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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
131

MICROSATELLITE ANALYSIS OF POPULATION STRUCTURE IN THE SANTA ANA SPECKLED DACE (RHINICTHYS OSCULUS)

Nerkowski, Stacey A 01 June 2015 (has links)
Rhinichthys osculus, the Speckled Dace, is one of the most ubiquitous fish in western North America. Within the Southern California region, the local taxon is known as the Santa Ana Speckled Dace. The purpose of this study was to characterize and identify polymorphic microsatellite markers for R. osculus in which twenty-three were identified through Illumina pair-end sequencing. Seven of these loci were then used to examine the patterns of genetic variation and population structure that occurred within and among the watersheds in the Southern California. The study also examined the regional relationships among Southern California, Central California and Owen’s River Valley. Analysis of the microsatellite data revealed highly significant moderate levels of population structure exist within the Southern California region (RST=0.160, p=0.001). This structure is best explained by watershed as well as isolation by distance (R2=.2286, p=0.010). Highly significant geographic structure also exists among the geographic regions of Southern California, Central Coast, and Owen’s River Valley regions (RST= 0.600, p-value=0.001) that are congruent with the regional differentiation elucidated by mtDNA sequence data. In both cases, the degree of population differentiation was correlated with isolation by distance. Utilizing this information we were able gain a better understanding of the evolutionary relationships among the Southern California populations of Santa Ana Speckled Dace. Within the Santa Ana Speckled Dace populations we examined four models to explain the geographic structure: watershed, mountain range, tributary, and isolation by distance. While all were significant, the tributary model exhibited the higher level of population structure (RST= 0.160, p-value=0.001) and a significant correlation was exhibited between geographic distance and population structure, suggesting isolation by distance may be playing a role. The results of the microsatellite analysis are congruent with an earlier broad scale analysis of mtDNA sequence data that suggests the Central California and the Owens Valley populations diverged from each other prior to the divergence of the Santa Ana Speckled Dace populations from the Colorado Basin populations, and that the Central Coast populations were not established as a result of a migration event from the Southern California populations, as was previously hypothesized. Primarily due to human activity, Santa Ana Speckled Dace habitat has become highly fragmented resulting in some populations becoming extirpated. We hope this study will guide the strategies for the conservation of the remaining populations of Santa Ana Speckled Dace and watershed management in Southern California.
132

Phylogeography and Evolution of the Florida Crown Conch (<em>Melongena Corona</em>)

Hayes, Kenneth A. 20 November 2003 (has links)
Melongena corona and closely related congeners are a conspicuous part of the marine intertidal benthic communities of Florida and southeastern Alabama. Significant genetic differentiation among adjacent populations has been conjectured based on variation in shell morphology, habitat discontinuity, low levels of adult motility, and the presence of an aplanic lecithotrophic larval stage. Furthermore, studies of the highly variable shell morphology often have resulted in confusing specific and subspecific definitions of these gastropods, which are often referred to as the "corona complex". Variation in shell morphology may indicate local adaptation or environmentally induced phenotypic plasticity. In this study I utilized mitochondrial DNA sequences in order to reconstruct the phylogenetic relationships of crown conchs, and nuclear microsatellite loci to investigate the patterns of relatedness within and among populations inhabiting the southeastern United States. Approximately 500 individuals from 20 populations throughout the known range of the Crown Conch were genotyped at eight microsatellite loci. Additionally, a 1200bp portion of the cytochrome oxidase subunit I gene was sequenced along with a 490bp fragment of the 16s ribosomal gene from individuals representing all known species and subspecies of the genus Melongena. Phylogenetic analyses completed with these data provide no support for current taxonomic designations within this group and these genetic data indicate that the corona complex is composed of a single polymorphic species. Furthermore, microsatellite data reveal population structure consistent with restricted gene flow between extant populations and phylogeography heavily influenced by historical sea-level fluctuations during the Late Pleistocene.
133

Molecular investigation of genetic diversity in ericoid mycorrhizal endophytes associated with Woollsia pungens (Cav.) F. Muell (Epacridaceae)

Liu, Guangwu, University of Western Sydney, Nepean, School of Science January 1998 (has links)
Two hundred and forty three fungal isolates were obtained from roots of four Woollsia pungens (Cav.) F. Muell plants collected from a field site in New South Wales, Australia. 175 sterile isolates were slow growing and dark-coloured on 2 percentage malt agar and were selected for further analysis. Microsatellite-primed PCR using the primers (GACA)4 and (GTG)5 separated these isolates into 50 genets. Isolates representative of 43 genets (including 168 isolates in total) formed typical ericoid mycorrhizal structures when inoculated onto roots of Vaccinium macrocarpon Ait (Ericaceae), confirming their status as mycorrhizal endophytes. It was estimated that a minimum of 43 genetically-distinct mycorrhizal mycelial genets were present in the root systems of the sampled W. pungens population with 7 to 15 distinct endophytic genets identified in each host plant, indicating that considerable genetic diversity exists within the endophyte population. While most genets were represented by less than 8 isolates, 3 genets contained up to 41 isolates, suggesting that root system colonisation by some mycelia may be extensive. While most fungal genets were shown to be confined to individual plants, 2 genets (genets 32 and 33), however, were present within the root systems of 2 adjacent plants (plants C and D), suggesting that the two root systems were interconnected by the endophyte mycelia. The ITS region of 13 mycorrhizal endophytes and a non-mycorrhizal isolate selected from the endophyte population were sequenced and compared to the sequence of Hymenoscyphus ericae as well as sequences from the GenBank database. A phylogenetic tree was generated from the nucleotide sequence data. This analysis revealed that 6 putative taxa were present in the root systems of 4 host plants. No isolates were positively identified to genus or species level. Closest matches with fungal sequences in the database indicated that most isolates probably belonged to the order Leotiales. Cluster analysis on the basis of the ITS sequences indicated that H. ericae was not clustered together with any endophytes from W. pungens, suggesting that endophytes of W. pungens are not identical to the known ericoid mycorrhizal fungus H. ericae. H. ericae had a low degree of sequence similarity with isolates from W. pungens, with similarities ranging from 68.3-80.6%. Cluster analysis based on DNA sequences of the ITS region did not fully support the groupings inferred from microsatellite-based fingerprinting. / Master of Science (Hons)
134

Construction of a microsatellite based genetic linkage map of almond.

Tavassolian, Iraj January 2008 (has links)
Almond (Prunus dulcis) is the most important nut crop in terms of world production. Due to its health benefit and high nutritional value the consumption and world supply of almond is increasing. To remain competitive in the world market, the Australian almond breeding program was established to produce cultivars with better adaptation to Australian conditions. As part of this program an almond mapping population consisting of 93 F₁ progeny derived from a cross between the American cultivar ‘Nonpareil’ (NP) and the European self-compatible cultivar ‘Lauranne’ (LA) was produced to construct the genetic linkage maps. The first almond linkage map developed prior to the commencement of this project failed to produce the eight linkage groups similar to the basic chromosome number of almond (x = 8) and many large gaps were also observed on the linkage groups. Therefore, more markers were needed to saturate the maps. Microsatellite markers are considered one of the best choices for mapping studies. 195 microsatellite markers isolated from Prunus species were obtained from published papers or by personal communication. Polymorphism was revealed by three different methods, and in general, polyacrylamide gel electrophoresis (PAGE) compared to the fluorescent labelled marker detection using an automated DNA sequencer or agarose gel electrophoresis, showed the most efficient and cost effective method of genotyping. A subset of 54 markers which produced reliable and easily interpretable polymorphic bands was selected to screen the whole mapping population. Microsatellites originally isolated from almond species showed the highest rate of amplification and polymorphism followed by peach microsatellites and the least informative markers were isolated from cherry. It seems that the level of transportability and usefulness of microsatellite markers is related to the genetic distance of the closely related species. Almond and peach belong to the same subgenus (Amygdalus) and other Prunus species are classified in Prunophora subgenus. The nut, or kernel, is the commercial part of the almond tree, thus to improve the quality of fruit an understanding of environmental influence, heritability and correlation of traits is required. Pomological and quality characters such as: shell hardness, kernel size, shape, taste, pubescence, colour, and percentage of doubles were measured during three consecutive years (2005-2007) on the total mapping population, but data analysis (ANOVA) was performed only on trees that survived for all three years. Most of the traits showed high broad-sense heritability and kernel shape showed the highest heritability of H² = 0.92 suggesting high genetic control of this trait. Occasionally larger kernels than either parent were found in the progeny indicating potential for improvement of this trait even with smaller kernel size parent that encompass many desirable characters. High correlation was also found between the in-shell and kernel weight (r = 0.74), kernel length / kernel width (r = 0.67), kernel weight to kernel length (r = 0.78) and kernel width (r = 0.80). This correlation estimation pointed out in this study indicates that the improvement of one character may result the progress in another trait. Neither of the parents in the mapping population had bitter or obvious slightly bitter taste but slightly bitter kernels were observed among the progeny. Amygdalin was assumed to be responsible for bitter taste in almond; therefore we measured the amount of amygdalin in sweet and slightly bitter kernel progeny by HPLC. However, the results showed that amygdalin exists in sweet kernels as well. Although the average amount of amygdalin in slightly bitter kernels (20.34 mg kg⁻¹ FW) was higher than sweet kernels (3.67 mg kg⁻¹ FW), some sweet kernels had higher amounts of amygdalin suggesting the impact of other components on slightly bitter kernel. The highest variability within the traits was observed in the percentage of double kernel, which showed the highest standard error. Strong environmental effects, particularly low temperature at pre-blossom time is speculated to produce much higher double kernels. Three genetic linkage maps, one for each parent and an integrated map were constructed by the addition of 54 new microsatellite markers to the previous dataset. All the data was scored and coded according to the coding system necessary by JoinMap3 which was used for map construction. 131 markers including microsatellite, ISSR, RAPD, SCAR and S-allele markers were placed on the integrated map covering 590.7 cM with the average density of 4.5 cM/marker. The minimum number of six microsatellite markers was placed on linkage group 8 and the linkage group 1 which is the longest linkage group has 14 microsatellite markers. Comparative mapping study with other Prunus maps, especially with the highly saturated reference map showed complete synteny and minor changes in the order of four markers on linkage groups compared with Prunus reference map. The conservation of molecular marker order observed in this study supports the idea of looking at Prunus genome as a single genetic system and practical application of this similarity would be in cross-transportability of microsatellite markers from well developed linkage maps to the less studied species in Prunus. Ten microsatellite loci placed on our map have not been reported before and could be used to improve the density of other Prunus maps, especially the reference map. This study contributed to the better understanding of the mode of inheritance and environmental effect on morphological traits and the effect of amygdalin on kernel taste. The most saturated microsatellite based almond linkage map developed in this study can serve as a framework for future almond breeding program in Australia and benefit Prunus improvement programs internationally. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1348850 / Thesis (Ph.D.) - University of Adelaide, School of Agriculture, Food and Wine, 2008
135

Acacia saligna as a sustainable agroforestry crop for southern Australia: a genetic assessment.

Millar, Melissa Ann January 2008 (has links)
Acacia saligna is a native species complex with a widespread natural distribution throughout the south west of Western Australia. It is being developed as an agroforestry crop to produce low value, bulk biomass products in the low rainfall agricultural areas of southern Australia. This thesis develops knowledge to assist the domestication and breeding program of A. saligna as an agroforestry cultivar. It also furthers development of a risk management plan for utilisation of the Acacia saligna species complex. Highly informative microsatellite markers for A. saligna were developed for use in mating system studies, paternity analysis and in the development of a diagnostic tool for the identification of individuals and populations at the subspecific level. Microsatellites developed in other Acacia species were also screened for utility in A. saligna. A high level of outcrossing (mean multilocus outcrossing rate of 0.98) and little true selfing was found for a planted stand of A. saligna subspecies saligna. Paternity analysis indicated heterogeneity in pollen clouds experienced by maternal trees and an essentially random pattern of mating within the stand. Inter-subspecific pollen immigration into the stand from trees of subspecies lindleyi was detected for 14% of progeny analysed and occurred over distances greater than 1500 m. Extensive intra-subspecific pollen-mediated gene flow is maintained between remnant natural populations of A. saligna subspecies lindleyi, and a high level of inter-subspecific pollen immigration from trees in the planted stand of A. saligna subspecies saligna was detected in remnant populations of subspecies lindleyi (32% of analysed progeny) occurring over distances greater than 1500 m. Polymorphic microsatellite markers used to investigate genetic structuring within A. saligna revealed a high level of genetic divergence between subspecific entities congruent with a taxonomic reclassification of the species complex. Selected microsatellite markers also proved suitable for use as a rapid diagnostic tool that can be used to characterise populations into one of the proposed subspecies of A. saligna with high probability. These results indicate that high levels of outcrossing and essentially random patterns of mating that maintain genetic diversity in seed crops should be achievable with the suitable management of seed production stands of A. saligna. Appropriate management techniques that limit genetic contamination into seed production stands will need to be employed to achieve this goal. Management techniques will also be required to minimise the risk of genetic contamination from stands planted for agroforestry purposes into remnant natural populations. Isolation distances greater than 1500 m between genetically divergent agroforestry crops and natural populations are suggested in both cases and key areas of further research are suggested. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1336865 / Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2008
136

Diversité génétique et gestion génétique des races canines

Leroy, Grégoire 30 May 2008 (has links) (PDF)
Afin d'apporter des outils d'aides à la gestion des races canines en France, cette étude cherche à analyser la structure génétique de l'espèce ainsi que les pratiques d'élevage sousjacentes. Trois approches ont été employées afin de caractériser cette structure : des données d'enquêtes, des analyses de généalogies ainsi que l'utilisation de marqueurs moléculaires. Sur la base de 985 questionnaires remplis par des éleveurs de chiens, tant amateurs que professionnels, il a été possible de mettre en évidence des différences claires sur les pratiques en fonction des races élevées, ou du degré d'implication des éleveurs dans leur activité. Les analyses des données généalogiques de 61 races ont permis de confirmer cette hétérogénéité de pratiques et de situations en terme de variabilité génétique, avec certaines des populations montrant des évolutions de consanguinité préoccupantes. A partir de génotypages réalisés sur un échantillonnage de 1514 animaux appartenant aux 61 races, les résultats obtenus divergeaient parfois des données généalogiques. Cependant ces divergences pouvaient en partie être expliqués par les différences théoriques existantes entre les deux approches. A l'échelle individuelle cependant, les corrélations entre parenté généalogique et similarité moléculaire étaient significatives pour les échantillons étudiés, et similaires à celles qui pouvaient être obtenues à partir de simulations. L'analyse des relations génétiques entre les populations a permis de confirmer que les races constituaient bien des structures génétiques homogènes. En effet, jusqu'à 98,3% des individus étaient correctement affectés au sein de leur race. Ce dernier résultat permet d'envisager des applications pratiques en terme de gestion des races.
137

Tracking an elusive predator: Studying the Scandinavian lynx population by use of genetic markers

Berlin, Ingrid January 2007 (has links)
<p>Abstract</p><p>Gaining accurate population information is crucial for the conservation and management of species. The National Monitoring Program for Large Carnivores monitors the Swedish lynx population (species Lynx lynx) by surveying family groups, non-invasive sampling and genetic analysis. Ten microsatellite regions were used as genetic markers to retrieve unique individual genotypes, through polymerase chain reactions (PCR) with specific primer-pairs and capillary-electrophoresis. Complete genotypes were matched using an internal database. The aim of this degree project was to show how monitoring of lynx through genetic analysis is carried out at the Department of Evolutionary Biology at Uppsala University, and to evaluate how effective these methods are and how they might be improved.</p><p>Even though most of the methods used were fairly robust and reproducible, non-invasive sampling and microsatellite analysis posed some problems regarding DNA quality and quantity, and increased the risks of certain genotyping errors. These risks might be worth taking though, as genetic analysis, in combination with field observations, gives a more comprehensive picture of the Swedish lynx population.</p>
138

Bioinformatic Analysis of Mutation and Selection in the Vertebrate Non-coding Genome

Brandström, Mikael January 2007 (has links)
<p>The majority of the vertebrate genome sequence is not coding for proteins. In recent years, the evolution of this noncoding fraction of the genome has gained interest. These studies have been greatly facilitated by the availability of full genome sequences. The aim of this thesis is to study evolution of the noncoding vertebrate genome through bioinformatic analysis of large-scale genomic datasets.</p><p>In a first analysis we addressed the use of conservation of sequence between highly diverged genomes to infer function. We provided evidence for a turnover of the patterns of negative selection. Hence, measures of constraint based on comparisons of diverged genomes might underestimate the functional proportion of the genome.</p><p>In the following analyses we focused on length variation as found in small-scale insertion and deletion (indel) polymorphisms and microsatellites. For indels in chicken, replication slippage is a likely mutation mechanism, as a large proportion of the indels are parts of tandem-duplicates. Using a set of microsatellite polymorphisms in chicken, where we avoid ascertainment bias, we showed that polymorphism is positively correlated with microsatellite length and AT-content. Furthermore, interruptions in the microsatellite sequence decrease the levels of polymorphism.</p><p>We also analysed the association between microsatellite polymorphism and recombination in the human genome. Here we found increased levels of microsatellite polymorphism in human recombination hotspots and also similar increases in the frequencies of single nucleotide polymorphisms (SNPs) and indels. This points towards natural selection shaping the levels of variation. Alternatively, recombination is mutagenic for all three kinds of polymorphisms. </p><p>Finally, I present the program ILAPlot. It is a tool for visualisation, exploration and data extraction based on BLAST.</p><p>Our combined results highlight the intricate connections between evolutionary phenomena. It also emphasises the importance of length variability in genome evolution, as well as the gradual difference between indels and microsatellites.</p>
139

Population Genetic Analyses of Natal Dispersal and Substructure in Three Bird Species

Sahlman, Tobias January 2007 (has links)
<p>Genetic variation within and among populations is a result of past and ongoing processes. Among the most important of such processes are dispersal, habitat fragmentation and selection. This thesis use neutral genetic variation as a tool to investigate these processes in three bird species.</p><p>In the Siberian jay, the timing of dispersal is dependent on social dominance among siblings. Mark-recapture data, radio-tracking and genetic variation was used to investigate whether timing of dispersal had an effect on dispersal distance. The results show that early dispersing individuals also disperse longer. In the same species, genetic correlation between neighbours was used to find areas with high production of philopatric individuals, which could be indicative of high habitat quality.</p><p>Great snipe populations in northern Europe have a breeding range divided into two regions. A Q<sub>ST</sub>-F<sub>ST </sub>approach was applied to study variation in selection between regions. Differentiation between the regions in neutral molecular markers was low, indicating high gene flow, or short time available for neutral divergence. Morphological divergence between the regions was high, and Q<sub>ST</sub> > F<sub>ST</sub>, which indicates divergent selection. Thus, neutral genetic markers can be misleading in identifying evolutionary significant units, and the Q<sub>ST</sub>-F<sub>ST</sub> approach might be valuable to identify targets for conservation.</p><p>Rock ptarmigan, or its ancestors, originated in Beringia, and spread throughout the Holarctic region. Their distribution has subsequently been affected by glaciations, most likely leading to withdrawals and re-colonisations. Neutral genetic variation among five populations around the northern Atlantic was investigated. There was strong genetic structure among the populations, and evidence that Scandinavian rock ptarmigan has been isolated from other populations for considerable time. Rock ptarmigan in Svalbard showed slightly lower genetic variation than others, and comparisons with other studies suggested an eastern colonisation route to Svalbard.</p>
140

Did bowhead whales (Balaena mysticetus) from the Bering-Chukchi-Beaufort Seas undergo a genetic bottleneck? A test using nuclear microsatellite loci

Hunter, Devra Denise 01 November 2005 (has links)
This study reexamines the nuclear microsatellite analysis by Rooney et al. (1999a) of Bering-Chukchi-Beaufort Seas bowhead whales (Balaena mysticetus) to determine if this population underwent a genetic bottleneck as a result of 19th and early 20th Century commercial whaling. This investigation used more accurate laboratory techniques to score alleles, had a larger sample size that was divided into two groups (mainland Alaska and St. Lawrence Island (SLI)), and used a moderately different set of microsatellite loci which are more variable and thus, more informative. The results corroborate the findings of Rooney et al. (1999a) for mainland Alaska showing no evidence of a genetic bottleneck. However, the SLI data analyses provide conflicting conclusions. The Wilcoxon test is significant for a heterozygote excess (p = 0.042) suggesting that a genetic bottleneck has occurred. This is not substantiated by the exact tests of each locus or the table-wide sign test. There is a possibility that a bottleneck has occurred, but due to the small sample size this is not a definitive conclusion and warrants reanalysis with a larger sample size.

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