The whitefly Bemisia tabaci species complex has been well documented as one of the most economically important emergent plant virus vectors, through serious feeding damage to its broad range of plant hosts and transmission of plant viruses to important agricultural crops. It has been shown to have associations with endosymbionts which have significant effects on the insect fitness. The purpose of this study was to provide information for the biotype and secondary endosymbiont distribution for B. tabaci populations in the relatively unstudied Arabian peninsula. The geographical localization and variation in endosymbiont populations across the region were identified using a sequence-driven analysis of the population genetics of the secondary endosymbiont. Live field specimens were collected from 22 different locations in the region and preserved in 70% ethanol for genetic studies. Previously established procedures were used to extract and purify total insect DNA from 24-30 individual whiteflies for each location (Frohlich et al., 1999; Chiel et al., 2007). Specimens were subjected to PCR amplification using the respective 16S rDNAprimers for the Rickettsia, Hamiltonella, and Wolbachia to amplify endosymbiont DNA. PCR was run with primers for the highly conserved whitefly mitochondrial cytochrome oxidase subunit I (COI) gene for biotyping. Samples were sequenced using the Sanger method and the data analyzed to correlate the presence, prevalence and geographical distribution of endosymbionts in B. tabaci. Phylogenies 5 were constructed to track evolutionary differences amongst the endosymbionts and insects and how they have influenced the evolution of the regional populations. Samples were characterized by differences in the genomes and endosymbionts of common whitefly ‘biotypes’ that have different host plant preferences, vector capacities and insecticide resistance characteristics. It was found that the B biotype is the predominant haplotype, with no evidence of the Q biotype. All endosymbionts were detected, with Hamiltonella as the most predominant. Several instances of co-infection by two or more endosymbionts were observed. Samples from the geographically isolated and mountainous region of Fayfa demonstrated higher genetic variability compared to the other locations, leading to the possible identification of a new haplotype, as well as the first time identification of the A biotype in the region.

Magister Artium - MA / In studies oor die swart Afrikaanse amateur gemeenskapsteater is voorheen beweer dat die platteland geen oorspronklike en noemenswaardige bydra gelewer het nie. Hiedie studie rig hom op aktiwiteite van hierdie aard in die Wolseley/CereslW oreester-area en bewys dié soort aannames verkeerd. Die swart Afrikaanse gemeenskapsteater van die area word hier beskryf gedokumenteer, maar terselfdertyd ook vergelyk met dit wat op dieselfde terrein in die stedelike gebiede van die Skiereiland plaasgevind het. Laasgenoemde was in die apartheidsjare meer dikwels openlik deel van die bevrydingstryd. Dit teenoor die meer sisteembevestigende aktiwiteite op die platteland. Oorsake hiervoor was onder meer die greep van die kerk op sy lidmate asook ook pogings om die gemeenskap van Ceres en omstreke op te beur ná die vernietigend aardbewing van 1969. Ook die verliese ná gedwonge verskuiwing ingevolge die Groepsgebiedewet is deur dié soort vermaak besweer. Hierteenoor het die middel jare tagtig 'n nuwe, militante generasie leerders op die verhoog gebring. Uit hulle het die streek se eerste anti-hegemoniese dramagroep voortgekom. Hulle het gesorg vir hulle eie treffende sisteem- kritiese drama. Hulle het ook grootliks bygedra om die gemeenskappe in die Boland en Karoo politiek bewus te maak. Die studie wil hierdie gemarginaliseerde teatergebeure aan die vergetelheid ontruk en so 'n bydra lewer tot 'n ewewigtiger Suid-Afrikaanse kultuurgeskiedenis. / South Africa

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The highly porous karst limestone of the Yucatan Peninsula promotes infiltration of rainwater into the subsurface, where it becomes part of the Yucatan Aquifer. The combination of high subsurface porosity, high evapotranspiration, and seasonal droughts results in relative scarcity of lakes or drinkable water at the surface. The majority of past and present people living on the Yucatan Peninsula have depended on groundwater resources for domestic purposes. Whereas coastal karst aquifers such as the one in the Yucatan Peninsula are important water resources, they are highly vulnerable to climate-related changes such as sea level (SL) rise, increased hurricane intensity and extended droughts. With ongoing development along the eastern coast of the Yucatan Peninsula (Quintana Roo), predicted increases in storm intensity, and rising population and potential pollutant output, it has become imperative to study the seasonal and long-term effects of climate and human activity on the Yucatan Aquifer. Like many coastal karst aquifers, the Yucatan Aquifer is stratified according to density, with the Meteoric Water Mass (MeWM) flowing towards the coast on top, and the Marine Water Mass (MaWM) flowing inland on the bottom. The current basis of our knowledge about how the two water masses interact has been from short-term instrumental monitoring and numerical modelling, which is useful for understanding straightforward relationships between salinity, precipitation and temperature across the two water masses and have paved the way for more complex analyses to be completed using the simple principles to guide geochemical studies of sediment within the systems. Generally, sediment cores have been analysed discretely using various methods including grain size analysis, micropaleontology, WD-XRF, and others, however the recent rise of µXRF Core Scanning provides a quicker, more cost effective and higher-resolution method for studying climate-related patterns in sediment cores. This thesis outlines and provides robust evidence for three new methods of using µXRF-CS to determine past and present climatological changes and their relationship to sediment elemental counts. We provide the first outline of the seasonal and spatial controls of geochemical changes in sedimentation in a coastal cave system (Yax Chen), using four years of in situ sediment collection. We then provide the first calibrated record of past salinity based on Cl counts within sediment cores taken from shallow lakes. Although instrumental monitoring has provided evidence that the aquifer is impacted by modern wet and dry periods, the effect of past climate on the aquifer has not been investigated. We provide the first record of water-column mixing at three locations within coastal Quintana Roo. This demonstrates that there has been a long-term climate impacts to coastal Yucatan Peninsula groundwater, which may be scaled to other karst islands and provides evidence that increased hurricane frequency and/or magnitude could change the baseline salinity of the fresh MeWM. / Dissertation / Doctor of Philosophy (PhD) / The porous limestone (karst) geology of the Yucatan Peninsula results in percolation of rainwater down into the subsurface where it is held in the vast Yucatan Aquifer that past and present people have depended on for water resources. Such aquifers are highly vulnerable to human activity and also climate change via increased sea level rise, hurricane intensity and droughts. The Yucatan Aquifer is made up of two separate water masses that have different salinities, and can interact physically and chemically due to changes in climate and weather. Sediment cores can be used to look at subannual geochemical changes which reflect long term behaviour of the aquifer, but first the relationship between sediment change and climate must be established. This thesis uses an iTRAX X-Ray Fluorescence Core Scanner (XRF-CS) to investigate changes in surface water and groundwater over the past 6000 years, and provides the first record of rainfall-induced mixing in a coastal karst aquifer. We also provide evidence of rapid salinity change in shallow lakes associated with intense dry periods, and reveal relationships between cave sedimentation and surface vegetation coverage.

Abstract Not Provided. / Thesis / Bachelor of Arts (BA)

Arthropods were collected at three sites on the Canaveral Peninsula of the east central Florida coast, from May until November, 1975. These sites were old fields dominated by grasses and herbs and one of them (site 1) was located near Launch Complex 41, Kennedy Space Center. A modified drop-trap of 0.5 m2 was used to trap arthropods at approximately 14-day intervals. A vacuum collector removed the arthropods and loose material which was visually inspected for arthropods by the unaided eye and a 7X dissecting scope. A total of 12,296 arthropods was collected during the study. Insects were by far the most numerous group, usually contributing 85 to 95% of the individuals. Ants were very numerous comprising 47% of all individuals and were most numerous at site 1. Arthropod density was greatest on site 1 and increased on all three sites until October and then declined November. A bimodal trend in herbivore density occurred with peaks in June-July and October-November. Predators increased during the study and this significantly correlated with the increase in all other arthropods on the three sites and with herbivores on site 2 and 3. Ants increased in density during the study, while parasites, scavengers, and omnivores remained at low densities. The percentage of predators was roughly constant over most of the study. New species were encountered on site 1 about 1.5 times a fast as on sites 2 and 3. The distribution of individuals among the insect families was similar for the three sites, but site 1 averaged more individuals per family. The average number of individuals per species on site 1 was about double that for sites 2 and 3. Species diversity (Shannon-Weaver) values indicated that arthropods at site 1 were more evenly distributed among the species. Dominance (Simpson) values were not significantly different among the three sites. Community similarity indicated that about 50% of the species on one site were found on one of the other two sites. The different plant communities or habitats surrounding the sites were apparently unrelated to the number of arthropod species present on the study sites. The number of arthropod species present did appear to be related to differences in the number of plant species and their relative abundance on the grids. The launches of two Viking spacecraft appeared to have no detrimental effect on the nearby arthropods.

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No description available.