scholarly journals Narrow safety margin in the phyllosphere during thermal extremes

2019 ◽  
Vol 116 (12) ◽  
pp. 5588-5596 ◽  
Author(s):  
Sylvain Pincebourde ◽  
Jérôme Casas
Keyword(s):  
Heat Waves ◽  
Safety Margin ◽  
Thermal Limit ◽  
Apparent Paradox ◽  
Feeding Mode ◽  
Thermal Limits ◽  
Single Leaf ◽  
Arthropod Species ◽  
Species Vulnerability ◽  
Leaf Transpiration

The thermal limit of ectotherms provides an estimate of vulnerability to climate change. It differs between contrasting microhabitats, consistent with thermal ecology predictions that a species’ temperature sensitivity matches the microclimate it experiences. However, observed thermal limits may differ between ectotherms from the same environment, challenging this theory. We resolved this apparent paradox by showing that ectotherm activity generates microclimatic deviations large enough to account for differences in thermal limits between species from the same microhabitat. We studied upper lethal temperature, effect of feeding mode on plant gas exchange, and temperature of attacked leaves in a community of six arthropod species feeding on apple leaves. Thermal limits differed by up to 8 °C among the species. Species that caused an increase in leaf transpiration (+182%), thus cooling the leaf, had a lower thermal limit than those that decreased leaf transpiration (−75%), causing the leaf to warm up. Therefore, cryptic microclimatic variations at the scale of a single leaf determine the thermal limit in this community of herbivores. We investigated the consequences of these changes in plant transpiration induced by plant–insect feedbacks for species vulnerability to thermal extremes. Warming tolerance was similar between species, at ±2 °C, providing little margin for resisting increasingly frequent and intense heat waves. The thermal safety margin (the difference between thermal limit and temperature) was greatly overestimated when air temperature or intact leaf temperature was erroneously used. We conclude that feedback processes define the vulnerability of species in the phyllosphere, and beyond, to thermal extremes.

scholarly journals Field application of the geometric framework reveals a multistep strategy of nutrient regulation in a leaf-miner

2019 ◽  
Author(s):  
Mélanie J.A. Body ◽  
Spencer T. Behmer ◽  
Pierre-François Pelisson ◽  
Jérôme Casas ◽  
David Giron
Keyword(s):  
Close Association ◽  
Sugar Content ◽  
Field Application ◽  
Leaf Miner ◽  
Compensatory Mechanisms ◽  
Geometric Framework ◽  
Feeding Mode ◽  
Body Protein ◽  
Symbiotic Associations ◽  
Single Leaf

AbstractAnimals have evolved a vast array of behavioral and physiological strategies that allow them to achieve a nutritionally balanced diet. Plants as food for herbivores are often considered suboptimal, but phytophagous insects can employ pre- and post-ingestive mechanisms and/or symbiotic associations to help overcome food nutritional imbalances. This is particularly crucial for permanent multivoltine leaf-miner insects such as the caterpillar Phyllonorycter blancardella which completes development within a restricted area of a single leaf and use deciduous leaves to fuel growth and reproduction even under senescing autumnal conditions. Using the geometric framework for nutrition under natural field conditions, we show that this insect has multiple strategies to deal with inadequate food supply from the plant. First, larvae manipulate the protein-sugar content of both normal, photosynthetically active, and senescing, photosynthetically inactive, leaf tissues. Control of nutritional homeostasis of mined tissues is however higher for late instars, which differ from younger larval instars in their feeding mode (fluid-vs. tissue-feeder). Second, slight differences in the protein-sugar environment remain between mined tissues on green and yellow leaves despite this manipulation of the leaf physiology. This insect uses post-ingestive mechanisms to achieve similar body protein, sugar and lipid composition. This study demonstrates, for the first time under natural conditions, the ability of an insect herbivore to practice a combination of pre- and post-ingestive compensatory mechanisms to attain similar growth and metabolic outcomes in fundamentally different nutritional environments. Additionally, a comparison of larval nutritional requirements of 117 species from various insect groups further reinforces the hypothesis of a close association between P. blancardella and endosymbiotic bacteria for nutritional purposes.

scholarly journals Could plasticity mediate highlands lizards’ resilience to climate change? A case study of the leopard iguana (Diplolaemus leopardinus) in central andes of Argentina

2021 ◽  
Author(s):  
Nadia Vicenzi ◽  
Leonardo D. Bacigalupe ◽  
Alejandro Laspiur ◽  
Nora Ibargüengoytía ◽  
Paola L. Sassi
Keyword(s):  
Climate Change ◽  
Thermal History ◽  
Heat Waves ◽  
Resting Metabolic Rate ◽  
Physiological Traits ◽  
Main Concern ◽  
Evaporative Water ◽  
Species Vulnerability ◽  
Acclimation Response ◽  
The Impact

The rising temperature predicted is of main concern for ectotherms because its direct impact on their behavior and physiology. Since physiological performance mediates a species’ resilience to warming exposure, physiological plasticity could greatly reduce the susceptibility to climate change. We studied the degree to which Diplolaemus leopardinus’ lizards are able to adjust behavioral and physiological traits in response to short periods of temperature change. We used a split cross design to measure acclimation response of preferred body temperature (Tp), and thermal performance curve of resting metabolic rate (RMR) and evaporative water loss (EWL). Our results showed that plasticity differs among traits; whereas Tp and EWL showed lower values in warm conditions, RMR increased the temperature at which its value is highest. Moreover, RMR was affected by thermal history, showing a great increase in response to cold exposure in the group initially acclimated to warm. The reduction of EWL and the increase in optimal temperature will give lizards the potential to partially mitigate the impact of rising temperatures in the energy cost and water balance. However, the decrease in Tp and the sensitivity to the warm thermal history in RMR could be detrimental to the energy net gain increasing the species vulnerability, especially considering the increase of heat waves predicted for the next fifty years. The integration of acclimation responses in behavioral and physiological traits provides a better understanding of the range of possible responses of lizards to cope with the upcoming climatic and environmental modifications expected due to climate change.

scholarly journals Oxygen limitation fails to explain upper chronic thermal limits and the temperature size rule in mayflies

2020 ◽  
pp. jeb.233338
Author(s):  
David H. Funk ◽  
Bernard W. Sweeney ◽  
John K. Jackson
Keyword(s):  
Cell Size ◽  
Aquatic Insects ◽  
Adult Size ◽  
Tissue Oxygen ◽  
Larval Life ◽  
Thermal Limit ◽  
Rearing Temperature ◽  
Thermal Limits ◽  
Cloeon Dipterum ◽  
Oxygen Concentrations

An inability to adequately meet tissue oxygen demands has been proposed as an important factor setting upper thermal limits in ectothermic invertebrates (especially aquatic species) as well as explaining the observed decline in adult size with increased rearing temperature during the immature stages (a phenomenon known as the Temperature Size Rule, or TSR). We tested this by rearing three aquatic insects (the mayflies Neocloeon triangulifer and two species of the Cloeon dipterum complex) through their entire larval life under a range of temperature and oxygen concentrations. Hyperoxia did not extend upper thermal limits, nor did it prevent the loss of size or fertility experienced near upper chronic thermal limits. At moderate temperatures, the TSR pattern was observed under conditions of hyperoxia, normoxia, and hypoxia, suggesting little or no influence of oxygen on this trend. However, for a given rearing temperature, adults were smaller and less fecund under hypoxia due to a lowering of growth rates. These mayflies greatly increased the size of their gills in response to lower dissolved oxygen concentrations but not under oxygen-saturated conditions over a temperature range yielding the classic TSR response. Using ommatidium diameter as a proxy for cell size we found the classic TSR pattern observed under moderate temperature conditions was due primarily to a change in the number of cells rather than cell size. We conclude overall that a failure to meet tissue oxygen demands is not a viable hypothesis for explaining either the chronic thermal limit or TSR pattern in these species.

scholarly journals Low potential for evolutionary rescue from climate change in a tropical fish

2020 ◽  
Vol 117 (52) ◽  
pp. 33365-33372 ◽  
Author(s):  
Rachael Morgan ◽  
Mette H. Finnøen ◽  
Henrik Jensen ◽  
Christophe Pélabon ◽  
Fredrik Jutfelt
Keyword(s):  
Climate Change ◽  
Danio Rerio ◽  
Thermal Tolerance ◽  
Heat Waves ◽  
Tropical Fish ◽  
Selected Lines ◽  
Thermal Limits ◽  
Evolutionary Rescue ◽  
Hard Limit ◽  
Upper Thermal Tolerance

Climate change is increasing global temperatures and intensifying the frequency and severity of extreme heat waves. How organisms will cope with these changes depends on their inherent thermal tolerance, acclimation capacity, and ability for evolutionary adaptation. Yet, the potential for adaptation of upper thermal tolerance in vertebrates is largely unknown. We artificially selected offspring from wild-caught zebrafish (Danio rerio) to increase (Up-selected) or decrease (Down-selected) upper thermal tolerance over six generations. Selection to increase upper thermal tolerance was also performed on warm-acclimated fish to test whether plasticity in the form of inducible warm tolerance also evolved. Upper thermal tolerance responded to selection in the predicted directions. However, compared to the control lines, the response was stronger in the Down-selected than in the Up-selected lines in which evolution toward higher upper thermal tolerance was slow (0.04 ± 0.008 °C per generation). Furthermore, the scope for plasticity resulting from warm acclimation decreased in the Up-selected lines. These results suggest the existence of a hard limit in upper thermal tolerance. Considering the rate at which global temperatures are increasing, the observed rates of adaptation and the possible hard limit in upper thermal tolerance suggest a low potential for evolutionary rescue in tropical fish living at the edge of their thermal limits.

Leaf energy balances: developments and applications

1989 ◽  
Vol 324 (1223) ◽  
pp. 191-206 ◽  
Keyword(s):  
Boundary Layer ◽  
Ambient Conditions ◽  
Single Leaf ◽  
Leaf Transpiration ◽  
Tree Transpiration ◽  
Small Influence ◽  
Energy Balances ◽  
Monteith Equation ◽  
Whole Tree ◽  
Good Agreement

Theory of leaf energy balances is outlined in the context of four applications: (1) prediction of leaf temperatures during clear nights; (2) estimation of transpiration rates and stomatal conductances of individual leaves by using pairs of coated and normal leaves; (3) measurement of leaf boundary-layer conductances using pairs of artificial, electrically heated leaves; and (4) use of method (2) to assess validity of whole-tree transpiration rates measured with large ventilated chambers. Good agreement was found between predicted and measured leaf temperatures on clear nights. Leaf temperatures were controlled mainly by loss of thermal radiation to cold skies and by gain of sensible and latent heat from surrounding air. Leaves with condensation on them were 1-2 °C warmer than dry leaves under otherwise similar ambient conditions. Free convection was unimportant relative to forced convection as a mechanism for heat transfer to leaves during calm, clear nights. Satisfactory estimates of single-leaf transpiration were obtained using pairs of coated and uncoated leaves provided both were equally exposed to incoming radiation. Electrically heated facsimile leaves gave satisfactory estimates of leaf boundary-layer conductances in the field. Large ventilated chambers had a small influence on measured transpiration rates according to estimates made with the Penman-Monteith equation for both chamber positions.

scholarly journals Emotions triggered by live arthropods shed light on spider phobia

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Daniel Frynta ◽  
Markéta Janovcová ◽  
Iveta Štolhoferová ◽  
Šárka Peléšková ◽  
Barbora Vobrubová ◽  
...  
Keyword(s):  
Body Size ◽  
Spider Phobia ◽  
Apparent Paradox ◽  
Arthropod Species ◽  
Original Stimulus ◽  
Animal Phobias ◽  
Cohesive Group ◽  
Close Relatives ◽  
Shed Light ◽  
Real Danger

AbstractSpiders are mostly harmless, yet they often trigger high levels of both fear and disgust, and arachnophobia (the phobia of spiders) ranks among the most common specific animal phobias. To investigate this apparent paradox, we turned to the only close relatives of spiders that pose a real danger to humans: scorpions. We adopted a unique methodology in order to assess authentic emotions elicited by arthropods. Over 300 respondents were asked to rate live specimens of 62 arthropod species (including spiders, scorpions, cockroaches, and other insects) based on perceived fear, disgust, and beauty. We found that species’ scores on all three scales depended on the higher taxon as well as on body size. Spiders, scorpions, and other arachnids scored the highest in fear and disgust, while beetles and crabs scored the highest in beauty. Moreover, all chelicerates were perceived as one cohesive group, distinct from other arthropods, such as insects or crabs. Based on these results, we hypothesize that the fear of spiders might be triggered by a generalized fear of chelicerates, with scorpions being the original stimulus that signals danger.

scholarly journals Local adaptation in thermal tolerance for a tropical butterfly across ecotone and rainforest habitats

Biology Open ◽  
2021 ◽  
Vol 10 (4) ◽  
pp. bio058619
Author(s):  
Michel A. K. Dongmo ◽  
Rachid Hanna ◽  
Thomas B. Smith ◽  
K. K. M. Fiaboe ◽  
Abraham Fomena ◽  
...  
Keyword(s):  
Environmental Change ◽  
Local Adaptation ◽  
Thermal Tolerance ◽  
Thermal Adaptation ◽  
Climate Change Impacts ◽  
Thermal Variation ◽  
Evolutionary Processes ◽  
Physiological Tolerance ◽  
Thermal Limits ◽  
Species Vulnerability

ABSTRACTThermal adaptation to habitat variability can determine species vulnerability to environmental change. For example, physiological tolerance to naturally low thermal variation in tropical forests species may alter their vulnerability to climate change impacts, compared with open habitat species. However, the extent to which habitat-specific differences in tolerance derive from within-generation versus across-generation ecological or evolutionary processes are not well characterized. Here we studied thermal tolerance limits of a Central African butterfly (Bicyclus dorothea) across two habitats in Cameroon: a thermally stable tropical forest and the more variable ecotone between rainforest and savanna. Second generation individuals originating from the ecotone, reared under conditions common to both populations, exhibited higher upper thermal limits (CTmax) than individuals originating from forest (∼3°C greater). Lower thermal limits (CTmin) were also slightly lower for the ecotone populations (∼1°C). Our results are suggestive of local adaptation driving habitat-specific differences in thermal tolerance (especially CTmax) that hold across generations. Such habitat-specific thermal limits may be widespread for tropical ectotherms and could affect species vulnerability to environmental change. However, microclimate and within-generation developmental processes (e.g. plasticity) will mediate these differences, and determining the fitness consequences of thermal variation for ecotone and rainforest species will require continued study of both within-generation and across-generation eco-evolutionary processes.This article has an associated First Person interview with the first author of the paper.

The limits of human performance

2008 ◽  
Vol 44 ◽  
pp. 11-26 ◽  
Author(s):  
Ralph Beneke ◽  
Dieter Böning
Keyword(s):  
Human Performance ◽  
Safety Margin ◽  
Afferent Input ◽  
Metabolic Energy ◽  
Human Organism ◽  
Mechanical Resistance ◽  
As Doping ◽  
Gene And Protein Expression ◽  
Underlying Mechanisms ◽  
Biochemical Research

Human performance, defined by mechanical resistance and distance per time, includes human, task and environmental factors, all interrelated. It requires metabolic energy provided by anaerobic and aerobic metabolic energy sources. These sources have specific limitations in the capacity and rate to provide re-phosphorylation energy, which determines individual ratios of aerobic and anaerobic metabolic power and their sustainability. In healthy athletes, limits to provide and utilize metabolic energy are multifactorial, carefully matched and include a safety margin imposed in order to protect the integrity of the human organism under maximal effort. Perception of afferent input associated with effort leads to conscious or unconscious decisions to modulate or terminate performance; however, the underlying mechanisms of cerebral control are not fully understood. The idea to move borders of performance with the help of biochemicals is two millennia old. Biochemical findings resulted in highly effective substances widely used to increase performance in daily life, during preparation for sport events and during competition, but many of them must be considered as doping and therefore illegal. Supplements and food have ergogenic potential; however, numerous concepts are controversially discussed with respect to legality and particularly evidence in terms of usefulness and risks. The effect of evidence-based nutritional strategies on adaptations in terms of gene and protein expression that occur in skeletal muscle during and after exercise training sessions is widely unknown. Biochemical research is essential for better understanding of the basic mechanisms causing fatigue and the regulation of the dynamic adaptation to physical and mental training.

Social Recourses of the Population under Conditions of Losing Economic Stability

2015 ◽  
pp. 86-99 ◽  
Author(s):  
E. Avraamova ◽  
T. Maleva
Keyword(s):  
Economic Development ◽  
Social Policy ◽  
Social Development ◽  
Safety Margin ◽  
Economic Stability ◽  
Socio Economic Development ◽  
Development Stability ◽  
Made In

The loss of country’s socio-economic development stability puts on the agenda the problem of finding solutions contributing to the maintenance of Russian households’ welfare. The authors believe that these solutions lie in the broader area than applying various instruments of monetary support. The most effective solutions are related to the actualization of own resources of households that can act as a safety margin as well as a source of social development. The attempt to evaluate the households’ resource provision and highlight the significance of each resource enabling or creating barriers to the growth of households’ welfare is made in this article. On the basis of received conclusions social policy areas directed at preserving or enhancing the welfare are defined.

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