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Author: Julie Charbonnier
Publisher:
ISBN:
Category : Environmental engineering
Languages : en
Pages :
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Book Description
Organisms with complex life cycles may experience diverse stressors during their development. Stressors experienced in early life stages may influence the quantity and quality of individuals in later life stages. However, it is unclear if these effects persist later in life and how they may influence population dynamics. This dissertation uses two amphibian species, the Western spadefoot toad (Pelobates cultripes) and the spotted salamander (Ambystoma maculatum) to explore how biotic and abiotic factors experienced in aquatic and terrestrial environments influence phenotype and survival. We use a combination of field mesoscosm studies, laboratory studies and modeling to explore how early life history stressors persist in diverse environmental contexts. In Chapter 1, pond drying and larval density negatively influence multiple aspects of phenotype in the Western spadefoot toad. In Chapter 2, reduced body size due to larval stressors persisted in the first year of life in spotted salamanders in both high and low terrestrial resource environments. Additionally, there was no relationship between size at metamorphosis and post-metamorphic terrestrial survival. In Chapter 3, low terrestrial moisture levels reduced post-metamorphic growth rates by reducing food intake in juvenile spotted salamanders from both high and low larval density treatments. In Chapter 4, we scale up the effects of reduced body size in the Western spadefoot toad to explore how reduced body size due to pond drying may influence population densities using a stage specific matrix model. Reduced body size, by delaying maturity, may reduce adult densities in the Western spadefoot toad. This dissertation suggests that life stages are highly interconnected, as stressors experienced early in life stage may persist through their effects on phenotype in the absence of compensatory mechanisms. Variation in later life stages may also influence phenotype, but may not completely erase effects of early environments. Stressors experienced early in life may also translate to population level consequences, especially when organisms experience multiple stressors across life stages.
Author: Julie Charbonnier
Publisher:
ISBN:
Category : Environmental engineering
Languages : en
Pages :
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Book Description
Organisms with complex life cycles may experience diverse stressors during their development. Stressors experienced in early life stages may influence the quantity and quality of individuals in later life stages. However, it is unclear if these effects persist later in life and how they may influence population dynamics. This dissertation uses two amphibian species, the Western spadefoot toad (Pelobates cultripes) and the spotted salamander (Ambystoma maculatum) to explore how biotic and abiotic factors experienced in aquatic and terrestrial environments influence phenotype and survival. We use a combination of field mesoscosm studies, laboratory studies and modeling to explore how early life history stressors persist in diverse environmental contexts. In Chapter 1, pond drying and larval density negatively influence multiple aspects of phenotype in the Western spadefoot toad. In Chapter 2, reduced body size due to larval stressors persisted in the first year of life in spotted salamanders in both high and low terrestrial resource environments. Additionally, there was no relationship between size at metamorphosis and post-metamorphic terrestrial survival. In Chapter 3, low terrestrial moisture levels reduced post-metamorphic growth rates by reducing food intake in juvenile spotted salamanders from both high and low larval density treatments. In Chapter 4, we scale up the effects of reduced body size in the Western spadefoot toad to explore how reduced body size due to pond drying may influence population densities using a stage specific matrix model. Reduced body size, by delaying maturity, may reduce adult densities in the Western spadefoot toad. This dissertation suggests that life stages are highly interconnected, as stressors experienced early in life stage may persist through their effects on phenotype in the absence of compensatory mechanisms. Variation in later life stages may also influence phenotype, but may not completely erase effects of early environments. Stressors experienced early in life may also translate to population level consequences, especially when organisms experience multiple stressors across life stages.
Author: Patrick Thomas Walsh
Publisher:
ISBN:
Category :
Languages : en
Pages : 206
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Book Description
The ability of animals to vary growth, development rate and behaviour in response to environmental conditions has been well documented, particularly during the larval phase in animals with complex life cycles. The evolution and maintenance of plasticity in response to environmental conditions is likely to be adaptive in animals that face unpredictable environments. However, there are two aspects of life histories in animals with complex life cycles, which would be expected to favour plasticity, that have received limited attention: traits during metamorphic climax and variation in the life history phase at which temperate species spend the winter. Therefore the aims of this thesis were to consider the environmental factors that are likely to result in plasticity in the timing and duration of metamorphic climax and contribute to variation in the over-wintering life stage, using amphibians as study animals. To assess the ability of animals to respond to environmental conditions during metamorphic climax conditions were manipulated during metamorphosis independent of larval treatment. Accordingly all larvae entered metamorphic climax having experienced the same conditions. The African clawed toad, Xenopus laevis, was used. I examined the influence of environmental temperature, predation risk and starting body size on several traits during the transitional stage (e.g. mass, snout-vent length (SVL), head width, tail morphology, duration and locomotor performance). Morphological measures and the duration of the life stage were shown to vary with temperature and predation risk. As predicted, higher temperatures and the risk of predation resulted in faster development through metamorphosis and smaller sizes on completion. The acceleration of metamorphosis was demonstrated to have potential costs, not in the form of reduced locomotor performance as predicted, but in a reduction in juvenile size as a result of faster metamorphic development. This suggests that, during this potentially vulnerable stage, it would be advantageous to take more time to complete in the absence of predators. Greater body size at the onset of metamorphosis requires a longer time to complete metamorphic climax suggesting that having a greater quantity of tissue to reconfigure during metamorphosis takes more time. Therefore, the conditions experienced during metamorphosis may have important implications for juvenile fitness and should be considered in studies of life history plasticity. In many temperate species with complex life cycles, the life history stage at which a species can survive the winter is generally fixed, imposing time limits on the timing of development. Most of these species must therefore often modify developmental rate to reach the appropriate stage or size at the onset of winter, usually at a cost to other traits. However, variation in the stage or developmental group that some amphibian, fish and insect species spend the winter has been observed, such as in the common frog Rana temporaria in the UK, which can spend the first winter as either a tadpole or as a juvenile frog. To investigate the factors that contribute to this variation in life history, I examined the influence of environmental temperature, food availability and water depth on the rate of larval development and growth. Data on development, growth and environmental temperature of a field population of R. temporaria, which have been observed to over-winter as larvae, were collected to determine how and when the two divergent early life history patterns of development were established. Development rate was slowed by reduced temperatures and food availability and greater water depth during rearing. Temperature and food availability also had a significant impact on the proportion of larvae that over-wintered, but in the field other factors are likely to contribute to the within-population variation in wintering strategy. While a greater water depth did prolong larval development, as predicted, this does not appear to be due to the cost of surfacing to respire acting as a constraint on development, since a similar slowing in development was observed in the lung-less Bufo bufo tadpoles. The results of these studies did not allow a definitive assessment of whether over-wintering as larvae represents an adaptive strategy or occurs as the result of developmental constraints. There is some evidence that over-wintering as larvae might be adaptive, since on completion of metamorphosis individuals that wintered as larvae were larger than those that completed metamorphosis late in the summer. Further work is necessary to identify other factors contributing to the over-wintering of larvae in Rana temporaria and to determine the adaptive significance, if any, of the alternative life history patterns.
Author: Hilary Byrne Rollins
Publisher:
ISBN:
Category : Amphibians
Languages : en
Pages : 113
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Book Description
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.
Author: Thomas Locker Doty
Publisher:
ISBN:
Category : Amphibians
Languages : en
Pages : 264
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Book Description
Author: Christine Marie Bridges
Publisher:
ISBN:
Category : Amphibians
Languages : en
Pages : 296
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Book Description
There are an increasing number of studies are now focusing on the effects that xenobiotics have on amphibians, an interest likely stimulated by widespread reports of amphibian declines. Chemical contamination may be partially to blame for these declines, by disrupting amphibian growth, reproduction, and behavior. However, evidence that xenobiotics, are directly to blame for these population declines is sparse, because environmental xenobiotic concentrations typically are not great enough to generate direct or immediate mortality. I, therefore, examined the effects of exposure of tadpoles to sublethal levels of contaminants because they may lead to the subtle changes that are ultimately contributing to population declines. Tadpoles acutely exposed to sublethal carbaryl concentrations decreased spontaneous swimming activity and swimming performance (i.e., sprint distance). When tadpoles were chronically exposed to sublethal carbaryl levels, there was an increase in mortality as well as the incidence of deformities. Furthermore, tadpoles exposed to carbaryl as eggs were smaller at metamorphosis than their corresponding controls. Consequently, it is possible that chemicals (e.g., carbaryl) in the environment are responsible for causing some amphibian declines by altering tadpole behavior, growth, and development, which ultimately may affect population dynamics. Using two assays (one lethal, one sublethal), I observed a significant degree of variation in tolerance to carbaryl at three of the hierarchical levels I examined: among nine ranid species, among ten populations of a single species, Rana sphenocephala, and within several populations of R, sphenocephala, and among full- and half-sibling families. Although it may be predicted that species in decline are more sensitive to environmental stressors (e.g., chemicals), two of the three species that are currently in decline were the most tolerant to carbaryl. Significant variation among R. sphenocephala populations and among families within these populations suggests that caution should be taken when making inferences to other populations or families, respectively. When examining differences among paternal half-sibling families, I found no significant variation in tolerance to carbaryl, indicating that little variation is available for adaptation to environmental stressors within this population. Determining the degree of variation in responses within and among amphibian species is important to amphibian conservation, because only when variation is present will amphibians have the ability to adapt and persist in changing environments.
Author: Aram J. K. Calhoun
Publisher: CRC Press
ISBN: 1420005391
Category : Nature
Languages : en
Pages : 406
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Book Description
Synthesizes Decades of Research on Vernal Pools Science Pulling together information from a broad array of sources, Science and Conservation of Vernal Pools in Northeastern North America is a guide to the issues and solutions surrounding seasonal pools. Drawing on 15 years of experience, the editors have mined published literature,
Author: Susan C. Walls
Publisher: Frontiers Media SA
ISBN: 2889636186
Category :
Languages : en
Pages : 141
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Book Description
Author: John B. Jensen
Publisher: University of Georgia Press
ISBN: 9780820331119
Category : Nature
Languages : en
Pages : 600
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Book Description
Featuring more than 475 full-color photographs and 182 maps, this comprehensive guide to the state's diverse herpetofauna makes accessible a wealth of information about 170 species of frogs, salamanders, crocodilians, lizards, snakes, and turtles, including species attributes, behavior, life cycles, habitat, and more.
Author: Matthew J. Gray
Publisher: Springer
ISBN: 9783319137568
Category : Science
Languages : en
Pages : 246
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Book Description
This is the first book on ranaviruses. Ranaviruses are double-stranded DNA viruses that cause hemorrhagic disease in amphibians, reptiles, and fish. They have caused mass die-offs of ectothermic vertebrates in wild and captive populations around the globe. There is evidence that this pathogen is emerging and responsible for population declines in certain locations. Considering that amphibians and freshwater turtles are suitable hosts and the most imperiled vertebrate taxa in the world, ranaviruses can have significant impacts on biodiversity and ecosystem function. Additionally, many fish that are raised in aquaculture facilities and traded internationally are suitable hosts; thus, the potential economic impact of ranaviruses is significant. Ranaviruses also serve as a model for replication and gene function of large double-stranded DNA viruses. There is an urgent need to assemble the contemporary information on ranaviruses and provide guidance on how to assess their threats in populations. Through the Global Ranavirus Consortium, 24 experts from six countries were organize to write this volume, the first book on ranaviruses. The book begins with a discussion on the global extent of ranaviruses, case histories of infection and disease in ectothermic vertebrates, and current phylogeny. Basic principles of ranavirus ecology and evolution are covered next, with a focus on host-pathogen interactions and how the virus emerges in its environment. There are two chapters that will discuss the molecular biology of ranaviruses, host response to infection, and the genes responsible for immune system evasion. One chapter establishes standards for testing for infection and diagnosing ranaviral disease. The book ends by providing guidance on how to design ranavirus surveillance studies and analyze data to determine risk, and discussing the role of the Global Ranavirus Consortium in organizing research and outreach activities.
Author: Roy W. McDiarmid
Publisher: University of Chicago Press
ISBN: 9780226557625
Category : Nature
Languages : en
Pages : 476
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Book Description
In our own juvenile stage, many of us received our wide-eyed introduction to the wonders of nature by watching the metamorphosis of swimming tadpoles into leaping frogs and toads. The recent alarming declines in amphibian populations worldwide and the suitability of amphibians for use in answering research questions in disciplines as diverse as molecular systematics, animal behavior, and evolutionary biology have focused enormous attention on tadpoles. Despite this popular and scientific interest, relatively little is known about these fascinating creatures. In this indispensable reference, leading experts on tadpole biology relate what we currently know about tadpoles and what we might learn from them in the future. Tadpoles provides detailed summaries of tadpole morphology, development, behavior, ecology, and environmental physiology; explores the evolutionary consequences of the tadpole stage; synthesizes available information on their biodiversity; and presents a standardized terminology and an exhaustive literature review of tadpole biology.
