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The microsporidian parasite Nadelspora canceri infects Dungeness crabs, Cancer magister, along the United States Pacific Northwest coast. The prevalence and seasonal variation of N. canceri in Dungeness crabs from Alsea Bay, Oregon, are described based on examination of 2991 crabs collected at monthly intervals from October, 1991 to June, 1993. The average prevalence in monthly samples was 21.0% and ranged from 8.2% to 33.0%. No significant differences in monthly or seasonal parasite prevalence were observed. A total of 3061 Dungeness crabs was examined from an additional seven Pacific Northwest estuaries and Puget Sound to document the geographic distribution of N. canceri and the prevalence of the parasite in these locations. The estuaries sampled and the prevalences observed were: Humboldt Bay, California (14.6%), Coos Bay (10.6%), Yaquina Bay (2.0%), Tillamook Bay (41.2%), and Nehalem Bay, Oregon (14.2%), Willapa Bay (6.9%), and Grays Harbor Washington (0.44%). Dungeness crabs were examined from the Dungeness spit, Kala Point, and Mukilteo areas in Puget Sound and no infected crabs were found. A total of 9317 male Dungeness crabs > 15.9 cm carapace width (CW) captured in the commercial ocean crab fishery was examined for N. canceri and 27 (0.3%) were infected with the parasite. No infections were found in crabs smaller than 3.0 cm CW and the prevalence of infection generally increased with crab size reaching a peak of 22.2% in 14 cm CW crabs. The overall infection prevalence in male crabs (19.2%) was more than twice that of female crabs (8.0%), and of the 821 infected crabs found, 629 (76.6%) were males. The mortality of laboratory-held Dungeness crabs naturally infected with N. canceri was compared to that of uninfected crabs in two separate experiments and in both cases a significantly higher mortality was observed for infected crabs. Nadelspora canceri infections were established in both juvenile and adult Dungeness crabs that were fed parasite spores in laboratory experiments indicating that transmission is direct and intermediate hosts or vectors are not required for transmitting the parasite between hosts. / Graduation date: 1995

Although nearshore macroinvertebrates are integral members of high mountain lentic systems, knowledge of ecological factors influencing their distributions is limited. Factors affecting distributions of nearshore macroinvertebrates were investigated, including microhabitat use and vertebrate predation, in the oligotrophic lakes of North Cascades National Park Service Complex, Washington, USA, and the conformity of distribution with a lake classification system was assessed (Lomnicky, unpublished manuscript; Liss et al. 1991). Forty-one lakes were assigned to six classification categories based on vegetation zone (forest, subalpine, alpine), elevation, and position relative to the west or east side of the crest of the Cascade Range. These classification variables represented fundamental characteristics of the terrestrial environment that indirectly reflected geology and climate. This geoclimatic perspective provided a broad, integrative framework for expressing the physical environment of lakes. Habitat conditions and macroinvertebrate distributions in study lakes were studied from 1989 through 1991. Distributions varied according to vegetation zone, elevation, and crest position, and reflected the concordance between habitat conditions and organism life history requirements. Habitat parameters affecting distributions included water temperature, the kinds of substrates in benthic microhabitats, water chemistry, and, to a limited extent, the presence of vertebrate predators. The number of taxa per lake was positively correlated with maximum temperature and negatively correlated with elevation. Forest zone lakes tended to have the highest number of taxa and alpine lakes the lowest. Substrates in nearshore microhabitats varied with vegetation zone. Organic substrates were more predominant than inorganic substrates in forest zone lakes. Organic substrates declined and inorganic substrates increased in the subalpine zone. There were virtually no organic substrates in alpine lakes. Taxa were placed into groups based on substrate preference. Ordinations indicated that the proportion of taxa in inorganic and organic-based substrate preference groups paralleled vegetation zone-substrate relationships. Lake water hardness and pH, as well as the presence of vertebrate predators affected the distribution of several taxa. Gastropods were limited to three forest lakes by their water hardness and pH requirements, and the dytiscid beetle, Potamonectes qriseostriatus appeared to be absent from forest lakes due, in part, to the pH requirements of this taxon. The distribution of three taxa (Taenionema, Ameletus, Desmona) appeared to be affected by the presence of vertebrate predators (salamanders and trout). Discriminant analysis was used to test the reliability of lake classification based on terrestrial characteristics. Discriminant analysis assigned lakes to categories based on similarities in kinds of substrates, substrate preference groups, and taxa. Strong concordance between both methods of lake classification supported the interconnection between terrestrial characteristics and processes and the abiotic and biotic conditions in lakes. / Graduation date: 1994

The importance of spatial variation in abundance for the assessment of climate change impacts was examined using the North American beaver ( Castor canadensis) in Quebec as a model species. A preliminary characterization of the beavers' range edge improved the core-sampling bias and revealed that beavers are present at low densities, in shrubby riparian habitats as far north as the communities of Tasiujaq and Umiujaq. Spatial variation in beaver abundance across the province follows a roughly logistic pattern, with abundance peaking in southern Quebec, declining steeply around 49°N, and remaining uniformly low as far as 58°N. Although climate sensitivity of beaver abundance and the greatest changes in future beaver density are predicted to occur near the middle of their range, beavers are expected to occupy most of the province by 2055. These results highlight the value of incorporating density estimates from across a species' range into climate envelope models.

The Agulhas Bank supports a speciose fish community, many of which are commercially important. Despite substantial research being conducted on aspects of their biology spatial aspects of their distribution and abundance in relation to environment parameters has been ignored. This study, therefore, addressed aspects related to the distribution and abundance of representative species on the Agulhas Bank within a Geographic Information System (GIS). Four candidate species were chosen due to their importance either in numbers or unit mass to the South African demersal trawl fishery. The species also shared morphological and taxonomic similarities. The candidate species chosen were the two Cape hake species, shallow-water hake Meluccius capensis, and deep-water hake Merluccius paradoxus, and the two pleuronectiform species being Agulhas sole Austroglossus pectoralis and redspotted tonguesole Cynoglossus zanzibarensis. The use of a GIS was appropriate and allowed for hidden spatial patterns be exposed and illustrated visually, while also facilitating the quantification of the relationships between distribution/abundance and certain environmental predictors using statistical methods The Department of Marine and Coastal Management, Cape Town, supplied biological data in the form of length frequency and biomass information from spring (AprillMay) and autumn (September/October) cruises conducted between 1986 and 1993 on the R. V. Africana. The Council for National Geoscience, Cape Town, supplied sediment data for the entire southern African coastline. Initial exploratory data analysis highlighted potential relationships between environmental variables and abundance for each specie's life-history stanzas. Variations in spatial distribution were found to be significantly different between each life-history stanzas within species. Fish density as a function of the additive effects of the various environmental parameters, including temperature, depth and sediment type, was assessed using a Poisson Generalized Additive Model (GAM), while distribution was analysed with a logistic GAM. A predictive logistic model was then created, taking into consideration the importance of the predictor variables for each species, allowing for predictive estimates to be made for each species by inputting environmental information within the study area. The importance of certain environmental variables influencing distribution and abundance were noted. General patterns indicated that sediment was the most important to both the distribution and abundance of the two pleuronectiform species and juvenile life-history stanzas, while the adult gadoids' distribution and abundance appeared to be depth dependent.

The objectives of the study were to determine the year-round distribution and habitat selection of four marsh passerine species, as described by vegetation type and its physical characteristics, and to investigate interspecific competition as a factor in the habitat selection of the Long-billed Marsh Wren and the Red-winged Blackbird. Fulfillment of these objectives should help the B.C. Fish and Wildlife Branch to assess the effects of their management plans on marsh passerines. I determined the abundance of four passerine species in different vegetation types via marsh census transects over the period of one year. Nesting habitat and breeding information on marsh wrens and redwings was obtained via nest study plots. The results were: Areas traversed from the central and deepest marsh outward towards higher ground are inhabited by redwings, marsh wrens. Common Yellowthroats, and Song Sparrows, respectively. Habitats of wrens and redwings are spatially and temporally segregated. Wrens use the "Dense Spiraea" (Hardhack shrub) habitat extensively, while redwings use it hardly at all in the marsh. Similarly, redwings are abundant in Scirpus cyperinus (Hairy-seeded Bulrush), whereas wrens seldom use this habitat. Both wrens and redwings use other vegetation types, but redwings use them in the late spring, whereas wrens use them in the summer. Both wrens and redwings have lower reproductive success when nesting in close proximity than when nesting apart. This supports the hypothesis that interspecific competition exists and indicates that selection may favour habitat segregation. I also found mutual suppression of reproductive success when the effects of different vegetation types were removed. The results were not statistically significant however, possibly due to small sample sizes. Of the observed differences between the physical nest site parameters of wrens and redwings, vegetation height and presence and/or depth of water require further investigation as factors in the habitat selection of the two species. Bren-wren competition does not appear to affect wren nesting success in the present study marsh. Management recommendations are given based on the objective of maintaining and possibly enhancing bird species diversity in the study marsh. / Science, Faculty of / Zoology, Department of / Graduate

Visual estimation techniques were used to quantify habitat characteristics, habitat type (pool, riffle) use and longitudinal distribution of steelhead (Oncorhynchus mykiss), cutthroat trout (0. clarki), and coho salmon (0. kisutch) in spring, summer and fall in 8.8 km of Cummins Creek, a basin in the central coast of Oregon. Fish were distributed significantly different than habitat type availability in most samples. Pool habitats contained a disproportionate percent of the salmonid assemblage and 1+ fish in each sample, and the percentage of fish in pools increased as flow decreased. In spring, coho salmon fry were concentrated in side channels and valley floor tributary habitats. Large woody debris formed 57- 68% of pool habitats and was significantly correlated with pool volume, maximum pool depth, slow surface velocity in pools, and pieces of small woody debris. Longitudinal distribution of the salmonid assemblage did not differ from habitat distribution seasonally or between years, even though certain species differed Coho salmon and cutthroat trout were distributed in proportion to longitudinal habitat availability only when fish abundance was relatively high and streamflow was low. In most samples, both 0+ and 1+ steelhead were distributed in proportion to longitudinal habitat availability. Differences in coho salmon abundance between years appeared to influence longitudinal distribution of each species and age class. Certain reaches had consistent numbers of fish between years while the number of fish in other reaches varied widely. In most samples, reaches with highest abundance for steelhead were in the lower basin, cutthroat trout in the upper basin and coho salmon between the two other species. Timing of reduction in number of fish varied among species. Fifty-five percent of 0+ steelhead and 73% of 1+ steelhead lost between August 1988 and April 1989 were lost between August and October during low flow conditions. However, only 18% of the losses, for 0+ coho salmon, occurred between August and October with the remaining losses occurring after October. This study illustrates that habitat availability is not a good index of fish distribution when fish abundance is low, and it highlights the importance of habitat in the lower portions of basins when fish abundance is high. It also demonstrates that the basin wide distribution of salmonids varies among species, age classes, seasons, and years and suggests that our understanding of salmonid distribution and abundance could be greatly enhanced by adopting a basin-wide, community, and seasonal perspective. In addition, the methods used in this study offer one way to assess the seasonal distribution and abundance of salmonids in a relatively quick, inexpensive, and non-destructive manner. / Graduation date: 1994

Thesis (MTech. Nature Conservaion) -- Tshwane University of Technology 2013. / The aim of this study was to determine the current population status of Aloe peglerae in the Magaliesberg Mountain Range.

Stress causes crops to grow below their potential and this affects the vitality and physiological functioning of the plants at all levels leading to reduction in yield. Remote sensing of vegetation is regarded as a valuable tool for the detection and discrimination of stress, especially over large or sensitive regions. The main aim of the research carried out is to assess the potential of remote sensing to detect CO2 leakage from CCS repositories. Further to this, the capability of remote sensing to discriminate between stresses with similar mode of action is explored. Two stress factors were selected for study: (1) elevated concentrations of soil CO2 in the plant root zone and; (2) herbicide, applied at sub-lethal levels. To understand the effects of soil CO2 and herbicide stress on vegetation reflectance, field experiments were carried out on maize (2009) and barley (2010) to investigate the effects of elevated soil CO2 concentrations and of different levels of herbicide treatments on vegetation growth and canopy reflectance using hyperspectral remote sensing techniques. The findings from this study shows that the average canopy reflectance response of maize and barley to CO2 and herbicide stress were increased reflectance in the visible and decrease in near infra-red region as well as changes in the position and shape of the red-edge. The red-edge first-derivative for barley treated with CO2 were composed of maximum peaks between 716 and 730nm and smaller peaks at 699 and 759nm, the control had peaks at 727 and 730 nm, with similar smaller peaks. Barley treated with herbicide had early peaks (a day after treatment) at 697, 715 and 717nm with a shoulder at 759nm, as the experiment progressed (16 days after treatment) the stress became apparent and the peak remained stationary at 730nm, the magnitude decreased to 712nm at late treatment period (35 days after treatment). The control had single peak at 726nm. CO2 treated maize had double peaks at 718 and 730nm, with secondary peaks at 707 and 794nm. Maize treated with herbicide had maximum peaks at 716 and 723nm, with the shoulder at 759 nm; the peaks were similar with the control plots but decreased in magnitude. The main differences between the treatments were in the shape and positions of the peaks that identify the red-edge. The canopy reflectances of the plants were further analysed using the blue (400-550nm) and red (550-750nm). In these regions the main feature of concern is chlorophyll content. The analysis showed that the band depths of controls plants were deeper compared to the stressed plants which is dependent on the stress and crop type. Other vegetation indices used in this study were the Chlorophyll Normalized Difference Index (Chl NDI), the Pigment Specific Simple Ratio for chlorophyll a and b (PSSRa and PSSRb) and the Physiological Reflectance Index (PRI). The results show that they were promising indicators of early stress detection, some indices performed better than others depending on the stress type, species and duration of stress. Chl NDI was sensitive to high soil CO2 concentration in maize and barley, sub-lethal herbicide treatment at 10% - 40% level in barley and was insensitive to both low CO2 in the barley and maize as well as 10% herbicide treatment in maize. PSSRa was a good indicator of early CO2 stress in maize and high CO2 in barley as well as 10- 40% herbicide treatments. PSSRb could detect high CO2 level in maize and barley and all levels (5-40%) of herbicide treatments. PRI was insensitive to 5% herbicide treatment in barley but sensitive to high CO2 in maize at early stage of the experiment. This study has demonstrated that remote sensing approach could be deployed for discriminating between different stressors using their red-edge first-derivative peaks, band depths and vegetation indices.

Marianne North was a major figure within the history of nineteenth-century botanical illustration. She produced a substantial body of botanical paintings as the result of extensive travels to many different parts of the world and was responsible for the founding of a major purpose-built gallery containing a representative collection of her work which still stands today in the Royal Botanical Gardens at Kew. Despite North's percieved importance as a botanical painter, relatively little of any critical/analytical substance has been written about her life and work from an art-historical or scientific perspective. North's place within nineteenth-century visual culture is arguably a contested one, despite having been a major contributor to nineteenth-century botanical painting. North's work therefore remains problematic to both botanists and art historians because it does not conform wholly to the established nineteenth century conventions of either scientific-botanical illustration or art. This thesis will explore the uncertain positioning of North's painting through a close analysis of its relationship to nineteenth and twentieth-century visual practices. In light of this analysis, it will be argued that North's painting does not successfully combine artistic and scientific perspectives, as some have argued, but instead presents an unidentifiable mode of visual representation that shifts uncertainly between art and science, thereby deconstructing any categorical distinction between the two.