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Eric T. Liknes - One of the best experts on this subject based on the ideXlab platform.
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A comparative analysis of thermogenic capacity and Cold Tolerance in small birds.
Journal of Experimental Biology, 2006Co-Authors: David L. Swanson, Eric T. LiknesAbstract:SUMMARY Small birds showing marked seasonal changes in Cold Tolerance also exhibit winter increases in summit metabolic rate ( M sum =maximum Cold-induced thermogenesis or thermogenic capacity) relative to summer birds. However, some birds show modest seasonal changes in Cold Tolerance without winter increases in M sum and others exhibit large seasonal changes in Cold Tolerance with only minor changes in M sum . Thus, the degree of correlation between Cold Tolerance and M sum is uncertain and no interspecific study has directly addressed this question. In this study, we measured Cold Tolerance and M sum in summer- (21 species) and winter- (11 species) acclimatized birds from southeastern South Dakota. M sum was measured as the maximum oxygen consumption attained during exposure of individual birds to a declining series of temperatures in 79% helium/21% oxygen (helox). Cold Tolerance was measured as the temperature at Cold limit ( T CL ), which is the helox temperature that induced hypothermia in individual birds. Residuals from allometric regressions of log M sum and log T CL were significantly and negatively related for summer ( R 2 =0.34, P =0.006) and winter ( R 2 =0.40, P =0.037) birds. Data were also subjected to a comparative analyses with phylogenetically independent contrasts to remove potential confounding effects of phylogeny, and results were similar to the non-phylogenetic analyses, with significant negative correlations in both summer ( R 2 =0.47, P R 2 =0.40, P =0.049). Thus, birds with high M sum tended to show reduced T CL (i.e. high Cold Tolerance), suggesting that Cold Tolerance and summit metabolism are phenotypically linked in small birds.
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A comparative analysis of thermogenic capacity and Cold Tolerance in small birds.
The Journal of experimental biology, 2006Co-Authors: David L. Swanson, Eric T. LiknesAbstract:Small birds showing marked seasonal changes in Cold Tolerance also exhibit winter increases in summit metabolic rate (Msum=maximum Cold-induced thermogenesis or thermogenic capacity) relative to summer birds. However, some birds show modest seasonal changes in Cold Tolerance without winter increases in Msum and others exhibit large seasonal changes in Cold Tolerance with only minor changes in Msum. Thus, the degree of correlation between Cold Tolerance and Msum is uncertain and no interspecific study has directly addressed this question. In this study, we measured Cold Tolerance and Msum in summer- (21 species) and winter- (11 species) acclimatized birds from southeastern South Dakota. Msum was measured as the maximum oxygen consumption attained during exposure of individual birds to a declining series of temperatures in 79% helium/21% oxygen (helox). Cold Tolerance was measured as the temperature at Cold limit (TCL), which is the helox temperature that induced hypothermia in individual birds. Residuals from allometric regressions of logMsum and logTCL were significantly and negatively related for summer (R2=0.34, P=0.006) and winter (R2=0.40, P=0.037) birds. Data were also subjected to a comparative analyses with phylogenetically independent contrasts to remove potential confounding effects of phylogeny, and results were similar to the non-phylogenetic analyses, with significant negative correlations in both summer (R2=0.47, P
David L. Swanson - One of the best experts on this subject based on the ideXlab platform.
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A comparative analysis of thermogenic capacity and Cold Tolerance in small birds.
Journal of Experimental Biology, 2006Co-Authors: David L. Swanson, Eric T. LiknesAbstract:SUMMARY Small birds showing marked seasonal changes in Cold Tolerance also exhibit winter increases in summit metabolic rate ( M sum =maximum Cold-induced thermogenesis or thermogenic capacity) relative to summer birds. However, some birds show modest seasonal changes in Cold Tolerance without winter increases in M sum and others exhibit large seasonal changes in Cold Tolerance with only minor changes in M sum . Thus, the degree of correlation between Cold Tolerance and M sum is uncertain and no interspecific study has directly addressed this question. In this study, we measured Cold Tolerance and M sum in summer- (21 species) and winter- (11 species) acclimatized birds from southeastern South Dakota. M sum was measured as the maximum oxygen consumption attained during exposure of individual birds to a declining series of temperatures in 79% helium/21% oxygen (helox). Cold Tolerance was measured as the temperature at Cold limit ( T CL ), which is the helox temperature that induced hypothermia in individual birds. Residuals from allometric regressions of log M sum and log T CL were significantly and negatively related for summer ( R 2 =0.34, P =0.006) and winter ( R 2 =0.40, P =0.037) birds. Data were also subjected to a comparative analyses with phylogenetically independent contrasts to remove potential confounding effects of phylogeny, and results were similar to the non-phylogenetic analyses, with significant negative correlations in both summer ( R 2 =0.47, P R 2 =0.40, P =0.049). Thus, birds with high M sum tended to show reduced T CL (i.e. high Cold Tolerance), suggesting that Cold Tolerance and summit metabolism are phenotypically linked in small birds.
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A comparative analysis of thermogenic capacity and Cold Tolerance in small birds.
The Journal of experimental biology, 2006Co-Authors: David L. Swanson, Eric T. LiknesAbstract:Small birds showing marked seasonal changes in Cold Tolerance also exhibit winter increases in summit metabolic rate (Msum=maximum Cold-induced thermogenesis or thermogenic capacity) relative to summer birds. However, some birds show modest seasonal changes in Cold Tolerance without winter increases in Msum and others exhibit large seasonal changes in Cold Tolerance with only minor changes in Msum. Thus, the degree of correlation between Cold Tolerance and Msum is uncertain and no interspecific study has directly addressed this question. In this study, we measured Cold Tolerance and Msum in summer- (21 species) and winter- (11 species) acclimatized birds from southeastern South Dakota. Msum was measured as the maximum oxygen consumption attained during exposure of individual birds to a declining series of temperatures in 79% helium/21% oxygen (helox). Cold Tolerance was measured as the temperature at Cold limit (TCL), which is the helox temperature that induced hypothermia in individual birds. Residuals from allometric regressions of logMsum and logTCL were significantly and negatively related for summer (R2=0.34, P=0.006) and winter (R2=0.40, P=0.037) birds. Data were also subjected to a comparative analyses with phylogenetically independent contrasts to remove potential confounding effects of phylogeny, and results were similar to the non-phylogenetic analyses, with significant negative correlations in both summer (R2=0.47, P
Brent J. Sinclair - One of the best experts on this subject based on the ideXlab platform.
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An invitation to measure insect Cold Tolerance: Methods, approaches, and workflow.
Journal of thermal biology, 2015Co-Authors: Brent J. Sinclair, Litza E. Coello Alvarado, Laura V. FergusonAbstract:Insect performance is limited by the temperature of the environment, and in temperate, polar, and alpine regions, the majority of insects must face the challenge of exposure to low temperatures. The physiological response to Cold exposure shapes the ability of insects to survive and thrive in these environments, and can be measured, without great technical difficulty, for both basic and applied research. For example, understanding insect Cold Tolerance allows us to predict the establishment and spread of insect pests and biological control agents. Additionally, the discipline provides the tools for drawing physiological comparisons among groups in wider studies that may not be focused primarily on the ability of insects to survive the Cold. Thus, the study of insect Cold Tolerance is of a broad interest, and several reviews have addressed the theories and advances in the field. Here, however, we aim to clarify and provide rationale for common practices used to study Cold Tolerance, as a guide for newcomers to the field, students, and those wishing to incorporate Cold Tolerance into a broader study. We cover the ‘tried and true’ measures of insect Cold Tolerance, the equipment necessary for these measurement, and summarize the ecological and biological significance of each. Finally, we suggest a framework and workflow for measuring Cold Tolerance and low temperature performance in insects.
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Cold Tolerance of the montane Sierra leaf beetle, Chrysomela aeneicollis
Journal of insect physiology, 2015Co-Authors: Evelyn C. Boychuk, Nathan E. Rank, John T. Smiley, Elizabeth P. Dahlhoff, Mark A. Bernards, Brent J. SinclairAbstract:Small ectothermic animals living at high altitude in temperate latitudes are vulnerable to lethal Cold throughout the year. Here we investigated the Cold Tolerance of the leaf beetle Chrysomela aeneicollis living at high elevation in California’s Sierra Nevada mountains. These insects spend over half their life cycle overwintering, and may therefore be vulnerable to winter Cold, and prior studies have demonstrated that survival is reduced by exposure to summertime Cold. We identify overwintering microhabitat of this insect, describe Cold Tolerance strategies in all life stages, and use microclimate data to determine the importance of snow cover and microhabitat buffering for overwinter survival. Cold Tolerance varies among life history stages and is typically correlated with microhabitat temperature: Cold hardiness is lowest in chill-susceptible larvae, and highest in freeze-tolerant adults. Hemolymph osmolality is higher in quiescent (overwintering) than summer adults, primarily, but not exclusively, due to elevated hemolymph glycerol. In nature, adult beetles overwinter primarily in leaf litter and suffer high mortality if early, unseasonable Cold prevents them from entering this refuge. These data suggest that Cold Tolerance is tightly linked to life stage. Thus, population persistence of montane insects may become problematic as climate becomes more unpredictable and climate change uncouples the phenology of Cold Tolerance and development from the timing of extreme Cold events.
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Parallel ionoregulatory adjustments underlie phenotypic plasticity and evolution of Drosophila Cold Tolerance
Journal of Experimental Biology, 2015Co-Authors: Heath A. Macmillan, Laura V. Ferguson, Annegret Nicolai, Andrew Donini, James F. Staples, Brent J. SinclairAbstract:Low temperature Tolerance is the main predictor of variation in the global distribution and performance of insects, yet the molecular mechanisms underlying Cold Tolerance variation are poorly known, and it is unclear whether the mechanisms that improve Cold Tolerance within the lifetime of an individual insect are similar to those that underlie evolved differences among species. The accumulation of Cold-induced injuries by hemimetabolous insects is associated with loss of Na+ and K+ homeostasis. Here we show that this model holds true for Drosophila; Cold exposure increases haemolymph [K+] in D. melanogaster, and Cold-acclimated flies maintain low haemolymph [Na+] and [K+], both at rest and during a Cold exposure. This pattern holds across 24 species of the Drosophila phylogeny, where improvements in Cold Tolerance have been consistently paired with reductions in haemolymph [Na+] and [K+]. Cold-acclimated D. melanogaster have low activity of Na+/K+-ATPase, which may contribute to the maintenance of low haemolymph [Na+] and underlie improvements in Cold Tolerance. Modifications to ion balance areassociated with both phenotypic plasticity within D. melanogaster and evolutionary differences in Cold Tolerance across the Drosophila phylogeny, which suggests that adaptation and acclimation of Cold Tolerance in insects may occur through similar mechanisms. Cold tolerantflies maintain haemolymph osmolality despite low haemolymph [Na+] and [K+], possibly through modest accumulations of organic osmolytes. We propose that this could have served as an evolutionary route by which chill-susceptible insects developed more extreme Cold Tolerance strategies.
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The evolution of Cold Tolerance in Drosophila larvae.
Physiological and biochemical zoology : PBZ, 2011Co-Authors: Lauren A. Strachan, Heather E. Tarnowski-garner, Katie E. Marshall, Brent J. SinclairAbstract:Abstract Temperature is a primary determinant of insect and other ectotherm distribution and activity. Physiological and behavioral adaptations allow many insects to survive at subzero temperatures, yet the evolutionary influences on insect Cold Tolerance are unclear. Supercooling points, basal Cold Tolerance, Cold-Tolerance strategy, and inducible Cold Tolerance from rapid Cold-hardening or acclimation were measured in a phylogenetically independent context in larvae of 27 phylogenetically diverse Drosophila species acquired from stock collections. Supercooling capacity is attributed primarily to physical factors, such as dry mass and water mass. Species of the obscura group were more resistant to acute Cold Tolerance than species of other groups within the genus, and plasticity in Cold Tolerance is constrained by phylogeny rather than by basal Cold Tolerance. The more Cold-tolerant freeze-avoiding species appear to have arisen multiple times in Drosophila and are distinct from chill-susceptible species,...
Justin B Lack - One of the best experts on this subject based on the ideXlab platform.
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parallel evolution of Cold Tolerance within drosophila melanogaster
Molecular Biology and Evolution, 2016Co-Authors: John E Pool, Dylan T Braun, Justin B LackAbstract:Drosophila melanogaster originated in tropical Africa before expanding into strikingly different temperate climates in Eurasia and beyond. Here, we find elevated Cold Tolerance in three distinct geographic regions: beyond the well-studied non-African case, we show that populations from the highlands of Ethiopia and South Africa have significantly increased Cold Tolerance as well. We observe greater Cold Tolerance in outbred versus inbred flies, but only in populations with higher inversion frequencies. Each Cold-adapted population shows lower inversion frequencies than a closely-related warm-adapted population, suggesting that inversion frequencies may decrease with altitude in addition to latitude. Using the FST-based "Population Branch Excess" statistic (PBE), we found only limited evidence for parallel genetic differentiation at the scale of ∼4 kb windows, specifically between Ethiopian and South African Cold-adapted populations. And yet, when we looked for single nucleotide polymorphisms (SNPs) with codirectional frequency change in two or three Cold-adapted populations, strong genomic enrichments were observed from all comparisons. These findings could reflect an important role for selection on standing genetic variation leading to "soft sweeps". One SNP showed sufficient codirectional frequency change in all Cold-adapted populations to achieve experiment-wide significance: an intronic variant in the synaptic gene Prosap. Another codirectional outlier SNP, at senseless-2, had a strong association with our Cold trait measurements, but in the opposite direction as predicted. More generally, proteins involved in neurotransmission were enriched as potential targets of parallel adaptation. The ability to study Cold Tolerance evolution in a parallel framework will enhance this classic study system for climate adaptation.
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parallel evolution of Cold Tolerance within drosophila melanogaster
bioRxiv, 2016Co-Authors: John E Pool, Dylan T Braun, Justin B LackAbstract:Drosophila melanogaster originated in tropical Africa before expanding into strikingly different temperate climates in Eurasia and beyond. Here, we show that elevated Cold Tolerance has arisen at least three times within this species: beyond the well-studied non-African case, we show that populations from the highlands of Ethiopia and South Africa have significantly increased Cold Tolerance as well. We observe greater Cold Tolerance in outbred versus inbred flies, but only in populations with higher inversion frequencies. Each Cold-adapted population shows lower inversion frequencies than a closely-related warm-adapted population, suggesting that inversion frequencies may decrease with altitude in addition to latitude. Using the FST-based "Population Branch Excess" statistic (PBE), we found only limited evidence for parallel genetic differentiation at the scale of ~4 kb windows, specifically between Ethiopian and South African Cold-adapted populations. And yet, when we looked for single nucleotide polymorphisms (SNPs) with codirectional frequency change in two or three Cold-adapted populations, strong genomic enrichments were observed from all comparisons. These findings could reflect an important role for selection on standing genetic variation leading to "soft sweeps". One SNP showed sufficient codirectional frequency change in all Cold-adapted populations to achieve experiment-wide significance: an intronic variant in the synaptic gene Prosap. More generally, proteins involved in neurotransmission were enriched as potential targets of parallel adaptation. The ability to study Cold Tolerance evolution in a parallel framework will enhance this classic study system for climate adaptation.
Gregor Aas - One of the best experts on this subject based on the ideXlab platform.
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Cold Tolerance of tree species is related to the climate of their native ranges
Journal of Biogeography, 2014Co-Authors: Jürgen Kreyling, Stephanie S. Schmid, Gregor AasAbstract:Aim Species ranges are confined by environmental parameters such as minimum temperatures. Beyond correlations of ranges and climatic parameters, however, physiological Tolerances (here: Cold Tolerance) have rarely been linked to the climate of species' ranges. We hypothesize that natural range shifts due to climate warming and proactive-assisted colonization may each be constrained by limits to the Tolerance of species to rare frost events. Location Bayreuth, Germany, and the Northern Hemisphere. Methods We quantified Cold Tolerance (LT50 obtained by relative electrolyte leakage method) of 27 native and exotic (Northern Hemisphere) tree species in the autumn, mid-winter and spring of 2011–12 at the Ecological Botanical Garden of the University of Bayreuth, Germany, and linked observed Cold Tolerances as well as changes in Cold Tolerance between sampling dates to the climate of the native ranges of the species. Results Observed Cold Tolerance was strongly related to the climate of the native ranges of the species (cross-validated correlations between climate and expressed Cold Tolerance determined by boosted regression trees were 0.50 in autumn, 0.49 in mid-winter, and 0.65 in spring). Cold Tolerance was generally greater for species that experienced Colder temperatures and lower levels of precipitation in their native ranges. Changes in Cold Tolerance between the three sampling dates over the winter, however, were not linked to the climate of the native ranges. Main conclusions Our results demonstrate the evolutionary importance of Cold Tolerance, which should be acknowledged in assisted colonization trials and projections of range shifts by considering absolute minimum temperature as an important ecological factor.