• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 34
  • 25
  • 8
  • 3
  • 3
  • 3
  • 3
  • 2
  • 1
  • Tagged with
  • 102
  • 27
  • 26
  • 23
  • 20
  • 19
  • 17
  • 17
  • 12
  • 11
  • 11
  • 10
  • 10
  • 9
  • 9
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Pollinating insect responses to grazing intensity, grassland characteristics, and landscape complexity : behaviour, species diversity, and composition /

Sjödin, N. Erik, January 2007 (has links)
Thesis (doctoral)--Swedish University of Agricultural Sciences, 2007. / Thesis documentation sheet inserted. Includes appendix of four papers and manuscripts, two co-authored with others. Includes bibliographical references. Also issued electronically via World Wide Web in PDF format; online version lacks appendix.

Pollinators of slender white prairieclover

Pearce, April Marie. January 2008 (has links) (PDF)
Thesis (MS)--Montana State University--Bozeman, 2008. / Typescript. Chairperson, Graduate Committee: Kevin O'Neill. Includes bibliographical references (leaves 95-102).

Nectar in nicotiana pollinator associations, sources of variation, and evolutionary consequences /

Kaczorowski, Rainee L., January 2007 (has links)
Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on September 25, 2007) Vita. Includes bibliographical references.

Frequency-dependent selection amongst floral variants through the foraging behaviour of bumblebees, Bombus terrestris

Smithson, Ann January 1995 (has links)
No description available.

Monitoring, assessing and evaluating the pollinator species (Hymenoptera: apoidea) found on a native brush site, a revegetated site and an urban garden

Cate, Carrie Ann 15 May 2009 (has links)
This research presents the findings of a pollinator diversity study that took place at three study sites. Although variation in pollinator diversity occurred between the three sites, fewer pollinators than expected were recorded from the La Joya Tract (revegetated site). Numerous genera and species were recorded from the Havana Tract (native site) as well as the Valley Nature Center (urban garden). In contrast, the La Joya Tract had a comparatively depauperate pollinator fauna. The numbers of pollinator genera and species recorded from the three study sites were decreased in comparison to the total number of genera and species recorded from Hidalgo County. Hidalgo County has 35 known genera and 75 species of bees documented to date. About 40% of the genera and 23% of the species recorded from Hidalgo County were recorded from the Havana Tract in this study, while a mere 8.5% of the genera and 4% of the species were reported from the La Joya Tract and 34% of the genera and 16% of the species were reported from the Valley Nature Center. Although the vascular plant species identified from these study sites were diverse, the floral rewards they provided yielded an insight as to what was going on in terms of pollinator diversity. Plants may yield nectar or pollen floral rewards or both in some cases to pollinators. The current study provides evidence that revegetation of land with plants that primarily provide nectar rewards will result in fewer observed bee taxa than from land revegetated with plants that provide a mix of nectar and pollen floral rewards.

Nectar in Nicotiana : pollinator associations, sources of variation, and evolutionary consequences /

Kaczorowski, Rainee L. January 2007 (has links) (PDF)
Thesis (Ph. D.)--University of Missouri-Columbia, 2007. / Includes bibliographical references. Also available in PDF format via the Internet.

Forest fragmentation and plant-pollinator interactions in Western Kenya /

Bergsdorf, Thomas. Unknown Date (has links)
Thesis (doctoral)--Universität Bonn, 2006. / Includes bibliographical references (leaves 88-93). Also available via the internet.

The feeding response of white-bellied sunbirds (Cinnyris [Nectarinia] talatala) to sugar concentration and viscosity of artificial nectar

Leseigneur, Carolina Del Carmen 19 November 2008 (has links)
Plant nectar is a simple food and is easily digested by many different species of pollinators. Many compounds make up the composition of floral nectars, but the most abundant are sugars, generally dominated by sucrose and the hexoses, glucose and fructose. Nectar sugars have been measured for many plant species visited by hummingbirds, sunbirds and other passerines, revealing a range of concentrations. The nectars of passerine-pollinated flowers are generally dilute compared to those of bee-pollinated flowers. The question why bird nectars are so dilute has been addressed in many studies. Many hypotheses have been proposed, among them the relationship between viscosity and drinking by birds. The viscosity of sugar solutions increases exponentially with increasing concentration, and capillarity is inversely proportional to viscosity. Nectarivorous birds imbibe nectar by capillarity, and high sugar concentrations could impose constraints on their feeding efficiency. Feeding in nectarivorous birds, especially hummingbirds, has been mostly devoted to assessing sugar type preferences. However, concentration preferences have received less attention, and the effect of viscosity on feeding has not been examined separately from sugar concentration for any bird species. Do nectarivorous birds show a preference for specific concentrations at a broad and a fine scale of difference, given a specific sugar type? Does viscosity impose a feeding limitation on nectarivorous birds? Does it affect their feeding behaviour? Sunbirds and other nectar-feeding birds can choose amongst various flowering plant species at any one time. Their feeding responses may have important consequences on pollination ecology. In this study, concentration preferences of white-bellied sunbirds were examined using paired solutions of either sucrose or equicaloric 1:1 mixtures of glucose and fructose, at a both a broad and a fine scale of difference between pairs over the concentration range of 0.25 to 2.5 M. I hypothesized that sunbirds would prefer concentrations of 1 M and higher on sucrose solutions, while preferring concentrations less than 1 M on hexose solutions. On both sugar types at the broad scale, the higher concentration was significantly preferred up to 1 M, suggesting a preference for 1 M sugar solutions. At a finer scale, white-bellied sunbirds were able to discriminate 0.03 and 0.05 M (1 and 2% w/w) concentration differences between sucrose and hexose solutions respectively. This discrimination is similar to that reported at low concentrations for other passerine nectar-feeders, and at higher concentrations for hummingbirds. To determine if high viscosity nectars limit the sugar intake of avian nectar consumers, white-bellied sunbirds were exposed to three different test series of sucrose solutions: control series (CS, pure sucrose 0.25 – 2.5 M), constant viscosity series (CVS, 0.25 – 0.7 M with increased viscosity equivalent to that of 1 M sucrose) and constant concentration series (CCS, 1 M with increased viscosities equivalent to that of 1.5, 2 and 2.5 M sucrose). Viscosities were artificially altered with Tylose®. The sunbirds had reduced intake rates and gained less energy on more viscous sucrose solutions. Also, sunbirds did not alter their feeding behaviour (feeding frequency, feeding duration, total feeding duration and feeding interval) in any significant way when feeding on more viscous sucrose solutions. This lack of change in feeding behaviour led to lower sugar intake rates and sugar consumption. These results suggest that sunbirds suffer a preingestional limitation when consuming nectars with viscosities higher than those due to sugar concentration alone. / Dissertation (MSc)--University of Pretoria, 2010. / Zoology and Entomology / unrestricted


Larson, Jonathan Lane 01 January 2014 (has links)
Turfgrass settings, including lawns, golf courses, and sports fields, support many beneficial invertebrates that provide important ecosystem services. These non-target organisms and their associated predation, decomposition, and pollination services can be disrupted by the use of certain insecticides. I compared the ecotoxicity of representatives from three major turf insecticide groups, the neonicotinoids, premix formulations, and the anthranilic diamides, in lab and field realistic settings in order to inform industry initiatives towards environmental sustainability. In lab and field bioassays clothianidin, a neonicotinoid, and a premix clothianidin/pyrethroid spray were acutely toxic to beneficial insects. Populations of predators, springtails, and earthworms, as well as parasitism, predation, and decomposition rates were all reduced. In contrast, chlorantraniliprole, a novel anthranilic diamide with a similar spectrum of pests controlled, had no apparent impact on natural enemies, decomposers, or ecosystem services. This newer class is a good fit for industry initiatives to use relatively less toxic pesticides, with the caveat that golf course superintendents may see secondary pest outbreaks of ants and earthworms. Bumble bee colonies exposed to clothianidin-treated white clover for two weeks suffered acute effects including increased mortality of workers and decreases in the number of honeypots constructed in the hive. When hives were exposed to clothianidin treated clover for six days and then allowed to develop naturally over six weeks they exhibited delayed weight gain and produced no new queens. Colonies exposed to chlorantraniliprole-treated flowers suffered no observable adverse effects. When treated blooms were mowed, colonies exposed to newly-formed blooms exhibited no ill effects. After a single mowing neonicotinoid residues in clover nectar were reduced from > 2000 ng/g, to < 10 ng/g. Residues of imidacloprid were also short-lived in guttation water. Some 50 species of bees and other pollinators were collected from flowering white clover and dandelions in lawns across an urbanization gradient. Such weeds, an underappreciated resource for urban bees, could play a role in pollinator conservation if tolerated and not over-sprayed with broad-spectrum insecticides. Informing the public about the potential benefits these weeds could have for pollinators may help lead to more environmentally conscious management decisions.

Nesting aggregation as a Determinant of Brood Parasitism in Mason Bees (Osmia spp.)

Groulx, Adam January 2016 (has links)
Identifying forces that affect population dynamics can allow us to better understand the distribution and abundance of animals. Both top-down and bottom-up factors can significantly influence animal populations. Mason bees (members of the genus Osmia; Hymenoptera: Megachilidae) are important pollinators for agricultural systems and are vulnerable to exploitation by brood parasites, such as kleptoparasitic wasps. High levels of nesting density have the potential to increase rates of brood parasitism by attracting larger numbers of parasites to areas with aggregations of nests. I conducted a field study in subalpine meadows at the Rocky Mountain Biological Laboratory in Colorado, USA, to assess whether mason bees suffer increased brood parasitism as the size of nesting aggregations increases. Mason bees were allowed to nest in artificial nest boxes and establish natural variations in numbers of nesting individuals within nest boxes. Nest cells constructed by bees were then checked for the presence of kleptoparasite larvae shortly after they were completed. Overall, nest cells constructed in blocks containing multiple active bees were significantly more likely to be oviposited in by brood parasites compared to cells constructed in blocks with fewer active nesting bees. This suggests that gathering in large aggregations for nesting can negatively affect populations of mason bees, given the high levels of brood parasitism observed in areas of high nesting density. In addition, the last nest cell in mason bee nests was significantly more likely to be parasitized than inner cells, suggesting bees may be abandoning nests that are parasitized, representing a potential defensive response of bees to brood parasitism. These results have implications for the management of mason bees as agricultural pollinators, as cultivating them in large groups could reduce their survival.

Page generated in 0.0722 seconds