The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Raymond B Huey - One of the best experts on this subject based on the ideXlab platform.
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three questions about the eco physiology of overwintering underground
Ecology Letters, 2021Co-Authors: Raymond B Huey, Ofir Levy, Michael R KearneyAbstract:In cold environments ectotherms can be dormant underground for long periods. In 1941 Cowles proposed an ecological trade-off involving the depth at which ectotherms overwintered: on warm days, only shallow reptiles could detect warming soils and become active; but on cold days, they risked freezing. Cowles discovered that most reptiles at a desert site overwintered at shallow depths. To extend his study, we compiled hourly soil temperatures (5 depths, 90 sites, continental USA) and physiological data, and simulated consequences of overwintering at fixed depths. In warm localities shallow ectotherms have lowest energy costs and largest reserves in spring, but in cold localities, they risk freezing. Ectotherms shifting hourly to the coldest depth potentially reduce energy expenses, but paradoxically sometimes have higher expenses than those at fixed depths. Biophysical simulations for a desert site predict that shallow ectotherms have increased opportunities for mid-winter activity but need to move deep to digest captured food. Our simulations generate testable predictions to eco-physiological questions but rely on physiological responses to acute cold rather than to natural cooling profiles. Furthermore, natural-history data to test most predictions do not exist. Thus, our simulation approach uncovers knowledge gaps and suggests research agendas for studying ectotherms overwintering underground.
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thermal safety margins and the necessity of thermoregulatory behavior across latitude and elevation
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Jennifer M Sunday, Amanda E Bates, Michael R Kearney, Robert K Colwell, Nicholas K Dulvy, John T Longino, Raymond B HueyAbstract:Physiological thermal-tolerance limits of terrestrial ectotherms often exceed local air temperatures, implying a high degree of thermal safety (an excess of warm or cold thermal tolerance). However, air temperatures can be very different from the equilibrium body temperature of an individual ectotherm. Here, we compile thermal-tolerance limits of ectotherms across a wide range of latitudes and elevations and compare these thermal limits both to air and to operative body temperatures (theoretically equilibrated body temperatures) of small ectothermic animals during the warmest and coldest times of the year. We show that extreme operative body temperatures in exposed habitats match or exceed the physiological thermal limits of most ectotherms. Therefore, contrary to previous findings using air temperatures, most ectotherms do not have a physiological thermal-safety margin. They must therefore rely on behavior to avoid overheating during the warmest times, especially in the lowland tropics. Likewise, species living at temperate latitudes and in alpine habitats must retreat to avoid lethal cold exposure. Behavioral plasticity of habitat use and the energetic consequences of thermal retreats are therefore critical aspects of species’ vulnerability to climate warming and extreme events.
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disentangling thermal preference and the thermal dependence of movement in ectotherms
Journal of Thermal Biology, 2012Co-Authors: Michael E Dillon, Rongsong Liu, George Wang, Raymond B HueyAbstract:Many ectotherms thermoregulate by choosing environmental temperatures that maximize diverse performance traits, including fitness. For this reason, physiological ecologists have measured preferred temperatures of diverse ectotherms for nearly a century. Thermal preference is usually measured by observing organism distributions on laboratory thermal gradients. This approach is appropriate for large ectotherms which have sufficient thermal inertia to decouple body temperatures from gradient temperatures. However, body temperatures and therefore speeds of movement of small ectotherms will closely track gradient temperature, making it difficult to distinguish between thermal preference and thermal dependence of movement. Here we develop and demonstrate the use of a patch model to derive the expected thermal gradient distribution given only the thermal dependence of movement. Comparison of this null distribution with the observed gradient distribution reveals thermal preference of small ectotherms.
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predicting organismal vulnerability to climate warming roles of behaviour physiology and adaptation
Philosophical Transactions of the Royal Society B, 2012Co-Authors: Raymond B Huey, Michael R Kearney, Andrew K Krockenberger, Joseph A M Holtum, Mellissa Jess, Stephen E WilliamsAbstract:A recently developed integrative framework proposes that the vulnerability of a species to environmental change depends on the species' exposure and sensitivity to environmental change, its resilience to perturbations and its potential to adapt to change. These vulnerability criteria require behavioural, physiological and genetic data. With this information in hand, biologists can predict organisms most at risk from environmental change. Biologists and managers can then target organisms and habitats most at risk. Unfortunately, the required data (e.g. optimal physiological temperatures) are rarely available. Here, we evaluate the reliability of potential proxies (e.g. critical temperatures) that are often available for some groups. Several proxies for ectotherms are promising, but analogous ones for endotherms are lacking. We also develop a simple graphical model of how behavioural thermoregulation, acclimation and adaptation may interact to influence vulnerability over time. After considering this model together with the proxies available for physiological sensitivity to climate change, we conclude that ectotherms sharing vulnerability traits seem concentrated in lowland tropical forests. Their vulnerability may be exacerbated by negative biotic interactions. Whether tropical forest (or other) species can adapt to warming environments is unclear, as genetic and selective data are scant. Nevertheless, the prospects for tropical forest ectotherms appear grim.
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why suboptimal is optimal jensen s inequality and ectotherm thermal preferences
The American Naturalist, 2008Co-Authors: Tara Laine Martin, Raymond B HueyAbstract:Body temperature (T(b)) profoundly affects the fitness of ectotherms. Many ectotherms use behavior to control T(b) within narrow levels. These temperatures are assumed to be optimal and therefore to match body temperatures (Trmax) that maximize fitness (r). We develop an optimality model and find that optimal body temperature (T(o)) should not be centered at Trmax but shifted to a lower temperature. This finding seems paradoxical but results from two considerations relating to Jensen's inequality, which deals with how variance and skew influence integrals of nonlinear functions. First, ectotherms are not perfect thermoregulators and so experience a range of T(b). Second, temperature-fitness curves are asymmetric, such that a T(b) higher than Trmax depresses fitness more than will a T(b) displaced an equivalent amount below Trmax. Our model makes several predictions. The magnitude of the optimal shift (Trmax - To) should increase with the degree of asymmetry of temperature-fitness curves and with T(b) variance. Deviations should be relatively large for thermal specialists but insensitive to whether fitness increases with Trmax ("hotter is better"). Asymmetric (left-skewed) T(b) distributions reduce the magnitude of the optimal shift but do not eliminate it. Comparative data (insects, lizards) support key predictions. Thus, "suboptimal" is optimal.
Julien Cote - One of the best experts on this subject based on the ideXlab platform.
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RESEARCH ARTICLE Live Fast, Die Young: Experimental Evidence of Population Extinction Risk due to Climate Change
2016Co-Authors: Elvire Bestion, Aimeric Teyssier, Murielle Richard, Jean Clobert, Julien CoteAbstract:Evidence has accumulated in recent decades on the drastic impact of climate change on bio-diversity. Warming temperatures have induced changes in species physiology, phenology, and have decreased body size. Such modifications can impact population dynamics and could lead to changes in life cycle and demography. More specifically, conceptual frame-works predict that global warming will severely threaten tropical ectotherms while temperate ectotherms should resist or even benefit from higher temperatures. However, experimental studies measuring the impacts of future warming trends on temperate ectotherms ' life cycle and population persistence are lacking. Here we investigate the impacts of future climates on a model vertebrate ectotherm species using a large-scale warming experiment. We manipulated climatic conditions in 18 seminatural populations over two years to obtain a present climate treatment and a warm climate treatment matching IPCC predictions for future climate. Warmer temperatures caused a faster body growth, an earlier reproductive onset, and an increased voltinism, leading to a highly accelerated life cycle but also to a decrease in adult survival. A matrix population model predicts that warm climate populations in ou
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Live Fast, Die Young: Experimental Evidence of Population Extinction Risk due to Climate Change
PLoS Biology, 2015Co-Authors: Elvire Bestion, Aimeric Teyssier, Murielle Richard, Jean Clobert, Julien CoteAbstract:Evidence has accumulated in recent decades on the drastic impact of climate change on biodiversity. Warming temperatures have induced changes in species physiology, phenology, and have decreased body size. Such modifications can impact population dynamics and could lead to changes in life cycle and demography. More specifically, conceptual frameworks predict that global warming will severely threaten tropical ectotherms while temperate ectotherms should resist or even benefit from higher temperatures. However, experimental studies measuring the impacts of future warming trends on temperate ectotherms' life cycle and population persistence are lacking. Here we investigate the impacts of future climates on a model vertebrate ectotherm species using a large-scale warming experiment. We manipulated climatic conditions in 18 seminatural populations over two years to obtain a present climate treatment and a warm climate treatment matching IPCC predictions for future climate. Warmer temperatures caused a faster body growth, an earlier reproductive onset, and an increased voltinism, leading to a highly accelerated life cycle but also to a decrease in adult survival. A matrix population model predicts that warm climate populations in our experiment should go extinct in around 20 y. Comparing our experimental climatic conditions to conditions encountered by populations across Europe, we suggest that warming climates should threaten a significant number of populations at the southern range of the distribution. Our findings stress the importance of experimental approaches on the entire life cycle to more accurately predict population and species persistence in future climates.
George N. Somero - One of the best experts on this subject based on the ideXlab platform.
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effects of thermal acclimation on transcriptional responses to acute heat stress in the eurythermal fish gillichthys mirabilis cooper
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 2011Co-Authors: Cheryl A Logan, George N. SomeroAbstract:The capacities of eurythermal ectotherms to withstand wide ranges of temperature are based, in part, on abilities to modulate gene expression as body temperature changes, notably genes encoding pro...
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transcriptional responses to thermal acclimation in the eurythermal fish gillichthys mirabilis cooper 1864
American Journal of Physiology-regulatory Integrative and Comparative Physiology, 2010Co-Authors: Cheryl A Logan, George N. SomeroAbstract:Thermal acclimation (acclimatization) capacity may be critical for determining how successfully an ectotherm can respond to temperature change, and adaptive shifts in gene expression may be pivotal...
Jennifer M Sunday - One of the best experts on this subject based on the ideXlab platform.
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thermal safety margins and the necessity of thermoregulatory behavior across latitude and elevation
Proceedings of the National Academy of Sciences of the United States of America, 2014Co-Authors: Jennifer M Sunday, Amanda E Bates, Michael R Kearney, Robert K Colwell, Nicholas K Dulvy, John T Longino, Raymond B HueyAbstract:Physiological thermal-tolerance limits of terrestrial ectotherms often exceed local air temperatures, implying a high degree of thermal safety (an excess of warm or cold thermal tolerance). However, air temperatures can be very different from the equilibrium body temperature of an individual ectotherm. Here, we compile thermal-tolerance limits of ectotherms across a wide range of latitudes and elevations and compare these thermal limits both to air and to operative body temperatures (theoretically equilibrated body temperatures) of small ectothermic animals during the warmest and coldest times of the year. We show that extreme operative body temperatures in exposed habitats match or exceed the physiological thermal limits of most ectotherms. Therefore, contrary to previous findings using air temperatures, most ectotherms do not have a physiological thermal-safety margin. They must therefore rely on behavior to avoid overheating during the warmest times, especially in the lowland tropics. Likewise, species living at temperate latitudes and in alpine habitats must retreat to avoid lethal cold exposure. Behavioral plasticity of habitat use and the energetic consequences of thermal retreats are therefore critical aspects of species’ vulnerability to climate warming and extreme events.
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global analysis of thermal tolerance and latitude in ectotherms
Proceedings of the Royal Society B: Biological Sciences, 2011Co-Authors: Jennifer M Sunday, Amanda E Bates, Nicholas K DulvyAbstract:A tenet of macroecology is that physiological processes of organisms are linked to large-scale geographical patterns in environmental conditions. Species at higher latitudes experience greater seasonal temperature variation and are consequently predicted to withstand greater temperature extremes. We tested for relationships between breadths of thermal tolerance in ectothermic animals and the latitude of specimen location using all available data, while accounting for habitat, hemisphere, methodological differences and taxonomic affinity. We found that thermal tolerance breadths generally increase with latitude, and do so at a greater rate in the Northern Hemisphere. In terrestrial ectotherms, upper thermal limits vary little while lower thermal limits decrease with latitude. By contrast, marine species display a coherent poleward decrease in both upper and lower thermal limits. Our findings provide comprehensive global support for hypotheses generated from studies at smaller taxonomic subsets and geographical scales. Our results further indicate differences between terrestrial and marine ectotherms in how thermal physiology varies with latitude that may relate to the degree of temperature variability experienced on land and in the ocean.
Jean Clobert - One of the best experts on this subject based on the ideXlab platform.
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RESEARCH ARTICLE Live Fast, Die Young: Experimental Evidence of Population Extinction Risk due to Climate Change
2016Co-Authors: Elvire Bestion, Aimeric Teyssier, Murielle Richard, Jean Clobert, Julien CoteAbstract:Evidence has accumulated in recent decades on the drastic impact of climate change on bio-diversity. Warming temperatures have induced changes in species physiology, phenology, and have decreased body size. Such modifications can impact population dynamics and could lead to changes in life cycle and demography. More specifically, conceptual frame-works predict that global warming will severely threaten tropical ectotherms while temperate ectotherms should resist or even benefit from higher temperatures. However, experimental studies measuring the impacts of future warming trends on temperate ectotherms ' life cycle and population persistence are lacking. Here we investigate the impacts of future climates on a model vertebrate ectotherm species using a large-scale warming experiment. We manipulated climatic conditions in 18 seminatural populations over two years to obtain a present climate treatment and a warm climate treatment matching IPCC predictions for future climate. Warmer temperatures caused a faster body growth, an earlier reproductive onset, and an increased voltinism, leading to a highly accelerated life cycle but also to a decrease in adult survival. A matrix population model predicts that warm climate populations in ou
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Live Fast, Die Young: Experimental Evidence of Population Extinction Risk due to Climate Change
PLoS Biology, 2015Co-Authors: Elvire Bestion, Aimeric Teyssier, Murielle Richard, Jean Clobert, Julien CoteAbstract:Evidence has accumulated in recent decades on the drastic impact of climate change on biodiversity. Warming temperatures have induced changes in species physiology, phenology, and have decreased body size. Such modifications can impact population dynamics and could lead to changes in life cycle and demography. More specifically, conceptual frameworks predict that global warming will severely threaten tropical ectotherms while temperate ectotherms should resist or even benefit from higher temperatures. However, experimental studies measuring the impacts of future warming trends on temperate ectotherms' life cycle and population persistence are lacking. Here we investigate the impacts of future climates on a model vertebrate ectotherm species using a large-scale warming experiment. We manipulated climatic conditions in 18 seminatural populations over two years to obtain a present climate treatment and a warm climate treatment matching IPCC predictions for future climate. Warmer temperatures caused a faster body growth, an earlier reproductive onset, and an increased voltinism, leading to a highly accelerated life cycle but also to a decrease in adult survival. A matrix population model predicts that warm climate populations in our experiment should go extinct in around 20 y. Comparing our experimental climatic conditions to conditions encountered by populations across Europe, we suggest that warming climates should threaten a significant number of populations at the southern range of the distribution. Our findings stress the importance of experimental approaches on the entire life cycle to more accurately predict population and species persistence in future climates.
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Spatial variation in age structure among colonies of a marine snake: the influence of Ectothermy
Journal of Animal Ecology, 2015Co-Authors: Xavier Bonnet, Jean Clobert, Francois Brischoux, David Pinaud, Catherine Louise Michel, Richard Shine, Thomas FauvelAbstract:1. Several tetrapod lineages that have evolved to exploit marine environments (e.g. seals, seabirds, sea kraits) continue to rely upon land for reproduction and, thus, form dense colonies on suitable islands. 2. In birds and mammals (endotherms), the offspring cannot survive without their parents. Terrestrial colonies contain all age classes. In reptiles (ectotherms), this constraint is relaxed, because offspring are independent from birth. Hence, each age class has the potential to select sites with characteristics that favour them. 3. Our studies of sea snakes (sea kraits) in the lagoon of New Caledonia reveal marked spatial heterogeneity in age structure among colonies. 4. Sea krait colonies exhibit the endothermic ‘seal–seabird’ pattern (mixed-age classes within populations) only where the lagoon is narrow. Where the lagoon is wide, most snake colonies are comprised primarily of a single age cohort. Nurseries are located near the coast, adult colonies offshore and mixed colonies in-between. 5. We suggest that Ectothermy allows individuals to utilize habitats that are best suited to their own ecological requirements, a flexibility not available to endothermic marine taxa with obligate parental care.
