Download or read book Effects of Spatial Subsidies and Canopy Cover on Pond Communities and Multiple Life Stages in Amphibians written by Julia E. Earl and published by . This book was released on 2012 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: Spatial subsidies are resources that move from one ecosystem to another. In aquatic systems, canopy cover determines both light availability and subsidy input in the form of senescing leaves. This phenomenon has been well studied in streams, and general patterns of ecosystem production, community structure, and the reciprocal export of animals have been discovered. I was interested in whether these patterns also occurred in ponds. I examined these patterns using experimental pond mesocosms and supported the results using an observational study of natural ponds. For the pond mesocosm experiment, I placed mesocosms along a canopy cover gradient and manipulated spatial subsidy input. I found a shift from net heterotrophy in closed canopy mesocosms to a balance between heterotrophy and autotrophy in open canopy mesocosms. The macroinvertebrate community structure responded to both canopy cover and subsidy input in mesocosms. The biomass of collectors (detritivores) was highest in mesocosms with litter input and increased with canopy cover, a pattern also present in natural ponds. Finally, I found that litter input increased the reciprocal export of amphibian biomass compared to no input. Amphibian biomass also decreased with increases in primary productivity. This research highlights the importance of spatial subsidies that connect different ecosystem types. Conserving these ecosystem connections will help maintain biodiversity and ecosystem function.

Download or read book The Influence of Canopy Cover and Climate on Early Life stage Vital Rates for Northern Red legged Frogs Rana Aurora and the Implications for Population Growth Rates written by Kecly W. McHarry and published by . This book was released on 2017 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt: Many amphibian species are in decline due to habitat loss and changing climates. Understanding how habitat characteristics and climate influence vital rates, and if they act in concert or in opposition can inform management decisions. This study investigated the potential interaction of canopy cover and climate on early stage vital rates of northern red-legged frogs. Demographic data were collected from sample populations in experimental canopy cover treatments across a latitudinal distribution. Rearing cages were used to estimate hatch success, and mark-recapture surveys to estimate tadpole survival. Ambient air temperature was used as an index of climate because it is easily relatable to the effects of climate change and collected at fine scales without specialized equipment. Estimates from field data, along with published accounts were used in a matrix modeling analysis to evaluate if tadpole survival impacted population growth rates. Egg hatch success did not differ between canopy treatments or among sites. Canopy cover did affect tadpole survival rates, but not tadpole development time. The effect of canopy over on tadpole survival varied depending on which population was being evaluated. There was no evidence that the effect of canopy cover on tadpole survival was dependent on air temperature. Tadpole survival rates did impact population growth rates. This research shows that the effect of canopy cover on early stage vital rates for this species is variable between populations, but not due to differences in average air temperatures. For some populations the effect of canopy cover on tadpole survival was large enough to change projected population growth rates from stable to decreases of 30%. These results demonstrate that manipulating canopy cover can influence tadpole survival sufficiently enough to alter population trajectories. However, the variable effects of canopy cover on vital rates suggest a universal management strategy through canopy cover manipulation will not have equal impacts across populations.

Download or read book Effects of Habitat Characteristics on Amphibian Use of Aquatic and Terrestrial Environments written by David Anthony Dimitrie and published by . This book was released on 2021 with total page 144 pages. Available in PDF, EPUB and Kindle. Book excerpt: Habitat characteristics can affect how organisms use environments. Individuals are expected to have evolved the ability assess habitat quality to maximize their fitness. I investigated the effects of habitat characteristics on aquatic and terrestrial environment use in multiple amphibian life-stages. In Chapter 1, I investigated how female breeding habitat selection is influenced by competitors and how this affects offspring performance. Female eastern gray treefrogs (Hyla versicolor) used pools without larval competitors more than pools with green frog (Rana clamitans) or bullfrog (Rana catesbeiana) tadpoles. Treefrog tadpoles developed faster and grew larger without heterospecifics, indicating larval performance matched female preference. Males may use habitat quality cues differently. In Chapter 2, I evaluated male use of these same habitats and the male quality as potential mates for females using recordings of male advertisement calls. Males used pools with heterospecifics the same as pools without, and the advertisements of males at all habitat types were similar. Thus, while females avoided pools with heterospecifics, males did not. In Chapter 3, I tested if male treefrogs using fringe habitats differ from residents at an adjacent core pond by comparing the calls of males in both habitats. I also evaluated how fringe males changed their calls at the core pond. Fringe males produced more yet shorter calls than males in the core habitat, but called at a similar effort. When fringe males were moved to the core habitat, they adjusted their calls to match the core males. Finally, in Chapter 4, I investigated how the terrestrial environment affects juvenile development. In collaboration with David Burke at the Holden Arboretum, I tested how forest acidification affects the American toad (Anaxyrus americanus) and its interaction with the invertebrate community. Toads tended to grow larger in elevated soil pH, although survival and diet were not affected by pH. I found no effect of pH on the invertebrate community or forest floor trophic dynamics. My studies found that biotic and abiotic habitat characteristics can affect amphibian development and male and female use of breeding habitats in complex ways. These effects have implications for individual fitness, population dynamics, and community assembly.

Download or read book Effect of Limited Canopy Removal on Pond breeding Amphibians written by Ginger Kinworthy Louder and published by . This book was released on 2003 with total page 124 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Influence of Forest Management on Headwater Stream Amphibians at Multiple Spatial Scales written by Margo A. Stoddard and published by . This book was released on 2004 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The Role of Forest Composition on Pool breeding Amphibians written by Michael Paul Graziano and published by . This book was released on 2017 with total page 135 pages. Available in PDF, EPUB and Kindle. Book excerpt: Few studies investigate the intricate effects that the plant community has on amphibian populations. Plants shape ecosystems, affecting both physical and chemical attributes of the landscape. Conspicuous artifacts of the plant community include canopy cover, physical structure, and modified temperature and moisture profiles. However, less conspicuous artifacts of the tree community, namely the physiochemical characteristics of their resulting leaf litter, have the ability to shape their ecosystem just as greatly as their more conspicuous traits. Leaf litter represents the primary energy source in vernal pools and other aquatic systems that are critical amphibian breeding habitat. As plant communities shift across the landscape due to ecosystem degradation, invasion by nonnative species, climate change, and shifting disturbance regimes, there is a critical need to investigate how these potential changes can influence the amphibian community and the mechanisms by which they occur. My research investigates how the vernal pool breeding amphibian community responds to differing plant communities across a heterogeneous forested landscape and throughout their life cycle. As such, my overall objectives are multi-faceted: (1) to determine if the tree community impacts colonization and use of vernal pool-breeding amphibians (2) to scale up mesocosm studies that document the strong regulatory response tree litter inputs can have on growth and development of amphibian larvae to a field setting (3) to determine if small, constructed ridge-top pools are a viable option for enhancing amphibian populations in the landscape, particularly with regards to increasing functional connectivity and maintaining diverse amphibian communities, and (4) to establish a landscape-level study design for conducting future, field-based experiments that can serve as a baseline to document changes in forest ecosystems. These objectives are addressed within each of my primary research pursuits below.

Download or read book Using Ecological Stoichiometry to Explain the Effects of Spatial Subsidies on Larval Amphibian Development and Disease written by and published by . This book was released on 2015 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: The cross-ecosystem transfer of matter is vital to the productivity of many ecosystems. Most prior studies have focuses on the total energy (biomass) of these spatial subsidies, but the quality (i.e., nutritional content) of subsidies can be equally important. Ecological Stoichiometry (ES) provides a theoretical framework to predict effects of subsidy quality, based on the elemental composition of the subsidy itself relative to the composition of the recipient system. In this dissertation I use ES theory to predict effects of a spatial subsidy (leaf litter) on the performance of a secondary aquatic consumer (wood frog Lithobates sylvaticus tadpoles). First, I show that ES can predict a priori the growth rates of wood frog tadpoles feeding on a leaf litter quality (nitrogen) gradient. Second, I show that the fitness benefits of maternal provisioning, a life history strategy to improve offspring competitive performance, are greater when leaf litter quality (nitrogen) is low. Third, I show that tadpole resource limitation changes as a function of ontogeny, due to shifts in tissue stoichiometry during periods of bone ossification. Finally, I show that rates of parasitism can increase in tadpoles when resource quality is low, mediated by bottom-up and top-down effects on exposure and susceptibility. Taken together, the results of this dissertation highlight the relevance of ES theory to spatial subsidy theory and to anuran biology in general.

Download or read book Density dependence and Dispersal Mechanisms in a Pond Breeding Amphibian written by Katharine Yagi and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: "In this thesis, I attempt to quantify the effect of density on toad dispersal in a series of steps that coincide with the amphibian's notable life stages, which are outlined by the five chapters of my thesis. Chapter 2 examines the direct effect of density on tadpole survival, growth and size at metamorphosis using a unique technique of density manipulation. I discuss potential downfalls of the traditional method of tadpole density-manipulations whereby raising them in crowded conditions might confound results as tadpoles are known to respond differently to chemical cues left in the water by conspecifics. My method of manipulating density by volume resulted in a strong negative relationship with tadpole survival, growth and size at metamorphosis, as predicted, while the traditional method showed similar but less striking trends. Chapter 3 addresses whether carry-over effects are present in the new metamorphs (i.e. toadlets) that emerge from a range of density treatments, by monitoring changes in behaviour between the tadpole and toadlet life stages. I discovered a significant change in activity levels in those grown under high densities as tadpoles, where their small post-metamorph body size coincided with a notable decrease in activity. My results support the concept of density-dependent carry-over effects being present in these amphibians, and that their post-metamorphic mobility may be impacted by their early-life growth conditions. Chapter 4 examines the behavioural plasticity of tadpoles under these effects using a controlled factorial experiment. My results showed that larger sized tadpoles had high activity levels under all temperature regimes only when they came from high density treatments. This suggests that the size of the animal is important, as it becomes relevant under more stressful conditions and that the behavioural plasticity of tadpoles is governed by an interaction among individual body size, water temperature and density. Chapter 5 follows the size-dependent movement capabilities of individual toadlets from density-treatments in a controlled performance test, and their subsequent free-ranging movement behaviour in the field. I discovered that the body size of toadlets predicted dispersal in a quadratic relationship, where intermediate sized toads, regardless of their tadpole density, move greater distances and had the highest probability for dispersal. Interestingly, these intermediate-sized toads became the largest in their cohort as adults, resulting in a positive logistic relationship between adult size and dispersal probability. Chapter 6 uses the information gathered for size-dependent dispersal probabilities, and calculates the populations density-dependent dispersal rates using historical data, to inform model simulations to predict the extinction risk of this Fowler's toad population. I discovered that this population has a quadratic relationship between dispersal probability and population density, where very low and very high densities coincided with the highest dispersal rates. Additionally, I was able to predict a low extinction risk for the population if carrying capacity was kept at a minimum of 16 toads, however if continuous habitat management, which translates into continuous habitat disturbances, were to be employed on a short 7-year cycle, extinction risk could be as high as 78%.Human activities, including fragmentation and restoration, continue to impact the animals living in the surrounding environment. As dispersal is a key process that can save many populations from local extinctions it is important to understand how movement is restricted on a species-specific level. My thesis provides a detailed examination of density-dependence and movement capabilities across multiple life stages in a pond breeding amphibian and advances our understanding of how density itself can impact dispersal under different mechanisms." --

Download or read book Ecological and Physiological Effects of Environmental Stressors Across Life stages in Amphibians written by Kacey Lynn Dananay and published by . This book was released on 2018 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the effects of environmental stressors includes identifying how stressors affect individual physiology and ecological communities. Considering carry-over effects, effects from one life-stage persisting into later life-stages, can further reduce the chances of under- or over-estimating the effects of environmental stressors. I investigated the effects of two environmental stressors on amphibian physiology across life-stages including direct and indirect effects. I first investigated road salt. Road salt, a de-icing agent used on highways, can spread up to 1km in wetlands during snowmelt. It may be particularly important for early breeding amphibians like wood frogs (Rana sylvatica). Road salt significantly increased larval frog growth and algal biomass which was likely due to an indirect effect of salt decreasing zooplankton abundance, an algal competitor of frogs. A second experiment found despite increased larval growth, exposure to road salt caused juvenile frogs to have higher mortality in low-density terrestrial environments. The second stressor I investigated was Artificial Light At Night (ALAN). ALAN reduced metamorphic duration of American toads (Anaxyrus americanus) and periphyton biomass but did not affect the colonization of toad predators. These results suggested the effects of ALAN are mediated through direct rather than indirect effects. Extending this experiment found juvenile growth was reduced by juvenile-stage exposure to ALAN. Increased juvenile activity, specifically the lack of suppressed nocturnal activity, likely reduced juvenile growth of individuals housed with ALAN. Furthermore, carry-over effects were also present; larval-stage ALAN marginally increased juvenile activity. In the final experiment, I added an additional stressor: predation. Predators reduced toad survival and mass, regardless of ALAN. This suggests ALAN did not increase predator consumption of toads. Neither predators nor ALAN affected corticosterone production in the tadpole or metamorph life-stages but larval-stage ALAN increased corticosterone production in juvenile toads. These experiments demonstrated environmental stressors can have direct and indirect effects. Furthermore, larval stage stressors can carry-over and affect later life-stages even if that stressor is no longer present. Future environmental stressor studies should investigate direct and indirect effects together and extend experiments beyond a single life-stage. As demonstrated here, failure to do so may under-estimated the effects of these environmental stressors.

Download or read book Reproductive and Spatial Ecology of a Pond breeding Amphibian Community written by Michelle Lynn Guidugli and published by . This book was released on 2009 with total page 204 pages. Available in PDF, EPUB and Kindle. Book excerpt: For many amphibian species the temporal and spatial patterns of migration are poorly understood. To better understand these processes, an ephemeral pond-breeding amphibian community was studied at Central Kentucky Wildlife Management Area, Madison County, Kentucky. The study pond was completely encircled using a drift fence-pitfall trap array and checked continually from January to October 2009. Meteorological variables including rainfall and air temperature and the habitat variable distance to forest edge were measured to determine their influence on amphibian migrations. Several amphibians including Rana catesbeiana (American Bullfrog), Ambystoma jeffersonianum (Jefferson's salamander), and A. maculatum (Spotted Salamander) inhabited this pond; however, A. jeffersonianum and A.maculatum were dominant in their abundance and length of time they occupied the pond for breeding. Breeding migrations for A.maculatum and A. jeffersonianum were correlated with variables such as daily cumulative precipitation and mean air temperature; however cumulative precipitation was not correlated with existing migrations for these species. Movements to the pond were non-randomly oriented for A. jeffersonianum and A.maculatum and non-randomly oriented away from the pond for A.maculatum. Both migrations were positively correlated with distance to forest edge for A.maculatum and A. jeffersonianum; however, the strongest association was found for A.maculatum exiting migrations. These results exemplify how closely movements of amphibian species are linked to their environment. Amphibian populations are declining due to habitat destruction and fragmentation; therefore, this understanding of when and where different aspects of their habitat are used will aid in future conservation and land management.

Download or read book The Effects of Nearshore Forest Thinning on Upland Habitat Use by Pond breeding Amphibians in a Montane Coniferous Forest written by Andrew Holt McIntyre and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Forest thinning removes woody fuels from coniferous forests in a way that mimics historic wildfire regimes by removing mid-story pines and increasing horizontal and vertical spacing. Thinning results in few long-term effects to habitat features required by sensitive amphibians including canopy cover, soil moisture and available cover objects. Though some research suggests minimal effects of thinning to amphibians, few studies have assessed effects to aquatic-breeding amphibians in forests of the Pacific Northwest. We conducted an experimental study evaluating effects of understory thinning on aquatic-adjacent habitat on forest conditions and amphibian movement patterns. Thinning treatments were implemented in 12 plots, alternating with matching controls, in the pine-fir forests surrounding Big Lake, a 10.7 ha ephemeral lake in northern California. We assessed effects of thinning on habitat variables relevant to amphibians and used pitfall traps to assess movement by long-toed salamanders (Ambystoma macrodactyllum), western toads (Anaxyrus boreas), and Pacific chorus frogs (Pseudacris regilla). We investigated associations between amphibian captures and upland habitat conditions and assessed amphibian use of debris piles created during treatments. We predicted metamorphic amphibians would seek cover and shade in control plots, while adults would find migration easier in treated plots. Tree density decreased while woody debris cover showed a moderate increase after treatments. A modest increase in captures of chorus frogs occurred in treatment plots, but no treatment effect was detected for toads or salamanders. Receding surface waters forced salamander larvae to develop and emerge at the eastern end of Big Lake. With a shorter development time, western toads and chorus frogs were able to emerge from the pond before surface waters receded. Salamanders and chorus frogs were captured in areas of high leaf litter and low tree density, suggesting a preference of these species for foraging in lower intensity forests. Foraging diurnally, toads preferred areas offering high levels of canopy cover. Our results suggest moderate understory thinning in forests adjacent to aquatic habitat may show no harmful short-term impacts to pond-breeding amphibians. No amphibians were found under debris piles; future research should survey such piles during different times of year and directly before burning.

Download or read book Suburbanization and Amphibians written by Alexander Jacob Felson and published by . This book was released on 2010 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: Regulations guiding land development around seasonal isolated wetlands disregard habitat requirements for specialized faunal inhabitants. This oversight needs to be addressed at multiple scales in order to sustain future seasonal pond inhabitants. In particular, pool-breeding amphibians are suffering worldwide decline and are susceptible to water quality, temperature, hydrology and watershed impacts. The complex aquatic-terrestrial lifecycle of amphibians makes them sensitive to terrestrial habitat alterations and fragmentation. The temporal variation in hydroperiod within individual ponds and variation in hydrology across ponds within a landscape create a stochastic system. In these systems amphibian populations likely function as metapopulations, and rely on juvenile dispersal and rescue effects to counter local extinction. Given the limited regulations at the local, state and federal level, maintaining amphibian breeding populations will require efforts at the pond, migration corridor, upland habitat, watersheds and regional connectivity levels. Addressing these gaps requires further basic research to expose hidden aspects of amphibian lifecycle patterns, in part due to their fossorial nature as well as the challenges of interpreting metapopulation connectivity. Addressing the gaps also requires translating the ecological requirements into preservation tactics within the pressures of land development, which poses substantial challenges. I utilized designed experiments, which serve as a hybrid research and planning approach, to navigate these complex circumstances. Here, I present a series of large-scale field experiments situated within a 500-hectare privately owned suburban development project located in Tuxedo, New York. The field experiments were implemented as part of the masterplanning process with the aim of exposing and addressing several of these regulatory gaps from both a basic science and applied solutions perspective. A series of drift fence and pit-fall trap experiments provides data at the scale of individual breeding populations and their migration patterns to and from ponds. Larval density studies utilizing replicate enclosures evaluate the impact of within pond density versus variability of habitat quality across ponds. This analysis provides a bioassay of species performance teasing apart the presumed dominant effect of density versus variation across ponds. The results of this study indicate that physical and biotic pond scale factors have a far greater effect on survival and fecundity than density. These results differ from the environmental consultant's evaluation of the same ponds and call into question the current rapid assessment of pond habitat.

Download or read book Effects of an Insecticide on Amphibian Communities written by Michelle Dawn Boone and published by . This book was released on 2000 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt: Rachel Carson's Silent Spring raised public awareness that there were ecological consequences to widespread pesticide use. Yet many of the pesticides used today are benign in comparison with the early synthetic pesticides. However, the effects of these chemicals are typically not tested on living communities. The effects of pesticides on natural community dynamics may be especially noteworthy for amphibians in light of recent concerns about amphibian declines. The main objective of my research was to determine how realistic, sublethal levels of the short-lived insecticide carbaryl may influence amphibian species that are experiencing stresses known to be important in the natural environment (e.g., competition, predation, pond drying). This research was conducted in artificial ponds (i.e., cattle tanks) and in small farm ponds to test the effects of carbaryl on amphibians. Carbaryl may serve as a model chemical for other contaminants with the same mode of action (acetyl cholinesterase inhibition: carbamates and organophosphates). I measured endpoints at metamorphosis (survival, mass, and age) to determine if exposure to carbaryl had lasting effects on tadpole development and survival. Studies in cattle tank indicated that the effects of carbaryl varied depending on the predator environment and initial larval density for some species. Interactions of carbaryl with predator and density may result in an indirect effect of carbaryl causing increased food resources through the elimination of zooplankton populations that may compete for similar resources as tadpoles; this resulted in greater survival and greater mass at metamorphosis for some species relative to individuals in control ponds. In an experiment where multiple exposures to carbaryl were applied, exposure led to higher rates of metamorphosis with the majority of metamorphs coming from high-density ponds dosed three times. This interaction suggests that exposure to carbaryl later in the larval period may have stimulated metamorphosis in high-density conditions. Because natural environments include a large range of factors typically excluded in experimental studies, we cannot assume contaminant levels that are safe in the laboratory or in mesocosms are protective of populations in the natural environment. A study in farm ponds, however, suggested that even a short-lived contaminant like carbaryl can affect amphibian species in field conditions. Carbaryl exposure positively influenced survival with approximately twice as many individuals leaving carbaryl treated ponds than control ponds. Our results indicate that differences in biotic conditions influenced the potency of carbaryl and that even low concentrations induce changes that may alter community dynamics in ways not predicted from single-factor, laboratory-based studies. Additionally, our results suggest that even in realistic conditions where predatory and competitive conditions may be strong, contaminants can still alter population dynamics.

Download or read book A Framework for Amphibian Habitat Conservation Across Spatial Scales Using Community Occupancy Models written by Vishnupriya Sankararaman and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Agricultural intensification and loss of native forest habitats have presented the most ubiquitous threats to faunal communities across the world. These land use modifications have caused loss of species richness, genetic diversity, biotic homogenization, and increased dominance structure from local, regional to global scales. Amphibians are amongst the most endangered vertebrate groups with high susceptibility to habitat modification. Their biphasic life history, poor mobility and low tolerance to chemical pollutants make it difficult for most species to adapt to intensively managed land uses. To combat pressures from habitat loss, commodity agroforests are recommended as suitable secondary habitats for many threatened faunal communities. However, there is little applied research on how individual land management strategies at various spatial scales can help design more wildlife-friendly landscapes. The research presented in this dissertation, uses community ecology theory to examine: (1) how land use gradients shape amphibian species and communities across local and regional spatial extents, (2) how individually evolved life history strategies influence adaptations to different habitats and land uses, (3) how conservation objectives and decisions can shape land use design in terrestrial and aquatic environments to maximize conservation potential of agroforests. In the first chapter, I studied patterns in alpha and beta diversity across areca, coffee and rubber agroforests across Karnataka's Western Ghats. A total of 106 agroforests across a 30,000 km2 landscape were surveyed for amphibians, and a multispecies occupancy model approach was used to analyze and estimate community-level and species-specific parameters. The broad-scale influence of elevation and latitude and fine-scale influences of microhabitat availability were examined on species occurrences. The availability and heterogeneity of microhabitats were also used to predict species occurrences. Overall, a heterogenous land use such as shade-grown coffee hosted much higher species richness than the more intensively managed areca and rubber agroforests. Our results indicate that site-specific diversity can be enhanced with careful management. The preservation of aquatic and terrestrial microhabitats can increase amphibian species richness by up to 75% in each agroforest. The second chapter focuses on examining the influence of life history traits on species occupancy and community structure across terrestrial and stream habitats in different land uses. I surveyed 223 transects for amphibians across tea, coffee and forest fragments in the Anamalai Hills of the Western Ghats. A joint-species distribution model was used to estimate species occupancies and cooccurrence patterns. Species richness was highest in forest fragments followed by coffee and lowest in tea agroforests. Life-history traits clearly defined habitat use, with fast-water breeding amphibians preferring forested streams first, followed by streams in coffee and the lowest occupancy was observed in tea streams. Slow-water breeding amphibians showed a reverse trend with higher preference for tea over coffee and forest stream sites. The study also revealed important patterns in species distributions across elevational ranges and the influence of annual climate patterns on amphibian populations. The results from this chapter highlight the importance of focusing conservation attention on amphibians with torrential habitat associations as they are the most vulnerable to land use intensification. In chapter three, I advance the understanding of amphibian community structure at broader spatial scales. Using results from chapter two, I estimate pairwise species dissimilarity across sites and examine the role of geographic distances, environmental distances, watershed aspects and land use on beta diversity. The mean beta diversity was lowest for within forest sites and highest for comparisons between coffee and forests. Also, terrestrial habitats displayed greater heterogeneity in species compositions than stream habitats. Rather than geographic distances, the difference in elevation was one of the strongest predictors of beta diversity patterns at the regional scale. The combined influences of the different predictors indicate that prioritizing conservation management across different land uses, elevation gradients and watersheds will be most effective in maintaining the regional diversity and heterogeneity of amphibian communities in the Anamalai Hills. Finally, in the fourth chapter, I use results from all three previous research findings with additional information about ecosystem services to identify where riparian forest restoration can have optimal conservation outcomes. Prioritization was based on predicted increase in alpha diversity, and topographic wetness index (TWI), along with elevational attributes. Five alternate scenarios were set up based on these criteria. The results were tested on ten coffee sites, ten tea sites and a combination of five coffee and tea sites. Species richness was revealed to be a poor criterion for prioritization as it resulted in the most spatially aggregated portfolio of sites and with lowest predicted gamma diversity. Incorporating TWI in land use prioritization yielded much higher gamma diversity and ecosystem function benefits. I also discuss the socioeconomic implications of restoring riparian buffers for private land owners in the region and propose mechanisms by which the restoration costs can be managed. Conservation management has to be scale dependent and rely on local and regional studies to provide empirical evidence for how decisions influence outcomes. I used a combination of theories in community ecology with applied conservation science to provide greater understanding of fine-scale and broad-scale factors influencing agrobiodiversity. This research also expands the use of hierarchical community occupancy models to examine different aspects of spatial variations in multispecies assemblages, particularly in poorly-studied and hyper-diverse tropical regions.

Download or read book Amphibian Conservation in 3D written by Carlos Guilherme Becker and published by . This book was released on 2014 with total page 342 pages. Available in PDF, EPUB and Kindle. Book excerpt: Habitat loss and chytridiomycosis (a disease caused by the chytrid fungus Batrachochytrium dendrobatidis - Bd) are major drivers of amphibian declines worldwide. Understanding how their independent and interactive effects lead to amphibian declines is critical for biodiversity conservation. For my doctoral research, I (1) developed a novel integrative approach for systematic conservation planning for tropical amphibians facing negative impacts of accelerated habitat loss, (2) quantified the influence of deforestation on the risk of chytridiomycosis, and (3) through a combination of field surveys and laboratory-controlled experiments, identified abiotic and biotic mechanisms that link deforestation to shifts in disease dynamics. Chapter 1 evaluates different scenarios of systematic conservation planning for Brazilian amphibians, integrating data on species life-history and ecologically relevant spatial metrics of deforestation and landscape configuration. Chapter 2 describes a paradoxical negative relationship between habitat loss and the risk of chytridiomycosis in amphibian populations from Costa Rica, Brazil, and Australia, laying the foundation for chapters 3, 4, and 5, which focus on mechanisms by which deforestation alters disease dynamics. Chapter 3 describes cascading effects of deforestation linking reduction in canopy cover to microclimatic shifts, which affect both Bd prevalence and infection intensity. Chapter 4 experimentally tests and finds support for the 'dilution effect' hypothesis, which predicts an inverse relationship between host diversity and disease. In Chapter 5, I show that temperate amphibian communities with higher population densities at pristine closed-canopy sites carry higher Bd loads due to density-dependent transmission. In contrast, tropical amphibian communities commonly found in pristine forests carry lower Bd infection loads than those in disturbed habitats, presumably due to their host species composition. These results combined highlight that deforestation shifts abiotic and biotic factors, which in turn can either increase or decrease disease risk and impact conservation efforts in amphibians. My dissertation work has important analytical and theoretical implications for the field of disease ecology and the management of amphibians facing the dual negative impacts of habitat loss and chytridiomycosis.

Download or read book Ecological Effects of Climate Change on Amphibians written by Hilary Byrne Rollins and published by . This book was released on 2019 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: With climate change, global average temperatures are increasing and becoming more variable. As a result, reproductive phenology is shifting earlier, body size is decreasing in ectotherms, and snow cover is decreasing. I examined how these effects of climate change affected amphibians and their ecological interactions across life stages. In Chapter 1, I investigated whether an early shift in phenology could alter subsequent life history events, if the organisms were able to compensate, and if compensation was costly. Despite a seven day difference in hatch date, frogs from the delayed egg phenology treatment accelerated growth and development to metamorphose at the same time as the early egg phenology treatment. Frogs that accelerated development metamorphosed at the same size as frogs that did not accelerate development but had the same food availability, indicating that there was no size cost of compensation. In Chapter 2, to understand how climate change-induced shifts in phenotype could affect important interspecific interactions, I examined how a shift in wood frog larval phenology, and body size altered post-metamorphic competition with American toads. The interaction of wood frog metamorphic size and phenology affected toad body condition such that wood frogs that metamorphosed earlier and smaller, as expected under climate change, led to toads with higher body condition.Finally, in Chapter 3, I tested whether the effects of climate change on wood frogs were altered by early ecological interactions. I examined how predation during larval development affected how wood frogs would tolerate a reduced snow cover winter. Exposure to predators during larval development increased mass at metamorphosis, time to metamorphosis, and larval growth rate. Snow removal increased frog mortality. The interaction of larval exposure to predators and reduced snow cover caused a steeper relationship between mass and body length in animals that experienced both. I found that the ecological effects of climate change shifted larval development and juvenile growth, reduced the ability to compete against interspecific competitors, increased winter mortality, and altered spring body condition. These effects may scale up to affect population dynamics and fitness, and demonstrate the importance of considering ecological effects of climate change.

Download or read book The Influence of Forest Management on Headwater Stream Amphibians at Multiple Spatial Scales written by Margo A. Stoddard and published by . This book was released on 2001 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: To effectively manage for biodiversity at broad, ecosystem scales, the influences of habitat structure at multiple spatial scales on vertebrate species must be understood. There are few studies on the broad-scale habitat requirements of stream amphibians despite their importance in streams in forest ecosystems in the Pacific Northwest (PNW) as predators and prey, and potentially as indicators of ecosystem health. In particular, studies on the influence of forest structure at landscape scales on stream amphibians are lacking. I examined stream amphibian-habitat relationships for Pacific giant salamanders (Dicamptodon tenebrosus), larval and metamorphosed tailed frogs (Ascaphus truei), and torrent salamanders (Rhyacotriton spp.) at four spatial scales (2-m sample unit, intermediate, sub-drainage, and drainage). Over two field seasons (1998 and 1999), I captured 1,568 amphibians in 702 sample units in 16 randomly chosen drainages in the Oregon Coast Range. I used an information theoretic approach of analysis to rank sets of a priori candidate models that described habitat relationships at each spatial scale. At the 2-m sample unit scale, all species of interest were negatively associated with fine sediments and were positively associated with either stream width or elevation. At the intermediate spatial scale, Pacific giant salamanders, metamorphosed tailed frogs, and torrent salamanders were positively associated with the presence of a 150-ft. forested band on each side of the stream, and larval tailed frogs were positively associated with the presence of forest>105 years old on at least one side of the stream. At the sub-drainage and drainage scales, all species were positively associated with the proportion of stream length in a sub-drainage or drainage with a 150-ft. forested band on each side of the stream. Heat load index (aspect) was also important for Pacific giant salamanders and larval tailed frogs at the intermediate and sub-drainage scales. Results at all spatial scales suggest that Pacific giant salamanders and larval tailed frogs occur lower in the drainage network, and metamorphosed tailed frogs and torrent salamanders occur higher in the drainage network. This study demonstrates the importance of examining headwater stream amphibian habitat at multiple spatial scales, provides insights on linkages between amphibian responses across spatial scales, and shows that broad-scale variables (e.g., the presence of forested bands or the percentage of stream length with forested bands) can be used to assess management approaches for stream amphibian communities. Geophysical characteristics such as stream aspect may also help identify areas that should not be harvested if protection of amphibian habitat is an objective.