Thesis (doctoral)--Universität, Bonn, 2002. / Includes bibliographical references (p. 138-152).

Thesis (M.U.D.)--University of Hong Kong, 1995. / Includes bibliographical references (leaves 74-75) Also available in print.

Thesis (Ph. D.)--University of Hong Kong, 2006. / Title proper from title frame. Also available in printed format.

The vast majority of flowering plants rely on pollinators for outcrossed reproduction. Unfortunately, many species of pollinators are in decline. Pollinators face a number of challenges, including shifting land use, climate change and pesticides. In addition, pollinator habitat may be altered or eliminated through urbanization. Fragmented urban landscapes may lengthen the distances among foraging patches, limit resources in a given patch, and reduce the availability of pollinator nesting sites. Here, I examine the effects of urbanization on pollination services by addressing the following questions: (1) Does bee species richness and/or abundance change along an urbanization gradient?; (2) Does the pollen limitation of a focal species vary along the same gradient?; (3) Do plants with a mixed mating system produce more selfed seeds in more urban environments? Using the percentage of impervious land cover in the space immediately surrounding the site as a proxy for site urbanization, 15 study sites were set up across the city of Ottawa to span a range from minimal percent impervious surface (mostly green space) to mostly impervious surface (little green space) at a range of spatial scales. At each site I set up an array of 20 potted Impatiens capensis plants as well as six pan traps in order to collect data on pollen limitation, seed production, and the number of selfed progeny, in addition to information about local pollinator species richness and abundance. Plants in the arrays were randomly assigned to either a hand or open pollination treatment in order to assess the level of pollen limitation. Surprisingly, pollinator species richness and abundance were not correlated with urbanization. Pollen limitation declined with urbanization, however, so did overall seed set, making it difficult to detangle the effects of resource limitation and hand pollination treatments. The number of selfed seeds produced by a plant was also significantly correlated with site urbanization. Further investigation is required to better understand the dynamics of pollination services in urban environments. I recommend that future studies explore how the presence of individual bee species in rural and urban habitats could be influencing pollen limitation and selfing in I. capensis.

abstract: The aboveground surfaces of plants (i.e. the phyllosphere) comprise the largest biological interface on Earth (over 108 km2). The phyllosphere is a diverse microbial environment where bacterial inhabitants have been shown to sequester and degrade airborne pollutants (i.e. phylloremediation). However, phyllosphere dynamics are not well understood in urban environments, and this environment has never been studied in the City of Phoenix, which maintains roughly 92,000 city trees. The phyllosphere will grow if the City of Phoenix is able to achieve its goal of 25% canopy coverage by 2030, but this begs the question: How and where should the urban canopy expand? I addressed this question from a phyllosphere perspective by sampling city trees of two species, Ulmus parvifolia (Chinese Elm) and Dalbergia sissoo (Indian Rosewood) in parks and on roadsides. I identified characteristics of the bacterial community structure and interpreted the ecosystem service potential of trees in these two settings. I used culture-independent methods to compare the abundance of each unique bacterial lineage (i.e. ontological taxonomic units or OTUs) on the leaves of park trees versus on roadside tree leaves. I found numerous bacteria (81 OTUs) that were significantly more abundant on park trees than on roadside trees. Many of these OTUs are ubiquitous to bacterial phyllosphere communities, are known to promote the health of the host tree, or have been shown to degrade airborne pollutants. Roadside trees had fewer bacteria (10 OTUs) that were significantly more abundant when compared to park trees, but several have been linked to the remediation of petroleum combustion by-products. These findings, that were not available prior to this study, may inform the City of Phoenix as it is designing its future urban forests. / Dissertation/Thesis / Masters Thesis Sustainability 2016

This research focusses on observing and modelling the suburban surface energy balance. The initial objective is to use measurements to elucidate the controls on the size and temporal variability of the latent heat flux. This is achieved by synchronous observations of suburban and rural energy balances. On the basis of this comparison it is proposed that the day-to-day variability of the partitioning of the suburban turbulent fluxes is linked both to larger-scale atmospheric influences and variations in the energy and moisture availability within the suburban 'canopy'. This hypothesis is examined through measurement and modelling. Further observations of the suburban energy balance components reveal that the size of the Bowen ratio is linked to the surface moisture availability. This is comprised of soil moisture variations in unirrigated greenspace areas and also the anthropogenic influence of lawn irrigation. However, in addition to this, the day-to-day variability of the Bowen ratio is a function of an advective influence upon the saturation deficit in the surface and mixed-layers. The mechanisms which determine this relationship are identified as meso-scale advective effects resulting from differing land-uses. This influences the nature of the mixed-layer and hence surface fluxes. In light of this interaction of scales and atmospheric processes, a model is developed that couples advectively-dominated mixed-layer dynamics with surface-layer exchanges of heat and mass. The acronym for the model is SCABLE, Suburban Canopy and Boundary Layer Evaporation model). It predicts the diurnal evolution of the mixed-layer depth, temperature and humidity. The saturation deficit of the mixed-layer is an input to the surface evaporation model. In turn this enables the surface sensible heat flux to be calculated from the surface energy balance (using measurements of the available energy). This modelled surface sensible heat flux drives the growth of this mixed-layer and thus the rate of entrainment from the capping inversion. The temperature and moisture structure of the mixed-layer is determined by both inputs from the surface-layer, and from the "free" atmosphere. The suburban canopy evaporation sub-model is based on the 'big leaf' Combination model, with a parameterisation scheme for the surface and aerodynamic resistances based upon the approaches taken by Shuttleworth (1976, 1978). The model performs adequately for simulating the day-to-day variability of the saturation deficit and surface evaporation. Its performance on an hourly basis indicates that the model weaknesses lie in the simulation of the diurnal behaviour of the surface resistance and potential temperature of the mixed-layer. It is concluded in the thesis that such an approach is necessary and valid for predicting and understanding the evaporation regime in areas the size of suburbia. This is especially true where there is likely to be a combination of factors determining the surface evaporation rate. / Arts, Faculty of / Geography, Department of / Graduate

Coastal cities have impacted negatively on freshwater and marine ecosystems - primarily through habitat loss, fragmentation and pollution. Globally, it has been found that otter's dependence on these ecosystems exposes them to a myriad of threats, including loss of habitat, human-wildlife conflict and the bioaccumulation of toxic pollutants. The Cape clawless otter, Aonyx capensis, is the most widely distributed otter species in southern Africa and persists in human-modified habitats, including large cities. The Cape Peninsula provides a unique opportunity to study the impacts of urbanisation on otters as it presents a gradient from densely populated urban areas in the north (City of Cape Town) to sparsely populated areas interspersed with large expanses of natural habitat (Table Mountain National Park) in the south. In this thesis, I investigate the distribution, diet and threats to otters living on the Cape Peninsula. I use sign-based occupancy surveys to determine both broad and fine scale drivers of otter presence within the Peninsula's river systems and predicted that otters would avoid densely populated urban areas and rivers or sections thereof that are heavily transformed and polluted. I collected spraint from living otters and vibrissae from dead otters to investigate their diet. I predicted that otters would show an increased reliance on marine foods in areas where freshwater habitats were degraded in addition to seasonal variation in diet associated with the marked seasonal variation in rainfall and primary productivity typical of temperate Mediterranean ecosystems. I explored both immediate and long-term threats to otters by collating all records of conflict, injury and mortality reported over 5 years in addition to determining PCB levels from road-killed otters. Contrary to my predictions, otters did not avoid urban areas, and were more frequently detected in transformed lowland freshwater river systems close to Marine Protected Areas (MPA). Within rivers otters avoided the relatively pristine, yet unproductive, upper reaches of rivers as well as canalised sections and those with consistently high E.coli counts. I found that otters were feeding on both marine and freshwater prey in both polluted and nonpolluted systems. Where large, transformed lowland wetlands were in close proximity to MPAs, otter diet consisted largely of a combination of freshwater crabs and exotic fish from the polluted systems as well as marine fish and rock lobster from the relatively unpolluted MPA. Isotope results complemented the faecal analyses and confirmed that otters show significant variation in diet between seasons, sites and individuals, suggesting an opportunistic and generalist foraging strategy. Importantly, the dietary results reinforce the distribution model that otters rely heavily on the interface between coastal and lowland wetland and river ecosystems close to the MPA, for both foraging and breeding habitat. However, these are the areas that are transformed and heavily impacted by urban development, and therefore the area where otters would most likely be at risk. I developed a hotspot map of otter conflict across the Peninsula and found that the Peninsula otter population experiences low to moderate levels of conflict throughout most of their current range. High conflict areas are associated with optimal habitat that has been fragmented by canalisation and urban development. Road-killed otters showed signs of accumulation of PCBs in liver tissue suggesting that despite otters being adaptable generalists, their dependence on polluted freshwater systems may have long-term health impacts. Mitigating these threats is possible with improved urban planning, waste water treatment and education of the public. However the success of these approaches requires long-term monitoring which is unlikely to be prioritised by resource constrained conservation authorities. I thus explored whether the large citizen science community in Cape Town can be used to monitor the population. I used Maxent to model otter distribution using citizen reported sightings over 5 years and compared the results with the occupancy model outputs. The predicted Maxent distribution mirrored that provided by occupancy models, and highlighted further areas of suitable otter habitat and routes for dispersal. Together my findings suggest that Cape clawless otters, like many other meso-carnivores in South Africa and globally, display a remarkable ability to adapt to human-modified environments using the interface between degraded freshwater systems and the inshore region to feed on a diverse range of prey. Of concern are the moderate to high levels of conflict with people and dogs, vehicle accidents and the accumulation of toxins. Long-term monitoring of the population and the effect of proposed interventions can be achieved by creating a platform for citizen sightings to be recorded in perpetuity at low cost. This platform can also serve as tool for educating the public on the global challenges of conserving biodiversity within and adjacent to large cities.

This thesis engages with urban ecology through the lens of garden amphibians within a community in Cape Town. The study explores habitat and maintenance features associated with amphibian presence and the social processes underpinning attitudes towards amphibians, with the aim of strengthening knowledge underpinning the "what" (knowledge of natural requirements), "Why" (social drivers for urban landscape form and management), and the "how" (working with people, for garden biodiversity initiatives. To explore the "Why" component, a social survey was conducted with 192 members of the community. One‐way anova and correspondence analysis were used to explore the relationship between values, culture, knowledge and memories of early childhood experiences against a general attitude towards frogs and toads. The findings are consistent with the theoretical framework of Connectedness To Nature where positive attitudes are supported by normative values, cultural beliefs, knowledge and positive experiences with care‐givers and role‐models. The garden habitat component of the study sought to explore the technical questions of the "What" requirement for amphibian presence in gardens. It was loosely based on the BIMBY tool with adaptations for context and targeted species. 50 gardens were visited and surveyed. They were divided into two groups for comparison: Those in which residents reported amphibian presence, and those which did not. Results indicate that the cape river frog (A. fuscigula) and clicking stream frog (S. grayii), are attracted to gardens with moderate to dense vegetation at groundcover level. Gardens with moderately planted beds were more likely to report frogs if they had additional resources, in particular, ponds and mulch. The "How" question brought together the two themes in a discussion on citizen mobilization and ways in which community groups are successfully implementing urban ecology conservation and reconciliation strategies. This work is important for urban nature conservation which seeks to engage private land‐owners (garden enthusiasts) and community and citizen groups in implementing urban biodiversity projects.

No description available.

We live in an increasingly urban world and ecologists are being called upon to provide thorough information on the effect of urbanization on ecosystems. However, urban ecology has historically focused almost exclusively on describing changes in species richness. Although this has been important as a first characterization of the effect of urbanization, the focus on describing species richness has restricted our understanding of the mechanisms determining ecological patterns and processes in cities. In this thesis, I apply a trait-based approach to a widespread urban invasive species, the guppy, Poecilia reticulata, in order to explore the mechanisms through which urbanization can affect reproductive and feeding ecology traits of the stream biota. I first review studies that use trait-based approaches in stream ecosystems and develop an intraspecific trait framework that can be used to link urbanization to changes in traits of the stream biota. Then, I combine this framework with existing information on trait evolution of guppies in their non-urban, native range in Trinidad, to explore the effect of urbanization on guppy life history related traits and population density in Brazil. Next, building on a study of drivers of diet and trophic morphology in Trinidadian guppies, I use a trait-based framework to explore the effect of urbanization on guppy diet and feeding morphology in Brazil. My review shows that intraspecific trait approaches in urban streams are rare, but have the potential to provide a mechanistic understanding of the effects of urbanization on stream biota. By using an intraspecific trait approach, I show that urbanization increases guppy body length, increases fecundity and improves condition. Concurrent investment in reproduction and somatic tissues suggests that urbanization relaxes life history traits trade-offs in guppies. Urban guppies also attain far higher densities than non-urban guppies. These changes in traits and populations are related to the large amount of high-quality food (i.e. chironomids) available for guppies in urban streams. Urban-induced changes in traits enhance guppy invasive potential. By studying guppies in Trinidad, I have found that each population is composed of two resource-use phenotypes with distinct diets and gut morphology (carnivorous guppies with short guts and detritivorous/algivorous guppies with long guts). The frequency of each resource-use phenotype appears to be determined by guppy density: low density appears to increase the frequency of the carnivorous phenotype. Guppy populations in Brazil are also composed of two resource-use phenotypes, and the existence of these phenotypes is related to the variation in individual feeding morphology (i.e. cranium shape) that affect feeding efficiency. Neither density nor urbanization appears to shift the distribution of the two resource use phenotypes. However, urban guppies have larger and wider crania, thus a more efficient insect feeding morphology, than non-urban guppies. Overall my study suggests that consumption of chironomids is important for the success of guppies in urban streams, and it is possible that similar mechanism also facilitates the success of other urban dwellers. My study also highlights the power of intraspecific trait approaches for understanding the ecology urban dwellers. Such knowledge can help us refine and advance ecological theories to better predict future ecological change in an increasingly urbanized world. / Graduate / 2020-08-08