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• 441. [Article] Evolution of a pheromone signaling system in the salamander genus Plethodon (Amphibia: Plethodontidae)

  Animal signaling systems frequently utilize multiple traits to produce and transmit a signal. These system elements may span multiple levels of organization. Functional integration of these traits may ...

  Citation × Citation Citation Abstract Copy Title: Evolution of a pheromone signaling system in the salamander genus Plethodon (Amphibia: Plethodontidae) Author: Picard, Amy L. Animal signaling systems frequently utilize multiple traits to produce and transmit a signal. These system elements may span multiple levels of organization. Functional integration of these traits may be expected to generate concordance in evolutionary pattern among system elements, such that evolutionary change in one system component is correlated with change in other system parts. This thesis investigates the evolution of multiple elements of a complex pheromone signaling system in a group of plethodontid salamanders (genus Plethodon). In this system, the transmitted signal is a multi-protein male pheromone that is delivered to a female during courtship interactions. This male courtship pheromone functions to increase female receptivity to mating. Pheromone delivery is achieved by the use of specialized morphological and behavioral characters. Two highly-conserved modes of pheromone delivery occur within this salamander clade, and each of these modes is associated with distinct morphological and behavioral traits. The transition from an ancestral to a derived mode of pheromone delivery presents a unique opportunity to address evolutionary concordance among elements of the signaling system. I investigated the evolution of (1) pheromone-delivery behaviors and (2) multiple protein components of the courtship pheromone, across this evolutionary transition. First, I conducted courtship observations in a transitional species in which pheromone delivery includes aspects of both the ancestral and derived modes of pheromone delivery. My findings suggest that the behavioral transition in delivery mode was gradual and consisted of several changes in pheromone delivery behavior. Second, I characterized evolutionary pattern in three pheromone components across the behavioral transition. This study revealed overall concordance in evolutionary pattern between morphology, behavior and the pheromone signal, despite discordance in the type of selection acting at these different levels. However, a detailed analysis of evolutionary pattern revealed a decoupling of evolutionary changes among the three pheromone components. Overall, my results demonstrate the complexity of this pheromone delivery transition at multiple levels of organization. In particular, my findings suggest that, for both pheromone-delivery behaviors and the pheromone signal itself, the evolutionary transition was more gradual than was previously realized. These findings lend empirical insight into (1) the nature of evolutionary transitions, and (2) the evolution of functionally integrated traits that span organizational levels. Title: Evolution of a pheromone signaling system in the salamander genus Plethodon (Amphibia: Plethodontidae) Author: Picard, Amy L. Animal signaling systems frequently utilize multiple traits to produce and transmit a signal. These system elements may span multiple levels of organization. Functional integration of these traits may be expected to generate concordance in evolutionary pattern among system elements, such that evolutionary change in one system component is correlated with change in other system parts. This thesis investigates the evolution of multiple elements of a complex pheromone signaling system in a group of plethodontid salamanders (genus Plethodon). In this system, the transmitted signal is a multi-protein male pheromone that is delivered to a female during courtship interactions. This male courtship pheromone functions to increase female receptivity to mating. Pheromone delivery is achieved by the use of specialized morphological and behavioral characters. Two highly-conserved modes of pheromone delivery occur within this salamander clade, and each of these modes is associated with distinct morphological and behavioral traits. The transition from an ancestral to a derived mode of pheromone delivery presents a unique opportunity to address evolutionary concordance among elements of the signaling system. I investigated the evolution of (1) pheromone-delivery behaviors and (2) multiple protein components of the courtship pheromone, across this evolutionary transition. First, I conducted courtship observations in a transitional species in which pheromone delivery includes aspects of both the ancestral and derived modes of pheromone delivery. My findings suggest that the behavioral transition in delivery mode was gradual and consisted of several changes in pheromone delivery behavior. Second, I characterized evolutionary pattern in three pheromone components across the behavioral transition. This study revealed overall concordance in evolutionary pattern between morphology, behavior and the pheromone signal, despite discordance in the type of selection acting at these different levels. However, a detailed analysis of evolutionary pattern revealed a decoupling of evolutionary changes among the three pheromone components. Overall, my results demonstrate the complexity of this pheromone delivery transition at multiple levels of organization. In particular, my findings suggest that, for both pheromone-delivery behaviors and the pheromone signal itself, the evolutionary transition was more gradual than was previously realized. These findings lend empirical insight into (1) the nature of evolutionary transitions, and (2) the evolution of functionally integrated traits that span organizational levels. Close

• 442. [Article] Fisheries Co-management: An Experiential Account from Phang Nga Bay, Thailand

  Research Paper

  Citation × Citation Citation Abstract Copy Title: Fisheries Co-management: An Experiential Account from Phang Nga Bay, Thailand Author: Tandavanitj, Sanchai, Nabhitabhata, Jaruwat, Silpachai, Damrong, Henocque, Yves, Pimoljinda, Jate Research Paper Title: Fisheries Co-management: An Experiential Account from Phang Nga Bay, Thailand Author: Tandavanitj, Sanchai, Nabhitabhata, Jaruwat, Silpachai, Damrong, Henocque, Yves, Pimoljinda, Jate Research Paper Close

• 443. [Article] Modeling hemlock dwarf mistletoe (Arceuthobium tsugense subsp. tsugense) spread and intensification in mature uneven-aged forests in southeast Alaska

  Hemlock dwarf mistletoe (Arceuthobium tsugense (Rosendahi) G.N. Jones subsp. tsugense (western hemlock race)) is the most important and widespread disease of old-growth western hemlock forests in the Pacific ...

  Citation × Citation Citation Abstract Copy Title: Modeling hemlock dwarf mistletoe (Arceuthobium tsugense subsp. tsugense) spread and intensification in mature uneven-aged forests in southeast Alaska Author: Trummer, Loreen M. Hemlock dwarf mistletoe (Arceuthobium tsugense (Rosendahi) G.N. Jones subsp. tsugense (western hemlock race)) is the most important and widespread disease of old-growth western hemlock forests in the Pacific Northwest. Although heavy infection of dwarf mistletoe can significantly increase growth loss and mortality of host trees, the parasite is also considered an important ecological component of forests influencing stand structure, species composition, and wildlife habitat. This retrospective study was conducted in stands that sustained extensive windthrow in the past and was designed as a simulation for stand structure and disease conditions expected after use of silvicultural systems that retain overstory canopy trees in a managed forest. The specific objectives were to: 1. characterize the forest structure and dwarf mistletoe component of stands that developed after catastrophic wind storms in the late 1800's; and 2. develop and validate a model, using site, plot, and tree variables, that predicts the dwarf mistletoe rating of hemlock trees that have been exposed to the pathogen for approximately a century. Results indicated that retention of overstory infected hemlock trees in southeast Alaska forests will result in pathogen spread to and intensification on hemlock trees that have developed since the late 1800's (post-disturbance trees), but not to the devastating levels predicted by previous research in the coastal forests of British Columbia, Washington, or Oregon. On Kuiu Island, the retention of an average of 3 heavily infected overstory residual trees/plot (83 residual trees/ha) resulted in nearly 100 percent infection of post-disturbance hemlock trees within a plot. Of those trees infected, less than one-fifth had heavy infection (a dwarf mistletoe rating of 5 or 6), and approximately one-half had moderate infection (a dwarf mistletoe rating of 3 or 4). On Chichagof Island, the retention of an average of 2 heavily infected residual trees/plot (69 residual trees/ha) resulted in nearly 100 percent infection of post-disturbance hemlock trees within a plot. Of those trees infected, less than ten percent had heavy infection and approximately one-third had moderate infection. A mathematical model that predicted dwarf mistletoe rating on post-disturbance hemlock trees was developed from eight stands on Kuiu Island and the generality of the variables was tested in two stands on Chichagof Island. The Kuiu Island model predicted that the mean dwarf mistletoe rating of post-disturbance hemlock trees within a plot increased with increasing numbers and dwarf mistletoe ratings of residual and advanced regeneration trees within a plot. No other factors that described site or tree conditions within a plot appeared important in the model. Sitka spruce trees, though rare hosts of dwarf mistletoe, did not appear to increase the mean dwarf mistletoe rating of postdisturbance hemlock trees within a plot. When present in sufficient numbers, spruce trees may act as barriers to pathogen spread, although further analysis is needed to confirm a barrier effect. The Chichagof Island models, developed separately for the two stands, also predicted that the mean dwarf mistletoe rating of post-disturbance hemlock trees within a plot increased with increasing numbers and dwarf mistletoe rating of residual trees within a plot. The importance of advanced regeneration trees could not be verified in either stand on Chichagof Island since most plots lacked this tree type. Title: Modeling hemlock dwarf mistletoe (Arceuthobium tsugense subsp. tsugense) spread and intensification in mature uneven-aged forests in southeast Alaska Author: Trummer, Loreen M. Hemlock dwarf mistletoe (Arceuthobium tsugense (Rosendahi) G.N. Jones subsp. tsugense (western hemlock race)) is the most important and widespread disease of old-growth western hemlock forests in the Pacific Northwest. Although heavy infection of dwarf mistletoe can significantly increase growth loss and mortality of host trees, the parasite is also considered an important ecological component of forests influencing stand structure, species composition, and wildlife habitat. This retrospective study was conducted in stands that sustained extensive windthrow in the past and was designed as a simulation for stand structure and disease conditions expected after use of silvicultural systems that retain overstory canopy trees in a managed forest. The specific objectives were to: 1. characterize the forest structure and dwarf mistletoe component of stands that developed after catastrophic wind storms in the late 1800's; and 2. develop and validate a model, using site, plot, and tree variables, that predicts the dwarf mistletoe rating of hemlock trees that have been exposed to the pathogen for approximately a century. Results indicated that retention of overstory infected hemlock trees in southeast Alaska forests will result in pathogen spread to and intensification on hemlock trees that have developed since the late 1800's (post-disturbance trees), but not to the devastating levels predicted by previous research in the coastal forests of British Columbia, Washington, or Oregon. On Kuiu Island, the retention of an average of 3 heavily infected overstory residual trees/plot (83 residual trees/ha) resulted in nearly 100 percent infection of post-disturbance hemlock trees within a plot. Of those trees infected, less than one-fifth had heavy infection (a dwarf mistletoe rating of 5 or 6), and approximately one-half had moderate infection (a dwarf mistletoe rating of 3 or 4). On Chichagof Island, the retention of an average of 2 heavily infected residual trees/plot (69 residual trees/ha) resulted in nearly 100 percent infection of post-disturbance hemlock trees within a plot. Of those trees infected, less than ten percent had heavy infection and approximately one-third had moderate infection. A mathematical model that predicted dwarf mistletoe rating on post-disturbance hemlock trees was developed from eight stands on Kuiu Island and the generality of the variables was tested in two stands on Chichagof Island. The Kuiu Island model predicted that the mean dwarf mistletoe rating of post-disturbance hemlock trees within a plot increased with increasing numbers and dwarf mistletoe ratings of residual and advanced regeneration trees within a plot. No other factors that described site or tree conditions within a plot appeared important in the model. Sitka spruce trees, though rare hosts of dwarf mistletoe, did not appear to increase the mean dwarf mistletoe rating of postdisturbance hemlock trees within a plot. When present in sufficient numbers, spruce trees may act as barriers to pathogen spread, although further analysis is needed to confirm a barrier effect. The Chichagof Island models, developed separately for the two stands, also predicted that the mean dwarf mistletoe rating of post-disturbance hemlock trees within a plot increased with increasing numbers and dwarf mistletoe rating of residual trees within a plot. The importance of advanced regeneration trees could not be verified in either stand on Chichagof Island since most plots lacked this tree type. Close

• 444. [Article] Creating Useful and Useable Climate Tools for Sagebrush Land Management Through Scientist and Manager Collaboration

  The sagebrush ecosystem, home to numerous plant and animal species including big sagebrush (Artemisia tridentata) and the endemic greater sage-grouse (Centrocercus urophasianus), has endured fragmentation ...

  Citation × Citation Citation Abstract Copy Title: Creating Useful and Useable Climate Tools for Sagebrush Land Management Through Scientist and Manager Collaboration Author: Brown, Melanie The sagebrush ecosystem, home to numerous plant and animal species including big sagebrush (Artemisia tridentata) and the endemic greater sage-grouse (Centrocercus urophasianus), has endured fragmentation and degradation of both quantity and quality due to the cumulative and synergistic relationships between an abundance of individual disturbances including grazing, invasive annuals and fire. Climate change may now be an additional threat that poses the greatest risk to these imperiled habitats. Natural resource agencies such as the Bureau of Land Management (BLM) seek to conserve sagelands through land management activities that ensure the survival of sage-grouse and continuity of the sagebrush biome. Web-based climate tools can help convey climate information that may be necessary for long-term land management, but these tools may not agree with the needs of land managers, may be too complex, or may be misinterpreted. To overcome barriers of user compatibility, the participation of both climate scientists and land managers is necessary during tool development. With the collaboration of Oregon and Idaho BLM sagebrush land managers and climate scientists, this study sought to assess land manager needs and define the criteria for useful and useable climate tools. Using an initial online survey, individual phone interviews with land managers, and a follow-up online survey, a series of land management activities and related climate variables were identified, and several web-based climate tools were assessed. Most managers perform vegetation management through a variety of means including seeding and herbicide application. Such activities are affected by the magnitude and timing of precipitation and temperature, as well as other variables, on seasonal and annual timeframes. For planning purposes land managers also need information on long-term 10-20 year climate trends. The act of listening to the needs of land managers uncovered communication barriers, and provided feedback on existing climate tools emphasizing accessibility, dependability and consistency, clear explanation of terminology, effective visualizations, and relevant spatial and temporal scales to the scope of management activities. We also identified a need for basic information and education on the location of existing climate tools and climate impacts, and a need for near-term forecasting tools that could bridge the gap between weather (≤ 6 months) and climate (≥ 30 years) projections. Keywords: sagebrush, sage-grouse, Oregon State University, climate change, BLM, Oregon, Idaho, Great Basin, land management, collaboration, climate tools Title: Creating Useful and Useable Climate Tools for Sagebrush Land Management Through Scientist and Manager Collaboration Author: Brown, Melanie The sagebrush ecosystem, home to numerous plant and animal species including big sagebrush (Artemisia tridentata) and the endemic greater sage-grouse (Centrocercus urophasianus), has endured fragmentation and degradation of both quantity and quality due to the cumulative and synergistic relationships between an abundance of individual disturbances including grazing, invasive annuals and fire. Climate change may now be an additional threat that poses the greatest risk to these imperiled habitats. Natural resource agencies such as the Bureau of Land Management (BLM) seek to conserve sagelands through land management activities that ensure the survival of sage-grouse and continuity of the sagebrush biome. Web-based climate tools can help convey climate information that may be necessary for long-term land management, but these tools may not agree with the needs of land managers, may be too complex, or may be misinterpreted. To overcome barriers of user compatibility, the participation of both climate scientists and land managers is necessary during tool development. With the collaboration of Oregon and Idaho BLM sagebrush land managers and climate scientists, this study sought to assess land manager needs and define the criteria for useful and useable climate tools. Using an initial online survey, individual phone interviews with land managers, and a follow-up online survey, a series of land management activities and related climate variables were identified, and several web-based climate tools were assessed. Most managers perform vegetation management through a variety of means including seeding and herbicide application. Such activities are affected by the magnitude and timing of precipitation and temperature, as well as other variables, on seasonal and annual timeframes. For planning purposes land managers also need information on long-term 10-20 year climate trends. The act of listening to the needs of land managers uncovered communication barriers, and provided feedback on existing climate tools emphasizing accessibility, dependability and consistency, clear explanation of terminology, effective visualizations, and relevant spatial and temporal scales to the scope of management activities. We also identified a need for basic information and education on the location of existing climate tools and climate impacts, and a need for near-term forecasting tools that could bridge the gap between weather (≤ 6 months) and climate (≥ 30 years) projections. Keywords: sagebrush, sage-grouse, Oregon State University, climate change, BLM, Oregon, Idaho, Great Basin, land management, collaboration, climate tools Close

• 445. [Article] Composition of flavonoid phenolic polymers isolated from red wine during maceration and significance of flavan-3-ols in foods pertaining to biological activity

  Representing the most common flavonoid consumed in the American diet, the flavanols and their polymeric condensation products, the proanthocyanidins, are regarded as functional ingredients in various beverages, ...

  Citation × Citation Citation Abstract Copy Title: Composition of flavonoid phenolic polymers isolated from red wine during maceration and significance of flavan-3-ols in foods pertaining to biological activity Author: Aron, Patricia M. Representing the most common flavonoid consumed in the American diet, the flavanols and their polymeric condensation products, the proanthocyanidins, are regarded as functional ingredients in various beverages, whole and processed foods, herbal remedies and supplements. Their presence in food affects food quality parameters including astringency, bitterness, sourness, sweetness, salivary viscosity, aroma, and color formation. The ability of flavonoids to aid food functionality has also been established in terms of microbial stability, foamability, oxidative stability, and heat stability. Phenolic polymer material of the flavonoid family is of considerable interest in the study of red wine, as phenolic quantity and structure can significantly affect wine quality. Although a considerable amount of the phenolic polymer material extracted into red wine during fermentation can be accounted for and characterized as known compounds, a substantial portion of the material remains uncharacterized. During this investigation phenolic polymer material extracted during commercial red wine fermentations (Vitis vinifera L.cv Pinot noir) was isolated and analyzed in order to characterize its chemical composition. Phenolic polymer isolates were prepared from samples taken throughout fermentation and isolated by adsorption chromatography. Isolates were subjected to phloroglucinolysis to analyze proanthocyanidin amount as well as subunit composition. Investigation results revealed that known proanthocyanidin content of individual phenolic polymer isolates varied from 27 to 54%. Subsequent analyses were performed in order to quantify material other than known proanthocyanidin subunits. Results of all experiments accounted for up to 82% of the phenolic polymer isolates by mass. Phenolic polymers such as the proanthocyanidins have also become the interest of several investigations due to their potential to provide a variety of health beneficial effects by acting as antioxidant, anticarcinogen, cardiopreventive, antimicrobial, anti-viral, and neuro-protective agents. Such health beneficial effects have been correlated to proanthocyanidin structure-related functionality that allows them to behave as signaling molecules at the molecular level. Consumption of proanthocyanidin rich foods has also reportedly been linked to health detrimental effects including the activation of procarcinogens, reactive oxygen species formation (pro-oxidant activity), hemorrhage formation, hepatotoxicity initiation, pharmacokinetics of therapeutic drug alteration, estrogenic tumor formation, mutagenicity, plasma biochemistry modification, gastroenteritis instigation, antinutritive activity and weight loss. Title: Composition of flavonoid phenolic polymers isolated from red wine during maceration and significance of flavan-3-ols in foods pertaining to biological activity Author: Aron, Patricia M. Representing the most common flavonoid consumed in the American diet, the flavanols and their polymeric condensation products, the proanthocyanidins, are regarded as functional ingredients in various beverages, whole and processed foods, herbal remedies and supplements. Their presence in food affects food quality parameters including astringency, bitterness, sourness, sweetness, salivary viscosity, aroma, and color formation. The ability of flavonoids to aid food functionality has also been established in terms of microbial stability, foamability, oxidative stability, and heat stability. Phenolic polymer material of the flavonoid family is of considerable interest in the study of red wine, as phenolic quantity and structure can significantly affect wine quality. Although a considerable amount of the phenolic polymer material extracted into red wine during fermentation can be accounted for and characterized as known compounds, a substantial portion of the material remains uncharacterized. During this investigation phenolic polymer material extracted during commercial red wine fermentations (Vitis vinifera L.cv Pinot noir) was isolated and analyzed in order to characterize its chemical composition. Phenolic polymer isolates were prepared from samples taken throughout fermentation and isolated by adsorption chromatography. Isolates were subjected to phloroglucinolysis to analyze proanthocyanidin amount as well as subunit composition. Investigation results revealed that known proanthocyanidin content of individual phenolic polymer isolates varied from 27 to 54%. Subsequent analyses were performed in order to quantify material other than known proanthocyanidin subunits. Results of all experiments accounted for up to 82% of the phenolic polymer isolates by mass. Phenolic polymers such as the proanthocyanidins have also become the interest of several investigations due to their potential to provide a variety of health beneficial effects by acting as antioxidant, anticarcinogen, cardiopreventive, antimicrobial, anti-viral, and neuro-protective agents. Such health beneficial effects have been correlated to proanthocyanidin structure-related functionality that allows them to behave as signaling molecules at the molecular level. Consumption of proanthocyanidin rich foods has also reportedly been linked to health detrimental effects including the activation of procarcinogens, reactive oxygen species formation (pro-oxidant activity), hemorrhage formation, hepatotoxicity initiation, pharmacokinetics of therapeutic drug alteration, estrogenic tumor formation, mutagenicity, plasma biochemistry modification, gastroenteritis instigation, antinutritive activity and weight loss. Close

• 446. [Article] Genetic and phenotypic variation associated with the resistance gene SOD1 in Biomphalaria glabrata, an important intermediate host of Schistosomiasis

  Schistosomiasis afflicts 200 million people and is responsible for 200,000 deaths per year. The infection is caused by a digenean trematode in the genus Schistosoma. The parasite must cycle through both ...

  Citation × Citation Citation Abstract Copy Title: Genetic and phenotypic variation associated with the resistance gene SOD1 in Biomphalaria glabrata, an important intermediate host of Schistosomiasis Author: Bonner, Kaitlin M. Schistosomiasis afflicts 200 million people and is responsible for 200,000 deaths per year. The infection is caused by a digenean trematode in the genus Schistosoma. The parasite must cycle through both a vertebrate (human) and invertebrate (snail) host to complete the life cycle. My dissertation focuses on the genetic mechanisms of resistance in the snail intermediate host Biomphalaria glabrata to the parasite Schistosoma mansoni. Understanding the underlying mechanisms controlling resistance in the intermediate host is essential for elucidating transmission dynamics and the development of appropriate biological control techniques. Much of what we know about the resistance of the intermediate host has been determined using established laboratory strains of both the snail and trematode species. The B. glabrata/S. mansoni system serves as a model system for studying schistosomiasis. Resistance to parasite infection in the snail is highly heritable. While many genes have been implicated, allelic variation correlating with resistance has only been observed at a single gene, copper-zinc superoxide dismutase (SOD1). SOD1 is functionally relevant because it catalyzes the conversion of the highly reactive superoxide into the less reactive hydrogen peroxide and water. In the snail, hydrogen peroxide is released as part of the immune response to the invading parasite. The goal of my dissertation was to further evaluate SOD1 as a resistance locus. In the second chapter I examined allelic variation at SOD1 and looked for evidence of selection on SOD1 in natural populations of B. glabrata. To determine the utility of SOD1 as a resistance locus in natural populations, we needed to first determine if there was indeed allelic variation in natural population of B. glabrata. This is important because if the alleles do not co-occur in natural populations, then the relative selective advantage of one allele over another in terms of resistance would be of little ecological relevance in natural transmission zones. Variation at SOD1 in natural populations cannot be assumed because the initial study describing the correlation between resistance to infection and allelic variation used a hybrid laboratory strain of B. glabrata (13-16-R1). Therefore, we did not know if the co-occurrence of particular alleles at SOD1 in the 13-16-R1 lab strain was a natural phenomenon or is an artifact of the breeding history of the strain. In this study we were able to identify the likely geographic origins of the alleles in the lab strain 13-16-R1 and determine that different alleles do co-occur in some natural populations. Additionally, we found heterozygote excess at SOD1 in all the populations segregating for the allele that confers highest resistance in 13-16-R1. This result raises the possibility that overdominance is acting at SOD1 or some locus closely linked to it. Title: Genetic and phenotypic variation associated with the resistance gene SOD1 in Biomphalaria glabrata, an important intermediate host of Schistosomiasis Author: Bonner, Kaitlin M. Schistosomiasis afflicts 200 million people and is responsible for 200,000 deaths per year. The infection is caused by a digenean trematode in the genus Schistosoma. The parasite must cycle through both a vertebrate (human) and invertebrate (snail) host to complete the life cycle. My dissertation focuses on the genetic mechanisms of resistance in the snail intermediate host Biomphalaria glabrata to the parasite Schistosoma mansoni. Understanding the underlying mechanisms controlling resistance in the intermediate host is essential for elucidating transmission dynamics and the development of appropriate biological control techniques. Much of what we know about the resistance of the intermediate host has been determined using established laboratory strains of both the snail and trematode species. The B. glabrata/S. mansoni system serves as a model system for studying schistosomiasis. Resistance to parasite infection in the snail is highly heritable. While many genes have been implicated, allelic variation correlating with resistance has only been observed at a single gene, copper-zinc superoxide dismutase (SOD1). SOD1 is functionally relevant because it catalyzes the conversion of the highly reactive superoxide into the less reactive hydrogen peroxide and water. In the snail, hydrogen peroxide is released as part of the immune response to the invading parasite. The goal of my dissertation was to further evaluate SOD1 as a resistance locus. In the second chapter I examined allelic variation at SOD1 and looked for evidence of selection on SOD1 in natural populations of B. glabrata. To determine the utility of SOD1 as a resistance locus in natural populations, we needed to first determine if there was indeed allelic variation in natural population of B. glabrata. This is important because if the alleles do not co-occur in natural populations, then the relative selective advantage of one allele over another in terms of resistance would be of little ecological relevance in natural transmission zones. Variation at SOD1 in natural populations cannot be assumed because the initial study describing the correlation between resistance to infection and allelic variation used a hybrid laboratory strain of B. glabrata (13-16-R1). Therefore, we did not know if the co-occurrence of particular alleles at SOD1 in the 13-16-R1 lab strain was a natural phenomenon or is an artifact of the breeding history of the strain. In this study we were able to identify the likely geographic origins of the alleles in the lab strain 13-16-R1 and determine that different alleles do co-occur in some natural populations. Additionally, we found heterozygote excess at SOD1 in all the populations segregating for the allele that confers highest resistance in 13-16-R1. This result raises the possibility that overdominance is acting at SOD1 or some locus closely linked to it. Close

• 447. [Article] Effects of single and multiple stressors on communities of wheat and wild oats

  Most plant toxicology tests developed in support of environmental laws use a single stress applied to an individual plant. While tests using individual species or stresses require fewer resources and are ...

  Citation × Citation Citation Abstract Copy Title: Effects of single and multiple stressors on communities of wheat and wild oats Author: Pfleeger, Thomas G. Most plant toxicology tests developed in support of environmental laws use a single stress applied to an individual plant. While tests using individual species or stresses require fewer resources and are easier to interpret, they are under increasing criticism for being unrealistic and missing important ecological interactions. The objective of this research was to increase our understanding of how plants and plant communities respond to a variety of stressors. Model plant communities of spring wheat (Triticum aestivum) and wild oats (Avena fatua) were planted at three densities and five proportions in the field. Puccinia recondita, the causal agent of wheat leaf rust, was inoculated on half of the plots. Disease severity was estimated as percent of wheat flag leaves covered by rust lesions. Plants were harvested at maturity and measured. Seeding density rarely had a significant influence on rust severity, probably because tiller density differed little as a result of compensation due to increased tillering at low seeding densities. In contrast, increasing the proportion of wheat in mixtures with wild oats consistently increased wheat leaf rust severity. There was no evidence to suggest that wild oats acted as a barrier to inoculum movement. Wild oats' effect on wheat leaf rust was probably through its competitive reduction of wheat tiller density. Both wheat and wild oats seed weight decreased as the proportion of wild oats increased in mixtures. This indicates that intraspecific competition was stronger in wild oats than was intraspecific competition with wheat in these mixtures. Wild oats generally did not respond to the presence of leaf rust on wheat, while wheat was negatively impacted. Thus, there was little competitive advantage to wild oats when its competitor (wheat) was diseased. A small subset of the field treatments was treated with ozone, because of the limited space available in the open-top ozone exposure chambers. Wheat height and aboveground biomass generally decreased with ozone exposure and with increasing disease severity in both years, while total grain weight decreased significantly only with disease and only in one year. There was no interaction between ozone and disease, regardless of cultivar, density, or plant response variable measured. There was little evidence that ozone exposure affected the severity of wheat leaf rust. In general, there seemed to be a lack of interactions among the different stressors and the results varied considerably depending on year and wheat cultivar. Title: Effects of single and multiple stressors on communities of wheat and wild oats Author: Pfleeger, Thomas G. Most plant toxicology tests developed in support of environmental laws use a single stress applied to an individual plant. While tests using individual species or stresses require fewer resources and are easier to interpret, they are under increasing criticism for being unrealistic and missing important ecological interactions. The objective of this research was to increase our understanding of how plants and plant communities respond to a variety of stressors. Model plant communities of spring wheat (Triticum aestivum) and wild oats (Avena fatua) were planted at three densities and five proportions in the field. Puccinia recondita, the causal agent of wheat leaf rust, was inoculated on half of the plots. Disease severity was estimated as percent of wheat flag leaves covered by rust lesions. Plants were harvested at maturity and measured. Seeding density rarely had a significant influence on rust severity, probably because tiller density differed little as a result of compensation due to increased tillering at low seeding densities. In contrast, increasing the proportion of wheat in mixtures with wild oats consistently increased wheat leaf rust severity. There was no evidence to suggest that wild oats acted as a barrier to inoculum movement. Wild oats' effect on wheat leaf rust was probably through its competitive reduction of wheat tiller density. Both wheat and wild oats seed weight decreased as the proportion of wild oats increased in mixtures. This indicates that intraspecific competition was stronger in wild oats than was intraspecific competition with wheat in these mixtures. Wild oats generally did not respond to the presence of leaf rust on wheat, while wheat was negatively impacted. Thus, there was little competitive advantage to wild oats when its competitor (wheat) was diseased. A small subset of the field treatments was treated with ozone, because of the limited space available in the open-top ozone exposure chambers. Wheat height and aboveground biomass generally decreased with ozone exposure and with increasing disease severity in both years, while total grain weight decreased significantly only with disease and only in one year. There was no interaction between ozone and disease, regardless of cultivar, density, or plant response variable measured. There was little evidence that ozone exposure affected the severity of wheat leaf rust. In general, there seemed to be a lack of interactions among the different stressors and the results varied considerably depending on year and wheat cultivar. Close

• 448. [Article] Influences of riparian canopy on aquatic communities in high desert streams of eastern Oregon

  Because riparian canopy controls most energy inputs to stream ecosystems, it directly affects the structure of aquatic food webs and the ecological processes that govern interactions among trophic levels. ...

  Citation × Citation Citation Abstract Copy Title: Influences of riparian canopy on aquatic communities in high desert streams of eastern Oregon Author: Tait, Cynthia K. Because riparian canopy controls most energy inputs to stream ecosystems, it directly affects the structure of aquatic food webs and the ecological processes that govern interactions among trophic levels. This study addresses the interdependence among riparian canopy, benthic community structure, and the carrying capacity of high desert streams for salmonid fishes. In streams in the lower John Day River Basin in eastern Oregon, algal, invertebrate, and fish communities were compared in reaches with varying densities of riparian canopy. Water temperatures varied with the density and upstream extent of canopy. Densely canopied sites were cool, while sites with high irradiances had temperatures exceeding the upper lethal limit for salmonids. Periphyton and grazer biomasses were greater in well-lighted sites, but 90% of grazer biomass consisted of Dicosmoecus gilvipes, a large caddisfly inedible by juvenile trout. Warmer water increased metabolic demands for salmonids, while the overwhelming dominance of Dicosmoecus in open sites shifted energy flow away from trout and shrunk their food base. High water temperatures, however, provided suitable habitat for many warmwater fishes which would otherwise not enter tributaries of this size. At higher elevation study sites in Camp Creek, light levels were higher and less variable than at the lower sites. Periphyton and invertebrate abundances were not correlated with irradiance. Rather, periphyton was maintained at low levels by grazers, particularly Dicosmoecus and snails. Manipulations of fish densities in enclosures showed that trout and dace had no negative impacts on numbers of invertebrate prey, and that grazers played a larger role in regulating lower trophic levels than did fish. Dicosmoecus acted as a keystone species in the benthic food web of Camp Creek by simultaneously influencing the trophic level both below and above its own. When irradiance was experimentally reduced under artificial canopies, periphyton standing crops were not different from those in open control pools after 4 wks. However, grazers were more abundant in open pools. The cropping of periphyton to uniform levels in both sunlight and shade indicated that mobile grazers targeted sites of varying productivities. Comparisons between benthic communities in Camp Creek and in a densely canopied reference stream suggested that benthic community structure shifted to accommodate changes in energy resources that occur when canopy density is altered. Title: Influences of riparian canopy on aquatic communities in high desert streams of eastern Oregon Author: Tait, Cynthia K. Because riparian canopy controls most energy inputs to stream ecosystems, it directly affects the structure of aquatic food webs and the ecological processes that govern interactions among trophic levels. This study addresses the interdependence among riparian canopy, benthic community structure, and the carrying capacity of high desert streams for salmonid fishes. In streams in the lower John Day River Basin in eastern Oregon, algal, invertebrate, and fish communities were compared in reaches with varying densities of riparian canopy. Water temperatures varied with the density and upstream extent of canopy. Densely canopied sites were cool, while sites with high irradiances had temperatures exceeding the upper lethal limit for salmonids. Periphyton and grazer biomasses were greater in well-lighted sites, but 90% of grazer biomass consisted of Dicosmoecus gilvipes, a large caddisfly inedible by juvenile trout. Warmer water increased metabolic demands for salmonids, while the overwhelming dominance of Dicosmoecus in open sites shifted energy flow away from trout and shrunk their food base. High water temperatures, however, provided suitable habitat for many warmwater fishes which would otherwise not enter tributaries of this size. At higher elevation study sites in Camp Creek, light levels were higher and less variable than at the lower sites. Periphyton and invertebrate abundances were not correlated with irradiance. Rather, periphyton was maintained at low levels by grazers, particularly Dicosmoecus and snails. Manipulations of fish densities in enclosures showed that trout and dace had no negative impacts on numbers of invertebrate prey, and that grazers played a larger role in regulating lower trophic levels than did fish. Dicosmoecus acted as a keystone species in the benthic food web of Camp Creek by simultaneously influencing the trophic level both below and above its own. When irradiance was experimentally reduced under artificial canopies, periphyton standing crops were not different from those in open control pools after 4 wks. However, grazers were more abundant in open pools. The cropping of periphyton to uniform levels in both sunlight and shade indicated that mobile grazers targeted sites of varying productivities. Comparisons between benthic communities in Camp Creek and in a densely canopied reference stream suggested that benthic community structure shifted to accommodate changes in energy resources that occur when canopy density is altered. Close

• 449. [Article] Lodging control and yield enhancement in Morex spring barley with paclobutrazol treatment

  Lodging in cereals can cause significant decreases in yield. It is both a problem in susceptible cereal cultivars with a tall-stemmed, weak-strawed growing habit and in lodging-resistant cereal cultivars ...

  Citation × Citation Citation Abstract Copy Title: Lodging control and yield enhancement in Morex spring barley with paclobutrazol treatment Author: Morrison, Laura A. Lodging in cereals can cause significant decreases in yield. It is both a problem in susceptible cereal cultivars with a tall-stemmed, weak-strawed growing habit and in lodging-resistant cereal cultivars when they are grown under high-nitrogen, high-moisture regimes. Plant growth regulators (PGR's) are chemical growth retardants that offer a method of lodging control. For the susceptible cultivars that are not amenable to genetic shortening through plant breeding, PGR's accomplish on a seasonal basis what has not been possible through gene manipulation. For cultivars that become susceptible in the high-intensive systems of modern agriculture, PGR's can be integrated into the chemical regime to control the lodging-promoting conditions created by yield-promotion practices. Morex spring barley is a lodging-susceptible cultivar that is tall-stemmed and weak-strawed. This growth habit aggravates the lodging problem when Morex is grown under intensive yield-promoting conditions. In greenhouse and field experiments, chemical control of the Morex lodging tendency was tested with an experimental chemical, Paclobutrazol. Paclobutrazol acts on the endogenous gibberellin hormone system in the plant by inhibiting its synthesis. The chemical's effect on the cereal plant is reported to occur in the internodes which Paclobutrazol shortens by decreasing longitudinal growth and strengthens by increasing transverse growth. Lodging control is realized through height reduction which lessens the torque effect created by the weather conditions that actually cause the event of lodging to occur. Paclobutrazol caused significant shortening of the basal internodes in the greenhouse and field experiments. Uncharacteristic of the expected effect, the PGR did not strengthen the shortened internodes. Specific stem weight and breaking strength values for the treated plants were significantly lower than the corresponding control values. In the field, Paclobutrazol delayed lodging until after the critical lodging period that occurs from approximately 15 days before anthesis to 15 days after anthesis. Lodging control was reflected in yield increases. Treated plots yielded significantly higher than did the control plots. The two high treatments of 800 and 1000 g/ha also yielded significantly higher than did the low treatments of 400 and 600 g/ha. Yield increases in the treated plots can be attributed to improved seed filling given the fact that lodging in the control plots occurred during the period when yield losses are caused by poor seed development. Unfortunately, the data did not give any clear indication of other possible sources of yield enhancement. Beneficial effects of Paclobutrazol on the tillering and inflorescence development that several researchers have reported for the PGR, Chlormequat, were not evident. The experiments showed that Paclobutrazol is effective on Morex spring barley as a chemical lodging control agent and yield enhancer. A clear association of reduced height with lodging control and concomitantly with yield increases was shown by the data. The absence of improved stem strength raised questions concerning the mechanism of Paclobutrazol's effect on the barley species and the possible mechanism of its effect in combination with nitrogen fertility. Title: Lodging control and yield enhancement in Morex spring barley with paclobutrazol treatment Author: Morrison, Laura A. Lodging in cereals can cause significant decreases in yield. It is both a problem in susceptible cereal cultivars with a tall-stemmed, weak-strawed growing habit and in lodging-resistant cereal cultivars when they are grown under high-nitrogen, high-moisture regimes. Plant growth regulators (PGR's) are chemical growth retardants that offer a method of lodging control. For the susceptible cultivars that are not amenable to genetic shortening through plant breeding, PGR's accomplish on a seasonal basis what has not been possible through gene manipulation. For cultivars that become susceptible in the high-intensive systems of modern agriculture, PGR's can be integrated into the chemical regime to control the lodging-promoting conditions created by yield-promotion practices. Morex spring barley is a lodging-susceptible cultivar that is tall-stemmed and weak-strawed. This growth habit aggravates the lodging problem when Morex is grown under intensive yield-promoting conditions. In greenhouse and field experiments, chemical control of the Morex lodging tendency was tested with an experimental chemical, Paclobutrazol. Paclobutrazol acts on the endogenous gibberellin hormone system in the plant by inhibiting its synthesis. The chemical's effect on the cereal plant is reported to occur in the internodes which Paclobutrazol shortens by decreasing longitudinal growth and strengthens by increasing transverse growth. Lodging control is realized through height reduction which lessens the torque effect created by the weather conditions that actually cause the event of lodging to occur. Paclobutrazol caused significant shortening of the basal internodes in the greenhouse and field experiments. Uncharacteristic of the expected effect, the PGR did not strengthen the shortened internodes. Specific stem weight and breaking strength values for the treated plants were significantly lower than the corresponding control values. In the field, Paclobutrazol delayed lodging until after the critical lodging period that occurs from approximately 15 days before anthesis to 15 days after anthesis. Lodging control was reflected in yield increases. Treated plots yielded significantly higher than did the control plots. The two high treatments of 800 and 1000 g/ha also yielded significantly higher than did the low treatments of 400 and 600 g/ha. Yield increases in the treated plots can be attributed to improved seed filling given the fact that lodging in the control plots occurred during the period when yield losses are caused by poor seed development. Unfortunately, the data did not give any clear indication of other possible sources of yield enhancement. Beneficial effects of Paclobutrazol on the tillering and inflorescence development that several researchers have reported for the PGR, Chlormequat, were not evident. The experiments showed that Paclobutrazol is effective on Morex spring barley as a chemical lodging control agent and yield enhancer. A clear association of reduced height with lodging control and concomitantly with yield increases was shown by the data. The absence of improved stem strength raised questions concerning the mechanism of Paclobutrazol's effect on the barley species and the possible mechanism of its effect in combination with nitrogen fertility. Close

• 450. [Article] Rift Valley fever in African buffalo (Syncerus caffer) : basic epidemiology and the role of bovine tuberculosis coinfection

  Rift Valley fever (RVF) is a mosquito-borne zoonotic viral disease native to the African continent. Outbreaks tend to occur in the wet seasons, and can affect numerous mammalian species including African ...

  Citation × Citation Citation Abstract Copy Title: Rift Valley fever in African buffalo (Syncerus caffer) : basic epidemiology and the role of bovine tuberculosis coinfection Author: Beechler, Brianna Rift Valley fever (RVF) is a mosquito-borne zoonotic viral disease native to the African continent. Outbreaks tend to occur in the wet seasons, and can affect numerous mammalian species including African buffalo. It is debated how the virus survives the inter-epidemic period when it is not detected in mammalian populations, either in cryptic wildlife hosts or by vertical transmission in mosquito hosts. In chapters 1 and 2 of this dissertation I show that buffalo do become infected in the inter-epidemic period although that is not sufficient to maintain viral cycling in the system without additional mammalian hosts and high vertical transmission rates. Bovine tuberculosis is an emerging disease in sub-Saharan Africa, first detected in Kruger National Park buffalo populations in 1990. African buffalo are a maintenance host for BTB in the ecosystem, and there has been detailed research about pathogen provenance and diversity, effects on the host and transmission dynamics. These studies have focused on a single invasive pathogen, BTB – despite the fact that buffalo act as hosts for a multitude of pathogens. Fundamental theory in community ecology and immunology suggests that parasites within a host should interact, by sharing resources, competing for resources or by altering the immune response. In chapter 3 I show that animals with BTB are more likely to become infected with RVF, more likely to show clinical signs and that the presence of BTB increases the size of RVF epidemics in African buffalo. In chapters 4 and 5 I demonstrate that one of the mechanisms underlying this pattern may be immune-mediated whereby animals with BTB have altered susceptibility to RVF. Understanding how emerging diseases, like BTB, may affect native host-pathogen or pathogen - pathogen interactions will help us understand the full impact that emerging diseases may have on an ecosystem. Title: Rift Valley fever in African buffalo (Syncerus caffer) : basic epidemiology and the role of bovine tuberculosis coinfection Author: Beechler, Brianna Rift Valley fever (RVF) is a mosquito-borne zoonotic viral disease native to the African continent. Outbreaks tend to occur in the wet seasons, and can affect numerous mammalian species including African buffalo. It is debated how the virus survives the inter-epidemic period when it is not detected in mammalian populations, either in cryptic wildlife hosts or by vertical transmission in mosquito hosts. In chapters 1 and 2 of this dissertation I show that buffalo do become infected in the inter-epidemic period although that is not sufficient to maintain viral cycling in the system without additional mammalian hosts and high vertical transmission rates. Bovine tuberculosis is an emerging disease in sub-Saharan Africa, first detected in Kruger National Park buffalo populations in 1990. African buffalo are a maintenance host for BTB in the ecosystem, and there has been detailed research about pathogen provenance and diversity, effects on the host and transmission dynamics. These studies have focused on a single invasive pathogen, BTB – despite the fact that buffalo act as hosts for a multitude of pathogens. Fundamental theory in community ecology and immunology suggests that parasites within a host should interact, by sharing resources, competing for resources or by altering the immune response. In chapter 3 I show that animals with BTB are more likely to become infected with RVF, more likely to show clinical signs and that the presence of BTB increases the size of RVF epidemics in African buffalo. In chapters 4 and 5 I demonstrate that one of the mechanisms underlying this pattern may be immune-mediated whereby animals with BTB have altered susceptibility to RVF. Understanding how emerging diseases, like BTB, may affect native host-pathogen or pathogen - pathogen interactions will help us understand the full impact that emerging diseases may have on an ecosystem. Close