This thesis investigates the influence of hedges and roads (linear landscape features) on the patch-to-patch foraging movements of insect pollinators and consequent pollen- mediated gene flow in white clover, Trifolium repens. Experimental arrays were located within the lowland UK agricultural landscape incorporating a range of patch separation distances from 25m to 250m (using both artificial and natural linear features). Mark-re-sight, “residence” (the number of visits per foraging bout) and pollen transport observations were used to observe pollinator movement characteristics between experimental patches and re-parameterise an existing model of patch-to-patch gene flow. Levels and directions of plant gene flow were observed with phenotypic and isozyme markers, allowing validation of model predictions. Harmonic radar technology was used for the first time to track butterfly flight paths; data support the hypothesis of a 150 to 200m perceptual range, and non-random flight direction but limited association to wind direction, hedges, tracks or fence lines. Mark-re-sight observations indicated similar levels of patch visitation regardless of patch location, and trap-lining by Bombus spp. only between patches 50m or less apart. A single track road significantly enhanced gene flow between connected patches and was not a barrier to gene flow across it. In contrast, a hedge did not facilitate enhanced gene flow between connected patches and was a partial barrier where it occurred between patches. Model predictions of gene flow (1.3%, range 0.8 to 2.5%) agreed well with observed levels (ranging from 0.2 to 31.4%). It is proposed that pollinator movement observations alone could not provide an accurate means of estimating low level gene flow unless the variables of residence and pollen carryover were also considered. The possible influence of spatial and temporal variables including the role of hetero-specific forage on pollinator foraging movements and consequent plant gene flow from the local to landscape scale is also discussed

Habitat restoration is an important tool in reducing the current decline in biodiversity. To determine the success of restoration, ecologists have previously focused on species richness or on the presence of rare species; little is known of species interactions. This study examines both the potential of restored landfill sites to support pollinating insects and how flower-insect interactions can be used in determining successful restoration. These are important attributes of ecosystem function. Standard belt transects were used to record flowering insect pollinated plants and flower-visiting insects on nine paired restored landfill and reference nature sites, in the broader Northamptonshire region (UK). Over the duration of this study, an area of 25,000m2 was surveyed for floral characteristics and approximately 138,000 floral units were counted from 98 plant species. A total of 201 flower visitor surveys were performed, with 942 flower-visiting insect samples taken. Flowering plant species richness and abundance of floral resources on restored landfill sites were not found to be significantly different from those on reference sites and the flower-visiting insect assemblages were similar in terms of species-richness and abundance. Interaction structures were examined and whilst the plant-insect assemblages had few species in common, both showed similar levels of nestedness and connectance. The differences in the species but similarity in the functioning of these assemblages emphasise the importance of examining interaction structures within a functional approach to the evaluation of restoration. There are 2,200 landfill sites in England and Wales covering some 28,000 ha, and this study highlights that their restoration can potentially provide an important resource for the conservation of pollinating insects and the services that they provide for both natural and agricultural plants.

Thesis (MScAgric)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: In South Africa tomato production in greenhouses normally occurs out of season when conditions are unfavourable for production and for the pollination process. Pollination is of special importance and the backbone of production. High temperatures contribute to the formation of abnormalities in flower morphology such as splitting of the anther cone and style exsertion. Low temperatures inhibit growth of the anther cone and therefore the style is uncovered. The movement of pollen from the anther to the style is inhibited by the higher style position in relation to the anther cone. Under humid conditions the pollen tends to stick to the anther surface. Another factor contributing to the problem is the banning of European bumble bees in South Africa. Alternative methods of pollen transport have to be found. Truss vibration, honey bees and plant growth regulators (PGR) are the most popular alternatives. Truss vibration and the use of PGR's are labour intensive and honey bees tend to get disorientated inside a plastic greenhouse. During the first part of this study pollen from plants, grown at four different B-levels (0.02; 0.16; 0.32 and 0.64 mg rl) was germinated in vitro. It was kept at different temperatures and periods before incubating on different growth media. No proof was found that pollen from B-deficient plants germinated poorly. Germination of pollen decreased significantly after one week storage. Deterioration of pollen viability could be lowered by storage at 5°C. At least 10% sucrose is needed in the growth medium for in vitro germination but addition ofB had no positive effect. In a second phase of the study, the influence of the mentioned B application rates were tested. The experiment was done in a glasshouse where temperatures were mechanically regulated (22°C and 10°C day/night). Seedlings of the greenhouse tomato cultivar, Abigail, were planted in acid washed river sand. Plants were grown with the main stem trellised vertically and the side shoots removed weekly. Only the first, third and fourth cluster were used for this part of the study. The uptake of all the essential nutrient elements, fruit set, the relation of larger to smaller fruits, physical and chemical quality and fruit shelf life were evaluated. The application of B at higher rates increased the uptake of Ca and decreased K-uptake. Fruit set, fruit development, fruit color and shelf life were the best at a B-Ievel of 0.16 mg r'. At this rate the abortion of flowers was the least. The same plants were used for the second part of the study, using the third cluster. The influence of the same four B-Ievels, the relative humidity (RH) of the truss atmosphere and truss vibrations were tested. The second cluster was covered with a plastic bag. Dry {<I 0% relative humidity (RH)}, normal {60-7S% RH} and moist {8S-97% RH} air were constantly applied to the bags at ± 50 ml min-I. As a third factor, truss vibration was applied daily by means of an electric vibrator (polli-bee), The amount of flowers per cluster, fruits per cluster, fruit set, weight of the cluster (yield), fruit weight, seed production, fruit weight per amount of seeds formed and fruits with blossom-end-rot (BER) were evaluated. The application of higher B-Ievels, air with the normal RH and the vibration of the clusters positively affected fruit weight, weight of the cluster and fruit set. High RH increased the occurrence of BER, probably due to a lack of transpiration from the fruit surface and therefor a lack in Ca translocation. / AFRIKAANSE OPSOMMING: Die verbouing van kweekhuistamaties in Suid-Afrika geskied meestalonder toestande wat ongunstig is vir produksieprosesse en veral die bestuiwingsproses wat die basis van produksie is. Onder toestande van hoë temperature is die voorkoms van afwykings in die blommorfologie (gesplete meeldraadbuis en verlengde styl) algemeen. Net so, onder toestande van lae temperature, sal gebrekkige groei van die meeldraadkrans ook tot die blootstelling van die stempel lei. Die oordraging van die stuifmeel vanaf die helmknop na die stempel word hierdeur benadeel. Tydens humiede toestande mag vasklewing van stuifmeel aan die helmknoppe ook die beweging van stuifmeel belemmer. 'n Verdere faktor wat tot die probleem bydra is die verbod op die invoer van hommelbye uit Europa. Alternatiewe metodes vir oordraging van stuifmeel moet dus gevind word. Trosvibrasie, heuningbye en die gebruik van plantgroeireguleerders (PGR's) is die mees populêre alternatiewe. Trosvibrasie met 'n 'polli-bee' en die aanwending van PGR's is arbeidsintensief. Heuningbye ondervind navigasieprobleme in plastiek kweekhuise en is nie so effektief as hommelbye nie. Tydens die eerste fase van die ondersoek is stuifmeel vanaf plante, wat by vier verskillende Bvoedingspeile (0.02; 0.16; 0.32 en 0.64 mg rl) verbou is, versamel en in vitro ontkiem. Dit is by verskillende temperature en periodes opgeberg en op verskillende media vir ontkieming geïnkubeer. Geen bewyse kon gevind word dat stuifmeel vanaf B-gebrekkige plante swak ontkiem nie. Kiemkrag van stuifmeel het na sewe dae opberging betekenisvol verswak. Verswakking in kiemkrag kon beperk word deur die stuifmeel by SoC op te berg. 'n Ontkiemingsmedium met ten minste 10% sukrose is vir goeie in vitro ontkieming van stuifmeelkorrels nodig terwyl die byvoeging van B geen voordelige effek getoon het nie. Tydens die tweede gedeelte van hierdie ondersoek is die invloed van die genoemde vier B-voedingspeile ondersoek. Die ondersoek is in 'n glashuis, waarvan die temperature meganies beheer is (22°C en 10°C dag/nag), uitgevoer. Plantmateriaal van die kweekhuistamatiekultivar, Abigail, is in suurgewasde riviersand geplant. Hoofstamme is vertikaalopgelei en die sylote is een maal per week uitgebreek. Die eerste, derde en vierde bloeiwyses is vir die ondersoek gebruik. Die opname van al die essensiële voedingselemente (blaarontledings), vrugset, die verhouding van groot vrugte tot kleiner vrugte, fisiese en chemiese kwaliteite van die vrugte en die raklewe daarvan is ge-evalueer. Die toediening van B teen hoër peile het die opname van Ca ten koste van K bevoordeel. Die beste resultate ten opsigte van vrugset, vrugontwikkeling, vrugkleur en die houvermoë (raklewe) van die vrugte is verkry teen 'n B-toedieningspeil van 0.16 mg.l'. Vir die derde gedeelte van die ondersoek is die tweede tros van dieselfde aanplanting gebruik. Die invloed van die vier B-voedingspeile, relatiewe humiditeit (RH) van die omgewing rondom die tros en trosvibrasie is ondersoek. Die tweede bloeiwyse is met 'n deursigtige plastieksakkie bedek. Droë {dO% relatiewe humiditeit (RH)}, normale {60-75% RH} en vogtige {85-97% RH} lug is teen 50 ml min-1 oor die tros gestuur. Trosvibrasie is as derde faktor teen twee peile gebruik deur trosse daagliks met 'n elekriese vibreerder ("polli-bee') te vibreer. Die aantal blomme per tros, vrugte per tros, vrugset, trosmassa (opbrengs), vrugmassa, aantal sade, vrugmassa per saad en blom-end-verrotting (BER) is ge-evalueer. Die toediening van hoër B-voedingspeile, 60-75% RH lug en trosvibrasies het vrugmassa, trosmassa en vrugset bevoordeel. Hoë lugvog het die omvang van BER verhoog, waarskynlik weens 'n gebrek aan transpirasie vanaf die vrugoppervlakke wat aanleiding tot 'n beperking in translokasie van Ca kon gee.

Recently, it was hypothesized that pollinator selectivity for large inflorescences has led to the evolution of monocarpic reproduction in agaves. To test this hypothesis, fruit set and stalk length data were collected for six species of paniculate agaves and two species of spicate agaves. Regression results, for all of the paniculate species and for one species of the spicate agaves, showed no significant correlation between fruit set and stalk length. These results do not support the pollinator selectivity hypothesis. The validity of the assumptions was then examined, utilizing the results from hand pollination, pruning, and tie down experiments. These results imply that factors other than pollinator availability might be important in determining fruit set in agaves. In an effort to determine the relative importance of resource and pollinator limitation to fruit set in Agave chrysantha, three treatments were applied to entire plants: (1) natural pollination, (2) natural and hand pollination, and (3) hand pollination. When fruits were collected, there were no significant differences between percent fruit set for the three treatments, implying that fruit set is not limited by the availability of pollinators. When additional plants were pruned to reduce the total number of flowers by approximately one-half, thereby doubling the amount of resources available to each flower, the percent fruit set was twice that for control plants, implying that percent fruit set is energy limited. It is common for plants that exhibit resource limited fruit set to have relatively low fruit-to-flower ratios. This is surprising, since it appears that the resources expended for production of these "excess flowers" could be allocated to fruit maturation and thereby increase fruit production. Four hypotheses explaining the fruit set in Agave mckelveyana are tested. Results from pruning, bagging, and hand pollination experiments indicate that the apparently "excess flowers" do not contribute to fruit production (female fitness). Additional data on nectar production imply that these flowers act primarily as pollen donors and contribute only to male fitness. The importance of pollen donation (male fitness) in determining fruit set is examined for hermaphroditic, monecious, and dioecious plants.

The evolution of wind pollination (anemophily) has occurred at least 65 times in the flowering plants and over 10% of angiosperm species are wind pollinated. However the pollination and mating of anemophily species is poorly understood, particularly in comparison with animal-pollinated species. My thesis employs a range of approaches and tools to examine the evolution and ecology of wind pollination. These include comparative analyses, theoretical modeling, field and glasshouse experiments, the use of genetic markers and quantitative genetics. Experimental studies on diverse taxa were used to address questions concerned with the efficacy of outcrossing mechanisms, the ecological and demographic context of pollination and mating, and the plasticity of sex allocation. Comparative analyses indicated that wind pollination is correlated with unisexual flowers, reduced ovule number, small unshowy flowers, an absence of nectar, and open habitats. These analyses also demonstrated that anemophily originates more often in lineages with unisexual flowers. This suggests that wind pollination evolves in diclinous taxa as a mechanism of reproductive assurance because autonomous selfing is mechanically precluded. Empirical data on stigmatic pollen loads in 19 anemophilous species challenge the widespread assumption that anemophilous plants commonly have uniovulate flowers because they capture few pollen grains. Further, a model based on floral costs and the aerodynamics of pollen capture demonstrated that when flowers are inexpensive it is optimal to produce many flowers each with few ovules, because this allows more efficient sampling of the airstream. Manipulative field experiments on seven Carex species indicated that neither monoecy nor protogyny, two putative outcrossing mechanisms, are effective at limiting selfing. Based on these results I suggest that geitonogamy can provide reproductive assurance in anemophilous species with unisexual flowers. Field experiments and the application of sex-specific markers in Rumex nivalis revealed that the local neighbourhood of maternal plants affects pollination intensity and progeny sex ratios. Finally, I demonstrated that plant density in Ambrosia artemisiifolia affects stigmatic pollen loads but not outcrossing rates. Through a quantitative genetics experiment in A. artemisiifolia, I detected significant genetic variation for plasticity in sex allocation, potentially enabling adaptive adjustment of sex allocation to local environmental conditions.

No description available.

Conclusions This thesis provides detailed insight into plant-animal relationships that are involved in reproduction of inselberg species. The results are interpreted in relation to the ecosystem functioning and they also contribute to the general knowledge on specialization in plant-animal interactions (Chapter 2 and 3), floral resources (Chapter 2, 3, and 5), pollinators' attraction (Chapter 2), relations between diaspore's characteristics and animal dispersal (Chapter 4), and conflicts among plant life stages that follow ovule fertilization (Chapter 4). As Clusia aff. sellowiana dominates the shrub vegetation, the study on its reproduction is the initial step to understanding the dynamics of the shrub patches and potential succession on the inselberg. The nocturnal pollination system of Clusia aff. sellowiana bears unusual characteristics and signs of specialization. Only one pollinator species, a cockroach Amazonina platystylata, was recorded and this species is apparently sensitive to olfactory attraction cues emitted by the flowers. This is the first evidence of pollination system that involves cockroaches as pollinators and is to some degree specialized. Clusia aff. sellowiana is dispersed by small birds. Because its diasporas are consumed by birds and there is a time lag before they are deposited,...

The bumblebees (genus Bombus) are an ecologically and economically important group in decline. Their decline is driven by many factors, but parasites are believed to play a role. This thesis examines the factors that influence the diversity and distribution of multihost viruses in bumblebees using molecular and modelling techniques. In Chapter 2, I performed viral discovery to isolate new multihost viruses in bumblebees. I investigated factors that explain prevalence differences between different host species using co-phylogenetic models. I found that related hosts are infected with similar viral assemblages, related viruses infect similar host assemblages and related hosts are on average infected with related viruses. Chapter 3 investigated the ecology of four of the novel viruses in greater detail. I applied a multivariate probit regression to investigate the abiotic factors that may drive infection. I found that precipitation may have a positive or negative effect depending on the virus. Also, we observe a strong non-random association between two of the viruses. The novel viruses have considerably more diversity than the previously known viruses. Chapter 4 investigated the effect of pesticides on viral and non-viral infection. I exposed Bombus terrestris colonies to field realistic doses of the neoticotinoid pesticide clothianidin in the laboratory, to the mimic pulsed exposure of crop blooms. I found some evidence for a positive effect of uncertain size on the infection rate of pesticide exposed colonies relative to non-pesticide exposed colonies, a potentially important result. Chapter 5 explored the evolution of avirulent multihost digital organisms across fluctuating fitness landscapes within a discrete sequence space. Consistent with theory, I found that evolution across a fluctuating discrete landscape leads to a faster rate of adaptation, greater diversity and greater specialism or generalism, depending on the correlation between the landscapes. A large range of factors are found to be important in the distribution of infection and diversity of viruses, and we find evidence for abiotic, biotic and anthropogenic factors all playing a role.

No description available.

Thesis (M.Sc. Agric. (Crop Science)) --University of Limpopo, 2013 / The study aims to provide insights into the nature and extent of development funding provided to various poverty eradication projects by the National Development Agency (NDA) and its subsequent impact on reducing poverty in the predominantly rural communities of the Makhuduthamaga Municipality in the Limpopo Province. It examines in detail the impact made by the NDA on community development through the disbursement of funds to poverty eradication projects. It also provides insights into the total number of the NDA-funded projects and the total proportion of the NDA-funds allocated to them in the Makhuduthamaga Municipality. The study further examines the nature of the NDA support regarding the design of the interventions, relevance, participation of communities, delivery modalities and sustainability. The effectiveness of the NDA-funded projects in community development is determined using employment opportunities created, income generated, skills transferred, assets accumulated, sustainability mechanisms and community empowerment indicators. Although all of these indicators are found to be tightly linked to the NDA’s mandate of poverty eradication, the extent to which the NDA has achieved its objectives in disbursing development funding earmarked for poverty eradication and strengthening of CSOs was yet to be determined, hence the relevance of this study. The study, therefore, highlights key issues regarding the types of employment opportunities created and levels of income emanating from the NDA-funded projects. The study further highlights various areas of community empowerment, financial and sustainability measures put in place for the sustainability of the NDA-funded projects. Using a combined method of research, that is the qualitative and quantitative case study approach, the study highlights in detail insights into the impact made by the NDA on community development, particularly on Makhuduthamaga Municipality. The study highlights that while the NDA made some strides in the creation of employment opportunities, income generation, food security and community empowerment, both financial and institutional sustainability proved to be a daunting challenge for the NDA-funded projects Tailor-made and accredited training interventions coupled with the introduction of market-driven products to the NDA-funded projects as opposed to heavy reliance on donor funding will go a long way in bringing about productivity and, most probably, positive balance sheets and the maximum impact on the NDA funded projects.