The Padthaway Ridge is overlain by a thin veneer (< 20 m) of Oligo-Miocene bioclastic carbonates representing the southern most extent of the Mannum Formation, Murray Supergroup, and Murray Basin limestones. The Mannum Formation is composed of warm-temperate carbonates rich in irregular echinoids, coralline algae, benthic foraminifers, and relict particles. The respective lithology are mostly structureless, burrow-mottled, and cross-cut by Thalassinoides burrows. These sediments are interpreted to have resulted from carbonate production along shallow, illuminated seafloors under high mesotrophic conditions. The composition and texture is similar to that of modern temperate seagrass accumulations with the exception of the abundant mobile infauna and bioturbation, which are more akin to associated intercalated and adjacent barren sands. The Mannum Formation is therefore interpreted as an amalgamation of these two environments. The ubiquitous relict grains and Fe-stained cements in the lithologies of the Mannum Formation are thought to be the product of Fe redox pumping within the subsurface of seagrass meadows, whereby consolidated sediments endured prolonged and repeated exposure to juxtaposed destructive and constructive diagenetic conditions at the redox boundary. Fluctuations in the organic carbon and oxygen influx to the subsurface are primarily a function of auto- and allogenic controls on seagrass density (i.e. turbidity, light, depth, hydrodynamics). The overlying Glenforslan Formation is interpreted as a seagrass-influenced deposit that accumulated under warm-temperate, low mesotrophic conditions and more rapid rates of sedimentation. Relict grains, however, are absent from the Glenforslan Formation. The subtle change in trophic resources is thought to have caused a significant shift in primary and secondary production, from organic carbon- to carbonate-dominated. Assessment of previously described temperate seagrass facies together with this research comprise reliable criteria for identification of temperate seagrass depositional settings. The signal of multigenerational accumulation, especially prominent in the Mannum Formation, represents an amalgamation of environments that would be difficult to assess in modern settings. The key attributes of temperate grass facies proposed herein allow for more accurate reevaluation of seagrass influenced, and relict rich lithologies in the rock record. / Thesis (Master, Geological Sciences & Geological Engineering) -- Queen's University, 2009-12-14 17:18:16.853

No description available.

Globally, stream invertebrate communities have been shown to respond to habitat degradation as a result of land use hanges. The effects of land use changes on stream communities have been well documented in temperate regions, however, their effects in the tropics are relatively unknown, particularly where land use activities can differ markedly (e.g., tea, maize and Eucalyptus plantations). To understand how land use affects tropical highland Nigerian stream communities, I surveyed 55 second and third order streams across four land use categories, ranging from continuous tropical montane forest to intensive crops/pasture. Streams were sampled in the dry season (October to March) for physico-chemical parameters (i.e., temperature, pH, conductivity, turbidity, current velocity, channel morphometry and riparian characteristics) and ecological characteristics (i.e., fine particulate organic matter [FPOM], coarse particulate organic matter [CPOM], algae and benthic invertebrates). Water temperature in all streams was high (up to 25oC) while levels of dissolved oxygen were frequently low (15–79 %). Physico-chemical conditions varied across land uses with continuous forested streams being cooler, with higher dissolved oxygen, larger bed substrate and more stable channels. Similarly, benthic invertebrate communities showed a strong response with the highest taxonomic diversity in forested streams and the lowest in streams within intensive crops (e.g., cabbage crops). Several of the taxa which occurred in forested streams (e.g., the mayflies Heptageniidae and Oligoneuridae and brachyuran crabs) were rare or absent in streams with more intensive land use. In contrast, damselflies and several true bugs (e.g., Notonectidae and Corixidae) were rare in forested streams but more common in other land uses. In order to test land use impacts on stream processes leaf litter decomposition experiments were carried out in nine streams, three in forest, three in tea plantations and three in maize fields. Leaf breakdown rates were slow compared with other reports for tropical streams, however leaves in forested streams broke down significantly faster (on a degree day basis) than in other land uses. This faster break down seemed to be driven by greater shredder densities in forested streams. Significantly lower densities of invertebrates were found in leaf bags incubated in streams draining tea plantation and maize fields than in forest streams. In the same nine streams food web components were sampled and analysed using gut content and stable isotope (N and C) analyses. Stream food webs in continuous forest were more complex than plantation and maize field streams. Stable isotope analysis indicated that primary consumers assimilated a mixture of autochthonous and allochthonous carbon resources, but the proportion varied among sites. Overall, my results suggest that in Nigerian highland tropical streams more intensive land use activities strongly affect the diversity and composition of benthic stream communities and ecosystem function, in similar ways to those reported in temperate streams.

No description available.

A Tropical Temperate Trough (TTT) is a type of weather system that links the tropics and the extra-tropics across southern Africa. TTT events have been studied statistically in detail, but very little research has been done to study this phenomenon dynamically and especially on a seasonal scale. This study therefore focuses on the predictability of the characteristics of TTTs across southern Africa on a seasonal scale, by using a state-of-the-art seasonal forecasting model, namely the GloSea5 developed by the UK Met Office. Gridded hindcast data for the months of November, December, January and February from 1996/1997 to 2009/2010 are compared to observed data. The different ensemble members of the GloSea5 model (with lead-times of 1 week up to 2 months) are first compared separately to the observed data, after which the model average, with a 0-month, a 1-month and a 2-month lead-time, is calculated and also compared to the observed dataset. TTT events have distinctive characteristics during the formation and the development phases. Most prominent of these characteristics are the cloud bands associated with these weather systems, which have a north-west to south-east orientation and move from west to east across southern Africa. To identify the TTTs, daily outgoing long-wave radiation values are processed by a Meteorological Robot (MetBot), with a strict criterion to identify the cloud bands that characterise these systems. The MetBot’s algorithm produces the information needed to further investigate the different characteristics of TTTs, such as the frequency, the location and the intensity of these systems. Analysis of the MetBot output includes calculating the Root Mean Square Error, the percentage error and in some cases the percentage deviation of the number of cloud bands, as well as the anchor point, the centroid position, the area, the tilt and the minimum and maximum OLR values of the cloud bands. This investigation revealed that the characteristics of TTT events can to some extent be predicted on a seasonal scale for the summer rainfall season of southern Africa. The model used in this study fared particularly well with a 1-month lead-time forecast (compared to a 0-month and a 2-month lead-time forecast). The intensity and the location of the cloud bands associated with TTT events are forecast with a smaller percentage error than the frequency of these systems, as the frequency of TTTs tend to be significantly under-predicted by the model. For some predicted quantities, such as the area of the cloud bands, a bias-adjustment is necessary which produces significantly better results with smaller percentage errors. In the conclusions, suggestions are made on possible future studies, and how to develop this study further to create seasonal forecasts with higher skill with special regards to TTT events. / Dissertation (MSc)--University of Pretoria, 2019. / Geography, Geoinformatics and Meteorology / MSc / Unrestricted

Conspicuous coloration is one of the main ways that animals communicate. The use of eye-catching color patterns to warn predators of an unprofitable trait is referred to as aposematism. Once predators learn to recognize the color pattern, a new signaling niche becomes available where other species can share the same signal. This mimicry niche can involve a “hide in plain sight” strategy by mimicking or parasitizing this signal, with mimics lacking the defense and associated costs that make them unprofitable. This is termed Batesian mimicry, and it decreases predation by taking advantage of the memory and learning of the predator community. Thus, a primary prediction in Batesian mimicry systems is that the model and mimic are found in sympatry. Another, fundamental prediction of Batesian mimicry is that the model outnumbers the mimic and that models emerge before the mimics to educate the predator guild. Some of these patterns were not significant in the California Coast Ranges as seen in Long et al., (2015), and no study has estimated population sizes for this temperate Batesian mimicry system. Furthermore, compared with community studies of mutualistic Müllerian mimicry in the tropics, no studies have tested predictions of parasitic Batesian mimicry on small scale patterns of habitat use and movement patterns. If mimicry is as an important part of the biology of these temperate species, as it is for their tropical counterparts, we predict that in addition to emerging first and being more abundant, the model and mimic will overlap strongly in habitat but the model will be more abundant in each habitat, and will move more and be more widespread among available habitats. Our results confirm these predictions and indicate that A. californica is effectively educating habitat specialist and generalist predators providing an umbrella of protection for the mimic L. lorquini.

No description available.

The American chestnut tree (Castanea dentata) is a deciduous tree that largely exists in the eastern United States along the Appalachian Mountain range. Approximately 100 years ago, a fungal pathogen (Cryphonectria parasitica) decimated chestnut populations, resulting in the loss of billions of trees. Disease-resistant American chestnut populations have been developed, but the introgression of wild adaptive diversity into these breeding populations will be necessary to develop locally adapted and disease resistant chestnut trees for reintroduction. In this dissertation, I presented our findings which addressed previous gaps in knowledge regarding the population genomics of wild and backcross American chestnut populations. I 1) estimated the genomic diversity, population structure, and demographic history of remnant wild American chestnut populations; 2) revealed the genomic basis of local climate adaptation in American chestnut, developed a novel method to make tree sampling estimates for germplasm conservation, and defined unique seed zones for American chestnut based on climate and genotype, and 3) determined the amount of wild adaptive diversity captured by the backcross breeding program and made recommendations for their replanting region. These results will inform the development of a breeding plan for the introgression of adaptive diversity into backcross and transgenic chestnut populations. / Doctor of Philosophy / The American chestnut tree (Castanea dentata) is a deciduous tree that largely exists in the eastern United States along the Appalachian Mountain range. Approximately 100 years, a fungal disease (Cryphonectria parasitica) decimated chestnut populations, resulting in the loss of billions of trees. The American Chestnut Foundation developed disease-resistant American chestnut backcross trees by breeding American chestnut trees with Chinese chestnut trees (Castanea mollissima). These trees will need additional breeding with wild American chestnut trees so that their offspring will have both the disease-resistant traits and the adaptations to the local environment where they will be replanted. This is important, because trees that are both disease-resistant and locally adapted will be most likely to survive and thrive in their replanting location. However, a comprehensive evaluation of the genomic basis for local adaptation in American chestnut populations is lacking. In this dissertation, I presented our findings which addressed previous gaps in knowledge regarding the population genomics of wild and backcross American chestnut populations. I 1) estimated the genomic diversity, number of unique populations, and population size changes over time in wild American chestnut; 2) revealed the genes related to local adaptation in American chestnut, developed a novel method to make tree sampling estimates for conserving wild American chestnut diversity, and defined unique seed zones (areas within the species range that have unique adaptations to environment) for American chestnut based on climate (ie, precipitation and temperature values) and genotype (DNA), and 3) determined the amount of wild genomic diversity related to local adaption captured by the backcross breeding program and made recommendations for their replanting region. These results will inform the development of a breeding plan of wild American chestnut with backcross and transgenic chestnut populations to create locally adapted and disease-resistant chestnut populations for reintroduction.

No description available.

No description available.