To understand the relative roles of local and regional processes in structuring local communities... more To understand the relative roles of local and regional processes in structuring local communities, and to compare sources of dispersal, we studied plant species composition in the context of a field experiment in vernal pool community assembly. In 1999, we constructed 256 vernal pools in a grid surrounding a group of over 60 naturally occurring reference pools. Each constructed pool received a seeding or control treatment. Seeding treatments involved several ''focal species'' native to vernal pools in this region. Earlier analyses identified local habitat quality (pool depth) and pool history (seeding treatment) as strong predictors of local species composition. For the current analysis, we asked how connectivity among pools might enhance models of focal species presence and cover within pools, using long-term data from control pools and from unseeded transects within a stratified random sample of all constructed pools. We fitted connectivity models for each of four focal species, and compared the relative support for connectivity, seeding treatment, and pool depth as predictors of local species presence and cover. We modeled connectivity in several ways to quantify the relative importance of immigration (1) from constructed pools, (2) from reference pools within the study site, (3) from a cluster of natural pools off-site, and (4) along ephemeral waterways. We found strongest support for effects of connectivity with reference pools. Species presence in a target pool was usually well predicted by an exponential decline in connectivity with distance to source pools, and our fitted estimates of mean dispersal distance indicate strong dispersal limitation in this system. Effects of target and source pool size were also supported in some models, and long-term effects of seeding were supported for most species. However, pool depth was by far the strongest predictor of focal species presence, and depth rivaled connectivity with reference pools as a top predictor of cover after accounting for species presence. We conclude that local species composition was determined primarily by local processes in this system, and we encourage more widespread use of a straightforward method for weighing local vs. regional influences.
CHAPTER 14 Potential effects of a keystone species on the dynamics of sylvatic plague Chris Ray a... more CHAPTER 14 Potential effects of a keystone species on the dynamics of sylvatic plague Chris Ray and Sharon K. Collinge 14.1 Background Of all zoonoses, plague has the most notorious record of emergence, being responsible for three human pandemics since the fifth ...
ABSTRACT Background/Question/Methods The Brown-headed Cowbird (Molothrus ater) is an obligate bro... more ABSTRACT Background/Question/Methods The Brown-headed Cowbird (Molothrus ater) is an obligate brood parasite that reduces the reproductive success of many of its host species. Cowbird-host research over the past few years has focused heavily on determining the relative effects of parasitism and predation. However, despite extensive efforts, it is still poorly understood to what extent cowbirds reduce host reproductive success. To better address this question, we have created a mechanistic model, based on a 3-year data set, to calculate and assess the relative costs of parasitism and predation for one host species, the Plumbeous Vireo (Vireo plumbeus). This vireo is the primary host of cowbirds within our study area, the Front Range of Colorado, USA. Results/Conclusions The results from this work show that the costs of both parasitism and predation depend sensitively on the Julian date on which eggs are layed. Specifically, cowbirds (at least within the Colorado Front Range population) have synchronized their reproductive cycle around the same day that vireos begin to lay eggs. Under these circumstances, the model demonstrates that cowbird parasitism decreases vireo nest success by 14.9%. However, the model also demonstrates a more interesting result regarding the influence of predation on these populations. When a vireo's nest fails due to predation or environmental destruction (i.e. severe weather), renesting occurs about two weeks after the temporal peak in cowbird parasitism. After failure of a first nest, the model suggests that vireos experience an increase in total nest success (total number of fledglings leaving the nest), from 25% to 40%, because they are released from cowbird parasitism. These results highlight the importance of temporal scale when assessing the consequences of parasitism and predation on avian reproductive success.
How does biodiversity affect disease prevalence? To paraphrase a prominent scholar on the subject... more How does biodiversity affect disease prevalence? To paraphrase a prominent scholar on the subject, there are many more plausible predictions than there are definitive answers. In this talk, I summarize these plausible predictions and ask how specific predictions may be ...
Measurement of stress hormone metabolites in fecal samples has become a common method to assess p... more Measurement of stress hormone metabolites in fecal samples has become a common method to assess physiological stress in wildlife populations. Glucocorticoid metabolite (GCM) measurements can be collected noninvasively, and studies relating this stress metric to anthropogenic disturbance are increasing. However, environmental characteristics (e.g., temperature) can alter measured GCM concentration when fecal samples cannot be collected immediately after defecation. This effect can confound efforts to separate environmental factors causing predeposition physiological stress in an individual from those acting on a fecal sample postdeposition. We used fecal samples from American pikas (Ochotona princeps) to examine the influence of environmental conditions on GCM concentration by (1) comparing GCM concentration measured in freshly collected control samples to those placed in natural habitats for timed exposure, and (2) relating GCM concentration in samples collected noninvasively throughout the western United States to local environmental characteristics measured before and after deposition. Our timed-exposure trials clarified the spatial scale at which exposure to environmental factors postdeposition influences GCM concentration in pika feces. Also, fecal samples collected from occupied pika habitats throughout the species' range revealed significant relationships between GCM and metrics of climate during the postdeposition period (maximum temperature, minimum temperature, and precipitation during the month of sample collection). Conversely, we found no such relationships between GCM and metrics of climate during the predeposition period (prior to the month of sample collection). Together, these results indicate that noninvasive measurement of physiological stress in pikas across the western US may be confounded by climatic conditions in the postdeposition environment when samples cannot be collected immediately after defecation. Our results reiterate the importance of considering postdeposition environmental influences on this stress metric, especially in multiregional comparisons. However, measurements of fecal GCM concentration should prove useful for population monitoring within an eco-region or when postdeposition exposure can be minimized.
Background/Question/Methods The Brown-headed Cowbird (Molothrus ater) is an obligate brood parasi... more Background/Question/Methods The Brown-headed Cowbird (Molothrus ater) is an obligate brood parasite that reduces the reproductive success of many of its host species. Cowbird-host research over the past few years has focused heavily on determining the relative effects of parasitism and predation. However, despite extensive efforts, it is still poorly understood to what extent cowbirds reduce host reproductive success. To better address this question, we have created a mechanistic model, based on a 3-year data set, to calculate and assess the relative costs of parasitism and predation for one host species, the Plumbeous Vireo (Vireo plumbeus). This vireo is the primary host of cowbirds within our study area, the Front Range of Colorado, USA. Results/Conclusions The results from this work show that the costs of both parasitism and predation depend sensitively on the Julian date on which eggs are layed. Specifically, cowbirds (at least within the Colorado Front Range population) have s...
The American pika (Ochotona princeps), a sentinel species for detecting ecological effects of cli... more The American pika (Ochotona princeps), a sentinel species for detecting ecological effects of climate change, is declining within a large portion of its range. Pikas have a narrow thermal tolerance and rely on access to subsurface microclimates to shed heat. Because pikas behaviorally thermoregulate, it can be difficult to assess the impact of local habitat characteristics on persistence. This underscores the importance of assessing individual response, such as physiological stress or survival, to specific habitat characteristics, such as microclimate. If local habitat variables can explain individual survival, then climate change may have relatively direct effects that are contributing to local extinctions of this species. Here we related individual survival in pikas to 2 different stress metrics, the concentration of glucocorticoid (GC) metabolites in fecal samples and GC concentration in plasma samples. Blood and fresh fecal samples were collected from marked pikas during a long-...
How does biodiversity affect disease prevalence? To paraphrase a prominent scholar on the subject... more How does biodiversity affect disease prevalence? To paraphrase a prominent scholar on the subject, there are many more plausible predictions than there are definitive answers. In this talk, I summarize these plausible predictions and ask how specific predictions may be ...
CHAPTER SIX Effects of Disease on Keystone Species, Dominant Species, and Their Communities Sharo... more CHAPTER SIX Effects of Disease on Keystone Species, Dominant Species, and Their Communities Sharon K. Collinge, Chris Ray, and Jack F. Cully, Jr. Summary KEYSTONE SPECIES DISPROPORTIONATELY AFFECT THE ABUNDANCE and distribution of other species and, because of their ...
ABSTRACT Background/Question/Methods Alpine species are among those most threatened by climatic s... more ABSTRACT Background/Question/Methods Alpine species are among those most threatened by climatic shifts due to their physiological and geographic constraints. One such species is the American pika (Ochotona princeps), an alpine mammal found in rocky habitats throughout much of western North America. Recent evidence from the Great Basin suggests that this species is responding to climate change through local population extirpation, but it remains unclear whether these patterns of climate-related loss extend to other portions of the species’ range. Our research focuses the impact of climate change on the distribution and abundance of pikas in the Southern Rocky Mountains, a region that represents the largest, most continuous, and southern-most range of the species. In a resurvey of 69 sites historically occupied by pikas, low annual precipitation was implicated as a limiting factor for pika persistence in the region. Due to the relatively low proportion of pika populations extirpated in the Southern Rockies, in this study we investigated local population density as a more precise metric of population response. In addition, we were able to utilize microclimatic data from temperature data loggers to better understand the mechanism by which climate affects this species. Results/Conclusions Local pika densities were highly variable across the Southern Rockies. This result is notable because individual pikas defend territories of relatively uniform size across their range, implying that territory size (and population density) does not vary in response to local resource availability. In an analysis of climatic, landscape, and microhabitat variables, the best predictors of pika population density were climatic factors. Density was lowest at sites with highest mean summer temperature and lowest mean annual precipitation. Changes in mean annual precipitation since 1980 in the Southern Rockies have been highly heterogeneous (-32 to +202 mm). Sites at which precipitation has increased were more likely to support higher pika densities than sites becoming drier. Site aspect, elevation, latitude, and talus depth were not predictive of pika population density. Our findings indicate that hotter, drier sites do not support pikas in high densities. Direct thermal stress is implicated as a driver of lower densities at hotter sites. Data from sub-talus temperature loggers implicate a lack of snowpack at drier sites as the precipitation-based driver behind low pika densities. Reduced snow cover reduces the thermal insulation available to pikas during winter, but may also reduce water content in the pika’s forage.
ABSTRACT Background/Question/Methods The goals of ecological restoration are to recover native po... more ABSTRACT Background/Question/Methods The goals of ecological restoration are to recover native populations, communities, and ecosystems degraded by human activities. Successful restoration therefore requires establishment of both ecological structure and function to degraded systems. We study plant communities of California vernal pools, which are ephemeral wetlands that support many rare or endangered species. In this system, we consider plant species composition as a key component of ecological structure, and hydrological processes as key components of ecological function. Here we present results of a long-term field experiment involving 256 constructed vernal pools in which we compare hydrologic and vegetative characteristics of restored vernal pools to that of adjacent, naturally occurring reference pools. At the outset of the experiment (1999), three-fourths of the restored pools were seeded with three different combinations of five native species (“seeded”), and one-fourth of the pools were left unseeded (“controls”). We tracked pools from 2000 to 2009 and characterized effects of hydrology and seeding on restoration success, comparing seeded and control pools with naturally occurring reference pools. We ask whether appropriate hydrological conditions alone are sufficient to promote establishment of vernal pool plant communities in constructed pools, or if seeding enhances native species persistence. Results/Conclusions As expected, cover of seeded species was significantly higher in seeded than control pools in every year of the study. The smallest observed difference in seeded species cover occurred in 2009. Furthermore, sampling plots in seeded and reference pools were similar through time in cover of seeded and other native species, as well as exotic species. Cover of seeded species in constructed pools was best modeled by seeding treatment and maximum depth of inundation. Pool depth and duration of inundation were similar among seeded, control, and reference pools through 2002, but by 2009 reference pools were significantly deeper than restored pools during the period of peak inundation. The depth of restored pools has decreased apparently as a result of climate-driven increases in the cover of exotic species that contribute to rapid thatch accumulation. These combined results suggest that vernal pool restoration can be facilitated by ensuring appropriate hydrological conditions and by seeding constructed pools with native species. However, our observed effects of climate on the outcome of competition between native and exotic species suggest impending effects of climate change, especially if exotic species facilitate their own dominance through thatch accumulation.
Background/Question/Methods Ecological restoration presents unique opportunities to examine facto... more Background/Question/Methods Ecological restoration presents unique opportunities to examine factors that affect the formation, structure and stability of ecological communities. Restoration of natural communities can furnish insights into whether community composition is deterministic, following predictable trajectories; or if it depends significantly on variation in species arrivals that can drive community trajectories in different directions. Our long-term studies of the ecological dynamics of vernal pool plant communities in California focus on: 1) effects of dispersal limitation, order of colonization, and frequency of colonization on plant community composition; 2) invasion of vernal pools by non-native species, and 3) comparison of restored vernal pools to that of naturally-occurring pools. We initiated a field experiment in 1999 by constructing 250 vernal pool basins that received different seeding treatments to assess environmental constraints on plant community formation. ...
Background/Question/Methods California’s vernal pools are ephemeral wetlands that host numerous e... more Background/Question/Methods California’s vernal pools are ephemeral wetlands that host numerous endemic species, many of which are now rare and endangered due to extensive habitat loss from agriculture and development. Conservation of existing wetlands, restoration projects, and long-term studies of population and community dynamics are critical aspects of vernal pool recovery. One little-studied aspect of vernal pool plant ecology is the role of the soil seed bank in the persistence of restored populations. We used a long-term experiment involving 256 constructed pools to determine whether constructed pools maintain a sufficient seed bank to perpetuate native species. We collected soil samples from 60 constructed pools to assess the identity and quantity of seeds present. Each soil sample was split into two equal parts, with one half sieved for manual seed sorting and the other planted in a greenhouse germination trial. Here, we compare these two methods for characterizing the seed...
To understand the relative roles of local and regional processes in structuring local communities... more To understand the relative roles of local and regional processes in structuring local communities, and to compare sources of dispersal, we studied plant species composition in the context of a field experiment in vernal pool community assembly. In 1999, we constructed 256 vernal pools in a grid surrounding a group of over 60 naturally occurring reference pools. Each constructed pool received a seeding or control treatment. Seeding treatments involved several ''focal species'' native to vernal pools in this region. Earlier analyses identified local habitat quality (pool depth) and pool history (seeding treatment) as strong predictors of local species composition. For the current analysis, we asked how connectivity among pools might enhance models of focal species presence and cover within pools, using long-term data from control pools and from unseeded transects within a stratified random sample of all constructed pools. We fitted connectivity models for each of four focal species, and compared the relative support for connectivity, seeding treatment, and pool depth as predictors of local species presence and cover. We modeled connectivity in several ways to quantify the relative importance of immigration (1) from constructed pools, (2) from reference pools within the study site, (3) from a cluster of natural pools off-site, and (4) along ephemeral waterways. We found strongest support for effects of connectivity with reference pools. Species presence in a target pool was usually well predicted by an exponential decline in connectivity with distance to source pools, and our fitted estimates of mean dispersal distance indicate strong dispersal limitation in this system. Effects of target and source pool size were also supported in some models, and long-term effects of seeding were supported for most species. However, pool depth was by far the strongest predictor of focal species presence, and depth rivaled connectivity with reference pools as a top predictor of cover after accounting for species presence. We conclude that local species composition was determined primarily by local processes in this system, and we encourage more widespread use of a straightforward method for weighing local vs. regional influences.
CHAPTER 14 Potential effects of a keystone species on the dynamics of sylvatic plague Chris Ray a... more CHAPTER 14 Potential effects of a keystone species on the dynamics of sylvatic plague Chris Ray and Sharon K. Collinge 14.1 Background Of all zoonoses, plague has the most notorious record of emergence, being responsible for three human pandemics since the fifth ...
ABSTRACT Background/Question/Methods The Brown-headed Cowbird (Molothrus ater) is an obligate bro... more ABSTRACT Background/Question/Methods The Brown-headed Cowbird (Molothrus ater) is an obligate brood parasite that reduces the reproductive success of many of its host species. Cowbird-host research over the past few years has focused heavily on determining the relative effects of parasitism and predation. However, despite extensive efforts, it is still poorly understood to what extent cowbirds reduce host reproductive success. To better address this question, we have created a mechanistic model, based on a 3-year data set, to calculate and assess the relative costs of parasitism and predation for one host species, the Plumbeous Vireo (Vireo plumbeus). This vireo is the primary host of cowbirds within our study area, the Front Range of Colorado, USA. Results/Conclusions The results from this work show that the costs of both parasitism and predation depend sensitively on the Julian date on which eggs are layed. Specifically, cowbirds (at least within the Colorado Front Range population) have synchronized their reproductive cycle around the same day that vireos begin to lay eggs. Under these circumstances, the model demonstrates that cowbird parasitism decreases vireo nest success by 14.9%. However, the model also demonstrates a more interesting result regarding the influence of predation on these populations. When a vireo's nest fails due to predation or environmental destruction (i.e. severe weather), renesting occurs about two weeks after the temporal peak in cowbird parasitism. After failure of a first nest, the model suggests that vireos experience an increase in total nest success (total number of fledglings leaving the nest), from 25% to 40%, because they are released from cowbird parasitism. These results highlight the importance of temporal scale when assessing the consequences of parasitism and predation on avian reproductive success.
How does biodiversity affect disease prevalence? To paraphrase a prominent scholar on the subject... more How does biodiversity affect disease prevalence? To paraphrase a prominent scholar on the subject, there are many more plausible predictions than there are definitive answers. In this talk, I summarize these plausible predictions and ask how specific predictions may be ...
Measurement of stress hormone metabolites in fecal samples has become a common method to assess p... more Measurement of stress hormone metabolites in fecal samples has become a common method to assess physiological stress in wildlife populations. Glucocorticoid metabolite (GCM) measurements can be collected noninvasively, and studies relating this stress metric to anthropogenic disturbance are increasing. However, environmental characteristics (e.g., temperature) can alter measured GCM concentration when fecal samples cannot be collected immediately after defecation. This effect can confound efforts to separate environmental factors causing predeposition physiological stress in an individual from those acting on a fecal sample postdeposition. We used fecal samples from American pikas (Ochotona princeps) to examine the influence of environmental conditions on GCM concentration by (1) comparing GCM concentration measured in freshly collected control samples to those placed in natural habitats for timed exposure, and (2) relating GCM concentration in samples collected noninvasively throughout the western United States to local environmental characteristics measured before and after deposition. Our timed-exposure trials clarified the spatial scale at which exposure to environmental factors postdeposition influences GCM concentration in pika feces. Also, fecal samples collected from occupied pika habitats throughout the species' range revealed significant relationships between GCM and metrics of climate during the postdeposition period (maximum temperature, minimum temperature, and precipitation during the month of sample collection). Conversely, we found no such relationships between GCM and metrics of climate during the predeposition period (prior to the month of sample collection). Together, these results indicate that noninvasive measurement of physiological stress in pikas across the western US may be confounded by climatic conditions in the postdeposition environment when samples cannot be collected immediately after defecation. Our results reiterate the importance of considering postdeposition environmental influences on this stress metric, especially in multiregional comparisons. However, measurements of fecal GCM concentration should prove useful for population monitoring within an eco-region or when postdeposition exposure can be minimized.
Background/Question/Methods The Brown-headed Cowbird (Molothrus ater) is an obligate brood parasi... more Background/Question/Methods The Brown-headed Cowbird (Molothrus ater) is an obligate brood parasite that reduces the reproductive success of many of its host species. Cowbird-host research over the past few years has focused heavily on determining the relative effects of parasitism and predation. However, despite extensive efforts, it is still poorly understood to what extent cowbirds reduce host reproductive success. To better address this question, we have created a mechanistic model, based on a 3-year data set, to calculate and assess the relative costs of parasitism and predation for one host species, the Plumbeous Vireo (Vireo plumbeus). This vireo is the primary host of cowbirds within our study area, the Front Range of Colorado, USA. Results/Conclusions The results from this work show that the costs of both parasitism and predation depend sensitively on the Julian date on which eggs are layed. Specifically, cowbirds (at least within the Colorado Front Range population) have s...
The American pika (Ochotona princeps), a sentinel species for detecting ecological effects of cli... more The American pika (Ochotona princeps), a sentinel species for detecting ecological effects of climate change, is declining within a large portion of its range. Pikas have a narrow thermal tolerance and rely on access to subsurface microclimates to shed heat. Because pikas behaviorally thermoregulate, it can be difficult to assess the impact of local habitat characteristics on persistence. This underscores the importance of assessing individual response, such as physiological stress or survival, to specific habitat characteristics, such as microclimate. If local habitat variables can explain individual survival, then climate change may have relatively direct effects that are contributing to local extinctions of this species. Here we related individual survival in pikas to 2 different stress metrics, the concentration of glucocorticoid (GC) metabolites in fecal samples and GC concentration in plasma samples. Blood and fresh fecal samples were collected from marked pikas during a long-...
How does biodiversity affect disease prevalence? To paraphrase a prominent scholar on the subject... more How does biodiversity affect disease prevalence? To paraphrase a prominent scholar on the subject, there are many more plausible predictions than there are definitive answers. In this talk, I summarize these plausible predictions and ask how specific predictions may be ...
CHAPTER SIX Effects of Disease on Keystone Species, Dominant Species, and Their Communities Sharo... more CHAPTER SIX Effects of Disease on Keystone Species, Dominant Species, and Their Communities Sharon K. Collinge, Chris Ray, and Jack F. Cully, Jr. Summary KEYSTONE SPECIES DISPROPORTIONATELY AFFECT THE ABUNDANCE and distribution of other species and, because of their ...
ABSTRACT Background/Question/Methods Alpine species are among those most threatened by climatic s... more ABSTRACT Background/Question/Methods Alpine species are among those most threatened by climatic shifts due to their physiological and geographic constraints. One such species is the American pika (Ochotona princeps), an alpine mammal found in rocky habitats throughout much of western North America. Recent evidence from the Great Basin suggests that this species is responding to climate change through local population extirpation, but it remains unclear whether these patterns of climate-related loss extend to other portions of the species’ range. Our research focuses the impact of climate change on the distribution and abundance of pikas in the Southern Rocky Mountains, a region that represents the largest, most continuous, and southern-most range of the species. In a resurvey of 69 sites historically occupied by pikas, low annual precipitation was implicated as a limiting factor for pika persistence in the region. Due to the relatively low proportion of pika populations extirpated in the Southern Rockies, in this study we investigated local population density as a more precise metric of population response. In addition, we were able to utilize microclimatic data from temperature data loggers to better understand the mechanism by which climate affects this species. Results/Conclusions Local pika densities were highly variable across the Southern Rockies. This result is notable because individual pikas defend territories of relatively uniform size across their range, implying that territory size (and population density) does not vary in response to local resource availability. In an analysis of climatic, landscape, and microhabitat variables, the best predictors of pika population density were climatic factors. Density was lowest at sites with highest mean summer temperature and lowest mean annual precipitation. Changes in mean annual precipitation since 1980 in the Southern Rockies have been highly heterogeneous (-32 to +202 mm). Sites at which precipitation has increased were more likely to support higher pika densities than sites becoming drier. Site aspect, elevation, latitude, and talus depth were not predictive of pika population density. Our findings indicate that hotter, drier sites do not support pikas in high densities. Direct thermal stress is implicated as a driver of lower densities at hotter sites. Data from sub-talus temperature loggers implicate a lack of snowpack at drier sites as the precipitation-based driver behind low pika densities. Reduced snow cover reduces the thermal insulation available to pikas during winter, but may also reduce water content in the pika’s forage.
ABSTRACT Background/Question/Methods The goals of ecological restoration are to recover native po... more ABSTRACT Background/Question/Methods The goals of ecological restoration are to recover native populations, communities, and ecosystems degraded by human activities. Successful restoration therefore requires establishment of both ecological structure and function to degraded systems. We study plant communities of California vernal pools, which are ephemeral wetlands that support many rare or endangered species. In this system, we consider plant species composition as a key component of ecological structure, and hydrological processes as key components of ecological function. Here we present results of a long-term field experiment involving 256 constructed vernal pools in which we compare hydrologic and vegetative characteristics of restored vernal pools to that of adjacent, naturally occurring reference pools. At the outset of the experiment (1999), three-fourths of the restored pools were seeded with three different combinations of five native species (“seeded”), and one-fourth of the pools were left unseeded (“controls”). We tracked pools from 2000 to 2009 and characterized effects of hydrology and seeding on restoration success, comparing seeded and control pools with naturally occurring reference pools. We ask whether appropriate hydrological conditions alone are sufficient to promote establishment of vernal pool plant communities in constructed pools, or if seeding enhances native species persistence. Results/Conclusions As expected, cover of seeded species was significantly higher in seeded than control pools in every year of the study. The smallest observed difference in seeded species cover occurred in 2009. Furthermore, sampling plots in seeded and reference pools were similar through time in cover of seeded and other native species, as well as exotic species. Cover of seeded species in constructed pools was best modeled by seeding treatment and maximum depth of inundation. Pool depth and duration of inundation were similar among seeded, control, and reference pools through 2002, but by 2009 reference pools were significantly deeper than restored pools during the period of peak inundation. The depth of restored pools has decreased apparently as a result of climate-driven increases in the cover of exotic species that contribute to rapid thatch accumulation. These combined results suggest that vernal pool restoration can be facilitated by ensuring appropriate hydrological conditions and by seeding constructed pools with native species. However, our observed effects of climate on the outcome of competition between native and exotic species suggest impending effects of climate change, especially if exotic species facilitate their own dominance through thatch accumulation.
Background/Question/Methods Ecological restoration presents unique opportunities to examine facto... more Background/Question/Methods Ecological restoration presents unique opportunities to examine factors that affect the formation, structure and stability of ecological communities. Restoration of natural communities can furnish insights into whether community composition is deterministic, following predictable trajectories; or if it depends significantly on variation in species arrivals that can drive community trajectories in different directions. Our long-term studies of the ecological dynamics of vernal pool plant communities in California focus on: 1) effects of dispersal limitation, order of colonization, and frequency of colonization on plant community composition; 2) invasion of vernal pools by non-native species, and 3) comparison of restored vernal pools to that of naturally-occurring pools. We initiated a field experiment in 1999 by constructing 250 vernal pool basins that received different seeding treatments to assess environmental constraints on plant community formation. ...
Background/Question/Methods California’s vernal pools are ephemeral wetlands that host numerous e... more Background/Question/Methods California’s vernal pools are ephemeral wetlands that host numerous endemic species, many of which are now rare and endangered due to extensive habitat loss from agriculture and development. Conservation of existing wetlands, restoration projects, and long-term studies of population and community dynamics are critical aspects of vernal pool recovery. One little-studied aspect of vernal pool plant ecology is the role of the soil seed bank in the persistence of restored populations. We used a long-term experiment involving 256 constructed pools to determine whether constructed pools maintain a sufficient seed bank to perpetuate native species. We collected soil samples from 60 constructed pools to assess the identity and quantity of seeds present. Each soil sample was split into two equal parts, with one half sieved for manual seed sorting and the other planted in a greenhouse germination trial. Here, we compare these two methods for characterizing the seed...
Natural Resources Report Series - National Park Service, 2017
Executive Summary During 2015-2016, we completed development of a new analytical framework for l... more Executive Summary During 2015-2016, we completed development of a new analytical framework for landbird population monitoring data from the National Park Service (NPS) North Coast and Cascades Inventory and Monitoring Network (NCCN). This new tool for analysis combines several recent advances in modeling population status and trends using point-count data and is designed to supersede the approach previously slated for analysis of trends in the NCCN and other networks, including the Sierra Nevada Network (SIEN). Advances supported by the new model-based approach include 1) the use of combined data on distance and time of detection to estimate detection probability without assuming perfect detection at zero distance, 2) seamless accommodation of variation in sampling effort and missing data, and 3) straightforward estimation of the effects of downscaled climate and other local habitat characteristics on spatial and temporal trends in landbird populations. No changes in the current field protocol are necessary to facilitate the new analyses. We applied several versions of the new model to data from each of 39 species recorded in the three mountain parks of the NCCN, estimating trends and climate relationships for each species during 2005-2014. Our methods and results are also reported in a manuscript in revision for the journal Ecosphere (hereafter, Ray et al.). Here, we summarize the methods and results outlined in depth by Ray et al., discuss benefits of the new analytical framework, and provide recommendations for its application to synthetic analyses of long-term data from the NCCN and SIEN. All code necessary for implementing the new analyses is provided within the Appendices to this report, in the form of fully annotated scripts written in the open-access programming languages R and JAGS.
Natural Resources Report Series - National Park Service, 2018
Executive Summary - Long-term monitoring of landbird populations within the National Park Service... more Executive Summary - Long-term monitoring of landbird populations within the National Park Service (NPS) North Coast and Cascades Inventory and Monitoring Network (NCCN) began in 2005, with the goal of detecting trends to inform the conservation and management of landbirds and their habitats. Here we use 2005–2016 data from over 3500 point-count stations to report landbird occurrence and trends in each of five NCCN parks, including three national parks in mountain wilderness areas (Mount Rainier National Park, North Cascades National Park Complex and Olympic National Park) and two historical parks (Lewis and Clark National Historical Park and San Juan Island National Historical Park). Recent advances in point-count modeling were applied to characterize population trends for 68 landbird species, including up to 41 species in each park. Fitted models suggest that almost all species exhibited stable or increasing trends over the study period. Notable exceptions were a decline in the Olive-sided Flycatcher in two parks and single-park declines in the Norther Flicker, Hutton’s Vireo, Clark’s Nutcracker, Mountain Chickadee, Wilson’s Warbler and Dark-eyed Junco. Negative effects of precipitation-as-snow were supported in over one-third of our population models. Lower precipitation-as-snow in the mountain parks might have contributed to rising landbird densities during the study period. Population density also varied with elevation in mountain parks, but temporal trends were similar among elevational strata for each species analyzed, suggesting no evidence of elevational range-shifts during this study. These results reinforce recent analyses of the first 10 years of point-count data from the three mountain parks (Ray et al. 2017 a). In the current analysis, models were extended to explore effects of covariates on species detection probability. Negative effects of ambient noise level on detection were supported in several cases, but adding covariates of detection generally did not lead to substantial improvements in model fit. In some cases, model fit was improved by reducing the scope of inference to a portion of the focal region, suggesting important effects of habitat heterogeneity.
Abstract. Monitoring species in National Parks facilitates inference regarding effects of climate... more Abstract. Monitoring species in National Parks facilitates inference regarding effects of climate change on population dynamics because parks are relatively unaffected by other forms of anthropogenic disturbance. Even at early points in a monitoring program, identifying climate covariates of population density can suggest vulnerabilities to future change. Monitoring landbird populations in parksduring the breeding season brings the added benefit of allowing a comparative approach to inference across a large suite of species with diverse requirements. For example, comparing resident and migratory species that vary in exposure to non-park habitats can reveal the relative importance of park effects, such as those related to local climate. We monitored landbirds using breeding-season point-count data collected during 2005–2014 in three wilderness areas of the Pacific Northwest (Mount Rainier, North Cascades, and Olympic National Parks). For 39 species, we estimated recent trends in population density while accounting for individual detection probability using Bayesian hierarchical N-mixture models. Our analyses integrated several recent developments in N-mixture modeling, incorporating interval and distance sampling to estimate distinct components of detection probability while also accommodating count intervals of varying duration, annual variation in the length and number of point-count transects, spatial autocorrelation, random effects, and covariates of detection and density. As covariates of density, we considered metrics of precipitation and temperature hypothesized to affect breeding success. We also considered effects of park and elevational stratum on trend. Regardless of model structure, we estimated stable or increasing densities during 2005–2014 for most populations. Mean trends across species were positive for migrants in every park and for residents in one park. A recent snowfall deficit in this region might have contributed to the positive trend, because population density varied inversely with precipitation-as-snow for both migrants and residents. Densities varied directly but much more weakly with mean spring temperature. Our approach exemplifies an analytical framework for estimating trends from point-count data, and for assessing the role of climatic and other spatiotemporal variables in driving those trends. Understanding population trends and the factors that drive them is critical for adaptive management and resource stewardship in the context of climate change.
ABSTRACT—National parks play a key role in conserving species by providing landscapes where threa... more ABSTRACT—National parks play a key role in conserving species by providing landscapes where threats from anthropogenic disturbance are reduced. In a recent study of 3 large wilderness parks in the Pacific Northwest, nearly all landbird species were found to be stable or increasing. Nonetheless, contemporary results from the Breeding Bird Survey and mark-recapture studies fuel concerns that some landbirds in the Pacific Northwest are trending in sync with many North America species in widespread decline. Although landbird populations might be thriving in large parks with extensive old-growth forest, those in smaller parks with less intact wilderness and higher ratios of edge-to-interior habitat might reflect the stressors inherent in more humandominated landscapes. We conducted landbird point-count surveys from 2005 to 2016 in 2 national historical parks situated in the more human-dominated landscapes of this region, San Juan Island National Historical Park and Lewis and Clark National Historical Park. Established primarily to protect cultural resources, these parks lack old-growth forest and consist of relatively small parcels embedded in fragmented, multi-use landscapes. Here, we apply recent developments in point-count analysis to estimate trends in population density for 50 landbird species commonly detected in these small parks, including lagged effects of precipitation and temperature on the annual density of each species, and effects of survey conditions on species detection. All but 3 species exhibited stable densities in both parks, and more than half of the populations analyzed clearly increased in density over the study period. Notable exceptions were single-park declines in Olive-sided Flycatcher (Contopus cooperi), Northern Flicker (Colaptes anratus), and Hutton’s Vireo (Vireo huttoni). Annual variation in population density was often related to climate, with generally positive responses to a recent deficit in annual precipitation-assnow, and more variable responses to higher mean spring temperature. These results reinforce trends estimated for 3 large national parks in the Pacific Northwest, suggesting recent stability of landbird populations in parks of this region, independent of park size or setting.
Additional file 1: Table S1. Five replicate entropy (Gompert et al. 2014) chains were run for k =... more Additional file 1: Table S1. Five replicate entropy (Gompert et al. 2014) chains were run for k = 2–11 for the full dataset of all pika populations. Table S2. Five replicate entropy (Gompert et al. 2014) chains were run for k = 2–8 for the Nevada subset of pika populations. Table S3. The loadings of bioclimatic variables onto the first two PCs for all 11 populations. Table S4. The loadings of bioclimatic variables onto the first two PCs for the six Nevadan populations. Table S5. Sample sizes (N) and estimates of genetic diversity for each population.
One .csv file per study site including the xy coordinates (UTM, NAD83) for each pika habitat patc... more One .csv file per study site including the xy coordinates (UTM, NAD83) for each pika habitat patch used in network analyses. Patch IDs correspond to Patch IDs in Patch Distance Matrices files. Centroids calculated in ArcGIS10.0
in fi eld workers, possibly contracted through rodent bites. Screening for antibodies to SNV in r... more in fi eld workers, possibly contracted through rodent bites. Screening for antibodies to SNV in rodents trapped in 2 seasons showed that 9.77 % were seropositive. Quantitative real-time PCR showed that 2 of 79 deer mice had detectable titers of SNV RNA. Hantaviruses are rodent-borne viruses that in the Americas have been implicated as the causative agents of hantavirus cardiopulmonary syndrome (HCPS) (1). In North America, Sin Nombre virus (SNV) is responsible for most cases of HCPS, and the deer mouse (Peromyscus maniculatus) is its main reservoir. Since the first reported outbreak of the disease in 1993 in the southwestern United States, rodent serologic surveys have confirmed that SNV is present through most of the range where deer mice exist, including Colorado (2,3). We report 2 cases of SNV infection in field workers in Colorado, who were infected with the virus despite protection with a powered air-purifying respirator. We also performed a serologic survey of wild rodents in ...
BackgroundDistributional responses by alpine taxa to repeated, glacial-interglacial cycles throug... more BackgroundDistributional responses by alpine taxa to repeated, glacial-interglacial cycles throughout the last two million years have significantly influenced the spatial genetic structure of populations. These effects have been exacerbated for the American pika (Ochotona princeps), a small alpine lagomorph constrained by thermal sensitivity and a limited dispersal capacity. As a species of conservation concern, long-term lack of gene flow has important consequences for landscape genetic structure and levels of diversity within populations. Here, we use reduced representation sequencing (ddRADseq) to provide a genome-wide perspective on patterns of genetic variation across pika populations representing distinct subspecies. To investigate how landscape and environmental features shape genetic variation, we collected genetic samples from distinct geographic regions as well as across finer spatial scales in two geographically proximate mountain ranges of eastern Nevada.ResultsOur genom...
ABSTRACT Background/Question/Methods The American pika (Ochotona princeps) is considered a sentin... more ABSTRACT Background/Question/Methods The American pika (Ochotona princeps) is considered a sentinel species for detecting ecological effects of climate change. Pikas are declining within a large portion of their range, and recent research implicates climate change in the extinction of local pika populations. Pikas have a narrow thermal tolerance; when ambient temperatures increase, pikas reduce their activity levels and rely on access to cooler microclimates within the talus to shed heat passively. Because pikas behaviorally thermoregulate, it can be difficult to assess the impact of local habitat characteristics on persistence. We developed a simple procedure designed to provide more direct evidence of physiological stress in pikas. Pikas were sampled at several locations in the Rocky Mountains, and we measured levels of stress hormone metabolites in collected fecal samples. Trapped pikas underwent a variety of data collection procedures known to induce stress. Individuals were held on site for up to 24 hours in a holding chamber specifically designed for non-invasive collection of fecal samples. Fecal samples were collected every 1-2 hours, and animals were released back into their home territories once the collection period was over. Samples were frozen immediately, and later transferred to a lab for extraction and measurement of stress hormone metabolites. Results/Conclusions Analyses of stress hormone metabolites in fecal material are increasingly employed to evaluate stress in sensitive populations of mammals, and concentrations of fecal glucocorticoid metabolites (GCMs) have become one of the best used of these stress metrics. Collected fecal samples were analyzed for GCM concentrations, and comparisons were made between GCM levels measured in samples collected at different times subsequent to capture. Results reflect the expected increase in GCM level following a stressful event, and also identify the time delay (12.5 hours) between a pika’s exposure to a known stressor and subsequent elevation of its GCM level. Results also display individual variation in measured GCM levels, and overall higher GCM levels in samples that had been urinated on when compared to those without urine. This is the first study to measure stress hormone metabolite levels in fecal samples for any species of pika, and the utility of GCM assays as a metric of stress in American pika populations has now been validated. Non-invasive collection of fecal samples can be utilized to assess the physiological condition of pikas inhabiting different environments, and to determine whether local habitat variables specifically related to climate can explain levels of physiological stress in pikas.
Climate change in mountain regions has exposed high-elevation species to rapidly changing tempera... more Climate change in mountain regions has exposed high-elevation species to rapidly changing temperatures. Although climate exposure can be reduced in certain microclimates, the quality of microclimatic refugia might also degrade with climate change. The American pika (Ochotona princeps) often inhabits high elevations, and is considered climate-sensitive due to its narrow thermal tolerance and recent extirpations in some warmer portions of its range. Pikas behaviorally thermoregulate by taking refuge in the subsurface microclimates found in taluses and other rocky habitats, where daily thermal fluctuations are attenuated and somewhat decoupled from free-air temperatures. Changes in microclimate might reduce the efficacy of this behavioral thermoregulation. This study compares recent (2009–2021) subsurface temperatures at a long-term pika study site with a rare instance of historical (1963–1964) data from the same location. We also place historical and recent microclimates in context us...
Exploratory plots showing the relationship between site occurrence probabilities and site distanc... more Exploratory plots showing the relationship between site occurrence probabilities and site distances to nearest roads for each park unit.
Comparison of climatic predictors among 18 study sites and the 69 sites historically occupied by ... more Comparison of climatic predictors among 18 study sites and the 69 sites historically occupied by pika from which they were selected via random sampling stratified by latitude, longitude, and elevation.
When can we measure stress noninvasively? Postdeposition effects on a fecal stress metric confoun... more When can we measure stress noninvasively? Postdeposition effects on a fecal stress metric confound a multiregional assessment
Uploads