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• 521. [Article] Top-down and Bottom-up Controls of Adelges tsugae in the Pacific Northwest Inform Its Biological Control in Eastern North America

  The hemlock woolly adelgid (Hemiptera: Adelgidae: Adelges tsugae; HWA) is an invasive and damaging pest on hemlock in eastern North America. HWA is native to the Pacific Northwest, where it does not damage ...

  Citation × Citation Citation Abstract Copy Title: Top-down and Bottom-up Controls of Adelges tsugae in the Pacific Northwest Inform Its Biological Control in Eastern North America Author: Rose, Alexander The hemlock woolly adelgid (Hemiptera: Adelgidae: Adelges tsugae; HWA) is an invasive and damaging pest on hemlock in eastern North America. HWA is native to the Pacific Northwest, where it does not damage hemlock. In support of classical biological control of HWA in eastern North America, abundances of native predators on HWA in the Pacific Northwest were assessed in an observational study. HWA and its predators were counted and identified on branch samples from western hemlock (Pinaceae: Tsuga heterophylla) in the Puget Sound area. Species densities were calculated on a per-centimeter basis. Two species of cryptic congeners, silver flies (Diptera: Chamaemyiidae: Leucopis argenticollis and Le. piniperda), were innovatively identified using DNA sequencing. More individuals of the two Leucopis spp. (120 in total) combined were found than the next most abundant predator (52 in total), a beetle (Coleoptera: Derodontidae: Laricobius nigrinus). Laricobius nigrinus has already been introduced by the hundreds of thousands and established on hemlock as part of HWA biological control efforts in eastern North America. However, La. nigrinus has not succeeded in perceptibly reducing hemlock decline or mortality there. Leucopis argenticollis was more abundant than Le. piniperda, with 55 flies identified as Le. argenticollis and 25 identified as Le. piniperda. Since ~67% of the flies were successfully identified to species, it was inferred using relative proportions that the most abundant predator collected was Le. argenticollis, with ~83 individuals, followed by La. nigrinus, and then Le. piniperda, with ~38 individuals. The occurrence of the Leucopis spp. on both seasonal generations of HWA, while La. nigrinus was found only on the early generation, confirmed a natural history difference between the flies and the beetle; Leucopis occurs and feeds on both generations of HWA, while La. nigrinus pupates underground during the late HWA generation. This implies that Leucopis could complement La. nigrinus in control of HWA. Because beetle pupae were not collected (whereas fly puparia were) due to this natural history difference, puparia were excluded for additional comparison. Leucopis spp. larvae and adults totaled 69 compared to 52 La. nigrinus. Since site was found to be non-significant as a factor in explaining mean cumulative species densities in three one-way ANOVAs (HWA: F-value = 1.88; d.f. = 3, 21, p-values = 0.17; Leucopis: F-value = 1.95; d.f. = 3, 21, p-values = 0.15; La. nigrinus: F-value = 0.4; d.f. = 3, 21, p-values = 0.75), densities were related across sites in further analysis. Pearson’s product-moment correlations of HWA and La. nigrinus densities were non-significant, while HWA and Leucopis spp. densities were positively correlated (e.g., for larval Leucopis densities, t-value = 2.64; d.f. = 23; p-value = < 0.01; 95% CI= 0.17 to 1; estimated correlation = 0.48). Combined larval and adult Leucopis spp. and La. nigrinus densities were moderately negatively correlated (t-value = -1.81; d.f. = 23; p-value = 0.04; 95% CI = -1 to 0.02; estimated correlation = -0.35). Leucopis argenticollis and Le. piniperda densities were negatively, though non-significantly, correlated (Spearman’s rank correlation coefficient: rho = -0.28; d.f. = 23; p-value = 0.09). In a companion project, HWA abundance levels were assessed on western hemlock clones of known genetics at a commercial seed orchard, allowing for consideration of spatial versus host resistance explanations for the distribution of HWA there. The results were not strongly supportive of potential resistance to HWA by western hemlock. Hence, evidence for bottom-up control of HWA in the Pacific Northwest was weak from this limited dataset, while the data on predators contributes to knowledge of top-down control of HWA in the Pacific Northwest. These results recommend further study of the Leucopis spp. for potential introduction as biocontrols of HWA in eastern North America. Title: Top-down and Bottom-up Controls of Adelges tsugae in the Pacific Northwest Inform Its Biological Control in Eastern North America Author: Rose, Alexander The hemlock woolly adelgid (Hemiptera: Adelgidae: Adelges tsugae; HWA) is an invasive and damaging pest on hemlock in eastern North America. HWA is native to the Pacific Northwest, where it does not damage hemlock. In support of classical biological control of HWA in eastern North America, abundances of native predators on HWA in the Pacific Northwest were assessed in an observational study. HWA and its predators were counted and identified on branch samples from western hemlock (Pinaceae: Tsuga heterophylla) in the Puget Sound area. Species densities were calculated on a per-centimeter basis. Two species of cryptic congeners, silver flies (Diptera: Chamaemyiidae: Leucopis argenticollis and Le. piniperda), were innovatively identified using DNA sequencing. More individuals of the two Leucopis spp. (120 in total) combined were found than the next most abundant predator (52 in total), a beetle (Coleoptera: Derodontidae: Laricobius nigrinus). Laricobius nigrinus has already been introduced by the hundreds of thousands and established on hemlock as part of HWA biological control efforts in eastern North America. However, La. nigrinus has not succeeded in perceptibly reducing hemlock decline or mortality there. Leucopis argenticollis was more abundant than Le. piniperda, with 55 flies identified as Le. argenticollis and 25 identified as Le. piniperda. Since ~67% of the flies were successfully identified to species, it was inferred using relative proportions that the most abundant predator collected was Le. argenticollis, with ~83 individuals, followed by La. nigrinus, and then Le. piniperda, with ~38 individuals. The occurrence of the Leucopis spp. on both seasonal generations of HWA, while La. nigrinus was found only on the early generation, confirmed a natural history difference between the flies and the beetle; Leucopis occurs and feeds on both generations of HWA, while La. nigrinus pupates underground during the late HWA generation. This implies that Leucopis could complement La. nigrinus in control of HWA. Because beetle pupae were not collected (whereas fly puparia were) due to this natural history difference, puparia were excluded for additional comparison. Leucopis spp. larvae and adults totaled 69 compared to 52 La. nigrinus. Since site was found to be non-significant as a factor in explaining mean cumulative species densities in three one-way ANOVAs (HWA: F-value = 1.88; d.f. = 3, 21, p-values = 0.17; Leucopis: F-value = 1.95; d.f. = 3, 21, p-values = 0.15; La. nigrinus: F-value = 0.4; d.f. = 3, 21, p-values = 0.75), densities were related across sites in further analysis. Pearson’s product-moment correlations of HWA and La. nigrinus densities were non-significant, while HWA and Leucopis spp. densities were positively correlated (e.g., for larval Leucopis densities, t-value = 2.64; d.f. = 23; p-value = < 0.01; 95% CI= 0.17 to 1; estimated correlation = 0.48). Combined larval and adult Leucopis spp. and La. nigrinus densities were moderately negatively correlated (t-value = -1.81; d.f. = 23; p-value = 0.04; 95% CI = -1 to 0.02; estimated correlation = -0.35). Leucopis argenticollis and Le. piniperda densities were negatively, though non-significantly, correlated (Spearman’s rank correlation coefficient: rho = -0.28; d.f. = 23; p-value = 0.09). In a companion project, HWA abundance levels were assessed on western hemlock clones of known genetics at a commercial seed orchard, allowing for consideration of spatial versus host resistance explanations for the distribution of HWA there. The results were not strongly supportive of potential resistance to HWA by western hemlock. Hence, evidence for bottom-up control of HWA in the Pacific Northwest was weak from this limited dataset, while the data on predators contributes to knowledge of top-down control of HWA in the Pacific Northwest. These results recommend further study of the Leucopis spp. for potential introduction as biocontrols of HWA in eastern North America. Close

• 522. [Article] Soil Resources Influence Vegetation and Response to Fire and Fire-Surrogate Treatments in Sagebrush-Steppe Ecosystems

  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 the Society ...

  Citation × Citation Citation Abstract Copy Title: Soil Resources Influence Vegetation and Response to Fire and Fire-Surrogate Treatments in Sagebrush-Steppe Ecosystems Author: Chambers, Jeanne C., Caldwell, Todd G., Schupp, Eugene W., Doescher, Paul, Rau, Benjamin M., Pyke, David A., Roundy, Bruce A. 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 the Society for Range Management and can be found at: http://www.bioone.org/loi/rama. Title: Soil Resources Influence Vegetation and Response to Fire and Fire-Surrogate Treatments in Sagebrush-Steppe Ecosystems Author: Chambers, Jeanne C., Caldwell, Todd G., Schupp, Eugene W., Doescher, Paul, Rau, Benjamin M., Pyke, David A., Roundy, Bruce A. 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 the Society for Range Management and can be found at: http://www.bioone.org/loi/rama. Close

• 523. [Article] Phenology, Host-Plant Resistance, and Biological Control of Stephanitis pyrioides in Oregon

  The azalea lace bug (Stephanitis pyrioides Scott) is a recently detected invasive pest to the Pacific Northwest and has become a major concern in Oregon. It feeds on azaleas as well as rhododendrons causing ...

  Citation × Citation Citation Abstract Copy Title: Phenology, Host-Plant Resistance, and Biological Control of Stephanitis pyrioides in Oregon Author: Flores, Salvador M. The azalea lace bug (Stephanitis pyrioides Scott) is a recently detected invasive pest to the Pacific Northwest and has become a major concern in Oregon. It feeds on azaleas as well as rhododendrons causing stippling on the top side of leaves. The damage is aesthetically displeasing and affects plant vigor and photosynthetic capabilities, and, in cases with severe damage, can kill plants. The objectives of this work were to: 1) monitor for the presence of potential natural enemies and life stages of S. pyrioides from 2014 to 2016 through sampling in the Willamette Valley in Oregon, 2) observe any resistant cultivars that may be present, and 3) examine biological control efficacy of S. pyrioides using a predator and pathogen. These three objectives were looked at to provide information on what natural enemies are present and what time of the year S. pyrioides control would be most effective, find potential plant characteristics that may confer resistance, and determine if biological control is a viable option to reduce S. pyrioides pest abundance. Two specialist natural enemies of S. pyrioides, Anagrus takeyanus Gordh and Stethoconus japonicus Schumacher were not found and only about 8% of all arthropods captured in sweep nets and 4% in sticky traps could potentially prey on S. pyrioides as generalist predators. From shake sampling and leaf collections, adults and eggs were found year round and a total of 8,780 S. pyrioides were collected for all stages. Over half of all collected adults were females. Nymphs were found almost exclusively during the spring and summer months. Roughly 3.5 generations, based on a total development time of 394 degree-days (DD) are estimated to have occurred using weather data from Salem, Oregon. Secondly, cultivar observations to evaluate natural resistance by assessing for infestation or damage provided a list of approximately 75 species and cultivars that had no evidence of azalea lace bug feeding. Of these 75, four cultivars, species and hybrids were tested in a laboratory for feeding and fecal deposition beside a susceptible cultivar. All four resistant rhododendrons had no feeding and resulted in mortality rates over 90%. Third, evaluations of biological control, specifically predation by a green lacewing, Chrysoperla rufilabris Burmeister, significantly reduced S. pyrioides per leaf in a nursery setting when combined with methyl salicylate in 2014. However, larger follow up studies in 2015 did not reflect these results. The pathogen Metarhizium anisopliae had a high mortality rate when sprayed, but only caused a marginally higher mortality rate when compared to water sprays. Overall, this work presents novel and valuable information on azaleas and rhododendrons and S. pyrioides in the Pacific Northwest. This work provides the framework of phenology, a mode of resistance and valuable information on biological control to consider and incorporate into future management of S. pyrioides in Oregon. Title: Phenology, Host-Plant Resistance, and Biological Control of Stephanitis pyrioides in Oregon Author: Flores, Salvador M. The azalea lace bug (Stephanitis pyrioides Scott) is a recently detected invasive pest to the Pacific Northwest and has become a major concern in Oregon. It feeds on azaleas as well as rhododendrons causing stippling on the top side of leaves. The damage is aesthetically displeasing and affects plant vigor and photosynthetic capabilities, and, in cases with severe damage, can kill plants. The objectives of this work were to: 1) monitor for the presence of potential natural enemies and life stages of S. pyrioides from 2014 to 2016 through sampling in the Willamette Valley in Oregon, 2) observe any resistant cultivars that may be present, and 3) examine biological control efficacy of S. pyrioides using a predator and pathogen. These three objectives were looked at to provide information on what natural enemies are present and what time of the year S. pyrioides control would be most effective, find potential plant characteristics that may confer resistance, and determine if biological control is a viable option to reduce S. pyrioides pest abundance. Two specialist natural enemies of S. pyrioides, Anagrus takeyanus Gordh and Stethoconus japonicus Schumacher were not found and only about 8% of all arthropods captured in sweep nets and 4% in sticky traps could potentially prey on S. pyrioides as generalist predators. From shake sampling and leaf collections, adults and eggs were found year round and a total of 8,780 S. pyrioides were collected for all stages. Over half of all collected adults were females. Nymphs were found almost exclusively during the spring and summer months. Roughly 3.5 generations, based on a total development time of 394 degree-days (DD) are estimated to have occurred using weather data from Salem, Oregon. Secondly, cultivar observations to evaluate natural resistance by assessing for infestation or damage provided a list of approximately 75 species and cultivars that had no evidence of azalea lace bug feeding. Of these 75, four cultivars, species and hybrids were tested in a laboratory for feeding and fecal deposition beside a susceptible cultivar. All four resistant rhododendrons had no feeding and resulted in mortality rates over 90%. Third, evaluations of biological control, specifically predation by a green lacewing, Chrysoperla rufilabris Burmeister, significantly reduced S. pyrioides per leaf in a nursery setting when combined with methyl salicylate in 2014. However, larger follow up studies in 2015 did not reflect these results. The pathogen Metarhizium anisopliae had a high mortality rate when sprayed, but only caused a marginally higher mortality rate when compared to water sprays. Overall, this work presents novel and valuable information on azaleas and rhododendrons and S. pyrioides in the Pacific Northwest. This work provides the framework of phenology, a mode of resistance and valuable information on biological control to consider and incorporate into future management of S. pyrioides in Oregon. Close

• 524. [Article] Native plant revegetation at Butterfly Meadows (Benton County), habitat for the endangered Fender's blue butterfly

  Native prairies, which once dominated the landscape of the Willamette Valley, are considered among the rarest of Oregon's ecosystems and are in critical need of conservation. One of the largest remaining ...

  Citation × Citation Citation Abstract Copy Title: Native plant revegetation at Butterfly Meadows (Benton County), habitat for the endangered Fender's blue butterfly Author: Clark, Deborah Louise, 1950- Native prairies, which once dominated the landscape of the Willamette Valley, are considered among the rarest of Oregon's ecosystems and are in critical need of conservation. One of the largest remaining parcels of native upland prairie, Butterfly Meadows (Benton County), is being invaded by Brachypodium sylvaticum (false brome). This site is one of three most important remaining habitats for the Fender's blue butterfly and Kincaid's lupine, federally listed as Endangered and Threatened respectively. Most of Butterfly Meadows is owned by Starker Forests (Corvallis) with a small portion owned by Oregon State University. A partnership was formed in 2002 of people and organizations interested in protecting and restoring Butterfly Meadows: Fred Pfund (Starker Forests) Matt Blakeley-Smith (Institute for Applied Ecology) Deborah Clark (Oregon State University, Biology Program) Paul Hammond (Entomologist, Private consultant) Debbie Johnson (Oregon State University, College Forests) Tom Kaye (Institute for Applied Ecology) Bruce Kelpsas (Helena Chemical Company) In fall 2002, the partnership submitted a proposal (Control of Brachypodium sylvaticum and Restoration of Rare Native Upland Prairie Habitat at Butterfly Meadows, Benton County) and received funding from the Oregon Department of Agriculture. The project goal was and is to protect and restore rare Willamette Valley upland prairie habitat at Butterfly Meadows (Benton County) from invasion by the noxious weed Brachypodium sylvaticum (false brome). Since receiving funding in 2002, the partnership has developed and implemented herbicide treatments, beginning with small scale experiments, which control Brachypodium sylvaticum without harming native prairie vegetation or the Fender's blue butterfly. We used the results of these small-scale experiments to develop strategies for restoration of larger areas of the Butterfly Meadows, which Starker Forests has implemented at its own expense. These strategies have been relatively successful in controlling false brome, but we are now at a time where we need to revegetate these areas where false brome has been controlled. These areas are too large to quickly revegetate with existing native herbaceous species, so we need to augment the site with additional seed. Transplanting greenhouse grown plants is also an option but is much more costly. We hope to apply for additional funding elsewhere for these transplants. Title: Native plant revegetation at Butterfly Meadows (Benton County), habitat for the endangered Fender's blue butterfly Author: Clark, Deborah Louise, 1950- Native prairies, which once dominated the landscape of the Willamette Valley, are considered among the rarest of Oregon's ecosystems and are in critical need of conservation. One of the largest remaining parcels of native upland prairie, Butterfly Meadows (Benton County), is being invaded by Brachypodium sylvaticum (false brome). This site is one of three most important remaining habitats for the Fender's blue butterfly and Kincaid's lupine, federally listed as Endangered and Threatened respectively. Most of Butterfly Meadows is owned by Starker Forests (Corvallis) with a small portion owned by Oregon State University. A partnership was formed in 2002 of people and organizations interested in protecting and restoring Butterfly Meadows: Fred Pfund (Starker Forests) Matt Blakeley-Smith (Institute for Applied Ecology) Deborah Clark (Oregon State University, Biology Program) Paul Hammond (Entomologist, Private consultant) Debbie Johnson (Oregon State University, College Forests) Tom Kaye (Institute for Applied Ecology) Bruce Kelpsas (Helena Chemical Company) In fall 2002, the partnership submitted a proposal (Control of Brachypodium sylvaticum and Restoration of Rare Native Upland Prairie Habitat at Butterfly Meadows, Benton County) and received funding from the Oregon Department of Agriculture. The project goal was and is to protect and restore rare Willamette Valley upland prairie habitat at Butterfly Meadows (Benton County) from invasion by the noxious weed Brachypodium sylvaticum (false brome). Since receiving funding in 2002, the partnership has developed and implemented herbicide treatments, beginning with small scale experiments, which control Brachypodium sylvaticum without harming native prairie vegetation or the Fender's blue butterfly. We used the results of these small-scale experiments to develop strategies for restoration of larger areas of the Butterfly Meadows, which Starker Forests has implemented at its own expense. These strategies have been relatively successful in controlling false brome, but we are now at a time where we need to revegetate these areas where false brome has been controlled. These areas are too large to quickly revegetate with existing native herbaceous species, so we need to augment the site with additional seed. Transplanting greenhouse grown plants is also an option but is much more costly. We hope to apply for additional funding elsewhere for these transplants. Close

• 525. [Article] Epichloë typhina (fungus) - Botanophila lobata (fly) interaction : an invasive "pollinator" system in its introduced range in western Oregon

  Epichloë typhina (Ascomycetes: Clavicipitaceae) is an endophytic fungus that infects perennial Pooid grasses and is the causal agent of choke disease. It is endemic to Europe and was inadvertently introduced ...

  Citation × Citation Citation Abstract Copy Title: Epichloë typhina (fungus) - Botanophila lobata (fly) interaction : an invasive "pollinator" system in its introduced range in western Oregon Author: Kaser, Joseph M. Epichloë typhina (Ascomycetes: Clavicipitaceae) is an endophytic fungus that infects perennial Pooid grasses and is the causal agent of choke disease. It is endemic to Europe and was inadvertently introduced into orchardgrass seed production fields in western Oregon. Choke disease, which was first recorded in Oregon in 1996, currently infects ~90% of cultivated orchardgrass seed fields in the region, resulting in yield losses >65%. Infective propagules (i.e. ascospores) are produced sexually by the bipolar heterothallic fungus and gamete outcross has been shown to be facilitated in the wild by Botanophila spp. (Diptera: Anthomyiidae), including Botanophila lobata. The fly - fungus interaction is generally considered to be one of obligatory mutualism based on studies conducted in areas endemism. However, recent evidence suggests that the fungus is able to sexually outcross in cultivated Oregon orchardgrass fields without the aid of fly "pollinators." Additionally, ascosporic fertilization has recently been implicated as an alternative mechanism for gamete transfer and might have important impacts on fungal reproduction in Oregon. The objectives of this study were to: 1) explore how two tightly linked species, which appear to have an obligate mutualistic relationship in areas of endemism, interact in a non-native context; 2) quantitatively examine the seasonal and diurnal presence of E. typhina ascospores in a cultivated Oregon orchardgrass field; and 3) test alternative transfer mechanisms of fungal spermatia for E. typhina. To address objective 1), the spatial variability and reproductive success of E. typhina and B. lobata were estimated during surveys of ten cultivated orchardgrass fields in 2008 and four fields in 2009. Fungal distributions were spatially aggregated at five of the study sites in 2008 and three in 2009. Fly distributions were spatially aggregated at three sites in 2008 and one in 2009. Botanophila lobata density exhibited a positive linear relationship with E. typhina density, suggestive of positive density dependence of fly oviposition with fungal density. However, fungal reproductive success was not affected by fly density or fungal density within the range of distributions observed in this study. To address objective 2), airborne ascospores were monitored in a single cultivated orchardgrass field during 2008 and 2009 using a Burkard volumetric spore trap. Ascospore production began in early to middle May and continued into late July during both years of the study. Daily ascospore production exhibited a circadian rhythm, with production peaking on average at 1:08 am and 12:36 am, in 2008 and 2009, respectively. The prolonged duration and high intensity of ascospore production during the growing season suggest a large window within which new plants are at risk to infection, and within which preventative management strategies must be adopted. To address objective 3), splash fertilization, contact fertilization and B. lobata fertilization were tested in the greenhouse. Although only two replicates were completed, both contact and splash fertilization appeared to be viable mechanisms of sexual outcross for E. typhina. The results of this study strongly indicate that E. typhina can successfully reproduce without the presence of B. lobata. Splash and contact fertilization, as well as ascosporic fertilization, provide opportunities for reproduction of the fungus in absence of fly pollinators. It appears that the fly - fungus interaction has shifted from an obligatory mutualism to facultative mutualism or simple fungivory within the introduced range in western Oregon. Title: Epichloë typhina (fungus) - Botanophila lobata (fly) interaction : an invasive "pollinator" system in its introduced range in western Oregon Author: Kaser, Joseph M. Epichloë typhina (Ascomycetes: Clavicipitaceae) is an endophytic fungus that infects perennial Pooid grasses and is the causal agent of choke disease. It is endemic to Europe and was inadvertently introduced into orchardgrass seed production fields in western Oregon. Choke disease, which was first recorded in Oregon in 1996, currently infects ~90% of cultivated orchardgrass seed fields in the region, resulting in yield losses >65%. Infective propagules (i.e. ascospores) are produced sexually by the bipolar heterothallic fungus and gamete outcross has been shown to be facilitated in the wild by Botanophila spp. (Diptera: Anthomyiidae), including Botanophila lobata. The fly - fungus interaction is generally considered to be one of obligatory mutualism based on studies conducted in areas endemism. However, recent evidence suggests that the fungus is able to sexually outcross in cultivated Oregon orchardgrass fields without the aid of fly "pollinators." Additionally, ascosporic fertilization has recently been implicated as an alternative mechanism for gamete transfer and might have important impacts on fungal reproduction in Oregon. The objectives of this study were to: 1) explore how two tightly linked species, which appear to have an obligate mutualistic relationship in areas of endemism, interact in a non-native context; 2) quantitatively examine the seasonal and diurnal presence of E. typhina ascospores in a cultivated Oregon orchardgrass field; and 3) test alternative transfer mechanisms of fungal spermatia for E. typhina. To address objective 1), the spatial variability and reproductive success of E. typhina and B. lobata were estimated during surveys of ten cultivated orchardgrass fields in 2008 and four fields in 2009. Fungal distributions were spatially aggregated at five of the study sites in 2008 and three in 2009. Fly distributions were spatially aggregated at three sites in 2008 and one in 2009. Botanophila lobata density exhibited a positive linear relationship with E. typhina density, suggestive of positive density dependence of fly oviposition with fungal density. However, fungal reproductive success was not affected by fly density or fungal density within the range of distributions observed in this study. To address objective 2), airborne ascospores were monitored in a single cultivated orchardgrass field during 2008 and 2009 using a Burkard volumetric spore trap. Ascospore production began in early to middle May and continued into late July during both years of the study. Daily ascospore production exhibited a circadian rhythm, with production peaking on average at 1:08 am and 12:36 am, in 2008 and 2009, respectively. The prolonged duration and high intensity of ascospore production during the growing season suggest a large window within which new plants are at risk to infection, and within which preventative management strategies must be adopted. To address objective 3), splash fertilization, contact fertilization and B. lobata fertilization were tested in the greenhouse. Although only two replicates were completed, both contact and splash fertilization appeared to be viable mechanisms of sexual outcross for E. typhina. The results of this study strongly indicate that E. typhina can successfully reproduce without the presence of B. lobata. Splash and contact fertilization, as well as ascosporic fertilization, provide opportunities for reproduction of the fungus in absence of fly pollinators. It appears that the fly - fungus interaction has shifted from an obligatory mutualism to facultative mutualism or simple fungivory within the introduced range in western Oregon. Close

• 526. [Image] The Endangered Species Act and claims of property rights "takings"

  	The Endangered Species Act and Claims of Property Rights "Takings" Summary The federal Endangered Species Act (ES A) has long been one of the major flash points in the "property rights" debate. This ...
  	Citation × Citation Citation Abstract Copy Title: The Endangered Species Act and claims of property rights "takings" Author: Meltz, Robert Year: 2005, 2008 The Endangered Species Act and Claims of Property Rights "Takings" Summary The federal Endangered Species Act (ES A) has long been one of the major flash points in the "property rights" debate. This report first outlines the ESA provisions most relevant to the act's impacts on private property, and then surveys the major ESA-relevant principles of Fifth Amendment takings law. The report then proceeds to its core topic: the court decisions adjudicating whether government measures based on the ESA effect a taking of property under the Fifth Amendment. The cases address four kinds of ESA measures: (1) restrictions on land uses that might adversely affect species listed as endangered or threatened; (2) reductions in water delivery to preserve instream flows needed by listed fish; (3) restrictions on the defensive measures a property owner may take to protect his/her property from listed animals; and (4) restrictions on commercial dealings in members of species acquired prior to listing as endangered or threatened. To date, only one of the 12 ESA-based takings decisions revealed by research has found a taking. Title: The Endangered Species Act and claims of property rights "takings" Author: Meltz, Robert Year: 2005, 2008 The Endangered Species Act and Claims of Property Rights "Takings" Summary The federal Endangered Species Act (ES A) has long been one of the major flash points in the "property rights" debate. This report first outlines the ESA provisions most relevant to the act's impacts on private property, and then surveys the major ESA-relevant principles of Fifth Amendment takings law. The report then proceeds to its core topic: the court decisions adjudicating whether government measures based on the ESA effect a taking of property under the Fifth Amendment. The cases address four kinds of ESA measures: (1) restrictions on land uses that might adversely affect species listed as endangered or threatened; (2) reductions in water delivery to preserve instream flows needed by listed fish; (3) restrictions on the defensive measures a property owner may take to protect his/her property from listed animals; and (4) restrictions on commercial dealings in members of species acquired prior to listing as endangered or threatened. To date, only one of the 12 ESA-based takings decisions revealed by research has found a taking. Close

• 527. [Article] Seed and seedling ecology of Artemisia tridentata in a restoration context

  The semi-arid sagebrush steppe ecosystem is one of the largest biomes in North America. The steppe provides critical habitat and forage for wildlife and is economically important to recreation and livestock ...

  Citation × Citation Citation Abstract Copy Title: Seed and seedling ecology of Artemisia tridentata in a restoration context Author: Wijayratne, Upekala C. The semi-arid sagebrush steppe ecosystem is one of the largest biomes in North America. The steppe provides critical habitat and forage for wildlife and is economically important to recreation and livestock industries. However, the ecosystem is threatened primarily due to several negative effects associated with expansion of the exotic annual grass Bromus tectorum (cheatgrass). Because of these changes rehabilitation of the habitat is extremely difficult and energy intensive. Restoration of one of the foundation species, Artemisia tridentata (big sagebrush), is a function of seed availability, seed germination, seedling establishment and mature plant survival. Many studies have addressed various aspects of A. tridentata seed germination and mature plant ecophysiology, but gaps in our knowledge include seed bank dynamics and biotic interactions that may hinder seedling survival. The prevalence of large fires in B. tectorum-invaded habitat limits availability of dispersed seeds in the interior of burned areas, leaving pre-existing viable seeds in the soil seed bank as the primary natural seed source. I investigated seed longevity of two A. tridentata subspecies over a 2-year period by retrieving seed bags that were placed at varying depths and sampling soil and litter fractions of the existing seed bank across six locations in the Great Basin. Artemisia tridentata ssp. wyomingensis and A. t. ssp. vaseyana exhibited patterns of a steadily decreasing abundance of viable seeds on the surface and beneath litter, with 100% loss of surface seed viability in 24 months. However, 29-36% (A. t. ssp. wyomingensis) and 30-40% (A. t. ssp. vaseyana) of buried seeds remained viable throughout the duration of the experiment. Abundance of naturally occurring seeds varied considerably among locations and between years across the Great Basin for both subspecies. Loss of viable seeds from the existing seed bank between post-dispersal and pre-dispersal the following season was higher in magnitude for A. t. ssp. wyomingensis soil fractions compared to litter fractions, and higher overall than for A. t. ssp. vaseyana. Access to resources is critical during early spring when resources are plentiful, and this access affects the probability of survival through the summer drought period. Artemisia tridentata resource acquisition may be adversely affected during this time via root interaction mechanisms that are not mediated through resources (interference competition). I examined whether and how root interactions affected growth of A. t. ssp. wyomingensis by forcing its roots to interact with roots of conspecifics, B. tectorum, Elymus wawawaiensis (Snake River wheatgrass), and Agropyron xhybrid (cultivar 'Hycrest'). Activated carbon was used to counteract any potentially negative effects of root exudates. Artemisia tridentata above- and belowground biomass was not affected when grown with E. wawawaiensis or A. xhybrid compared to control seedlings, but root growth rate and branching density decreased when grown with B. tectorum (root growth: p < 0.01; branching density: p = 0.07). These effects did not occur in potting media amended with activated carbon but may have been the result of unintentional fertilization. Roots of A. tridentata seedlings changed direction or stopped growing altogether more often when grown into roots of conspecific seedlings than when contacting roots of other species (p = 0.08). The odds of this occurring decreased when seedlings were grown in activated carbon-amended potting medium. These results suggest that A. tridentata may have a chemical signaling mechanism to avoid roots of conspecifics. I also assessed whether root and shoot competition (resource-mediated or exploitative competition) of the three grass species affected A. t. ssp. wyomingensis seedling growth and survival, and whether root and shoot competition interacted to affect growth. Size-asymmetric competition takes place when a resource is preempted by a larger individual over a smaller individual, and the larger individual receives a disproportionately larger share of the resource for its relative size. Following wildfires, B. tectorum cover can increase significantly more than that of other species, potentially promoting asymmetric aboveground competition between it and A. tridentata seedlings. Root and shoot competition from B. tectorum lowered A. tridentata biomass dramatically compared to that of control seedlings, with shoot competition alone decreasing growth by over 80%. Only full competition from E. wawawaiensis tended to decrease A. tridentata growth compared to control seedlings, while A. xhybrid had no significant effect at all seedling growth. Bromus tectorum had an average of 92% cover and may explain why shoot competition from this species had such a substantial effect, whereas cover of E. wawawaiensis and A. xhybrid was 71% and 43%, respectively. Root and shoot competition did not interact for any of the grasses, indicating that there was no mechanism for positive or negative feedbacks between one form of competition and the other. Competition from shoots is likely not severe enough for asymmetric light competition to occur. The first study provides land managers with a bet-hedging application while the others offer insight into why the seedling life history stage, already vulnerable, has become more so with B. tectorum invasion. Reseeding techniques promoting burial of some A. tridentata seeds in the soil seed bank may increase restoration success by hedging against the potential for failure of establishment in the initial year of seeding. Selective thinning or removal of potential competitors may be required to benefit resource status of A. tridentata seedlings before the summer drought period commences. This is especially important in areas that are dominated by B. tectorum as competition from the annual reduces A. tridentata root growth substantially and may impact its ability to take up soil resources. Title: Seed and seedling ecology of Artemisia tridentata in a restoration context Author: Wijayratne, Upekala C. The semi-arid sagebrush steppe ecosystem is one of the largest biomes in North America. The steppe provides critical habitat and forage for wildlife and is economically important to recreation and livestock industries. However, the ecosystem is threatened primarily due to several negative effects associated with expansion of the exotic annual grass Bromus tectorum (cheatgrass). Because of these changes rehabilitation of the habitat is extremely difficult and energy intensive. Restoration of one of the foundation species, Artemisia tridentata (big sagebrush), is a function of seed availability, seed germination, seedling establishment and mature plant survival. Many studies have addressed various aspects of A. tridentata seed germination and mature plant ecophysiology, but gaps in our knowledge include seed bank dynamics and biotic interactions that may hinder seedling survival. The prevalence of large fires in B. tectorum-invaded habitat limits availability of dispersed seeds in the interior of burned areas, leaving pre-existing viable seeds in the soil seed bank as the primary natural seed source. I investigated seed longevity of two A. tridentata subspecies over a 2-year period by retrieving seed bags that were placed at varying depths and sampling soil and litter fractions of the existing seed bank across six locations in the Great Basin. Artemisia tridentata ssp. wyomingensis and A. t. ssp. vaseyana exhibited patterns of a steadily decreasing abundance of viable seeds on the surface and beneath litter, with 100% loss of surface seed viability in 24 months. However, 29-36% (A. t. ssp. wyomingensis) and 30-40% (A. t. ssp. vaseyana) of buried seeds remained viable throughout the duration of the experiment. Abundance of naturally occurring seeds varied considerably among locations and between years across the Great Basin for both subspecies. Loss of viable seeds from the existing seed bank between post-dispersal and pre-dispersal the following season was higher in magnitude for A. t. ssp. wyomingensis soil fractions compared to litter fractions, and higher overall than for A. t. ssp. vaseyana. Access to resources is critical during early spring when resources are plentiful, and this access affects the probability of survival through the summer drought period. Artemisia tridentata resource acquisition may be adversely affected during this time via root interaction mechanisms that are not mediated through resources (interference competition). I examined whether and how root interactions affected growth of A. t. ssp. wyomingensis by forcing its roots to interact with roots of conspecifics, B. tectorum, Elymus wawawaiensis (Snake River wheatgrass), and Agropyron xhybrid (cultivar 'Hycrest'). Activated carbon was used to counteract any potentially negative effects of root exudates. Artemisia tridentata above- and belowground biomass was not affected when grown with E. wawawaiensis or A. xhybrid compared to control seedlings, but root growth rate and branching density decreased when grown with B. tectorum (root growth: p < 0.01; branching density: p = 0.07). These effects did not occur in potting media amended with activated carbon but may have been the result of unintentional fertilization. Roots of A. tridentata seedlings changed direction or stopped growing altogether more often when grown into roots of conspecific seedlings than when contacting roots of other species (p = 0.08). The odds of this occurring decreased when seedlings were grown in activated carbon-amended potting medium. These results suggest that A. tridentata may have a chemical signaling mechanism to avoid roots of conspecifics. I also assessed whether root and shoot competition (resource-mediated or exploitative competition) of the three grass species affected A. t. ssp. wyomingensis seedling growth and survival, and whether root and shoot competition interacted to affect growth. Size-asymmetric competition takes place when a resource is preempted by a larger individual over a smaller individual, and the larger individual receives a disproportionately larger share of the resource for its relative size. Following wildfires, B. tectorum cover can increase significantly more than that of other species, potentially promoting asymmetric aboveground competition between it and A. tridentata seedlings. Root and shoot competition from B. tectorum lowered A. tridentata biomass dramatically compared to that of control seedlings, with shoot competition alone decreasing growth by over 80%. Only full competition from E. wawawaiensis tended to decrease A. tridentata growth compared to control seedlings, while A. xhybrid had no significant effect at all seedling growth. Bromus tectorum had an average of 92% cover and may explain why shoot competition from this species had such a substantial effect, whereas cover of E. wawawaiensis and A. xhybrid was 71% and 43%, respectively. Root and shoot competition did not interact for any of the grasses, indicating that there was no mechanism for positive or negative feedbacks between one form of competition and the other. Competition from shoots is likely not severe enough for asymmetric light competition to occur. The first study provides land managers with a bet-hedging application while the others offer insight into why the seedling life history stage, already vulnerable, has become more so with B. tectorum invasion. Reseeding techniques promoting burial of some A. tridentata seeds in the soil seed bank may increase restoration success by hedging against the potential for failure of establishment in the initial year of seeding. Selective thinning or removal of potential competitors may be required to benefit resource status of A. tridentata seedlings before the summer drought period commences. This is especially important in areas that are dominated by B. tectorum as competition from the annual reduces A. tridentata root growth substantially and may impact its ability to take up soil resources. Close

• 528. [Article] Recreational Boats as Potential Vectors of Marine Organisms at an Invasion Hotspot

  With more than 200 aquatic nonindigenous species (NIS), San Francisco Bay (California, USA) is among the world’s most invaded harbors. Hard-substratum benthic (biofouling) organisms, which dominate NIS ...

  Citation × Citation Citation Abstract Copy Title: Recreational Boats as Potential Vectors of Marine Organisms at an Invasion Hotspot Author: Davidson, Ian C., Zabin, Chela J., Chang, Andrew L., Brown, Christopher W., Sytsma, Mark, Ruiz, Gregory M. Year: 2010 With more than 200 aquatic nonindigenous species (NIS), San Francisco Bay (California, USA) is among the world’s most invaded harbors. Hard-substratum benthic (biofouling) organisms, which dominate NIS richness, have arrived primarily as a result of shipping and aquaculture activity over past centuries. To date there has been no assessment of the leisure craft vector in the Bay. We aimed to characterize (1) biofouling on boats’ submerged surfaces and (2) boater behavior likely to affect the risk of NIS transfers. We used an underwater pole-cam, specimen collections, and a boater questionnaire to quantify the extent and composition of biofouling on recreational boats and to evaluate boater behavior at a subset of the Bay’s marinas. Several NIS, already established within the Bay, were recorded from vessel hulls, including the bryozoans Bugula neritina, Membranipora chesapeakensis and Watersipora sp., the ascidians Botrylloides violaceus, Styela clava and Ciona intestinalis, the polychaete Ficopomatus enigmaticus, and the sponge Clathria prolifera. Only 16% of questionnaire respondents had traveled to sites outside the Bay in the previous 12 mo. Frequency of hull painting and cleaning varied substantially, but we did not find strong patterns of biofouling extent associated with hull husbandry or boat usage. The potential for within-Bay and coastwise regional spread of NIS is high, and recreational boats probably interact in close proximity to other vectors (e.g. commercial ships), causing a ratchet effect of vector events; however, there remains a gap in understanding the levels and condition of biofouling on transient boats. Transient vessels from San Francisco Bay and other West Coast sites should be the focus of future studies to evaluate the extent to which organisms are being transferred among bays and how vector management could be applied to prevent NIS transfers and impacts. Title: Recreational Boats as Potential Vectors of Marine Organisms at an Invasion Hotspot Author: Davidson, Ian C., Zabin, Chela J., Chang, Andrew L., Brown, Christopher W., Sytsma, Mark, Ruiz, Gregory M. Year: 2010 With more than 200 aquatic nonindigenous species (NIS), San Francisco Bay (California, USA) is among the world’s most invaded harbors. Hard-substratum benthic (biofouling) organisms, which dominate NIS richness, have arrived primarily as a result of shipping and aquaculture activity over past centuries. To date there has been no assessment of the leisure craft vector in the Bay. We aimed to characterize (1) biofouling on boats’ submerged surfaces and (2) boater behavior likely to affect the risk of NIS transfers. We used an underwater pole-cam, specimen collections, and a boater questionnaire to quantify the extent and composition of biofouling on recreational boats and to evaluate boater behavior at a subset of the Bay’s marinas. Several NIS, already established within the Bay, were recorded from vessel hulls, including the bryozoans Bugula neritina, Membranipora chesapeakensis and Watersipora sp., the ascidians Botrylloides violaceus, Styela clava and Ciona intestinalis, the polychaete Ficopomatus enigmaticus, and the sponge Clathria prolifera. Only 16% of questionnaire respondents had traveled to sites outside the Bay in the previous 12 mo. Frequency of hull painting and cleaning varied substantially, but we did not find strong patterns of biofouling extent associated with hull husbandry or boat usage. The potential for within-Bay and coastwise regional spread of NIS is high, and recreational boats probably interact in close proximity to other vectors (e.g. commercial ships), causing a ratchet effect of vector events; however, there remains a gap in understanding the levels and condition of biofouling on transient boats. Transient vessels from San Francisco Bay and other West Coast sites should be the focus of future studies to evaluate the extent to which organisms are being transferred among bays and how vector management could be applied to prevent NIS transfers and impacts. Close

• 529. [Article] OSMB Final Report: Task 5. Zebra and Quagga Mussel Early-Detection Monitoring in High Risk Oregon Waters

  Neither zebra nor quagga mussels (Dreissena polymorpha and D. rostriformis bugensis, respectively) were detected by Portland State University (PSU) during their early detection sampling in Oregon water ...

  Citation × Citation Citation Abstract Copy Title: OSMB Final Report: Task 5. Zebra and Quagga Mussel Early-Detection Monitoring in High Risk Oregon Waters Author: Wells, Steve W., Sytsma, Mark Year: 2014 Neither zebra nor quagga mussels (Dreissena polymorpha and D. rostriformis bugensis, respectively) were detected by Portland State University (PSU) during their early detection sampling in Oregon water bodies during 2013. PSU conducted sampling for planktonic larvae, juvenile, and adult mussels at nine Oregon water bodies during the July to August period coinciding with water temperatures favorable for mussel spawning. A total of 113 plankton samples were collected and over 1.6 million liters of lake water were filtered through 63-μm mesh nets during plankton sample collection. The greatest sampling effort occurred in East Lake, Prineville Reservoir, and Paulina Lake; these water bodies were identified as high risk for both mussel establishment and introduction according to Wells et al. (2009). The sampling effort, however, was fairly uniform amongst the targeted water bodies, and sampling also occurred in Upper Klamath Lake, Howard Prairie Lake, Hyatt Reservoir, Emigrant Lake, Ochoco Reservoir, and Lake Billy Chinook. Non-native invertebrates and macrophytes were opportunistically collected during Dreissena spp. sampling in 2013. Corbicula fluminea (Asian clam) straight-hinge juveniles were collected in plankton samples from East Lake and Howard Prairie Lake. Potamopyrgus antipodarum (New Zealand mud snails) were collected in Lake Billy Chinook. Radix auricularia (big-ear radix) snails were collected in Hyatt Reservoir, Lake Billy Chinook and Paulina Lake. Orconectes neglectus (ringed crayfish) were collected in Hyatt Reservoir. Potamogeton crispus (curly leaf pondweed) were collected in Howard Prairie Lake, Hyatt Reservoir, Lake Billy Chinook, and Upper Klamath Lake. Most of these collections were not the first detections for these species in these locations; however, to the authors’ knowledge, the following represent first detections: R. auricularia in Hyatt Reservoir and Paulina Lake, O. neglectus in Hyatt Reservoir and C. fluminea in Howard Prairie Lake. Title: OSMB Final Report: Task 5. Zebra and Quagga Mussel Early-Detection Monitoring in High Risk Oregon Waters Author: Wells, Steve W., Sytsma, Mark Year: 2014 Neither zebra nor quagga mussels (Dreissena polymorpha and D. rostriformis bugensis, respectively) were detected by Portland State University (PSU) during their early detection sampling in Oregon water bodies during 2013. PSU conducted sampling for planktonic larvae, juvenile, and adult mussels at nine Oregon water bodies during the July to August period coinciding with water temperatures favorable for mussel spawning. A total of 113 plankton samples were collected and over 1.6 million liters of lake water were filtered through 63-μm mesh nets during plankton sample collection. The greatest sampling effort occurred in East Lake, Prineville Reservoir, and Paulina Lake; these water bodies were identified as high risk for both mussel establishment and introduction according to Wells et al. (2009). The sampling effort, however, was fairly uniform amongst the targeted water bodies, and sampling also occurred in Upper Klamath Lake, Howard Prairie Lake, Hyatt Reservoir, Emigrant Lake, Ochoco Reservoir, and Lake Billy Chinook. Non-native invertebrates and macrophytes were opportunistically collected during Dreissena spp. sampling in 2013. Corbicula fluminea (Asian clam) straight-hinge juveniles were collected in plankton samples from East Lake and Howard Prairie Lake. Potamopyrgus antipodarum (New Zealand mud snails) were collected in Lake Billy Chinook. Radix auricularia (big-ear radix) snails were collected in Hyatt Reservoir, Lake Billy Chinook and Paulina Lake. Orconectes neglectus (ringed crayfish) were collected in Hyatt Reservoir. Potamogeton crispus (curly leaf pondweed) were collected in Howard Prairie Lake, Hyatt Reservoir, Lake Billy Chinook, and Upper Klamath Lake. Most of these collections were not the first detections for these species in these locations; however, to the authors’ knowledge, the following represent first detections: R. auricularia in Hyatt Reservoir and Paulina Lake, O. neglectus in Hyatt Reservoir and C. fluminea in Howard Prairie Lake. Close

• 530. [Article] Quantifying the Impacts of a Novel Predator: The Distinctive Case of the Oregon Spotted Frog (<i>Rana pretiosa</i>) and the Invasive American Bullfrog (<i>Rana (Aquarana) catesbeiana</i>)

  The decline of the Oregon Spotted Frog (Rana pretiosa), a Pacific Northwest endemic now federally listed as threatened, has been attributed to several aspects of ecosystem alteration, primarily habitat ...

  Citation × Citation Citation Abstract Copy Title: Quantifying the Impacts of a Novel Predator: The Distinctive Case of the Oregon Spotted Frog (<i>Rana pretiosa</i>) and the Invasive American Bullfrog (<i>Rana (Aquarana) catesbeiana</i>) Author: Tidwell, Kyle Scott Year: 2017 The decline of the Oregon Spotted Frog (Rana pretiosa), a Pacific Northwest endemic now federally listed as threatened, has been attributed to several aspects of ecosystem alteration, primarily habitat degradation and loss. The introduced American Bullfrog (Rana (Aquarana) catesbeiana) has been widely implicated in those declines, but the basis of that contention has been difficult to characterize. The bullfrog occurring at every site of recent Oregon Spotted Frog extirpation has focused concern about its impact. Here, I present a suite of interconnected studies that examine the behavioral ecology of both species to better understand the potential for bullfrog-mediated Oregon Spotted Frog extirpation. I quantified Oregon Spotted Frog anti-predator behavior from the only known population successfully co-occurring with bullfrogs (Conboy Lake) and a population devoid of bullfrog impact (Big Marsh), and compared these behaviors to the predatory traits of the bullfrog. The initial study revealed that captive-reared individuals from the Oregon Spotted Frog population that has successfully co-occurred with bullfrogs respond faster to a predatory stimulus (measured as latency to response) than Oregon Spotted Frogs from a population not to exposed to bullfrogs. Subsequent field investigations of the approach distance allowed by a predator stimulus before taking evasive action (termed the flight initiation distance: FID) conducted with the Oregon Spotted Frog population co-occurring with bullfrogs first demonstrated that FID of recently metamorphosed bullfrogs is consistently greater than that of recently metamorphosed Oregon Spotted Frogs. Further, examination of FID across all post-metamorphic age classes of Oregon Spotted Frogs revealed that older frogs do not allow as close approach as recently metamorphosed Oregon Spotted Frogs. This age class shift in FID did not occur in the Oregon Spotted Frog population not exposed to bullfrogs. In the latter population, FID did not differ among age classes. Since the bullfrog might be driving this age-based change in anti-predator behavior, I explored the variation in strike distance of bullfrogs from the site of co-occurrence in both the field and laboratory to determine the extent of overlap with Oregon Spotted Frog FID. I found that the bullfrog strike distance significantly overlaps the FID of all ages of Oregon Spotted Frogs from the bullfrog-free site but only that of youngest (recently metamorphosed) frogs at the site of co-occurrence. Older Oregon Spotted Frogs from the site of co-occurrence generally escaped at distances greater than the strike distance of bullfrogs. I also collected > 880 bullfrogs from the site of co-occurrence and analyzed the stomach contents to assess their dietary trends. I found that bullfrogs consume Oregon Spotted Frogs at the site, but do not eat the larger (older) frogs. Moreover, the body size ratio between Oregon Spotted Frogs as prey and bullfrogs as predators suggests that nearly all of the adult size distribution of bullfrogs at Conboy would be incapable of preying on adult Oregon Spotted Frogs. Collectively, these studies strongly suggest that bullfrogs have altered the escape behavior of Oregon Spotted Frogs at Conboy Lake and that most adult Oregon Spotted Frogs at Conboy may have a size-based release from predation by bullfrogs. Implicit in this finding is that bullfrogs may pose a real threat via predation to other Oregon Spotted Frog populations with which they might come into contact where the distribution of bullfrog body sizes differ substantially from that at Conboy Lake. Title: Quantifying the Impacts of a Novel Predator: The Distinctive Case of the Oregon Spotted Frog (<i>Rana pretiosa</i>) and the Invasive American Bullfrog (<i>Rana (Aquarana) catesbeiana</i>) Author: Tidwell, Kyle Scott Year: 2017 The decline of the Oregon Spotted Frog (Rana pretiosa), a Pacific Northwest endemic now federally listed as threatened, has been attributed to several aspects of ecosystem alteration, primarily habitat degradation and loss. The introduced American Bullfrog (Rana (Aquarana) catesbeiana) has been widely implicated in those declines, but the basis of that contention has been difficult to characterize. The bullfrog occurring at every site of recent Oregon Spotted Frog extirpation has focused concern about its impact. Here, I present a suite of interconnected studies that examine the behavioral ecology of both species to better understand the potential for bullfrog-mediated Oregon Spotted Frog extirpation. I quantified Oregon Spotted Frog anti-predator behavior from the only known population successfully co-occurring with bullfrogs (Conboy Lake) and a population devoid of bullfrog impact (Big Marsh), and compared these behaviors to the predatory traits of the bullfrog. The initial study revealed that captive-reared individuals from the Oregon Spotted Frog population that has successfully co-occurred with bullfrogs respond faster to a predatory stimulus (measured as latency to response) than Oregon Spotted Frogs from a population not to exposed to bullfrogs. Subsequent field investigations of the approach distance allowed by a predator stimulus before taking evasive action (termed the flight initiation distance: FID) conducted with the Oregon Spotted Frog population co-occurring with bullfrogs first demonstrated that FID of recently metamorphosed bullfrogs is consistently greater than that of recently metamorphosed Oregon Spotted Frogs. Further, examination of FID across all post-metamorphic age classes of Oregon Spotted Frogs revealed that older frogs do not allow as close approach as recently metamorphosed Oregon Spotted Frogs. This age class shift in FID did not occur in the Oregon Spotted Frog population not exposed to bullfrogs. In the latter population, FID did not differ among age classes. Since the bullfrog might be driving this age-based change in anti-predator behavior, I explored the variation in strike distance of bullfrogs from the site of co-occurrence in both the field and laboratory to determine the extent of overlap with Oregon Spotted Frog FID. I found that the bullfrog strike distance significantly overlaps the FID of all ages of Oregon Spotted Frogs from the bullfrog-free site but only that of youngest (recently metamorphosed) frogs at the site of co-occurrence. Older Oregon Spotted Frogs from the site of co-occurrence generally escaped at distances greater than the strike distance of bullfrogs. I also collected > 880 bullfrogs from the site of co-occurrence and analyzed the stomach contents to assess their dietary trends. I found that bullfrogs consume Oregon Spotted Frogs at the site, but do not eat the larger (older) frogs. Moreover, the body size ratio between Oregon Spotted Frogs as prey and bullfrogs as predators suggests that nearly all of the adult size distribution of bullfrogs at Conboy would be incapable of preying on adult Oregon Spotted Frogs. Collectively, these studies strongly suggest that bullfrogs have altered the escape behavior of Oregon Spotted Frogs at Conboy Lake and that most adult Oregon Spotted Frogs at Conboy may have a size-based release from predation by bullfrogs. Implicit in this finding is that bullfrogs may pose a real threat via predation to other Oregon Spotted Frog populations with which they might come into contact where the distribution of bullfrog body sizes differ substantially from that at Conboy Lake. Close