival are suggested to be the underlying factors. No historic bottlenecks could be detected in the fly populations, but strong genetic indications suggest a fine grained genetic population structure of wild Lucilia flies. Bottlenecks had unpredictable effects on wing morphology as well as on genetic variation and fitness in a laboratory stock of L. sericata. Thus a bottlenecked population will not necessarily have a higher chance of evolving morphological novelties than one which has not undergone a bottleneck. However, among many bottlenecked populations there is a good chance that in at least one of them the conditions will be conducive to morphological change and evolution. In this statistical sense, thus, strong population fluctuations may enhance the probability of speciation events.