Cooperation is pervasive in nature but paradoxically also provides opportunity to cheaters. My dissertation involves the study of both cooperation and conflict in two species of Megalopta bees. Megalopta is a Neotropical genus of halictid bees whose biology is characterized by complex life cycles that can range from solitary to eusocial. These bees nest in dead wood and forage under dim light conditions. Megalopta’s nests are inhabited by an extensive array of organisms and each nest therefore constitutes a miniature ecosystem providing opportunities for cooperation and conflict, both within and between species. I first delineate the social structure of M. genalis and M. ecuadoria nests in several Panamanian populations and integrate the factors that play a role in the behavioral decisions of females when joining a social group or not. Within a kin-selection framework, I discuss how genetic relatedness plays a role in the formation of social nests. Second, I investigate the conflict between host bees and a congener social parasite, and I elucidate reproductive structures that are relevant for understanding the evolution of parasitism. Finally, I describe a cleaning mutualism between Megalopta bees and their mite associates. Bee-mite associations encompass a broad spectrum of interspecific interactions. Some bee-mites are thought to perform cleaning services for their hosts in exchange for suitable environments for reproduction and dispersal. Field observations and experimental manipulation reveal a significant correlation between the presence of mites and the absence of fungi inside the brood cells, as well as between the absence of mites and increased bee mortality. This study therefore provides evidence of the sanitary effect of mites in nests of Megalopta bees. This bee-mite association constitutes one of the few examples of terrestrial cleaning mutualisms. / text

Social insect workers can vary in terms of body size, space use, division of labor, and reproductive potential. Here, I begin to 'dissect' a social insect colony, using the bumble bee Bombus impatiens, to determine how this variation affects colony organization. I found that workers are spatially organized inside the nest and they remain at a specific distance from the colony center. Bees that feed larvae tend to remain in the center, whereas foragers are more often found on the periphery when not foraging. Smaller workers are more likely to feed larvae and incubate brood, and larger workers are more likely to fan or guard the nest. Still, workers perform multiple tasks throughout their life. The size of this task repertoire does not depend on body size or age. Furthermore, workers that remain further from the queen while inside the nest and avoid energy-expensive tasks during the ergonomic phase are more likely to reproduce by the end of the colony cycle. Inactive bees are not, however, defensive reserves. Although inactive bees increase their speed inside the nest when the nest was disturbed, they were not more likely to leave the nest (presumably to attack the simulated attacker) or switch to guarding behavior. This suggests that inactive bumble bees that remain farther from the queen may be storing fat reserves to later develop reproductive organs. Finally, I examined how within-group variation affects colony performance. I reduced variation in body size or temperature response thresholds by removing individuals from the colony with extreme phenotypes, and compared colony performance to colonies where random bees were removed. Colonies took longer to cool down the nest after bees were removed, but this effect was most striking when variation in temperature thresholds was reduced. Further, although larger bees are better at carrying items and are more likely to fan, the ability of colonies to perform undertaking behavior or thermoregulation was not affected when size variation was reduced. These studies provide evidence that (1) within-group variation affects colony organization and (2) variation among workers in their inherent tendencies to respond to stimuli positively affects colony performance.

Funding requirements is one of the first criteria to consider when restructuring a business. Companies and taxpayers would choose the best option when acquiring shares to minimise tax liabilities. The purpose of this study is to formulate an interest deductibility test which provides guidance to taxpayers regarding the main criteria to investigate when restructuring a business transaction to ensure that interest will be deductible on the acquisition of shares with borrowed funds. The findings reveal the similarities and differences of the interest deductibility as seen by South Africa, Australia and Canada. This study will present the legislation as well as court cases in South Africa, Australia and Canada to demonstrate the interest deductibility principles when funds are borrowed to acquire shares when restructuring a business. The focus will be on these principles to provide guidelines from which taxpayers can determine the interest deductibility with respect to share purchasing transactions. The study will indicate recommendations to South African legislation based on the findings of alternative treatments applied by Canada and Australia. / Thesis (MCom (South African and International Taxation))--North-West University, Potchefstroom Campus, 2013.

Funding requirements is one of the first criteria to consider when restructuring a business. Companies and taxpayers would choose the best option when acquiring shares to minimise tax liabilities. The purpose of this study is to formulate an interest deductibility test which provides guidance to taxpayers regarding the main criteria to investigate when restructuring a business transaction to ensure that interest will be deductible on the acquisition of shares with borrowed funds. The findings reveal the similarities and differences of the interest deductibility as seen by South Africa, Australia and Canada. This study will present the legislation as well as court cases in South Africa, Australia and Canada to demonstrate the interest deductibility principles when funds are borrowed to acquire shares when restructuring a business. The focus will be on these principles to provide guidelines from which taxpayers can determine the interest deductibility with respect to share purchasing transactions. The study will indicate recommendations to South African legislation based on the findings of alternative treatments applied by Canada and Australia. / Thesis (MCom (South African and International Taxation))--North-West University, Potchefstroom Campus, 2013.

Broad Based Black Economic Empowerment could possibly be the utmost strategic issue, challenge, threat and potential opportunity facing businesses of all sizes, structures and shapes currently in South Africa. Broad–Based BEE is a government initiative to promote economic transformation in order to enable meaningful participation in the economy by black people. Broad–Based BEE is a reality and a business imperative. Broad–based BEE already have a huge impact in the way business is done in South Africa by large corporate entities, family businesses, small and medium sized businesses and professional practitioners. Broad–based BEE affects almost every participant in the South African economy. Broad–Based BEE can be divided into three components, which holds the seven elements of Broad–Based BEE, namely direct empowerment, human resource development and indirect empowerment. These elements include Equity Ownership, Management, Employment Equity, Skills Development, Preferential Procurement, Enterprise Development and Corporate Social Investment. The agricultural businesses in South Africa have implemented unique types of Broad–Based BEE strategies to conform to Broad–Based BEE. These strategies include shareholding by external Broad–Based BEE companies, and registering Broad–Based BEE employee trusts that obtains shareholding in the company. According to the AgriBEE Framework its vision is to pursue Broad–Based BEE in support of a United and Prosperous Agricultural Sector. The objectives of AgriBEE as described by the AgriBEE Steering Committee are to facilitate broad–based black economic empowerment in the agricultural sector by implementing initiatives to include Black South Africans at all levels of agricultural activity and enterprises along the entire agricultural value chain by following certain steps and ideologies. The contribution of the agribusinesses has some clear indications of shortcomings within the industry as well as and indication of possible elements to be pursued in future. There are however also serious implications to the respondents actions and attitude towards Broad–Based BEE now and in future. It also very apparent that the agribusiness does not distance themselves from the Broad–Based BEE Act and its requirements as well as the consequences thereof. The agribusiness industry is actively involved in Broad–Based BEE. / Thesis (MBA)--North-West University, Potchefstroom Campus, 2012.

Broad Based Black Economic Empowerment could possibly be the utmost strategic issue, challenge, threat and potential opportunity facing businesses of all sizes, structures and shapes currently in South Africa. Broad–Based BEE is a government initiative to promote economic transformation in order to enable meaningful participation in the economy by black people. Broad–Based BEE is a reality and a business imperative. Broad–based BEE already have a huge impact in the way business is done in South Africa by large corporate entities, family businesses, small and medium sized businesses and professional practitioners. Broad–based BEE affects almost every participant in the South African economy. Broad–Based BEE can be divided into three components, which holds the seven elements of Broad–Based BEE, namely direct empowerment, human resource development and indirect empowerment. These elements include Equity Ownership, Management, Employment Equity, Skills Development, Preferential Procurement, Enterprise Development and Corporate Social Investment. The agricultural businesses in South Africa have implemented unique types of Broad–Based BEE strategies to conform to Broad–Based BEE. These strategies include shareholding by external Broad–Based BEE companies, and registering Broad–Based BEE employee trusts that obtains shareholding in the company. According to the AgriBEE Framework its vision is to pursue Broad–Based BEE in support of a United and Prosperous Agricultural Sector. The objectives of AgriBEE as described by the AgriBEE Steering Committee are to facilitate broad–based black economic empowerment in the agricultural sector by implementing initiatives to include Black South Africans at all levels of agricultural activity and enterprises along the entire agricultural value chain by following certain steps and ideologies. The contribution of the agribusinesses has some clear indications of shortcomings within the industry as well as and indication of possible elements to be pursued in future. There are however also serious implications to the respondents actions and attitude towards Broad–Based BEE now and in future. It also very apparent that the agribusiness does not distance themselves from the Broad–Based BEE Act and its requirements as well as the consequences thereof. The agribusiness industry is actively involved in Broad–Based BEE. / Thesis (MBA)--North-West University, Potchefstroom Campus, 2012.

Managed honey bee colonies face severe winter losses in northern climates. In my studies, interactions between genotypes of bees (genetically selected stock and unselected stock) with different levels of resistance and tolerance to varroa mites were assessed under a variety of treatment combinations to quantify effects of queen pheromone, acaricide treatment, wintering method, ventilation condition and pathogen infection on the costs and benefits associated with mite removal and mite-tolerance behaviors. In most of the experiments, mite-resistance caused greater varroa mite mortality within selected stock relative to unselected stock. Artificial and natural sources of queen pheromone caused greater varroa mite mortality within honey bee colonies relative to queenless colonies. While mite resistance had significant benefits, I showed that when producers selected colonies containing some mite resistance traits, it was traits associated with mite-tolerance and not mite-resistance were maintained and contributed to wintering success. Tolerance was effective at two levels of mites as obtained by late autumn treatment of colonies with oxalic but treatment did not improve wintering performance of either stock. Selected stock showed greater colony size, survival and resulted in more viable colonies in spring in comparison to unselected stock with similar initial mite levels (0.16 mites per bee). Selected stock showed greater relative wintering success than unselected stock when wintered indoors than when wintered outdoors but indoor wintering improved colony survival in both stocks relative to outdoor wintering. Carbon dioxide level increased within the winter bee cluster when colonies were maintained under restricted-ventilation (mean 3.82±0.031%, range 0.43-8.44%) and restricted ventilation increased mite mortality by 138% relative to standard-ventilation (mean 1.29±0.031%, range 0.09-5.26%), but restricted-ventilation did not affect bee mortality in comparison to standard-ventilation. In a laboratory study, I showed that Nosema inoculation (with co-infections of N. ceranae and N. apis) suppressed the effectiveness of mite removal behavior within selected bees relative to unselected bees. N. ceranae was more abundant than N. apis. Bees with greater mite removal capacities had higher costs associated with varroa-resistance as indicated by greater bee mortality rates when inoculated with varroa but bee mortality was not affected in Nosema inoculated bees.

ABSTRACT MORPHOMETRIC, MtDNA AND MICROSATELLITE ANALYSIS IN HONEYBEE POPULATIONS (Apis mellifera L.) OF NORTH AND NORTHWEST IRAN Morphometric measurements, mitochondrial DNA analyses and 5 microsatellite loci were used to investigate variation in the honeybee populations of Iran and comparing it with the Turkish populations. Five honeybee populations were sampled from North and west north of Iran. In morphometric aspect of the study 23 characters were measured from left forewings and hindlegs of honey bee samples. The data were analysed by multivariate statistical analyses. By using mtDNA analyses length polymorphism of the intergenic region COI-COII of mitochondrial DNA was studied. After amplification of this region by the polymerase chain reaction, DraI enzyme was used for restriction of amplified region. Results of mtDNA studies show no diversity between four populations and all of them exhibit the same C1 pattern. Five microsatellite loci (A7, A24, A28, A43 and A113) were used in this studies.A high level of average heterozygosity changing between 0.611 and 0.709 was detected in Iranian honey bee populations, and a significant degree of polymorphism was observed. Although Urmia, Sarein and Viladereg populations are similar, Amol population which has located in northern Iran shows a significant difference from other populations. Result obtained form morphometric studies are supporting microsatellite analyses. By comparing data obtained form Iranian honey bee populations with Turkish population (Hakkari), western populations (Urmia, Sarein and Viladereg) are more similar to Hakkari population. It is found Amol is significantly different form other populations and better represents Iranian honeybee.

Thesis (Ph.D.)--University of Western Sydney, 2008. / A thesis submitted to the University of Western Sydney, College of Health and Science, Centre for Plant and Food Science, in fulfilment of the requirements for the degree of Doctor of Philosophy. Includes bibliography.

Made available in DSpace on 2014-06-11T19:35:43Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-08-23Bitstream added on 2014-06-13T21:07:59Z : No. of bitstreams: 1 pereira_am_dr_rcla.pdf: 830341 bytes, checksum: de8af8468e88b6f5c5cf902007f24ed7 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / As abelhas Apis mellifera são insetos ecologicamente e economicamente importantes. Elas asseguram a polinização de diversas plantas contribuindo para a manutenção da biodiversidade. Seu valor econômico resulta não somente de seus produtos diretos mas também pela ativa polinização que exercem em culturas. A polinização feita por animais é importante para a reprodução sexuada de muitas culturas e para a maioria das plantas nativas, as quais também podem ser importantes como fonte de calorias e micronutrientes para os seres humanos. Além do mais, o declínio no número de polinizadores pode acarretar uma redução concomitante no número de espécies vegetais. A abelha A. mellifera, destaca-se como polinizador economicamente mais valioso para culturas em todo o mundo. Por outro lado, a agricultura moderna cada vez mais depende do uso de produtos químicos para controlar plantas daninhas, fungos e insetos-praga para assegurar a produtividade. Abelhas melíferas podem entrar em contato com tais agentes químicos devido suas atividades de coleta de água, resinas vegetais, pólen e néctar. A intoxicação resultante desta exposição pode ser letal, o que é facilmente identificável, ou causar efeitos na fisiologia e no comportamento do inseto. Tais efeitos, ocasionados por doses subletais, são difíceis de serem mensurados, como paralisia, desorientação ou mudanças comportamentais; porém, podem comprometer toda a estrutura social da colônia. Visando um melhor conhecimento dos efeitos de doses subletais de inseticidas em abelhas, estudou-se a ação dos ingredientes ativos Acetamiprido, Tiametoxam e Fipronil na sobrevivência e nos comportamentos de reflexo de extensão da probóscide e da atividade locomotora em operárias de A. mellifera. Preliminarmente, observou-se a DL50 vinte e quatro horas após o tratamento tópico do Acetamiprido Tiametoxam e Fipronil foram registrados... / the pollination of many wild flowers, and thus contributing to plant biodiversity. Their economic value derives not only from their direct products but also from their pollinating activity in crop plants. Animal pollination is important to sexual reproduction of many crops and the majority of wild plants, which can also be important for providing calories and micronutrients for humans. Furthermore, the decline of pollinating species can lead to a parallel decline in number of plant species. A. mellifera stands out as the most economically valuable crop pollinator in the world. Modern agriculture increasingly depends on the use of chemicals substances to control weeds, fungi and insect pests to ensure high yields. Honey bees may frequently become exposed to such chemicals as a consequence of their foraging activities collecting water, natural resins, pollen and nectar. Intoxication resulting from this exposure can be lethal, which is easily identifiable, or cause effects on the physiology and insect behavior. These effects, caused by sublethal doses are difficult to measure (such as paralysis, disorientation or behavioral changes), and can compromise the entire social structure of the colony. To improve the knowledge about the effects of insecticides sublethal doses effects in honey bees, we studied the action of the active ingredients Acetamiprid, Thiamethoxam and Fipronil on survival and behavior of the proboscis extension reflex (PER) and locomotor activity in workers of A. mellifera. Twenty-four hours after topic application, the LD50 values of Acetamiprid, Thiamethoxam and Fipronil were 9,3 μg/bee, 17 ng/bee and 1,9 ng/bee, respectively. We also estimated a LT50 with values of 1,4 hours, 3,8 hours and 19,8 hours to Acetamiprid, Thiamethoxam and Fipronil respectively. The behaviors were analyzed 1, 4 and 24 hours after topical application of active ingredients at doses corresponding... (Complete abstract click electronic access below)