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Author: Lindsey Ann Bruckerhoff Publisher: ISBN: Category : Languages : en Pages :
Book Description
The role of predators in ecosystems has not only intrigued and puzzled ecologists over time, but predators are charismatic icons of conservation whose status indicates threats of global change. Through habitat alteration and fragmentation, climate change, and species introductions, predation pressure has been altered globally through the loss of apex predators, introduction of predators, and changes in predator distributions and abundance. While we know predators can influence ecosystems through top-down processes, managing changes in predation pressure requires quantifying effects of predators at scales relevant to management and conservation. In lotic systems, scales relevant to management often span across drainage basins, so predator effects must be quantified across stream networks. Because lotic communities also respond to landscape change, understanding the role of predators across stream networks requires careful consideration of local and broad scale abiotic factors influencing both predators and prey. I combined simulated, experimental, and observational data to 1) assess sampling strategies to determine effects of landscape change on stream fish communities, 2) measure changes in predator consumption rates across spatial scales and the role of prey behavior in driving scaling relationships, and 3) quantify the relationship between the presence of predators and stream fish community structure while controlling for abiotic variability across stream networks. In chapter 2, I compared how the distribution of sample sites (completely random, highly skewed, or uniform distributions) across landscape gradients influenced variability in measured responses of stream fish community metrics. Strong responses (species richness) to environmental gradients were robust to sample distributions, but large sample size and uniform distributions of samples across gradients were necessary to quantify more complex ecological responses (community composition). In chapter 3, I conducted a mesocosm study to quantify differences in per capita consumption across different arena sizes and measured three aspects of prey behavior hypothesized to be important in driving consumption rates: aggregation, movement, and spatial overlap with predators. Per capita consumption was highest in the largest arena relative to the smallest. I hypothesize the positive relationship between consumption and spatial scale was driven by lower group vigilance because prey aggregated less in large arenas. In chapter 4, I compared fish community structure, including richness and abundance of species, at sites in which a predatory fish, largemouth bass (Micropterus salmoides), were present or absent. I first identified which abiotic factors, including both natural stream attributes and anthropogenic landscape changes, drove the presence of largemouth bass and stream fish community structure. I then controlled for important abiotic factors to determine relationships between largemouth bass and stream fish community structure. Richness was higher than predicted based on abiotic factors at sites where bass were present. Several species associated with small impoundments exhibited significant co-occurrence patterns with largemouth bass, likely driving the heightened richness at sites with bass. Complex ecological phenomena such as community responses to predators are difficult to measures, especially in the context of landscape change. These studies highlight the importance of thoughtful study design, the scale-dependence of biotic interactions, and challenges of quantifying responses to predators at scales relevant to conservation and management.
Author: Lindsey Ann Bruckerhoff Publisher: ISBN: Category : Languages : en Pages :
Book Description
The role of predators in ecosystems has not only intrigued and puzzled ecologists over time, but predators are charismatic icons of conservation whose status indicates threats of global change. Through habitat alteration and fragmentation, climate change, and species introductions, predation pressure has been altered globally through the loss of apex predators, introduction of predators, and changes in predator distributions and abundance. While we know predators can influence ecosystems through top-down processes, managing changes in predation pressure requires quantifying effects of predators at scales relevant to management and conservation. In lotic systems, scales relevant to management often span across drainage basins, so predator effects must be quantified across stream networks. Because lotic communities also respond to landscape change, understanding the role of predators across stream networks requires careful consideration of local and broad scale abiotic factors influencing both predators and prey. I combined simulated, experimental, and observational data to 1) assess sampling strategies to determine effects of landscape change on stream fish communities, 2) measure changes in predator consumption rates across spatial scales and the role of prey behavior in driving scaling relationships, and 3) quantify the relationship between the presence of predators and stream fish community structure while controlling for abiotic variability across stream networks. In chapter 2, I compared how the distribution of sample sites (completely random, highly skewed, or uniform distributions) across landscape gradients influenced variability in measured responses of stream fish community metrics. Strong responses (species richness) to environmental gradients were robust to sample distributions, but large sample size and uniform distributions of samples across gradients were necessary to quantify more complex ecological responses (community composition). In chapter 3, I conducted a mesocosm study to quantify differences in per capita consumption across different arena sizes and measured three aspects of prey behavior hypothesized to be important in driving consumption rates: aggregation, movement, and spatial overlap with predators. Per capita consumption was highest in the largest arena relative to the smallest. I hypothesize the positive relationship between consumption and spatial scale was driven by lower group vigilance because prey aggregated less in large arenas. In chapter 4, I compared fish community structure, including richness and abundance of species, at sites in which a predatory fish, largemouth bass (Micropterus salmoides), were present or absent. I first identified which abiotic factors, including both natural stream attributes and anthropogenic landscape changes, drove the presence of largemouth bass and stream fish community structure. I then controlled for important abiotic factors to determine relationships between largemouth bass and stream fish community structure. Richness was higher than predicted based on abiotic factors at sites where bass were present. Several species associated with small impoundments exhibited significant co-occurrence patterns with largemouth bass, likely driving the heightened richness at sites with bass. Complex ecological phenomena such as community responses to predators are difficult to measures, especially in the context of landscape change. These studies highlight the importance of thoughtful study design, the scale-dependence of biotic interactions, and challenges of quantifying responses to predators at scales relevant to conservation and management.
Author: Catherine L. Hein Publisher: ISBN: Category : Electronic dissertations Languages : en Pages :
Book Description
A landscape perspective is critically important for understanding community structure, particularly in systems dominated by migratory fauna. I aimed to understand how the structure of riverscapes in Puerto Rico mediates potential anthropogenic impacts, predator-prey interactions, and the migratory behavior of a diadromous species. I surveyed fishes and shrimps at sites throughout two watersheds, designed transplant experiments that investigated the role of natural barriers on predator-prey interactions, and developed models of shrimp migration specific to a particular river network. I did not detect an effect of anthropogenic changes to the landscape on fish and shrimp species distributions in two watersheds that drain the Luquillo Experimental Forest. These communities were primarily affected by the position of natural barriers: predatory fish distributions were limited by waterfalls and most shrimp species were found upstream from fish barriers. Thus, steep terrain mediated predator-prey interactions between fishes and shrimps, with one shrimp (Atya lanipes) likely avoiding predation by migrating iv above fish barriers. Lab and field experiments provided the first mechanistic evidence for landscape-level predator-avoidance behavior by A. lanipes. Both postlarval and adult shrimp avoided the scent of three predatory fish species in a y-maze fluvarium. In natural streams above fish barriers, adult A. lanipes did not respond to the addition of fish scent, but adult abundances did decline when fish were added to in-stream cages. To integrate our ideas about how shrimp behaviors scale up to observed adult A. lanipes distributions across the landscape, we developed a set of nested models specific to a particular river network. The best models parameterized branch choice at nodes within the river network to be heavily weighted toward particular mid-elevation tributaries above fish barriers. Our models indicated that distance traveled above and below fish barriers had little effect on adult distributions. Because the number of migrants decreases with distance upstream, the latter result was likely an artifact of the model. In montane river systems with migratory fauna, scientists would benefit by creatively designing new experiments and models that incorporate river network structure, as this is the template upon which all processes occur.
Author: William J. Matthews Publisher: JHU Press ISBN: 1421422026 Category : Nature Languages : en Pages : 359
Book Description
The most comprehensive synthesis of stream fish community research ever produced. Winner of the CHOICE Outstanding Academic Title of the Choice ACRL Ecologists have long struggled to understand community dynamics. In this groundbreaking book, leading fish ecologists William Matthews and Edie Marsh-Matthews apply long-term studies of stream fish communities to several enduring questions. This critical synthesis reaches to the heart of ecological theory, testing concepts against the four decades of data the authors have collected from numerous warm-water stream fish communities in the central and eastern United States. Stream Fish Community Dynamics draws together the work of a single research team to provide fresh analyses of the short- and long-term dynamics of numerous streams, each with multiple sampling sites. Conducting repeated surveys of fish communities at temporal scales from months to decades, the authors' research findings will fascinate anyone searching for a deeper understanding of community ecology. The study sites covered by this book range from small headwater creeks to large prairie rivers in Oklahoma and from Ozark and Ouachita mountain streams in Arkansas to the upland Roanoke River in Virginia. The book includes • A comparison of all global and local communities with respect to community composition at the species and family level, emergent community properties, and the relationship between those emergent properties and the environments of the study sites • Analyses of traits of individual species that are important to their distribution or success in harsh environments • A review of evidence for the importance of interactions—including competition and predation—in community dynamics of stream fishes • An assessment of disturbance effects in fish community dynamics • New analysis of the short- and long-term dynamics of variation in stream fish communities, illustrating the applicability and importance of the "loose equilibrium concept" • New analyses and comparisons of spatiotemporal variation in community dynamics and beta diversity partitioning • An overview of the effects of fish in ecosystems in the central and eastern United States The book ends with a summary chapter that places the authors' findings in broader contexts and describes how the "loose equilibrium concept"—which may be the most appropriate default assumption for dynamics of stream fishes in the changing climate of the future—applies to many kinds of stream fish communities.
Author: Corbin Cox Kuntze Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Habitat changes and prey depletion are among the most prominent drivers of near-global declines in predator populations. In particular, landscape homogenization - driven by climate change, anthropogenic land use, and management policies - can destabilize essential trophic interactions and represents a continuing threat to biodiversity and ecosystem function. Many predator and prey species occur, and likely evolved, in complex landscapes with heterogeneously distributed resources that shape many of their ecological interactions. A growing body of research has explored the role of spatial heterogeneity in predator-prey interactions, suggesting that heterogeneous landscapes containing prey refuges can decouple prey availability from abundance, with consequences when any one habitat type predominates. However, most of these studies are theoretical or lab-based, limited to controlled settings and by simplifying assumptions. Moreover, many studies of natural predator-prey systems are conducted at limited spatial scales, do not involve mobile predators, or fail to consider the role of alternative prey. As a result, our understanding of spatial heterogeneity - and the consequences of landscape simplification - remain limited by the available literature. This dissertation seeks to reduce key uncertainties and assess the emergent consequences of environmental change and landscape simplification on wildlife populations. Chapter 1 (Kuntze et al., 2024; Journal of Mammalogy) leveraged a 13-year monitoring dataset, stable isotope analysis, and high-resolution climate and habitat imagery to evaluate demographic responses of an isolated and endangered distinct population segment of fishers (Pekania pennanti) to rapid environmental change in the southern Sierra Nevada, California, USA. Fisher survival was sensitive to both biotic and abiotic factors, although the strength and direction of these effects were ultimately mediated by age and sex. These findings suggest that continued climate change will likely have consequences for Fishers through both incremental stressors and extreme weather events but increasing forest heterogeneity may help to buffer against the impacts of such change. Further, this study illustrates the importance of disentangling the effects of intrinsic and extrinsic factors on survival, especially among species with distinct sexual or ontogenetic differences.Chapter 2 (Kuntze et al., 2023; Ecological Applications) is the first of three that focuses on predator-prey dynamics between the spotted owl (Strix occidentalis) - an iconic old-forest species at the center of forest management planning in western North America - and one of its principal prey species, the dusky-footed woodrat (Neotoma fuscipes) - a younger forest species. This chapter explores the hypothesis that heterogeneous landscapes can create sources or spatial refuges for prey that ultimately benefit predator and prey populations when each are associated with different habitats. Here, we combined mark-recapture and survival monitoring of woodrats with direct observations of prey deliveries by spotted owls, and found that (1) woodrat abundance was higher within spotted owl home ranges defined by a heterogeneous mix of mature forest, young forest, and open areas, (2) woodrat mortality rates were low across all forest types (although all observed owl predation occurred within mature forests) and did not differ between heterogeneous and homogeneous owl home ranges, (3) owl consumption of woodrats increased linearly with woodrat abundance, and (4) consumption of alternative prey could not reconcile the deficit of reduced woodrat captures in homogeneous home ranges, as owls in heterogeneous landscapes delivered 30% more total prey biomass - equivalent to the energetic needs of producing one additional young. These findings represent some of the first empirical evidence from natural systems that promoting landscape heterogeneity can provide co-benefits to both predator and prey populations and constitute an effective strategy for conserving endangered predator populations. Chapter 3 (in review at Journal of Animal Ecology) contrasts foraging strategies within the context of a primary and secondary prey species to experimentally evaluate whether the magnitude of perceived risk, and in turn, the nature and strength of anti-predator investment, is governed by both predation intensity and the setting in which an encounter takes place. We studied the effects of spotted owls on two species experiencing asymmetrical predation pressures: dusky-footed woodrats (primary prey) and deer mice (Peromyscus spp., alternative prey). Woodrats exhibited behavioral responses to both background and acute risk at each stage of the foraging process, while deer mice only responded to acute risk. This suggests that prey may conform to or depart from the risk allocation hypothesis (i.e., that background risk modulates responses to immediate cues of predation risk) depending on relative predation risk from a shared predator. Furthermore, woodrats and deer mice employed time allocation and apprehension in different manners and under opposing circumstances, highlighting that primary and secondary prey can exhibit profound differences in both how risk is perceived, as well as how it is managed. Finally, Chapter 4 (prepared for Forest Ecology and Management) characterizes patterns in woodrat site occupancy at site-, patch-, and landscape-scales within landscapes where forest heterogeneity was created by even-aged timber management. Woodrats were more likely to occupy sites with greater canopy cover, understory cover, and hardwoods - particularly tanoak (Notholithocarpus densiflorus) - and smaller patches of young forest. Woodrats were also more likely to occur in mature forests in close proximity to younger forest, suggesting that high-quality habitat patches can produce dense populations that recruit into adjacent, lower-quality patches. These findings highlight the benefit of multiscale studies and provide insight into management activities that may benefit species conservation without compromising resilience in forest ecosystems. These latter three chapters collectively demonstrate that heterogeneity in vegetation types including high-density young forests increased the abundance and availability of early-successional woodrats that, in turn, provided energetic and potentially reproductive benefits to mature forest-associated spotted owls. Overall, this dissertation provides empirical support for theoretical studies on the role of heterogeneity (and the mechanisms conferring co-benefits), as well as contingencies mediating anti-predator behaviors, fit to the appropriate spatial scales.
Author: Evan Faulk Publisher: ISBN: Category : Languages : en Pages :
Book Description
Stream fish communities are frequently utilized as bioindicators of water quality and stream ecosystem health, because environmental and anthropogenic processes that control and alter physicochemical properties of streams are often reflected in fish community composition. Research staff of the Eastern Rivers and Mountains Network (ERMN), an Inventory and Monitoring network of the National Park Service, annually monitor core indicators of wadeable stream condition using measures of ecological integrity; however, no continuous stream fish community monitoring existed. Given the usefulness of stream fish as bioindicators and the potential benefits of adding long-term fish monitoring to the ERMN wadeable stream monitoring program, I developed and initiated the framework and methodology of a continuous, long-term fish community monitoring program for ERMN wadeable streams. During spring and summer of 2013 and 2014, an occupancy sampling framework was used to collect stream fish detection/non-detection data at 68 randomly-selected, spatially-balanced sites across two ERMN parks: Delaware Water Gap National Recreation Area (DEWA) and New River Gorge National River (NERI). Hierarchical community occupancy models were used to describe stream fish distribution and determine the relative importance of stream habitat, measured at multiple spatial scales, in structuring stream fish communities. Results indicated that occupancy probabilities and effects of habitat, with respect to direction and magnitude, differed among species. In most cases, natural longitudinal gradients of stream habitat were reflected in species-specific and species group-specific occupancy probabilities, but anthropogenic disturbance (e.g., species introductions, impoundments, deforestation, and water quality impairment) also influenced the frequency of species occurrence and native-introduced species dynamics. These results highlighted the importance of considering multiple processes and spatial scales when studying how stream fish communities are shaped by stream habitat; moreover, that occupancy may be a valuable state variable for use in long-term species monitoring programs.
Author: Matthew John Troia Publisher: ISBN: Category : Languages : en Pages :
Book Description
A fundamental goal of ecology is to understand environmental associations of species. These associations can provide a basis for predicting spatial distributions in contemporary habitats as well as how those distributions might change in response to anthropogenic environmental change. Developing species distribution models is limited by an incomplete understanding of functional traits, spatial scaling, and the mechanisms and generalities of correlations among abundance and environmental gradients. I address these four issues using observational and experimental approaches. First, I tested opposing mechanisms of community assembly by measuring the dispersion (i.e., diversity) of three types of functional strategies at three spatial scales and along environmental gradients. I found that communities are assembled via abiotic environmental filtering, but the strength of this filtering depends on the spatial scale of investigation, longitudinal network position, and type of functional strategy. Second, I quantified community-environment relationships across thirteen sub-basins, nested within the three major basins within Kansas to evaluate the consistency (i.e., generality) in predictive capability of environmental variables among sub-basins and across spatial extents. I found that longitudinal network position is consistently the strongest predictor of community composition among sub-basins, but in-stream and catchment predictors become stronger correlates of community composition with increasing spatial extent. Third, I used environmental niche models to quantify distributions of four pairs of congeneric cyprinids and found that species within each pair exhibited contrasting stream-size preferences. I then used field experiments to test for differences in individual-level performance between one pair of species (Pimephales notatus and P. vigilax) along a gradient of stream size. I found that adult spawn success and juvenile growth and condition increased with stream size for both species, indicating that these congeners respond similarly to abiotic gradients associated with the river continuum. I concluded that complementary distributions are a consequence of biotic interactions, differential environmental filtering evident in an unmeasured performance metric, or differential environmental filtering by an environmental factor operating at longer timescales. These studies demonstrate the context dependencies of characterizing habitat associations of stream fishes, but also reveal the general importance of stream size and associated environmental gradients in structuring stream fish communities.
Author: Donna S. McCollum Publisher: ISBN: Category : Biotic communities Languages : en Pages : 162
Book Description
Stream ecosystems are holistic systems that incorporate disturbances and abiotic influences at many spatial and temporal scales. This view supports a three-tiered model of variables that determine biotic integrity in streams, with causes and effects flowing from large-scale to fine-scale processes. Tier One characteristics include variables important at the scale of geomorphological processes and land use over entire watersheds. These variables largely determine Tier Two factors, abiotic conditions in a stream reach. Tier Two variables, in turn, largely structure the Tier Three variables, the stream's biotic communities. Through field studies and GIS analysis, relationships among these three tiers of variables were examined in this research to explore the question of how agriculture exerts its influence on stream fishes. This study investigated 27 streams, in two ecoregions and the transition area, or ecotone, between them, in south-central Ohio. The study design allowed questions to be asked concerning the relative influence of geomorphology and land use in varied landscapes, as well as relative impacts of watershed versus riparian land use. The region also contained relatively equal proportions of three types of agriculture (hay, row crops, and pasture) allowing the study to address the question of which land use might be most harmful to stream fish. This study supported the importance of row crop agriculture, finding it to be the most degrading type of agriculture for stream fish, but also found pasture to be an important causal factor in stream community degradation. This study also supported the importance of riparian buffers, finding riparian agriculture to be more degrading than agriculture over the entire watershed. A more interesting finding is the suggestion that a minor amount of nutrient enrichment from agricultural land use may benefit streams that are naturally oligotrophic. A possible mechanism could be increased primary production, which increases macroinvertebrate density, and provides a larger food base for fishes. This study also reports the possible existence of a biodiversity "hotspot" in the transitional region between the two ecoregions. Some evidence exists that greater habitat heterogeneity increases species richness, suggesting a possible cause for higher biodiversity in this ecotonal region. Since habitat heterogeneity over whole streams was not measured in this study, both the existence and mechanism of such a hotspot needs more study. A final conclusion is that geomorphology and agricultural land use may be equally important in structuring stream conditions, and thus, biological stream communities. This study illustrates the difficulties associated with overlapping causes and effects in complex systems such as streams and their catchments. Several variables in the study reported here required examination at multiple scales and with multiple statistical techniques in order to understand relationships that varied across different regions. The effects of a particular agricultural variable were not always equal in the diverse landscapes of southern Ohio. Lotic ecologists must examine a variety of ecoregions, and incorporate a variety of scales with a variety of analytic tools, if predictive stream ecology is to become a reality.
Author: Lindsey Ann Bruckerhoff
Author: Lindsey Ann Bruckerhoff
Author: Catherine L. Hein
Author: William J. Matthews
Author: Corbin Cox Kuntze
Author: Mark B. Bain
Author: 
Author: Evan Faulk
Author: Joshua Jeffers Woodward
Author: Matthew John Troia
Author: Donna S. McCollum