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• 51. [Article] Marine, Estuarine, and Diadromous Fish Stocks at Risk of Extinction in North America (Exclusive of Pacific Salmonids)

  The problem of extinction in the sea has been recognized only recently by the scientific community (Roberts and Hawkins 1999). For the last decade, the American Fisheries Society (AFS) has pursued an initiative ...

  Citation × Citation Citation Abstract Copy Title: Marine, Estuarine, and Diadromous Fish Stocks at Risk of Extinction in North America (Exclusive of Pacific Salmonids) Author: Sala, E., Musick, J.A., Gilmore, R.G., Sedberry, G.R., Harbin, M.M., McGovern, J.C., Poss, S.G., Weeks, H., Parker, S.J., Schmidt, T.W., Burgess, G.H., Eklund, A.M., Golden, J.T., Ha, D.S., Findley, L., Berkeley, S.A., Huntsman, G.R., Wright, S.G. The problem of extinction in the sea has been recognized only recently by the scientific community (Roberts and Hawkins 1999). For the last decade, the American Fisheries Society (AFS) has pursued an initiative to identify marine fish stocks that may be at risk of extinction in North America (Musick 1998; Coleman et al. 2000; Musick et al. 2000a; Musick et al. 2000b; Parker et al. 2000). The present paper presents the first recognized AFS list of marine, estuarine, and diadromous fishes that may be at risk of extinction in North America (exclusive of Pacific salmonids). The geographic scope of this review includes the coastal waters of Mexico, the continental United States, Alaska, and Canada. The objectives in preparing this list have been to identify stocks at risk at a sufficiently early stage of decline to avoid listing as threatened or endangered, minimize the probability of under- or overestimating the risk of extinction, use the best existing knowledge of stock dynamics at low population levels, and allow experts on stocks to bring to bear all the available knowledge about life history and conservation status in order to categorize risk of extinction. Title: Marine, Estuarine, and Diadromous Fish Stocks at Risk of Extinction in North America (Exclusive of Pacific Salmonids) Author: Sala, E., Musick, J.A., Gilmore, R.G., Sedberry, G.R., Harbin, M.M., McGovern, J.C., Poss, S.G., Weeks, H., Parker, S.J., Schmidt, T.W., Burgess, G.H., Eklund, A.M., Golden, J.T., Ha, D.S., Findley, L., Berkeley, S.A., Huntsman, G.R., Wright, S.G. The problem of extinction in the sea has been recognized only recently by the scientific community (Roberts and Hawkins 1999). For the last decade, the American Fisheries Society (AFS) has pursued an initiative to identify marine fish stocks that may be at risk of extinction in North America (Musick 1998; Coleman et al. 2000; Musick et al. 2000a; Musick et al. 2000b; Parker et al. 2000). The present paper presents the first recognized AFS list of marine, estuarine, and diadromous fishes that may be at risk of extinction in North America (exclusive of Pacific salmonids). The geographic scope of this review includes the coastal waters of Mexico, the continental United States, Alaska, and Canada. The objectives in preparing this list have been to identify stocks at risk at a sufficiently early stage of decline to avoid listing as threatened or endangered, minimize the probability of under- or overestimating the risk of extinction, use the best existing knowledge of stock dynamics at low population levels, and allow experts on stocks to bring to bear all the available knowledge about life history and conservation status in order to categorize risk of extinction. Close

• 52. [Article] Reproductive isolation and interspecific hybridization in the threatened species, Sidalcea nelsoniana

  In addition to its longstanding recognition as an influential evolutionary process, interspecific hybridization is increasingly regarded as a potential threat to the genetic integrity and survival of rare ...

  Citation × Citation Citation Abstract Copy Title: Reproductive isolation and interspecific hybridization in the threatened species, Sidalcea nelsoniana Author: Gisler, Steven D. In addition to its longstanding recognition as an influential evolutionary process, interspecific hybridization is increasingly regarded as a potential threat to the genetic integrity and survival of rare plant species, manifested through gamete wasting, increased pest and disease pressures, outbreeding depression, competitive exclusion, and genetic assimilation. Alternatively, hybridization has also been interpreted as a theoretically beneficial process for rare species suffering from low adaptive genetic diversity and accumulated genetic load. As such, interspecific hybridization, and the underlying pre- and post-mating reproductive barriers that influence its progression, should be considered fundamental components of conservation planning for many rare species, particularly those predisposed to hybridization by various ecological, genetic, and anthropogenic risk factors. In this study I evaluate the nature and efficacy of preand post-mating hybridization barriers in the threatened species, Sidalcea nelsoniana, which is sympatric (or nearly so) with three other congeners in the scarce native grasslands of the Willamette Valley in western Oregon. These four perennial species share a high risk of hybridization due to their mutual proximity, common occupation of disturbed habitats, susceptibility to anthropogenic dispersal, predominantly outcrossing mating systems, their capability of longlived persistence and vegetative expansion, and demonstrated hybridization tendencies among other members of the family and genus. Results show S. nelsoniana is reproductively isolated from all three of its congeners by a complex interplay of pre- and post-mating barriers. Although S. nelsoniana overlaps with S. campestris in the ecological attributes of flowering time, fine-scale geographic distribution, and pollinators, interspecific hybridization is discouraged through the post-mating barrier of sexual incompatibility (expressed primarily as reduced seed set). Hybridization between S. nelsoniana and S. virgata is limited by the premating barrier of asynchronous flowering (temporal isolation) and the supplemental post-mating barrier of sexual incompatibility, though the completeness of the latter varies in relation to crossing direction and S. virgata phenotype. Lastly, although S. nelsoniana and S. cusickii exhibit full interspecific sexual compatibility and produce fully fertile hybrids, hybridization in this species pair is discouraged by the pre-mating barrier of geographic isolation (the two species are narrowly parapatric). Additional findings of this study show that 1) pollinators transferred significantly more S. nelsoniana pollen to the heterospecific flowers of S. virgata and S. cusickii than to conspecific flowers (or those of S. campestris) in a mixed species array, 2) anthropogenic disturbance is ubiquitous across extant S. nelsoniana study populations so cannot be conclusively linked with the breakdown of spatial reproductive barriers, 3) polyploidy is confirmed in the species group and appears to directly influence the observed patterns of interspecific sexual compatibility and the chromosome numbers of hybrids, and 4) Fl hybrids exhibit a mosaic of parental, intermediate, and transgressive phenotypic characters that render hybrid discrimination difficult (especially in light of pronounced parental phenotypic variability). Ultimately, despite the presence of pre- and post-mating reproductive barriers, hybridization between Sidalcea nelsoniana and its local congeners is still possible through human intervention. Preserving the species' current genetic integrity will require prevention of Sidalcea dispersal that could lead to the breakdown of spatial, temporal, and sexual barriers between species. Development of useful molecular markers will be needed to help recognize hybrids in the wild, as traditional morphological methods appear inadequate for this endeavor. Title: Reproductive isolation and interspecific hybridization in the threatened species, Sidalcea nelsoniana Author: Gisler, Steven D. In addition to its longstanding recognition as an influential evolutionary process, interspecific hybridization is increasingly regarded as a potential threat to the genetic integrity and survival of rare plant species, manifested through gamete wasting, increased pest and disease pressures, outbreeding depression, competitive exclusion, and genetic assimilation. Alternatively, hybridization has also been interpreted as a theoretically beneficial process for rare species suffering from low adaptive genetic diversity and accumulated genetic load. As such, interspecific hybridization, and the underlying pre- and post-mating reproductive barriers that influence its progression, should be considered fundamental components of conservation planning for many rare species, particularly those predisposed to hybridization by various ecological, genetic, and anthropogenic risk factors. In this study I evaluate the nature and efficacy of preand post-mating hybridization barriers in the threatened species, Sidalcea nelsoniana, which is sympatric (or nearly so) with three other congeners in the scarce native grasslands of the Willamette Valley in western Oregon. These four perennial species share a high risk of hybridization due to their mutual proximity, common occupation of disturbed habitats, susceptibility to anthropogenic dispersal, predominantly outcrossing mating systems, their capability of longlived persistence and vegetative expansion, and demonstrated hybridization tendencies among other members of the family and genus. Results show S. nelsoniana is reproductively isolated from all three of its congeners by a complex interplay of pre- and post-mating barriers. Although S. nelsoniana overlaps with S. campestris in the ecological attributes of flowering time, fine-scale geographic distribution, and pollinators, interspecific hybridization is discouraged through the post-mating barrier of sexual incompatibility (expressed primarily as reduced seed set). Hybridization between S. nelsoniana and S. virgata is limited by the premating barrier of asynchronous flowering (temporal isolation) and the supplemental post-mating barrier of sexual incompatibility, though the completeness of the latter varies in relation to crossing direction and S. virgata phenotype. Lastly, although S. nelsoniana and S. cusickii exhibit full interspecific sexual compatibility and produce fully fertile hybrids, hybridization in this species pair is discouraged by the pre-mating barrier of geographic isolation (the two species are narrowly parapatric). Additional findings of this study show that 1) pollinators transferred significantly more S. nelsoniana pollen to the heterospecific flowers of S. virgata and S. cusickii than to conspecific flowers (or those of S. campestris) in a mixed species array, 2) anthropogenic disturbance is ubiquitous across extant S. nelsoniana study populations so cannot be conclusively linked with the breakdown of spatial reproductive barriers, 3) polyploidy is confirmed in the species group and appears to directly influence the observed patterns of interspecific sexual compatibility and the chromosome numbers of hybrids, and 4) Fl hybrids exhibit a mosaic of parental, intermediate, and transgressive phenotypic characters that render hybrid discrimination difficult (especially in light of pronounced parental phenotypic variability). Ultimately, despite the presence of pre- and post-mating reproductive barriers, hybridization between Sidalcea nelsoniana and its local congeners is still possible through human intervention. Preserving the species' current genetic integrity will require prevention of Sidalcea dispersal that could lead to the breakdown of spatial, temporal, and sexual barriers between species. Development of useful molecular markers will be needed to help recognize hybrids in the wild, as traditional morphological methods appear inadequate for this endeavor. Close

• 53. [Article] Age, growth and maturity of the longnose skate (Raja rhina) for the U.S. west coast and sensitivity to fishing impacts

  In the past, sharks, skates and ray species have mainly occurred in incidental fisheries. Now they are increasingly being directly targeted due to the depleted status of traditionally targeted species. ...

  Citation × Citation Citation Abstract Copy Title: Age, growth and maturity of the longnose skate (Raja rhina) for the U.S. west coast and sensitivity to fishing impacts Author: Thompson, Josie E. In the past, sharks, skates and ray species have mainly occurred in incidental fisheries. Now they are increasingly being directly targeted due to the depleted status of traditionally targeted species. The life history characteristics of many elasmobranch species make them more sensitive to high rates of fishing mortality. The combination of these factors has resulted in the known local depletion of several elasmobranch species; including the barndoor skate, Raja laevis, of the Northwest Atlantic and the common skate, Raja batis, of Irish Sea. The longnose skate, Raja rhina, occurs commonly as incidental catch in trawl fisheries off the coast of California, Oregon and Washington. Commercial landings of skates, including R. rhina, have increased dramatically along the U.S. West coast. The objectives of this study have been to calculate accurate growth and maturity parameters for Raja rhina in order that the vulnerability of this species to fishing mortality can be assessed. The slow growth rates (k=0.04 to 0.06) and late ages-at-50% maturity (11 to 16 years with maximum ages between 15 and 22 years, depending on sex and region) which were calculated indicate that this species may be at great risk of depletion in the future. Survey biomass trends indicate that R. rhina populations have remained stable over the past twenty years. However, the possibility that biomass levels in the distant past were much higher than they are at present cannot be ruled out. It is recommended that the collection of fishery-dependent data for this species and other skate species begins immediately. This information, along with the results found in this are needed for a proper assessment for Raja rhina, so that the effects of current fishing pressures can be evaluated and regulated appropriately. Title: Age, growth and maturity of the longnose skate (Raja rhina) for the U.S. west coast and sensitivity to fishing impacts Author: Thompson, Josie E. In the past, sharks, skates and ray species have mainly occurred in incidental fisheries. Now they are increasingly being directly targeted due to the depleted status of traditionally targeted species. The life history characteristics of many elasmobranch species make them more sensitive to high rates of fishing mortality. The combination of these factors has resulted in the known local depletion of several elasmobranch species; including the barndoor skate, Raja laevis, of the Northwest Atlantic and the common skate, Raja batis, of Irish Sea. The longnose skate, Raja rhina, occurs commonly as incidental catch in trawl fisheries off the coast of California, Oregon and Washington. Commercial landings of skates, including R. rhina, have increased dramatically along the U.S. West coast. The objectives of this study have been to calculate accurate growth and maturity parameters for Raja rhina in order that the vulnerability of this species to fishing mortality can be assessed. The slow growth rates (k=0.04 to 0.06) and late ages-at-50% maturity (11 to 16 years with maximum ages between 15 and 22 years, depending on sex and region) which were calculated indicate that this species may be at great risk of depletion in the future. Survey biomass trends indicate that R. rhina populations have remained stable over the past twenty years. However, the possibility that biomass levels in the distant past were much higher than they are at present cannot be ruled out. It is recommended that the collection of fishery-dependent data for this species and other skate species begins immediately. This information, along with the results found in this are needed for a proper assessment for Raja rhina, so that the effects of current fishing pressures can be evaluated and regulated appropriately. Close

• 54. [Article] Performance of Willamette Valley native plants following herbicide exposure

  Prairies were once the dominant vegetation type in Oregon's Willamette Valley. Land use conversion, fire suppression, succession, and invasive species have reduced Willamette Valley prairies to less than ...

  Citation × Citation Citation Abstract Copy Title: Performance of Willamette Valley native plants following herbicide exposure Author: Blakeley-Smith, Matthew R. Prairies were once the dominant vegetation type in Oregon's Willamette Valley. Land use conversion, fire suppression, succession, and invasive species have reduced Willamette Valley prairies to less than 1% of their historical area. The remnant prairies that persist today are small in size and are highly fragmented. Marginal strips of habitat along roadsides and agricultural fields play an important role as refugia for native species and provide important resources for wildlife. These seemingly insignificant habitat units may also play an important role in facilitating gene flow between disjunct populations of prairie plants, thus reducing the potential for the negative effects of inbreeding depression. Presently, much of the land area in the Willamette Valley is dedicated to commercial agricultural which is heavily reliant on herbicides for weed control and field preparation. Since herbicide applications are imprecise and prone to drift, there is potential to impact the native plants surrounding these agricultural fields. Current EPA methods for assessing the ecological effects of herbicides may not be robust enough to account for potential impacts on native plants since the suggested test species are ten annual agricultural crops. To address the need for improved phytotoxicity testing protocols, we incorporated non-crop plant species into the EPA vegetative vigor test methodology for use in determining effects of low concentrations of chemical herbicides on Willamette Valley terrestrial plants. A separate experiment was conducted in order to determine how herbicides might be used to restore Butterfly Meadows, a degraded Willamette Valley prairie. The specific objective of this study were to: 1.) determine which herbicide treatments were most effective at reducing dominance of an invasive species, Brachypodium sylvaticum, 2.) determine if native species declined following herbicide treatments, and 3.) describe the compositional changes in the plant communities over a four-year period. The EPA vegetative vigor test study showed that there was a wide variety of responses among 17 species (14 native and 3 introduced) to each herbicide tested (glyphosate, tribenuron, and fluazifop). For glyphosate, Potentilla gracilis was the most sensitive species based on an EC25 value of 0.012 x f.a.r. for dry weight; while Bromus carinatus, Clarkia amoena, Gilia capitata, and Lupinus albicaulis were tolerant to glyphosate as indicated by no effect on dry weight. Seven Willamette Valley forb species were sensitive to tribenuron based on EC25 values ranging from 0.001 to 0.012 x f.a.r.; Clarkia amoena, Collinsia grandflora, Leucanthemum vulgare, Potentilla gracilis, Prunella vulgaris, Ranunculus occidentalis and Sanquisorba occidentalis. Six grass species and Eriophyllum lanatum were resistant to tribenuron showing no reduction in dry weight. Fluazifop primarily affected grass species as expected due to the grass-specific activity for this herbicide. Two native grasses, Elymus trachycaulus and Danthonia californica were the most sensitive to fluazifop, based on low EC25 values of 0.002 to 0.010 x f.a.r. A native fescue grass, Festuca roemeri, and nearly all the forb species were resistant to fluazifop, showing no response at any herbicide rate applied. The results from this research will be useful as background information for evaluating potential modifications in the EPA's Vegetative Vigor Test to assess the risk of herbicides to non-target plants. Seven different herbicide combinations were effective at reducing the cover of Brachypodium sylvaticum in test plots at Butterfly Meadows one year after treatment. The reduction of B. sylvaticum was short lived however, since the cover of this grass species was not different from control plots during the second growing season. Native plant species were not negatively impacted by the herbicide treatments, as shown by MRPP analysis. Successional trajectories illustrate that control plots that were dominated by B. sylvaticum remained relatively unchanged over the course of four years. Some treatments exhibited a sharp decline in dominance by graminoids after the first year, a recovery the second year, but never returned exactly to their pretreatment community composition after the third year. The reduction of the dominant species after the first growing season was associated with colonization by a number of introduced species into the newly created open habitat. Over the same period there was no overall increase in native species cover, suggesting that the native species at this site may be recruitment limited. Future restoration activities at this site should include multiple years of B. sylvaticum control, with special attention to the seed bank and tolerant individuals. Seed additions of native species may help fill empty niches and afford resistance to invasion by introduced species. Title: Performance of Willamette Valley native plants following herbicide exposure Author: Blakeley-Smith, Matthew R. Prairies were once the dominant vegetation type in Oregon's Willamette Valley. Land use conversion, fire suppression, succession, and invasive species have reduced Willamette Valley prairies to less than 1% of their historical area. The remnant prairies that persist today are small in size and are highly fragmented. Marginal strips of habitat along roadsides and agricultural fields play an important role as refugia for native species and provide important resources for wildlife. These seemingly insignificant habitat units may also play an important role in facilitating gene flow between disjunct populations of prairie plants, thus reducing the potential for the negative effects of inbreeding depression. Presently, much of the land area in the Willamette Valley is dedicated to commercial agricultural which is heavily reliant on herbicides for weed control and field preparation. Since herbicide applications are imprecise and prone to drift, there is potential to impact the native plants surrounding these agricultural fields. Current EPA methods for assessing the ecological effects of herbicides may not be robust enough to account for potential impacts on native plants since the suggested test species are ten annual agricultural crops. To address the need for improved phytotoxicity testing protocols, we incorporated non-crop plant species into the EPA vegetative vigor test methodology for use in determining effects of low concentrations of chemical herbicides on Willamette Valley terrestrial plants. A separate experiment was conducted in order to determine how herbicides might be used to restore Butterfly Meadows, a degraded Willamette Valley prairie. The specific objective of this study were to: 1.) determine which herbicide treatments were most effective at reducing dominance of an invasive species, Brachypodium sylvaticum, 2.) determine if native species declined following herbicide treatments, and 3.) describe the compositional changes in the plant communities over a four-year period. The EPA vegetative vigor test study showed that there was a wide variety of responses among 17 species (14 native and 3 introduced) to each herbicide tested (glyphosate, tribenuron, and fluazifop). For glyphosate, Potentilla gracilis was the most sensitive species based on an EC25 value of 0.012 x f.a.r. for dry weight; while Bromus carinatus, Clarkia amoena, Gilia capitata, and Lupinus albicaulis were tolerant to glyphosate as indicated by no effect on dry weight. Seven Willamette Valley forb species were sensitive to tribenuron based on EC25 values ranging from 0.001 to 0.012 x f.a.r.; Clarkia amoena, Collinsia grandflora, Leucanthemum vulgare, Potentilla gracilis, Prunella vulgaris, Ranunculus occidentalis and Sanquisorba occidentalis. Six grass species and Eriophyllum lanatum were resistant to tribenuron showing no reduction in dry weight. Fluazifop primarily affected grass species as expected due to the grass-specific activity for this herbicide. Two native grasses, Elymus trachycaulus and Danthonia californica were the most sensitive to fluazifop, based on low EC25 values of 0.002 to 0.010 x f.a.r. A native fescue grass, Festuca roemeri, and nearly all the forb species were resistant to fluazifop, showing no response at any herbicide rate applied. The results from this research will be useful as background information for evaluating potential modifications in the EPA's Vegetative Vigor Test to assess the risk of herbicides to non-target plants. Seven different herbicide combinations were effective at reducing the cover of Brachypodium sylvaticum in test plots at Butterfly Meadows one year after treatment. The reduction of B. sylvaticum was short lived however, since the cover of this grass species was not different from control plots during the second growing season. Native plant species were not negatively impacted by the herbicide treatments, as shown by MRPP analysis. Successional trajectories illustrate that control plots that were dominated by B. sylvaticum remained relatively unchanged over the course of four years. Some treatments exhibited a sharp decline in dominance by graminoids after the first year, a recovery the second year, but never returned exactly to their pretreatment community composition after the third year. The reduction of the dominant species after the first growing season was associated with colonization by a number of introduced species into the newly created open habitat. Over the same period there was no overall increase in native species cover, suggesting that the native species at this site may be recruitment limited. Future restoration activities at this site should include multiple years of B. sylvaticum control, with special attention to the seed bank and tolerant individuals. Seed additions of native species may help fill empty niches and afford resistance to invasion by introduced species. Close

• 55. [Article] Per capita invasion probabilities: an empirical model to predict rates of invasion via ballast water

  To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Ecological ...

  Citation × Citation Citation Abstract Copy Title: Per capita invasion probabilities: an empirical model to predict rates of invasion via ballast water Author: Minton, Mark S., Lee, Henry II, Reusser, Deborah A., Fofonoff, Paul W., Frazier, Melanie, Miller, Whitman, Ruiz, Gregory M. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Ecological Society of America and can be found at: http://esa.org/. Title: Per capita invasion probabilities: an empirical model to predict rates of invasion via ballast water Author: Minton, Mark S., Lee, Henry II, Reusser, Deborah A., Fofonoff, Paul W., Frazier, Melanie, Miller, Whitman, Ruiz, Gregory M. To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work. This is the publisher’s final pdf. The published article is copyrighted by Ecological Society of America and can be found at: http://esa.org/. Close

• 56. [Article] Host-pathogen dynamics in a changing environment : susceptibility of amphibians to an emerging infectious disease

  Infectious diseases are a growing concern for both humans and wildlife. The negative effects of infectious disease have been exemplified by the recent global amphibian population declines associated with ...

  Citation × Citation Citation Abstract Copy Title: Host-pathogen dynamics in a changing environment : susceptibility of amphibians to an emerging infectious disease Author: Searle, Catherine L. Infectious diseases are a growing concern for both humans and wildlife. The negative effects of infectious disease have been exemplified by the recent global amphibian population declines associated with disease outbreaks. Although multiple pathogens and factors play a role in these declines, the aquatic fungal pathogen, Batrachochytrium dendrobatidis (Bd), has received considerable attention due to its substantial contribution to amphibian population declines around the world. Bd prevalence and severity appears to be increasing worldwide, either from recent anthropogenic spread of the pathogen or from changes in the environment that have altered host-pathogen dynamics. This dissertation explores the factors that affect host susceptibility to Bd. I first tested the effects of hormonal stress on susceptibility to Bd (Chapter 2). Using corticosterone, the major chronic stress hormone in amphibians, I was able to mimic the physiological effects of stress without altering other factors that may affect the host-pathogen relationship. I exposed three species of larval amphibians to corticosterone for two weeks to induce chronic stress before challenging them with exposure to Bd. I found that exposure to corticosterone did not alter infection prevalence or severity in any species, indicating that chronically elevated levels of corticosterone do not affect susceptibility to Bd. I next examined the interactive effects of the ubiquitous stressor, ultraviolet-B radiation (UVB), and host infection by Bd (Chapter 3). UVB can cause lethal and sublethal effects in amphibians, including increased susceptibility to pathogens. In outdoor mesocosms, I used ambient levels of UVB to stress larval amphibians while simultaneously exposing them to Bd. Although exposure to UVB increased mortality, it did not alter infection. To investigate the effects of community structure on infection prevalence and severity, I studied how six anuran species (frogs and toads) differed in susceptibility to Bd (Chapter 4). I experimentally exposed post-metamorphic amphibians native to North America to Bd under identical laboratory conditions. All species tested had higher rates of mortality when exposed to Bd compared to unexposed controls. However, the species differed widely in their rates of Bd-associated mortality, even though there was no difference in infection levels among species. I also found that within species, the relationship between body size and infection varied, indicating physiological differences in the way that amphibian species respond to pathogen infection. Finally, I studied the effects of the amphibian host community on infection. I experimentally exposed larval amphibians to Bd after manipulating host density and species richness in the laboratory (Chapter 5). I recorded five measures of disease risk and found a dilution effect where greater species richness decreased disease risk, even after taking into account changes in density. Together with Chapter 4, this study emphasizes the need to understand the effects of the community on host-pathogen dynamics. This dissertation provides insight into the effects of stress and community structure on disease dynamics. Although there has been a great effort to understand Bd since it was discovered, the ecology of Bd remains relatively unknown. My research represents an important step in understanding the host-pathogen relationship in a changing environment. Title: Host-pathogen dynamics in a changing environment : susceptibility of amphibians to an emerging infectious disease Author: Searle, Catherine L. Infectious diseases are a growing concern for both humans and wildlife. The negative effects of infectious disease have been exemplified by the recent global amphibian population declines associated with disease outbreaks. Although multiple pathogens and factors play a role in these declines, the aquatic fungal pathogen, Batrachochytrium dendrobatidis (Bd), has received considerable attention due to its substantial contribution to amphibian population declines around the world. Bd prevalence and severity appears to be increasing worldwide, either from recent anthropogenic spread of the pathogen or from changes in the environment that have altered host-pathogen dynamics. This dissertation explores the factors that affect host susceptibility to Bd. I first tested the effects of hormonal stress on susceptibility to Bd (Chapter 2). Using corticosterone, the major chronic stress hormone in amphibians, I was able to mimic the physiological effects of stress without altering other factors that may affect the host-pathogen relationship. I exposed three species of larval amphibians to corticosterone for two weeks to induce chronic stress before challenging them with exposure to Bd. I found that exposure to corticosterone did not alter infection prevalence or severity in any species, indicating that chronically elevated levels of corticosterone do not affect susceptibility to Bd. I next examined the interactive effects of the ubiquitous stressor, ultraviolet-B radiation (UVB), and host infection by Bd (Chapter 3). UVB can cause lethal and sublethal effects in amphibians, including increased susceptibility to pathogens. In outdoor mesocosms, I used ambient levels of UVB to stress larval amphibians while simultaneously exposing them to Bd. Although exposure to UVB increased mortality, it did not alter infection. To investigate the effects of community structure on infection prevalence and severity, I studied how six anuran species (frogs and toads) differed in susceptibility to Bd (Chapter 4). I experimentally exposed post-metamorphic amphibians native to North America to Bd under identical laboratory conditions. All species tested had higher rates of mortality when exposed to Bd compared to unexposed controls. However, the species differed widely in their rates of Bd-associated mortality, even though there was no difference in infection levels among species. I also found that within species, the relationship between body size and infection varied, indicating physiological differences in the way that amphibian species respond to pathogen infection. Finally, I studied the effects of the amphibian host community on infection. I experimentally exposed larval amphibians to Bd after manipulating host density and species richness in the laboratory (Chapter 5). I recorded five measures of disease risk and found a dilution effect where greater species richness decreased disease risk, even after taking into account changes in density. Together with Chapter 4, this study emphasizes the need to understand the effects of the community on host-pathogen dynamics. This dissertation provides insight into the effects of stress and community structure on disease dynamics. Although there has been a great effort to understand Bd since it was discovered, the ecology of Bd remains relatively unknown. My research represents an important step in understanding the host-pathogen relationship in a changing environment. Close

• 57. [Article] Yellowfin Tuna: A Global and Uk Supply Chain Analysis

  No poster available.

  Citation × Citation Citation Abstract Copy Title: Yellowfin Tuna: A Global and Uk Supply Chain Analysis Author: Brown, Adam, Garrett, Angus No poster available. Title: Yellowfin Tuna: A Global and Uk Supply Chain Analysis Author: Brown, Adam, Garrett, Angus No poster available. Close

• 58. [Article] A population viability analysis of the Oregon chub (Oregonichthys crameri) in the Willamette Valley, Oregon

  The Oregon chub (Oregonichthys crameri) is a small minnow (Family: Cyprinidae) endemic to Oregon’s Willamette Valley. In 1993, the Oregon chub was listed as endangered because of habitat loss and predation ...

  Citation × Citation Citation Abstract Copy Title: A population viability analysis of the Oregon chub (Oregonichthys crameri) in the Willamette Valley, Oregon Author: Peterson, Erin The Oregon chub (Oregonichthys crameri) is a small minnow (Family: Cyprinidae) endemic to Oregon’s Willamette Valley. In 1993, the Oregon chub was listed as endangered because of habitat loss and predation and competition by nonnative fishes. Conservation efforts by the Oregon Department of Fish and Wildlife (ODFW) and other agencies have led the Oregon chub to become the first fish ever proposed for delisting due to recovery. The goal of this project was to analyze population parameters from 18 sites containing Oregon chub and determine how factors such as the presence of nonnative species and the supplementation of other chub might affect them. I used regression to determine overall trends for each population and a population viability analysis to evaluate quasi-extinction risk for each population. Results indicate that over long time periods, the supplementation of chub can reduce extinction risk, while the presence of nonnative fishes may cause populations to drop below critical thresholds for population size. The outcome of this project is important because it supports current management practices by showing that continued monitoring is needed to maintain the progress that has been made towards the recovery of the Oregon chub. Title: A population viability analysis of the Oregon chub (Oregonichthys crameri) in the Willamette Valley, Oregon Author: Peterson, Erin The Oregon chub (Oregonichthys crameri) is a small minnow (Family: Cyprinidae) endemic to Oregon’s Willamette Valley. In 1993, the Oregon chub was listed as endangered because of habitat loss and predation and competition by nonnative fishes. Conservation efforts by the Oregon Department of Fish and Wildlife (ODFW) and other agencies have led the Oregon chub to become the first fish ever proposed for delisting due to recovery. The goal of this project was to analyze population parameters from 18 sites containing Oregon chub and determine how factors such as the presence of nonnative species and the supplementation of other chub might affect them. I used regression to determine overall trends for each population and a population viability analysis to evaluate quasi-extinction risk for each population. Results indicate that over long time periods, the supplementation of chub can reduce extinction risk, while the presence of nonnative fishes may cause populations to drop below critical thresholds for population size. The outcome of this project is important because it supports current management practices by showing that continued monitoring is needed to maintain the progress that has been made towards the recovery of the Oregon chub. Close

• 59. [Article] Trait-based diet selection: Prey behaviour and morphology predict vulnerability to predation in reef fish communities

  This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the Author(s) and the British Ecological Society. It is published by John Wiley ...

  Citation × Citation Citation Abstract Copy Title: Trait-based diet selection: Prey behaviour and morphology predict vulnerability to predation in reef fish communities Author: Côté, Isabelle M., Green, Stephanie J. This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the Author(s) and the British Ecological Society. It is published by John Wiley & Sons, Inc., and can be found at: http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291365-2656 Title: Trait-based diet selection: Prey behaviour and morphology predict vulnerability to predation in reef fish communities Author: Côté, Isabelle M., Green, Stephanie J. This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the Author(s) and the British Ecological Society. It is published by John Wiley & Sons, Inc., and can be found at: http://onlinelibrary.wiley.com/journal/10.1111/%28ISSN%291365-2656 Close

• 60. [Article] Plant and amphibian assemblages in zero-order basins in the Oregon Coast Range

  We have a poor understanding of the biotic communities in zero-order basins, drainages extending from ridgelines to the initiation of first-order streams. This study describes baseline plant and amphibian ...

  Citation × Citation Citation Abstract Copy Title: Plant and amphibian assemblages in zero-order basins in the Oregon Coast Range Author: Sheridan, Chris D. We have a poor understanding of the biotic communities in zero-order basins, drainages extending from ridgelines to the initiation of first-order streams. This study describes baseline plant and amphibian composition in unmanaged zero-order basins in the Oregon Coast Range. Specifically, I studied: i) the spatial distribution and diversity of species, including riparian-associates; and ii) the dominant environmental, spatial and geomorphic gradients in species composition The results of this research have implications for riparian management in steep, forested landscapes in the Pacific Northwest. The composition of tree and shrub layers in zero-order basins was more similar to upland areas than to larger-order riparian areas. Douglas-fir, western hemlock, and western red cedar had highest basal areas; bigleaf maple had highest hardwood density. Convergent areas (areas collecting surface flow) had significantly lower relative densities than surrounding slopes. I identified 138 forest floor herb, shrub, and seedling tree species in zero-order basins. Gradient analysis and empirical modeling suggested that the composition of forest floor plant assemblages was associated with environmental parameters related to geomorphic position and overstory characteristics, such as distance from basin center, basin aspect and overstory relative density. Vegetation types, developed using classification, followed similar environmental patterns. Vegetation types were useful in clarifying environmental gradients acting on groups of plant species, and in delineating the lateral extent of geomorphic and fluvial influences. Riparian-associated vegetation types were mostly restricted to valley floors and lower slope areas. Geomorphic and lateral surfaces were drivers of environmental gradients in zero-order basins; plant species composition followed these geomorphic gradients. Surfaces close to basin center ("inner gorges"), including valley centers, splash zones, and lower slope areas, supported the highest plant species diversity and most distinct plant assemblages. The spatial distribution patterns of amphibian species and assemblages were characterized along longitudinal and lateral gradients, and relative to three geomorphic surfaces (valleys, headmost areas and slopes), and empirical species-habitat models were developed. I identified eight amphibian species in zero-order basins (865 total captures), and analyzed data for six. Headmost areas supported a distinctive upland amphibian assemblage, while valley floors had the highest riparian amphibian diversity. Captures of three riparian species were higher in valley surfaces, within S m of the center of zero-order basins, while captures of three upland species were highest in areas 2-5 m from center. Upland-associated species were captured two times farther from basin centers than riparian-associated species. The best predictors of amphibian captures in empirical models were geomorphic, stability/ disturbance, moisture and overstory parameters. Ordination and indicator species analysis facilitated characterization of amphibian species assemblages within geomorphic surface zones, and suggested spatial compression of habitats and species in zero-order basins, in comparison to broader spatial extents in larger basins. Plant and amphibian assemblages in unmanaged zero-order basins were most similar to each other in their lateral and geomorphic spatial patterning, including the importance of inner gorge areas for support of diverse communities. Plant species were strongly associated with geomorphic position parameters, while amphibians had stronger ties to discrete microhabitat elements such as moisture levels and large substrate. Amphibians appeared to have a more distinctive assemblage in headmost areas than plant species. Results suggest that assemblages of plants and amphibians in these basins are distinct from both larger-order riparian assemblages and from vegetation in surrounding hillslopes. Riparian management designs could take these spatial patterns and habitat associations into account to maintain the ecological integrity of headwater communities. The longitudinal and lateral extents of landscape areas managed to minimize risk to persistence of zero-order basin plant and amphibian assemblages would need to incorporate both fluvial and hillslope disturbance regimes, and microhabitat features associated with them. Title: Plant and amphibian assemblages in zero-order basins in the Oregon Coast Range Author: Sheridan, Chris D. We have a poor understanding of the biotic communities in zero-order basins, drainages extending from ridgelines to the initiation of first-order streams. This study describes baseline plant and amphibian composition in unmanaged zero-order basins in the Oregon Coast Range. Specifically, I studied: i) the spatial distribution and diversity of species, including riparian-associates; and ii) the dominant environmental, spatial and geomorphic gradients in species composition The results of this research have implications for riparian management in steep, forested landscapes in the Pacific Northwest. The composition of tree and shrub layers in zero-order basins was more similar to upland areas than to larger-order riparian areas. Douglas-fir, western hemlock, and western red cedar had highest basal areas; bigleaf maple had highest hardwood density. Convergent areas (areas collecting surface flow) had significantly lower relative densities than surrounding slopes. I identified 138 forest floor herb, shrub, and seedling tree species in zero-order basins. Gradient analysis and empirical modeling suggested that the composition of forest floor plant assemblages was associated with environmental parameters related to geomorphic position and overstory characteristics, such as distance from basin center, basin aspect and overstory relative density. Vegetation types, developed using classification, followed similar environmental patterns. Vegetation types were useful in clarifying environmental gradients acting on groups of plant species, and in delineating the lateral extent of geomorphic and fluvial influences. Riparian-associated vegetation types were mostly restricted to valley floors and lower slope areas. Geomorphic and lateral surfaces were drivers of environmental gradients in zero-order basins; plant species composition followed these geomorphic gradients. Surfaces close to basin center ("inner gorges"), including valley centers, splash zones, and lower slope areas, supported the highest plant species diversity and most distinct plant assemblages. The spatial distribution patterns of amphibian species and assemblages were characterized along longitudinal and lateral gradients, and relative to three geomorphic surfaces (valleys, headmost areas and slopes), and empirical species-habitat models were developed. I identified eight amphibian species in zero-order basins (865 total captures), and analyzed data for six. Headmost areas supported a distinctive upland amphibian assemblage, while valley floors had the highest riparian amphibian diversity. Captures of three riparian species were higher in valley surfaces, within S m of the center of zero-order basins, while captures of three upland species were highest in areas 2-5 m from center. Upland-associated species were captured two times farther from basin centers than riparian-associated species. The best predictors of amphibian captures in empirical models were geomorphic, stability/ disturbance, moisture and overstory parameters. Ordination and indicator species analysis facilitated characterization of amphibian species assemblages within geomorphic surface zones, and suggested spatial compression of habitats and species in zero-order basins, in comparison to broader spatial extents in larger basins. Plant and amphibian assemblages in unmanaged zero-order basins were most similar to each other in their lateral and geomorphic spatial patterning, including the importance of inner gorge areas for support of diverse communities. Plant species were strongly associated with geomorphic position parameters, while amphibians had stronger ties to discrete microhabitat elements such as moisture levels and large substrate. Amphibians appeared to have a more distinctive assemblage in headmost areas than plant species. Results suggest that assemblages of plants and amphibians in these basins are distinct from both larger-order riparian assemblages and from vegetation in surrounding hillslopes. Riparian management designs could take these spatial patterns and habitat associations into account to maintain the ecological integrity of headwater communities. The longitudinal and lateral extents of landscape areas managed to minimize risk to persistence of zero-order basin plant and amphibian assemblages would need to incorporate both fluvial and hillslope disturbance regimes, and microhabitat features associated with them. Close