Thesis (Ph. D.)--University of Wisconsin--Madison, 2000. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (p. 251-283).

Thesis (M. Sc.)--University of Hong Kong, 2005.

Thesis (M.S.)--Oregon State University, 2007. / Printout. Includes bibliographical references (leaves 39-47). Also available on the World Wide Web.

Thesis (Ph. D.)--University of Chicago, Committee on Evolutionary Biology, March 2001. / Includes bibliographical references. Also available on the Internet.

This thesis documents the research that has led to advances in the Artificial Neural Network (ANN) approach to analysing flow cytometric data from phytoplankton cells. The superiority of radial basis function networks (RBF) over multi-layer perception networks (MLP), for data of this nature, has been established, and analysis of 62 marine species of phytoplankton represents an advancement in the number of classes investigated. The complexity and abundance of heterogeneous phytoplankton populations, renders an original multi-class network redundant each time a novel species is encountered. To encompass the additional species, the original multiclass network requires complete retraining, involving long optimisation procedures to be carried out by ANN scientists. An alternative multiple network approach presented (and compared to the multi-class network), allows identification of the expanse of real world data sets and the easy addition of new species. The structure comprises a number of pre-trained single species networks as the front end to a combinatorial decision process for determining species identification. The simplicity of the architecture, and of the subsequent data produced by the technique, allows scientists unfamiliar with ANNs to dynamically alter the species of interest as required, without the need for complete re-training. Kohonens Self Organising Map (SOM), capable of discovering its own classification scheme, indicated areas of discrepancy between flow cytometric signatures of some species and their respective morphological groupings. In an attempt to improve identification to taxonomic group or genus level by supervised networks, class labels more reflective of flow cytometric signatures must be introduced. Methods for boundary recognition and cluster distinction in the output space of the SOM have been investigated, directed towards the possibility of an alternative flow cytometric structuring system. Performance of the alternative multiple network approach was comparable to that of the original multi-class network when identifying data from various environmental and laboratory culturing conditions. Improved generalisation can be achieved through employment of optical characteristics more representative of those found in nature.

Cytogenetic studies in the genus Matthiola by Magda I.M. Soliman The present study on the genus Matthiola has been carried out from the cytological view-point. The following taxa were used: M. farinose, M. fruticulosa ssp. fruticulosa. M. fruticulosa ssp. perennis, M. fruticulosa ssp. valesiaca, M. incana, M. longipetala ssp. bicornis, M. lunata, M. maderensis, M. maroccana, M. parviflora, M. odoratissima, M. ovatifolia, M. sinuate, and M. tricuspidata. All the species were of wild origin except M. longipetala ssp. bicornis which is a cultivated strain. All the species examined are diploid. More than one basic number is present in the genus; x=6 and x=7. The somatic chromosome number reports for M. farinosa collected from U.S.S.R., M. lunata from Algeria, M. maderensis from Madeira (Porto Santo and San Gorge) and M. maroccana from Morocco were new reports. Geographically Matthiola is a Mediterranean genus. From the results of this work, it appears that the 14 chromosome species occur mainly in the western and the 12 chromosome species mainly in the eastern part of the generic range. It is evident from the karyotype studies that none of the Matthiola species have an identical chromosome set. Nuclear DNA contents have been estimated for Matthiola species for the first time in this study. In Matthiola, the variation in the amount of DNA is not related to chromosome numbers but there is a positive relationship between 2C DNA content and complement length. The mean 2C DNA values of the different accessions of Matthiola species were statistically significantly different at the 0.001% level. The mean 2C nuclear DNA content for annuals and perennials did not show any difference in Matthiola, however inbreeding species had greater amounts of DNA than outbreeding. Meiosis is regular in most of the species studied, but in M. sinuata and M. longipetala ssp. bicornis it is slightly irregular. Mean chiasma frequency per cell was highest in M. incana and lowest in M. lunata. Species of the genus Matthiola have been artificially hybridized in this study for the first time. Some crosses were successful in producing F1 flowering plants, and meiotic analysis of these hybrids was undertaken. The evolution of chromosome numbers in the genus is discussed, in relation to the results incorporated in this thesis.

Species richness of virtually all high-level taxonomic groups is strongly statistically related to climatic variables such as temperature and precipitation, and consistently so across space and time. These observations are consistent with a causal link between the number of species that occur in a given region and its climate. Although dozens of hypotheses have been proposed, the main mechanisms underlying this pattern remain largely unresolved. And, few ecological studies have attempted to identify regularities in the individual species distributions that make up the richness–climate relationship. Despite the complexities of species’ biologies, I found that, to a first approximation, species’ probability of occupancy at continental scales were generally well statistically explained by a Gaussian function of temperature and precipitation. This simple model appeared general among species, taxa and regions. However, although individual species’ ranges are strongly statistically related to climate, spatial variations in richness cannot be explained by systematic variations in species’ climatic niches. And, individual species track changes in climatic variables through time much more weakly than species richness tracks these changes, suggesting that richness is at least partly constrained by mechanisms independent of species identities. Moreover, at macro-scales, species richness was also not strongly predictable from the temperature at which clades have originated, from historical variability in climatic variables nor from local short-term extirpation rates. In sum, I rejected several prominent hypotheses aiming to explain richness–climate relationship and found several lines of evidence inconsistent with the common idea that climatic constraints on individual species, by themselves, can explain richness–climate relationship. I propose a mechanism to explain, as a first approximation, the continental biogeography of species distributions that relies on neutral processes of dispersal and local extinctions within species’ broad deterministic thermal tolerances.

This investigation involved the production of specific antisera against known International Streptomyces project strains of Streptomyces.

Culicoides biting midges (Diptera: Ceratopogonidae) are of economic and veterinary significance worldwide. Of principal importance to equids in sub-Saharan Africa are Culicoides (Avaritia) imicola Kieffer and Culicoides (Avaritia) bolitinos Meiswinkel which have been implicated in the transmission of African horse sickness virus (AHSV) and equine encephalosis virus (EEV). Various species of Culicoides are associated with equine insect hypersensitivity, a common equine skin allergy. Recommended measures to prevent diseases associated with Culicoides in equids include vaccination for African horse sickness (AHS), stabling at night, meshing of stables, and application of insect repellents both to the animal and its stable environment. The effects of repellents against Culicoides on humans have been documented, with most studies reporting the repellency of compounds against that of N,N-diethyl-3-methylbenzamide (DEET). DEET is registered for human use in South Africa, whilst citronella oil and cypermethrin are included in topical ectoparasiticides registered for use on horses. The aim of this study was to determine and compare repellent efficacy of 15% DEET, 0.6% citronella oil, and 0.3% á-cyanocypermethrin against Culicoides species when applied to polyester mesh under South African conditions. The repellent efficacy against Culicoides species was compared in three 5 X 5 Latin squares (15 replicates). DEET, citronella oil or á-cyano-cypermethrin was applied to polyester meshes that were fitted to down-draught suction 220 V ultraviolet (UV) light traps which were operated overnight. A total of 107,204 Culicoides midges was collected in hourly light-trap collections made over 15 nights from five light traps operated simultaneously. Of 34 Culicoides species collected C. Imicola was the most abundant and comprised 79.1% of midges collected, followed by C. Bolitinos which comprised 5.3%. The mean number of Culicoides midges as well as the mean number of C. Imicola collected hourly with DEET was significantly (P < 0.05) lower than for all other treatments at all times except the first (19h00) and the last (06h00) sampling points. The study concluded that DEET had a significant repellent effect against Culicoides species, including C. Imicola, for all catches made from after sunset to before sunrise, when applied to polyester mesh as tested with a down-draught suction light trap. No significant repellent effect against Culicoides was found for the citronella oil or the á-cyano-cypermethrin treatments. Copyright / Dissertation (MMedVet)--University of Pretoria, 2009. / Companion Animal Clinical Studies / unrestricted

The genus Erica has undergone an extreme radiation in the Cape and exhibits a diversity of pollination syndromes and floral traits. This makes Erica well-suited to study the evolution of floral traits and how they impact speciation. The first chapter explored the role of ultraviolet colouration by recording its prevalence across Erica pollination syndromes. Ultraviolet was rare in wind-, rodent and small insect-pollinated species, but it was common in bird-pollinated species and ubiquitous in long-proboscid fly (LPF)-pollinated species. Testing their preference revealed that sunbirds can see ultraviolet, but they have no innate preference. LPFs on the other hand were not attracted to flowers where ultraviolet reflectance was removed, thus displaying a strong preference. Chapter 2 focused on the role of stickiness for nectar robbers. I experimentally added stickiness to Erica flowers of one species and further compared stickiness to nectar robbing across several communities. Stickiness appears to reduce damage due to nectar robbing within and between species. Further, I found that stickiness is strongly correlated with pollination by birds and LPFs which might be due to their large nectar rewards. Chapter 3 investigated how the sister species Erica shannonea and Erica ampullacea co-occur despite sharing a pollination syndrome. Pollination experiments and observations showed that they are pollinated by LPFs from two families. The horizontal flowers of E. shannonea are pollinated by a tabanid which has a fixed forward-pointing proboscis, while the vertical flowers of E. ampullacea are pollinated by a nemestrinid which can swivel its proboscis downwards. The nemestrinid in turn has a shorter proboscis which prevents it from accessing nectar in the long-tubed E. shannonea. Due to their different biomechanics, each fly can only access the flower it pollinates resulting in effective reproductive isolation between these species. Chapter 4 compared flower orientation in relation to the two LPF families across all LPF-pollinated species. Using a phylogenetically corrected analysis, I found that flowers pollinated by Tabanidae tend to be horizontal, while nemestrinid flowers are more variable in orientation and more often vertical. This confirms the importance of pollinator biomechanics for the evolution of floral traits. The last chapter investigated how pollen transfer efficiency differs between Erica pollination syndromes. I found that LPF- and bird-pollinated species have higher pollen transfer efficiency in comparison to bee-pollinated species which might have facilitated the shifts from ancestral bee pollination.