Simple regulatory mechanisms based on the idea of the saturable 'common stomach' can control the regulation of protein foraging and protein allocation in honeybee colonies and colony-level responses to environmental changes. To study the economic benefits of pollen and nectar foraging strategies of honeybees to both plants and honeybees under different environmental conditions, a model was developed and analyzed. Reallocation of the foraging workforce according to the quality and availability of resources (an 'adaptive' strategy used by honeybees) is not only a successful strategy for the bees but also for plants, because intensified pollen foraging after rain periods (when nectar quality is low) compensates a major fraction of the pollination flights lost during the rain. The 'adaptive' strategy performed better than the'fixed' (steady, minimalistic, and non-adaptive foraging without feedback) or the 'proactive' (stockpiling in anticipation of rain) strategies in brood survival and or in nectar/sugar economics. The time pattern of rain periods has profound effect on the supply-and-demand of proteins. A tropical rain pattern leads to a shortage of the influx of pollen and nectar, but it has a less profound impact on brood mortality than a typical continental rainfall pattern. Allocating more bees for pollen foraging has a detrimental effect on the nectar stores, therefore while saving larvae from starvation the 'proactive' strategy could fail to collect enough nectar for surviving winter.

A defining feature of the non-flying mammal pollinated (NMP) syndrome is inflorescence crypsis whereby flowers are close to the ground and somewhat hidden within the canopy. A number of species in the Cape Proteaceae are NMP, two of which were chosen as focal species for this study: Protea amplexicaulis and Protea humiflora. This study investigated the two previously suggested hypotheses for crypsis: hidden flowers are more difficult for nectarivorous birds to access, or hidden flowers provide greater cover for small mammal pollinators from aerial predators. Using remote triggered cameras, P. amplexicaulis and P. humiflora inflorescences were observed over the 2017 flowering period, noting visitation by birds and small mammals and assessing the legitimacy of birds as pollinators. In the literature, bird visitation to exposed inflorescences is suggested to be rare, but this study showed that it is considerable. Observations of camera footage suggest that birds are in fact illegitimate pollinators and thus nectar rob. Bird visitation to exposed inflorescences was more than tenfold that of hidden inflorescences, suggesting that crypsis is likely a strategy to avoid nectar robbing by birds. Both P. amplexicaulis and P. humiflora have been observed to retain dead leaves, which may contribute to their cryptic nature. Alternative hypotheses for dead leaf retention in Proteaceae – that it may increase flammability or result in a below canopy spike in nutrients post fire (selfish fertilization) – were assessed and rejected. Sampling of eight local Protea species showed that dead leaf retention is not a consequence of prolonged live leaf retention, with P. amplexicaulis retaining dead leaves for up to 6 years. The removal of dead leaves in 30 P. amplexicaulis individuals resulted in a significant decrease in the number of inflorescences hidden from aerial view, thus suggesting that dead leaf retention may be a strategy to enhance crypsis and thus forms part of the NMP syndrome. This research expands on the knowledge of the NMP syndrome; providing evidence in support of an anti- nectar robbing crypsis function, discovering a novel crypsis adaptation regarding dead leaf retention, and casting doubt on the Restricted Distributions hypothesis for the evolution of the syndrome.

No description available.

No description available.

Pollination success of animal-pollinated flowers depends on rate of pollinator visits and on pollen deposition per visit, both of which should vary with the pollen and nectar "neighborhoods" of a plant, i.e., with pollen and nectar availability in nearby plants. One determinant of these neighborhoods is per-flower production of pollen and nectar, which is likely to respond to environmental influences. In this study, we explored environmental effects on pollen and nectar production and on pollination success in order to follow up a surprising result from a previous study: flowers of Ipomopsis aggregata received less pollen in years of high visitation by their hummingbird pollinators. A new analysis of the earlier data indicated that high bird visitation corresponded to drought years. We hypothesized that drought might contribute to the enigmatic prior result if it decreases both nectar and pollen production: in dry years, low nectar availability could cause hummingbirds to visit flowers at a higher rate, and low pollen availability could cause them to deposit less pollen per visit. A greenhouse experiment demonstrated that drought does reduce both pollen and nectar production by I. aggregata flowers. This result was corroborated across 6 yr of variable precipitation and soil moisture in four unmanipulated field populations. In addition, experimental removal of pollen from flowers reduced the pollen received by nearby flowers. We conclude that there is much to learn about how abiotic and biotic environmental drivers jointly affect pollen and nectar production and availability, and how this contributes to pollen and nectar neighborhoods and thus influences pollination success.

Flower seed mixes are increasingly used to enhance the biodiversity and amenity values of urban green spaces. Urban or “pictorial” flower seed mixes are often used because they are designed using cultivars and non-native species to provide more colourful and longer-lasting flower displays. Although these seed mixes are effective in providing a high density of large colourful flowers, over an extended season, their value for biodiversity, and in particular the floral rewards they provide for flower-visitors, is largely unknown. The overall aim of my thesis was to assess and improve the value of these new urban habitats as forage resources for flower-visiting insects. My approach was to quantify and compare floral reward provision and insect visitation between meadows grown from three exemplar commercial pictorial flower meadow seed mixes (called Marmalade Annual, Short Annual and Cornfield Annual). I also compared these standard commercial mixes with corresponding ‘nectar-enriched’ formulations, which were designed by increasing the proportional seed weight contribution of selected species predicted to produce high quantities of nectar within each mix. To compare floral rewards and visitation between meadows grown from these seed mixes, I set up a field experiment in Sheffield, UK, using a complete randomised block design with six replicate blocks, each with six 25 m2 plots sown with one of the six seed mix treatments. My first objective was to quantify the floral nectar and pollen rewards provided by each flowering species recorded in the meadows (on the scale of a single flower or inflorescence). My second objective was to use these data to quantify the floral rewards provided per unit area by replicate meadows of different seed mix treatments, testing whether enrichment of seed mixes is an effective method of increasing floral nectar sugar rewards. My third objective was to corroborate/correct my morphology-based flower-visitor identifications using DNA barcoding to screen for misidentifications and morphologically cryptic species. I then used these DNA barcode-based identifications to assess whether there are systematic biases in the structure of flower-visitor networks constructed using molecular taxon identifications compared to traditional morphology-based taxon identifications. My fourth objective was to quantify patterns of insect visitation to meadows, testing whether meadows of different seed mix types attract different flower-visitor assemblages. Meadow floral composition surveys revealed that contamination by unintended horticultural species was widespread across replicate seed mix treatments, with contaminants likely germinating from a seed bank laid down during a failed attempt at this experiment the previous year. Contamination particularly affected Marmalade mixes, mainly because the common contaminant species were often also components of the Short and Cornfield mixes. For example, contaminants contributed on average about a third of nectar sugar mass or pollen volume per unit area in Marmalade mix meadows. Hence, contamination fundamentally undermined the internal validity of seed mix treatments, reducing the ability to directly attribute meadow level patterns in floral rewards or flower-visitors to seed mixes. As result, examination of patterns of floral resource provision and insect visitation were more informative at a species scale. In terms of patterns of insect visitation, Centaurea cyanus received 91% of bumblebee visits, 88% of honeybee visits and 29% of hoverfly visits, whilst T. inodorum received 27% of hoverfly visits. Patterns of bumblebee and honeybee visitation indicated preferential visitation to floral units of Centaurea cyanus. Although this species produced high quantities of nectar sugar mass and pollen volume, this did not differentiate it from other Asteraceae, such as Glebionis segetum, Rudbeckia hirta and Coreopsis tinctoria, which all produced high quantities of both floral rewards. Hence, it is likely that floral traits not measured in this study, such as nectar accessibility (‘nectar-holder depth’) or concentration/volume characteristics (which can affect accessibility due to constraints imposed by feeding morphology), drove patterns of preferential visitation in bumblebees and honeybees to C. cyanus. Given that in the absence of contamination there would have been very few bumblebee or honeybee visitors to Marmalade mix meadows, aesthetically designed pictorial meadows can fail to jointly provide benefits for people and some important flower-visiting insect taxa. DNA barcoding did not change specimen identifications for most morphotaxa. However, splitting and/or lumping processes affected almost one third of morphotaxa, with lumping of morphotaxa the most common type of change. This was in part because males and females from sexually dimorphic species were often separated by morphological identification. These DNA barcode-based changes to visitor taxonomy resulted in consistent minor changes in network size and structure across replicate networks. Lumping of morphotaxa decreased taxon richness, reducing the number of unique links and interaction diversity (the effective number of links). Lumping also increased flower-visitor generality, reducing plant vulnerability and increasing overall network connectance. However, taxonomic changes had no effect on interaction evenness or network specialisation. Thus, for this well-studied fauna, DNA barcode-based flower-visitor networks were systematically biased toward fewer taxa and links, with more generalist visitors and specialist plants. Given that many tropical faunas have more species and are less described than in Britain this pattern may not be replicated in other studies. Further studies in contrasting plant-pollinator communities are required before generalisations can be made about systematic biases between networks constructed using morphological versus molecular data. Overall, meadows grown from annual pictorial flower meadow seed mixes provide abundant floral units per unit area of meadow and are a valuable alternative to traditional horticultural flower beds or amenity grasslands in high profile urban contexts. Nevertheless, care must be taken during design of seed mixes and selection of mixes for planting to ensure that species in the mix provide suitable floral resources for an array of flower-visitors, including bees. This would be aided by the integration of informative measures for candidate species of floral rewards or visitor types and visitation rates during seed mix design.

Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul / This study aimed to determine the details of the offer and quality of floral resources in Bauhinia forficata Link, native species of Seasonal Deciduous Forest in Rio Grande do Sul, and how they influence the attraction and interaction with the flower visitors and other plant species. It sought to further determine the ecological mechanisms that are established from the plant interactions / animal that can be used as a theoretical basis for the creation of ecological restoration strategies. The work was conducted in the municipality of Santa Maria, central region of Rio Grande do Sul. Were selected 11 matrices based on the environmental quality of the fragments their surroundings and morphophysiological and phytosanitary characteristics of individuals, of which was evaluates the phenology, volume and concentration of nectar instanding crop (NID), pollinic viability, suitability for autogamy, floristic diversity of the surrounding areas, diversity, intensity and behavior of diurnal and nocturnal flower visitors and ditrophic networks of plant-pollinator interaction. The variables were tested by comparison of means, Principal Component Analysis (PCA) and correlation analysis. The average volume of NID observed for the species was 40.3 μl and the mean concentration was 0.265 mg / μl. The average pollen viability was 81.43%, and the species has proved unfit to autogamy. The average number of floral visitors was 18.24 per matrices and the average intensity of interaction was 59.94%. Were accounted for 730 floral visitors belonging to 29 morphospecies, 657 at the diurnal monitoring and 73 at nocturnal monitoring. The main order observed was Lepidoptera. The suborder Rhopalocera was the most abundant between diurnal visitors (30.43%), and the suborder Heterocera the most abundant among the nocturnal visitors (50%). Proved to be effective pollinators of Bauhinia forficata the bumblebee (Hymenoptera) morphospecies, gray-moth (Pyrgus sp.) (Lepidoptera: Heperiidae) and orange-black-butterfly (Helyconius sp.) (Lepidoptera: Nymphalidae). The functionally effective pollination systems for Bauhinia forficata in the study area are the Psychophily (butterflies) and Melittophily (bumblebees). In the analysis of floristic diversity were found 34 species, the Shannon diversity index ranged between 1.46 and 2.43 between plots. The Bauhinia forficata species, Acacia velutina and Strychnos brasiliensis have the greatest relative densities, respectively, 10.97%, 10.42% and 8.78%. It can be concluded that both the supply and quality of resources influence at the attraction of visitors, as the interaction of visitors with flowers interfered at the availability of resources. The quantity, quality and plasticity of the offered floral resources, the generalist attraction of visitors, the time and intensity of flowering, the inability to autogamy and geitonogamy, high rates of pollen viability and the high degree of connectance of ditróficas webs, are responsible for initiate important ecological mechanisms between this and other ecosystem agents, being them: compensation mechanisms, of species coexistence, induction of gene flow and competition and partilhamento of the resources. These results demonstrate that Bauhinia forficata is an important energy source for the diet of a wide range of pollinators and acts as an inducer of ecological processes and gene flow in the study area. / O presente estudo teve por objetivo determinar as características da oferta e qualidade dos recursos florais em Bauhinia forficata Link, espécie nativa da floresta Estacional Decidual do Rio Grande do Sul, e a forma como estas influenciam na atração e na interação com os visitantes florais e com as demais espécies vegetais. Buscou-se ainda determinar os mecanismos ecológicos que se estabelecem a partir das interações planta/animal que possam ser utilizados como base teórica para a criação de estratégias de restauração ecológica. O trabalho foi conduzido no Município de Santa Maria, região central do Rio Grande do Sul. Foram selecionadas 11 matrizes com base na qualidade ambiental dos fragmentos de seu entorno e nas características morfofisiológicas e fitossanitárias dos indivíduos, das quais se avaliou a fenologia, volume e concentração de néctar instantaneamente disponível (NID), viabilidade polínica, aptidão à autogamia, diversidade florística das áreas adjacentes, diversidade, intensidade e comportamento de visitantes florais diurnos e noturnos, e teias ditróficas de interação planta-polinizador. As variáveis foram testadas por comparação de médias, Análise de Componentes Principais (PCA) e análise de correlação. O volume médio de NID observado para a espécie foi de 40,3 μl e a concentração média foi de 0,265 mg/μl. A viabilidade polínica média foi de 81,43%, sendo que a espécie demonstrou ser inapta à autogamia. O número médio de visitantes florais foi 18,24 por matriz e a intensidade média de interação foi 59,94%. Foram contabilizados 730 visitantes florais pertencentes a 29 morfoespécies, sendo 657 no monitoramento diurno e 73 no monitoramento noturno. A principal ordem observada foi Lepidoptera. A subordem Rhopalocera foi a mais abundante entre os visitantes diurnos (30,43%) e a subordem Heterocera a mais abundante entre os visitantes noturnos (50%). Demonstraram serem polinizadores efetivos da Bauhinia forficata as morfoespécies mamangava (Hymenoptera), mariposa-cinza (Pyrgus sp. (Lepidoptera: Hesperiidae) e a borboleta-laranja-preta (Helyconius sp. (Lepidoptera: Nymphalidae)). Os sistemas de polinização funcionalmente efetivos para Bauhinia forficata na área de estudo são a Psicofilia (borboletas) e a Melitofilia (mamangavas). O grau de conectância total das teias ditróficas foi de 53,47% para as redes de visitantes diurnos e de 44% para as redes de visitantes noturnos. Na análise da diversidade florística foram encontradas 34 espécies, o índice de diversidade de Shannon variou entre 1,46 e 2,43 entre parcelas. As espécies Bauhinia forficata, Acacia velutina e Strychnos brasiliensis apresentaram as maiores densidades relativas, respectivamente, 10,97%, 10,42% e 8,78%. Foi encontrada correlação entre a concentração do néctar e diversidade florística, entre volume de néctar e diversidade de visitantes e entre a viabilidade polínica e volume e concentração do néctar. Pode-se concluir que tanto a oferta e a qualidade dos recursos influenciaram na atração dos visitantes, quanto a interação dos visitantes com as flores interferiu na disponibilidade dos recursos. A quantidade, qualidade e plasticidade dos recursos florais ofertados, a atração generalista de visitantes, a sincronia e intensidade de floração, a inaptidão à autogamia e geitonogamia, as altas taxas de viabilidade polínica e o alto grau de conectância das teias ditróficas, são responsáveis por desencadear importantes mecanismos ecológicos entre esta e os demais agentes do ecossistema, sendo eles: mecanismos de compensação, de coexistência de espécies, indução do fluxo gênico e de competição e partilhamento de recursos. Tais resultados demonstram que Bauhinia forficata é uma importante fonte energética para a dieta de uma vasta gama de polinizadores e atua como indutora dos processos ecológicos e do fluxo gênico na área de estudo.

No description available.

Orientadores: Marcelo Cristianini, Pilar Rodriguez de Massaguer / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-12T13:04:24Z (GMT). No. of bitstreams: 1 Tribst_AllineArtigianiLima_M.pdf: 3194893 bytes, checksum: 2ef1a8dcf449b5ddd301d699b525063b (MD5) Previous issue date: 2008 / Resumo: O néctar de manga é apreciado por sua cor e aroma. Este produto, pela sua alta acidez, pode ser contaminado por bolores, dentre os quais são de grande relevância aqueles capazes de sobreviver ao processamento térmico. O processamento a alta pressão dinâmica (APD) é um tratamento ¿a frio¿ realizado para inativação de microrganismos visando uma melhor qualidade sensorial e nutricional do produto obtido. Neste estudo, avaliou-se o efeito do processamento a APD isoladamente ou combinado com tratamento térmico (TT) brando na inativação de Aspergillus niger em néctar de manga e, posteriormente, foi realizada a avaliação do efeito dos processos sobre a cor e a concentração de vitamina C do néctar. Paralelamente foi desenvolvida uma metodologia para limpeza e sanificação do equipamento e um processo para a redução de viscosidade do néctar de manga. Foram estudadas pressões entre 100 e 300 MPa para a inativação do Aspergillus niger. A pressão de 300 MPa inativou toda a carga inicial (> 6,24 reduções decimais), 200 MPa provocou uma inativação parcial (aproximadamente 2 ciclos) e, pressões inferiores a 150 MPa não resultaram em inativação significativa do A. niger. Quando o processo de APD foi associado à TT brando (80ºC/15minutos) foi observado um efeito sinérgico entre pré tratamento a APD e posterior TT (aproximadamente 1 ciclo logaritmo); já quando utilizado pré TT seguido de tratamento a APD, foi observado apenas um efeito aditivo. Utilizando-se aplicação de APD seguida de TT, foi realizado um planejamento experimental fixando-se a pressão em 200 MPa e variando-se temperatura e tempo do TT e ratio do néctar de manga (brix/acidez), de forma a obter um modelo que descrevesse o processo. Os resultados indicaram que tempo e temperatura afetaram positivamente a inativação e o ratio do néctar afetou negativamente. A partir do modelo foram estabelecidos que processos a 200 MPa seguido de TT a 73,5ºC/10 minutos ou 61,5ºC/20 minutos eram suficientes para obter 5 reduções decimais do bolor. A avaliação desses processos combinados, do processo térmico tradicional (100ºC/10 minutos) e do processo utilizando apenas pressão (300 MPa) sobre o conteúdo de vitamina C e cor do néctar demonstrou uma inativação de vitamina C muito similar para todos os processos (perdas de aproximadamente 45%) e uma melhor retenção de cor para os produtos processados à APD. O desenho do processo de limpeza e sanificação para o equipamento foi considerado eficaz uma vez que reduziu para < 1 UFC.mL-1 a contaminação de A.niger inicial de aproximadamente 106 UFC.mL-1 na água de enxágüe. Foi utilizada concentração de 0,05% de ácido peracético e 2,5% de detergente comercial cujos princípios ativos eram o toluenosulfonato de sódio e cloreto de didecilmetilamônio. O processo de redução de viscosidade do néctar também foi efetivo através de seu pré tratamento com enzimas pectinolíticas e celulases, que reduziram a viscosidade inicial do néctar em 50%. Pelos resultados obtidos no presente trabalho, observa-se que a APD isoladamente ou aplicada junto com TT brando é uma alternativa viável para a inativação de A. niger termorresistente em néctar de manga. O processo teve efeito negativo sobre a vitamina C do néctar de manga, o que pode ser atribuído tanto à presença de oxigênio na amostra quanto à presença de selos metálicos no equipamento (selos de berílio-cobre) que promovem a passagem de íons metálicos para o suco, os quais atuam como pró-oxidantes de vitamina C, agravando a oxidação da vitamina / Abstract: Mango nectar is appreciated by its color and flavor. Due to its high acidity, this nectar can be contaminated by molds and the most important molds are those able to survive to the heating process. The dynamic high pressure (DHP) is a cold treatment used to inactivate microorganisms with better nutritional and sensory retention in food. In this study, the DHP process isolated or combined with mild thermal treatment (TT) was used to inactivate Aspergillus niger in mango nectar. The effects of these processes were evaluated on color and vitamin C retention. In parallel, a methodology was developed to clean in place (CIP) the DHP equipment. A process to reduce the viscosity of mango nectar was also developed. Pressures between 100 and 300 MPa were studied to Aspergillus niger inactivation. Pressure of 300 MPa completely inactivated the initial load (> 6.24 decimal reduction), 200 MPa caused a partial inactivation (2 log cycles) and pressures up to 150 MPa did not inactivate the mold. A synergistic effect was observed when pre treatment of DHP was associated to mild TT (80ºC/ 15 minutes) with increase of 1 log cycle on mold inactivation. However, only an additive effect was observed when pre TT was associated to DHP. An experimental design was carried out using fixed pressure of 200 Mpa followed by mild TT. Temperature and time of thermal treatment and ratio of mango nectar (brix/acidity) was select as experimental design variables. The results indicated that time and temperature affected positively and nectar ratio affected negatively the mold inactivation. By the mathematical model, process of 200 MPa followed by 73.5ºC/10 minutes or by 61.5ºC/20 minutes was able to promote 5 decimal reduction of A. niger. The effect of these processes, the conventional heat and DHP at 300 MPa on vitamin C concentration and nectar color retention was evaluated. The vitamin C losses were around 45% for all processes studied but better color retention was observed on the nectar processed by DHP. The CIP design was considered efficient once it was able to reduce the initial load of A. niger from ~106 CFU.mL-1 to <1 CFU.mL-1. 2.5% of a commercial detergent (active agents: sodium toluenosulfonate and didecylmethilamonium chlorine) and peracetic acid at 0.05% were used in this process. The nectar viscosity reduction was effective by using pectic enzymes and celullase, being able to reduce natural mango nectar viscosity by 50%. The results obtained indicated that DHP isolated or combined with mild thermal treatment are a viable alternative to inactivate A. niger in mango nectar. The process has a negative effect on vitamin C retention. It can be attributed to the oxygen dissolved in mango nectar and also to metals seals of equipment (Be-Cu) which can had promoted an increase in metallic ions concentration in nectar. These ions are pro oxidant of vitamin C, resulting in intense vitamin oxidation / Mestrado / Mestre em Tecnologia de Alimentos

Xylose is an unusual nectar sugar found in the nectar of Protea and Faurea (Proteaceae). Since nectar composition is an important floral characteristic in plant strategies for ensuring reproductive success, the unexplained presence of xylose in Protea nectar prompted this study of the interaction between pollinators and Protea species. Among pollinators that visit Proteaflowers in the south-western Cape Floral Kingdom, South Africa, insects and birds show an aversion to, and are poor assimilators of, xylose, whereas rodents such as Namaqua rock mice Aethomys namaquensis are the only pollinators so far shown to consume xylose willingly, and are able to obtain metabolic energy from this sugar. Mammalian tissues are not capable of catabolizing xylose efficiently, but certain gastrointestinal microflora are, through a process of fermentation which produces short-chain fatty acids used by host animals in oxidative metabolism. I explored mechanisms enabling Aethomys namaquensis to utilize xylose, in particular, the role of resident intestinal microflora in this process. Chapter One discusses pollination syndromes and the definitions thereof, mammal pollination, with particular reference to Australia and South Africa, and explains the rationale behind the questions addressed in this thesis. To assess xylose utilization in wild-caught mice with and without their natural gastrointestinal microflora, an antibiotic treatment was developed (Chapter Two). The veterinary antimicrobial agent, Baytril 10% oral solution, was found to be effective in significantly reducing gut microflora in animals on a four-day treatment protocol. The protocol developed here reduced the gut microflora sufficiently for subsequent experiments comparing xylose utilization in mice with and without intact microflora. Xylose utilization was assessed using 14C-labelled xylose (Chapter Three). Rock mice were caught during Protea humifloraflowering and non-flowering seasons, and fed 14C-labelled xylose. Exhaled CO 2 and excreted urine and faeces were collected, and label recovery determined. These experiments showed that xylose-utilizing bacteria in the rock mouse gut are very important for xylose utilization. More efficient xylose utilization during the flowering season suggests that this component of the gut microflora is inducible. Culturable gut microflora were then isolated from rock mouse faecal and caecal samples, assessed for xylose utilization to identify positive xylose-fermenters and classified by 16S rRNA based taxonomy (Chapter Four). Faecal isolates were Lactobacillus murinus and Enterococcus faecium, and caecal isolates were three Bacillus species, Shigella boydii, one Arthrobacter species and two fungal isolates from Aspergillus and Penicillium genera. The types and concentrations of short-chain fatty acids arising from xylose fermentation by caecal microflora were measured using gas chromatography. The fatty acid profile produced by rock mouse gut microflora is similar to that for other animals that rely on gut microbial fermentation to produce fatty acids then used in oxidative metabolism. Chapter Five concludes with a discussion of possible explanations for the presence of xylose as a nectar sugar, its ecological significance, and the relevance of the fermentative capacity of pollinator digestive systems for xylose utilization in animals. / Thesis (PhD (Zoology))--University of Pretoria, 2007. / Zoology and Entomology / unrestricted