Thesis (M.A.)--Humboldt State University, 2007. / Includes bibliographical references (leaves 38-41). Also available via Humboldt Digital Scholar.

Thesis (Ph. D.)--Ohio State University, 2004. / Title from first page of PDF file. Document formatted into pages; contains xii, 138 p.; also includes graphics. Includes abstract and vita. Advisor: Richard A. Bradley, Dept. of Evolution, Ecology, and Organismal Biology. Includes bibliographical references (p. 124-138).

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.

Experiments were conducted to determine the effects of cultural practices such as irrigation, planting date, and maturity group on soybean nectar production. Multiple interactions between different factors influences the amount of total sugar present in soybean flowers. Pod production was increased in later planted soybean, but later planting resulted in reduction in yield. Another study was conducted to explore the effects that variety selection had on soybean nectar production. Soybean nectar production was highly variable among varieties and was influenced further depending on their growing location. Later maturing varieties produced significantly more soybean pods. This increase in pod production was not reflected in yield, as the later maturing varieties usually yielded less.

Up to 96% of angiosperms are dependent on animal pollinators for successful reproduction thus providing a key ecosystem service. Recent studies however, have indicated that micro-organisms inhabiting floral nectar can influence interactions between plants and their pollinators with consequences for plant fitness. Specifically, floral nectar provides suitable habitat for fungal and bacterial species i.e., the nectar microbiome (NMB), which can alter the amount and quality of nectar, floral volatile composition and impact pollinator preference and plant reproductive success. While the extent and consequences of these interactions are well understood for one or few plant species, community-level studies on the structure, drivers and fitness consequences of interactions between plants and nectar inhabiting microorganism are scarce. Community-level of studies of the drivers and consequences of interactions between plants and nectar microorganisms can help advance our understanding of the mechanisms that mediate the structure of plant-pollinator networks and mediate plant community assembly. In this study, we describe the structure of a plant-nectar microbiome network in a serpentine plant community in Northern California. We further evaluate how the structural properties of such network are mediated by the abundance and diversity of floral visitors and its effects on plant reproductive success. Nectar samples were collected from 15 plant species and cultured on agar plates until isolated. Fungal ITS and bacterial 16s DNA sequences were used for identification by Sanger sequencing. We further explored the effects pollinator visitation on of plant-microbiome network properties and the effects of the latter on pollen deposition and pollen tube production. Plant-nectar microbiome network was composed of 52 fungal and 27 bacterial morphospecies (79 total cultured CFU). Filamentous fungi (i.e. molds) comprise 80% of all fungal colonies. Network analysis also revealed network connectance and specialization were lower (0.07 and 0.39 respectively) than reported for plant-pollinator networks in the same community. On average, individual plants have 2.32 links with modularity and nestedness values of 0.36 and 0.32, respectively, which are comparable to plant-pollinator network values. An increase in diversity of insect visitors species significantly increased NMB richness. Furthermore, increased NMB species richness seemed to have a marginal positive effect on conspecific pollen deposition but nor on pollen tube production. Our results suggest that community-level patterns of NMB composition can be determined by the diversity and abundance of the pollinator community, with potential consequences for plant reproductive success.

No description available.

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

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

Most studies of foraging behavior in bees have been performed under artificial conditions. One highly neglected area is the daily nectar secretion rhythm in flowers including how nectar properties may vary with time of day. As a first step in understanding the connections between forager behavior and nectar presentation under more natural conditions, we examined nectar secretion patterns in flowers of the squash Cucurbita pepo. Under greenhouse conditions, squash flowers exhibit consistent diel changes in nectar volume and concentration through anthesis. These temporal patterns are robust, persisting under field conditions as well as simulated drought conditions in the greenhouse. In the presence of active pollinators, diel patterns are evident but with highly variable, severely reduced volumes. The potential consequences of these factors for pollinator behavior are discussed.

Class of 2009 Abstract / OBJECTIVES: An estimated 26.3 million Americans have Diabetes Mellitus (DM). Currently six classes of agents are approved for the treatments of Type 2 DM. Problems with current options have led to searches for new medications and adjunctive therapy. Prickly pear (Opuntia species) has been traditionally used by Mexicans and Pima Indians for the treatment of DM. This is a retrospective analysis of data obtained from a randomized placebo-controlled prospective experiment in 28 Type 2 DM rodents (ZDF). There were 2 negative control groups which consisted of non-DM rodents and ZDFs; each receiving water. The positive control group consisted of ZDFs who received rosiglitazone 4.75 mg/kg/day. The treatment group consisted of ZDFs who received 5-10 mL/kg/dose of Opuntia ficus indica (Jugo De Nopal) liquid, given twice daily. Weight, blood glucose and platelet aggregation were recorded and analyzed. At baseline, there were no significant differences in weight or blood glucose among ZDF groups. The lean control rodents had significantly lower blood glucose compared to the ZDF rodents (p<0.001). Treatment with Jugo de Nopal resulted in a statistically significant reduction in blood glucose (p<0.001), with a mean decrease in blood glucose of 7%. All treatment groups demonstrated a significant weight gain, however, the prickly pear group had significantly less weight gain than the rosiglitazone group (p=0.028). CONCLUSIONS: There was not a significant difference among the treatment groups with regard to platelet responsiveness. Further studies are necessary to determine the efficacy of prickly pear as a blood glucose lowering agent.