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Swarm Intelligence (SI) is a young field of study from which solutions to complex problems have been proposed based on how some natural organisms (e.g. ants, bees and others) achieve many of their daily tasks through simple sets of interactions. This thesis proposes two models for area exploration and coverage based on SI principles. These two models present a novel approach based on the combination of: ants’ pheromones, in order to keep track of visited places; and bird flocks or fish schooling, so as to move and collaborate. An implementation of both models was done in order to simulate and evaluate both the emergent behavior of the agents as well as their area exploration and coverage performance. Based on the outcome of the simulations it is concluded that both models are able to perform the exploration and coverage task and that one model is better than the other.

Social insects have complex forms of social organization. Molecular mechanisms involved in the regulation of their reproduction are not fully understood. This dissertation investigated the vitellogenin receptor (VgR), short neuropeptide F (sNPF) receptor, and two insulin receptors (InRs) in the red imported fire ant Solenopsis invicta, focusing on their possible roles in the regulation of queen reproduction. Knowledge of these receptors may provide novel ways to manipulate either reproductive castes or overall reproductive outcome, diminishing the fire ant impact as invasive pest. Fire ant virgin queens have more abundant VgR (SiVgR) transcripts than newly-mated queens, but limited egg formation. To elucidate whether queen maturation involved changes in SiVgR expression, we investigated both virgin and mated queens. In both queens, immunofluorescence analysis of ovaries revealed differential SiVgR localization in early and late stage oocytes; however, mated queens showed higher SiVgR expression than virgin queens. In virgin queens, the SiVgR signal was first observed at the oocyte membrane beginning at day 12 post-emergence, coinciding with the maturation period required before a mating flight. SiVgR silencing in virgins through RNA interference abolished egg formation, demonstrating that SiVgR is involved in queen ovarian development pre-mating. The sNPF and insulin signaling pathways have been implicated in the regulation of food intake and body size, and these peptides also play a gonadotropic role in the ovaries of some insect species. To elucidate the sites of action of the sNPF peptide(s), the sNPF receptor tissue expression and cellular localization were analyzed in the queen brain, subesophageal ganglion (SEG), and ovaries by immunofluorescence. Results suggest that the sNPF signaling cascade may be involved in diverse functions, and the sNPF peptide(s) may act in the brain and SEG as neurotransmitter(s) or neuromodulator(s), and in the ovaries as neurohormone(s). In addition, to elucidate the role of insulin signaling pathway in the fire ant, two putative InRs were cloned. Transcriptional expression analyses show that the receptor abundance was negatively correlated with body size and nutrition status in fire ant immatures. In queens, the expression of InRs in different queen tissues correlates with tissue requirements for queen reproductive physiology and behaviors.

Demographic, biological and behavioural knowledge, together with information on the ecological interactions and impact of a species is fundamental to effective management of most mammal species. In this study, these aspects were investigated for a population of feral horses in the Namib Naukluft Park of Namibia, which lies within a part of the Namib Desert. An attempt was made to evaluate the justification of the continued existence of this exotic species in a conservation area, as well as to provide baseline information and recommendations regarding management of these horses. The study investigated the botanical component and grazing capacity of the area inhabited by the horses, as well as the demography and quality of life of the horses. The study further examined the possible negative impact the horses may have on the natural biodiversity of the area. Finally, it looked at the historic, scientific, aesthetic and economic values of the horses. The collected data was then used as a technical basis for the development of a draft management plan during a stakeholder workshop. The study proposed a range of grazing capacity values related to the total rainfall of the preceding twelve months, based on grass production in response to rainfall in different plant communities. The horses, as well as the native large herbivores, utilized the study area according to the patchy rainfall patterns typically found in the Namib Desert. The population size of the horses fluctuated between 89 and 149 over a ten year period. The social structure of the population was more significantly influenced by artificial interference than natural disasters which had implications on natality, mortality and genetic viability. Termite activity, measured as utilization of grass provided in bait boxes, did not correlate with horse density and seems, instead, to be influenced by soil properties. The results of ant and tenebrionid beetle species composition surveys and analyses did not indicate a significant negative impact from the horses on the study area. No indication could be found that the horses threaten the survival of any native species in the area or that they change the vegetation structure. It appears as if the biodiversity of the area is subjected to large natural stresses due to the continued and frequent desiccation in the desert environment. The impact of the horses is therefore probably minor to that of the climatic stochasticity. It also became apparent that the horses have developed significant historical, scientific and tourism value. The general public opinion is that the horses should be managed as a wild population with minimal artificial interference. / Thesis (Ph.D. (Zoology))--North-West University, Potchefstroom Campus, 2006.

The quality of terrestrial invertebrates as indicators for the detection of ecological change associated with disturbance is widely acknowledged. Invertebrates, at the community level, are often more sensitive to changes than are plants or vertebrates. Both ants and beetles have been studied extensively; changes in ant community composition have been applied successfully as an indication of restoration success. Ants are ideal due to their high abundances and diversity, their ecological importance at all trophic levels, their relative sampling and sorting ease and their sensitivity to ecological change. A detailed understanding of community dynamics greatly facilitates the correct interpretation of signals provided by indicator taxa. Beetles to a great extent, are useful ecological or biodiversity indicators and have been adopted as suitable indicators in environmental monitoring and assessment, as well as to facilitate the evaluation of conservation of biodiversity in landscapes subjected to harvesting. It is well known that ground-dwelling beetle assemblages (especially ground and rove beetles) are sensitive to habitat structure, microclimate and biodiversity management strategies. The use of bio-indicators with regard to land management is becoming increasingly common in ecological studies, because the results obtained can hopefully provide a framework of reference for the prediction of ecosystem response and the means to select the best land use practices. Such predictions will become useful when considering the consequences of ecological perturbations such as fire regimes, bush encroachment, grazing, mining activity, etc. The objectives of this particular study are to determine the effect that past fire treatments may have had on vegetation structure and how ant and beetle assemblages respond to such changes, and what such changes in habitat structure mean in terms of increased bush density. It is expected that the results obtained will provide an indication of the manner in which ecosystem change affects bio-indicator community assemblages, and how this can be applied with regard to future restoration efforts. These organisms were sampled by means of pitfall traps placed within strategic sites varying in vegetation composition and sampled over a number of days. The content of each trap was sorted to genus level, and where possible, to species level and their application of selected invertebrates as indicators of ecosystem change due to veld fires, species richness, abundance and composition determined. The data obtained was analysed statistically using STATISTICA, CANOCO, PRIMER and Microsoft Excel. Four sites with different burn histories were selected: an unburnt site, one burnt in 2002, one burnt in 1997, and one burnt in 1992. Soil characteristics were found to be relatively homogenous throughout all the sample sites, while each of the burn treatment replicates could be characterised by a particular plant structural arrangement. With regards to the ant assemblages, both in terms of species composition and functional group composition, low species diversity appeared to segregate the 1997 burn treatment replicates markedly from the other three burn treatments, with a high degree of species dominance exhibited by Anaplolepis steingroeveri. The ants seem to indicate higher species diversity in the burn treatment sites that had a more diverse vegetation structure. This occurrence however seems to alter over time after a fire incident, before returning to as close to its original state as possible. The beetles, however, displayed very haphazard assemblages, and did not show any discernable significant results that may be used to describe the environmental parameters in question.The reaction of the ants seemed to occur over an extended period of time, with immediate effects of the burn being an increase in non-specialised and opportunistic species abundances, possibly due to a decrease in competition with other species and taxa. Changes in ant assemblages became more apparent after seven years of the burn incident, seemingly linked to structural changes in the plant community. Ant species diversity increased again at the twelve year recovery time, with and associated change in plant habitat structure. The ants thus, in conclusion, show significant results towards indicating a response to habitat change brought on by fire. It is a requirement that this experiment be replicated in order to establish more discernable patterns. Additional recommendations to improve on this study are also discussed. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2009.

The quality of terrestrial invertebrates as indicators for the detection of ecological change associated with disturbance is widely acknowledged. Invertebrates, at the community level, are often more sensitive to changes than are plants or vertebrates. Both ants and beetles have been studied extensively; changes in ant community composition have been applied successfully as an indication of restoration success. Ants are ideal due to their high abundances and diversity, their ecological importance at all trophic levels, their relative sampling and sorting ease and their sensitivity to ecological change. A detailed understanding of community dynamics greatly facilitates the correct interpretation of signals provided by indicator taxa. Beetles to a great extent, are useful ecological or biodiversity indicators and have been adopted as suitable indicators in environmental monitoring and assessment, as well as to facilitate the evaluation of conservation of biodiversity in landscapes subjected to harvesting. It is well known that ground-dwelling beetle assemblages (especially ground and rove beetles) are sensitive to habitat structure, microclimate and biodiversity management strategies. The use of bio-indicators with regard to land management is becoming increasingly common in ecological studies, because the results obtained can hopefully provide a framework of reference for the prediction of ecosystem response and the means to select the best land use practices. Such predictions will become useful when considering the consequences of ecological perturbations such as fire regimes, bush encroachment, grazing, mining activity, etc. The objectives of this particular study are to determine the effect that past fire treatments may have had on vegetation structure and how ant and beetle assemblages respond to such changes, and what such changes in habitat structure mean in terms of increased bush density. It is expected that the results obtained will provide an indication of the manner in which ecosystem change affects bio-indicator community assemblages, and how this can be applied with regard to future restoration efforts. These organisms were sampled by means of pitfall traps placed within strategic sites varying in vegetation composition and sampled over a number of days. The content of each trap was sorted to genus level, and where possible, to species level and their application of selected invertebrates as indicators of ecosystem change due to veld fires, species richness, abundance and composition determined. The data obtained was analysed statistically using STATISTICA, CANOCO, PRIMER and Microsoft Excel. Four sites with different burn histories were selected: an unburnt site, one burnt in 2002, one burnt in 1997, and one burnt in 1992. Soil characteristics were found to be relatively homogenous throughout all the sample sites, while each of the burn treatment replicates could be characterised by a particular plant structural arrangement. With regards to the ant assemblages, both in terms of species composition and functional group composition, low species diversity appeared to segregate the 1997 burn treatment replicates markedly from the other three burn treatments, with a high degree of species dominance exhibited by Anaplolepis steingroeveri. The ants seem to indicate higher species diversity in the burn treatment sites that had a more diverse vegetation structure. This occurrence however seems to alter over time after a fire incident, before returning to as close to its original state as possible. The beetles, however, displayed very haphazard assemblages, and did not show any discernable significant results that may be used to describe the environmental parameters in question.The reaction of the ants seemed to occur over an extended period of time, with immediate effects of the burn being an increase in non-specialised and opportunistic species abundances, possibly due to a decrease in competition with other species and taxa. Changes in ant assemblages became more apparent after seven years of the burn incident, seemingly linked to structural changes in the plant community. Ant species diversity increased again at the twelve year recovery time, with and associated change in plant habitat structure. The ants thus, in conclusion, show significant results towards indicating a response to habitat change brought on by fire. It is a requirement that this experiment be replicated in order to establish more discernable patterns. Additional recommendations to improve on this study are also discussed. / Thesis (M. Environmental Science)--North-West University, Potchefstroom Campus, 2009.

Habitat fragmentation involves the break-up of continuous native vegetation into remnant patches that are set in a matrix of altered habitat. The consequences of habitat fragmentation include the loss of original habitat which is followed by reductions in remnant size that increase edge effects and reduce habitat quality, and also increase the isolation of remnants from one another. Habitat fragmentation is an international environmental concern that also effects Australia. Over the last ten years Queensland has been responsible for some ninety percent of the clearing occurring in Australia, and as a result recorded some of the highest vegetation clearing rates in the world. / thesis (PhDEnvironmentalManagement)--University of South Australia, 2004.

Mémoire (M.Inf.)-- Université du Québec à Chicoutimi, 2002. / Document électronique également accessible en format PDF. CaQCU

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.