Thermal Hypothesis Research Articles

Altitude and ground brightness explain interpopulation variation in dorsal coloration in a lizard

Abstract Non-signaling functions of coloration include thermoregulation (thermal melanism hypothesis), protection against ultraviolet radiation (photoprotection hypothesis), and concealment from predators (crypsis hypothesis). We investigated whether dorsal coloration in 19 populations of spiny-footed lizards, Acanthodactylus erythrurus, across the Iberian Peninsula varies according to these functions. We captured adult males and females in each population and calculated standardized dorsum brightness estimates from photographs. We also calculated standardized ground luminosity estimates and gathered information on latitude, altitude, mean annual temperature, and mean annual solar radiation for each location. Males showed a higher percentage of black coloration and a more contrasted dorsum than females, suggesting different selection pressures on dorsal coloration in both sexes. Furthermore, males showed a darker dorsum and a higher percentage of black coloration at higher altitudes and when the ground was darker. In contrast, females exhibited a darker dorsum only when the ground was darker and a higher percentage of black coloration only at higher altitudes. We also observed that the variation of dorsum luminosity within males and the variation of dorsum luminosity among females within populations were both positively related to the variation of ground luminosity among different points within locations. Latitude, temperature, and solar radiation were not significantly related to dorsal coloration in either sex. Our results support the photoprotection and crypsis hypotheses in males and, to some extent, in females, whereas the thermal melanism hypothesis is weakly supported in both sexes. These findings suggest that there is local adaptation in the dorsal coloration of the spiny-footed lizard.

Melanism in Polymorphic Terrestrial Snakes: A Meta‐Analysis and Systematic Review

ABSTRACTBackground and AimColour polymorphic populations constitute excellent model systems for testing ecological and evolutionary hypotheses, as alternate colourations are associated with differences in various biological, behavioural and life‐history traits. Melanism is the most common and most obvious form of polymorphism. In reptiles in general (and snakes in particular), thermal melanism has been a popular hypothesis used to explain the appearance of black individuals. It suggests that a trade‐off exists between superior thermoregulation and reduced protection through the loss of crypsis. Surprisingly, despite the growing body of literature available, to date, there are only two qualitative reviews on the evolutionary significance of melanism in reptiles and no quantitative synthesis. We conducted the first systematic review and meta‐analysis summarising the current knowledge on melanism in polymorphic terrestrial snakes and synthesised the evidence for an adaptive advantage of the melanistic morph.LocationNorthern Hemisphere.TaxonPolymorphic terrestrial snakes.ResultsMean prevalence of melanism is 31% with no significant differences between species. Annual precipitation was a significant moderator of melanism prevalence. Our results revealed no significant differences in odds ratios of melanism between sexes or in mean body size.Main ConclusionsEnvironmental plasticity can be considered the primary cause of melanism, possibly as a result of seasonal climatic variations, a result corroborated by the formal meta‐analysis conducted. Conclusions from the meta‐analysis are that melanism in snakes follows Gloger's rule, as is the case in birds and mammals, and as opposed to the thermal melanism hypothesis. Further, our findings do not lend support for other predictions from the thermal melanism hypothesis, such as skewed frequency of melanistics in favour of males or females, or larger body sizes in black individuals. Our results hold implications for the future diversity of animal populations, as climate change is predicted to decrease the degree of colour variation.

It is hot and cold here: the role of thermotolerance in the ability of spiders to colonize tree plantations in the southern Atlantic Forest.

Worldwide, with the decline of natural habitats, species with reduced niche breadth (specialists) are at greater risk of extinction as they cannot colonise or persist in disturbed habitat types. However, the role of thermal tolerance as a critical trait in understanding changes in species diversity in disturbed habitats, e.g., due to forest replacement by tree plantations, is still understudied. To examine the role of thermal tolerance on the responses of specialist and generalist species to habitat disturbances, we measured and compared local temperature throughout the year and thermotolerance traits [upper (CTmax) and lower (CTmin) thermal limits] of the most abundant species of spiders from different guilds inhabiting pine tree plantations and native Atlantic Forests in South America. Following the thermal adaptation hypothesis, we predicted that generalist species would show a wider thermal tolerance range (i.e., lower CTmin and higher CTmax) than forest specialist species. As expected, generalist species showed significantly higher CTmax and lower CTmin values than specialist species with wider thermal tolerance ranges than forest specialist species. These differences are more marked in orb weavers than in aerial hunter spiders. Our study supports the specialisation disturbance and thermal hypotheses. It highlights that habitat-specialist species are more vulnerable to environmental changes associated with vegetation structure and microclimatic conditions. Moreover, thermal tolerance is a key response trait to explain the Atlantic Forest spider's ability (or inability) to colonise and persist in human-productive land uses.

Temperature differently affects body pigmentation of the paper wasp Polistes dominula along an urban and a wider geographical gradient

In insects, different pigments, such as melanins and pterins, are involved in thermoregulation. The degree of melanisation often varies along geographical gradients, according to the so-called thermal melanism hypothesis, i.e. darker forms are found in colder places because they can warm up more quickly. Similarly, pterins work as heat sinks and thus are expected to be more abundant in colder sites. Cities, which are warmer than surrounding areas (Urban Heat Island (UHI) effect), might also be expected to influence pigmentation, although studies are lacking. Here, we sampled workers of the social paper wasp Polistes dominula (Christ, 1791) (Vespidae) across an urbanisation gradient in an Italian metropolis and used iNaturalist pictures of this species across Italy to study pigmentation patterns at both urban and larger geographical scales. We found a lower yellow intensity of abdominal spots at warmer locations. Scanning Electron Microscopy strongly suggested that yellow colouration is due xanthopterin, known to be the heat sink molecule in other social vespids. Thus, wasps from warmer (i.e., urban) environments are likely to have fewer xanthopterin granules, in line with the lack of need for heat storage due to the local thermal gradient (UHI effect). At the country level, we found that wasps at higher latitudes had smaller yellow spots on the thorax and only two spots instead of four at higher altitudes, in full accordance with the thermal melanism hypothesis. In conclusion, climatic conditions seem to affect insect colour patterns both along urban and wider geographical gradients, although colour changes may affect different body parts and pigments likely according to different needs.

Temperature seasonality drives taxonomic and functional homogenization of tropical butterflies

AbstractAimTo better understand the potential impact of climate change on butterfly assemblages across a tropical island, we model the potential for taxonomic and functional homogenization and determine climate‐ and trait‐mediated shifts in projected species distributions.LocationPuerto Rico.MethodsWe used thousands of museum records of diurnal Lepidoptera to model current (1970–2000) and forecast future (2061–2080) species distributions and combined these to test for taxonomic and functional homogenization. We then quantified climatic‐mediated effects on current and forecasted taxonomic and functional composition and, specifically, whether temperature was a primary driver, as predicted by the temperature–size rule and the thermal melanism hypotheses. Finally, we measured wing traits important in thermoregulation (size and colour) and determined trait‐mediated changes in forecasted species distributions over time.ResultsBased on ensemble model outputs, taxonomic and functional richness and turnover were predicted to vary across the island's complex topography. Our models projected an increase in taxonomic and functional richness over time, and a decrease in taxonomic and functional turnover – a signature of biotic homogenization. Under future climate scenarios, models projected a decrease in wing length and an increase in wing brightness at higher elevations. One variable, temperature seasonality, was the strongest predicted driver of both the current spatial distribution and the projected per cent change over time for not only wing traits but also taxonomic and functional richness and turnover.Main conclusionsThe species distribution models generated here identify several priority regions and species for future research and conservation efforts. Our work also highlights the role of seasonality and climatic variability on diverse tropical Lepidoptera assemblages, suggesting that climatic variability may be an important, albeit overlooked, driver of climate change responses.

A simulated natural heatwave perturbs bumblebee immunity and resistance to infection.

As a consequence of ongoing climate change, heatwaves are predicted to increase in frequency, intensity, and duration in many regions. Such extreme events can shift organisms from thermal optima for physiology and behaviour, with the thermal stress hypothesis predicting reduced performance at temperatures where the maintenance of biological functions is energetically costly. Performance includes the ability to resist biotic stressors, including infectious diseases, with increased exposure to extreme temperatures having the potential to synergise with parasite infection. Climate change is a proposed threat to native bee pollinators, directly and through indirect effects on floral resources, but the thermal stress hypothesis, particularly pertaining to infectious disease resistance, has received limited attention. We exposed adult Bombus impatiens bumblebee workers to simulated, ecologically relevant heatwave or control thermal regimes and assessed longevity, immunity, and resistance to concurrent or future parasite infections. We demonstrate that survival and induced antibacterial immunity are reduced following heatwaves. Supporting that heatwave exposure compromised immunity, the cost of immune activation was thermal regime dependent, with survival costs in control but not heatwave exposed bees. However, in the face of real infections, an inability to mount an optimal immune response will be detrimental, which was reflected by increased trypanosomatid parasite infections following heatwave exposure. These results demonstrate interactions between heatwave exposure and bumblebee performance, including immune and infection outcomes. Thus, the health of bumblebee pollinator populations may be affected through altered interactions with parasites and pathogens, in addition to other effects of extreme manifestations of climate change.

Thermal comfort and retail sales: A big data analysis of extreme temperature's impact on brick-and-mortar stores

The effect of weather on retail sales has long been of great interest to both the business and academic fields. This study investigated the impact of extreme temperatures on brick-and-mortar retail stores in Seoul, Korea. Using a comprehensive credit card transaction dataset, high-resolution weather data, and a semiparametric model, we found a significant increase in sales during extreme temperature events: 4% during heatwaves exceeding 35 °C and 11% during cold spells below −15 °C. This finding is supported by the thermal comfort hypothesis in retail sales, which suggests that consumers are driven to temperature-controlled indoor environments and are inclined to purchase products that provide thermal comfort, such as hot or cold beverages. As extreme weather events become more frequent owing to climate change, accurate sales forecasting during such conditions becomes crucial for retailers. Insights from our research enable retailers to better predict sales under extreme temperature conditions and to strategize accordingly, such as by highlighting thermal comfort products or ensuring optimal indoor temperatures with efficient air conditioning or heating systems.

현대물리학의 시간에 대한 존재론적 고찰

This paper examines the change of the concept of time and its ontological meaning in physics, focusing on modern physics. The concept of absolute time was presented in Newton's classical physics, and since then, the concepts of relativistic time and quantized time have been introduced in Einstein's theory of relativity and quantum gravity theory, respectively. This change raises question about the true concept of time in the universe. In this paper, in order to find an answer to this question, the ontological meaning of the concept of time presented by each theory is compared. First, the concept of absolute time is regarded as a concept of time that we usually accept, and it is revealed that the meanings of uniqueness, independent reality, separability, directionality, continuity, uniformity, transcendence, and objectivity are included in it. And, in the concepts of relativistic time and quantized time, these characteristics are dismantled one by one. Nevertheless, whether the concept of time in the world we experience is compatible with the concept of quantized time is investigated through the thermal time hypothesis. Finally, we examine the implications of time quantization in philosophy of science, even though (loop) quantum gravity theory is a theoretical imagination that has not yet been empirically verified.

Two-temperature ablative material response model with application to Stardust and MSL atmospheric entries

Ablative material response codes currently in use consider local thermal equilibrium between the solid phases and the pyrolysis gases. For typical entry conditions, this hypothesis may be justified by the fact that the thermal Peclet number within the pores is small, which is a necessary condition for thermal equilibrium in non-reactive materials. However, the validity of this analysis may fall under some circumstances. The thermal Peclet number may become large due to high pyrolysis gas velocities. Additional physical phenomena not accounted for in the Peclet analysis may become non-negligible, such as the change of enthalpy due to chemical reactions. The objective of this study is two-fold. First, a detailed two temperature material response model for porous reactive materials is presented. This model has been implemented and made available in the Porous material Analysis Toolbox based on OpenFOAM (PATO). Second, the model is applied to the Theoretical Ablative Composite for Open Testing (TACOT) in a wide range of conditions to assess the true range of validity of the thermal equilibrium hypothesis. Simulations are carried out on the Stardust and Mars Science Laboratory (MSL) atmospheric entries. The main design variables have been monitored and compared between the two models: temperature evolution and species concentration within the material, pyrolysis gas blowing rate, extension of the pyrolysis zone, and wall recession due to ablation. Results show that under chemical equilibrium conditions, no significant deviation in the monitored quantities are observed, while under chemical non-equilibrium conditions there is a large impact on the species concentration.

Colour scales with climate in North American ratsnakes: a test of the thermal melanism hypothesis using community science images.

Animal colour is a complex trait shaped by multiple selection pressures that can vary across geography. The thermal melanism hypothesis predicts that darker coloration is beneficial to animals in colder regions because it allows for more rapid solar absorption. Here, we use community science images of three closely related species of North American ratsnakes (genus Pantherophis) to examine if climate predicts colour variation across range-wide scales. We predicted that darker individuals are found in colder regions and higher elevations, in accordance with the thermal melanism hypothesis. Using an unprecedented dataset of over 8000 images, we found strong support for temperature as a key predictor of darker colour, supporting thermal melanism. We also found that elevation and precipitation are predictive of colour, but the direction and magnitude of these effects were more variable across species. Our study is the first to quantify colour variation in Pantherophis ratsnakes, highlighting the value of community science images for studying range-wide colour variation.

Mechanistic Thermal Modeling of Late Triassic Terrestrial Amniotes Predicts Biogeographic Distribution

The biogeography of terrestrial amniotes is controlled by historical contingency interacting with paleoclimate, morphology and physiological constraints to dispersal. Thermal tolerance is the intersection between organismal requirements and climate conditions which constrains modern organisms to specific locations and was likely a major control on ancient tetrapods. Here, we test the extent of controls exerted by thermal tolerance on the biogeography of 13 Late Triassic tetrapods using a mechanistic modeling program, Niche Mapper. This program accounts for heat and mass transfer into and out of organisms within microclimates. We model our 13 tetrapods in four different climates (cool and warm at low and high latitudes) using environmental conditions that are set using geochemical proxy-based general circulation models. Organismal conditions for the taxa are from proxy-based physiological values and phylogenetic bracketing. We find that thermal tolerances are a sufficient predictor for the latitudinal distribution of our 13 test taxa in the Late Triassic. Our modeled small mammaliamorph can persist at high latitudes with nocturnal activity and daytime burrowing but large pseudosuchians are excluded because they cannot seek nighttime shelter in burrows to retain elevated body temperatures. Our work demonstrates physiological modeling is useful for quantitative testing of the thermal exclusion hypothesis for tetrapods in deep time.

Environmental conditions and male quality traits simultaneously explain variation of multiple colour signals in male lizards.

Male lizards often display multiple pigment‐based and structural colour signals which may reflect various quality traits (e.g. performance, parasitism), with testosterone (T) often mediating these relationships. Furthermore, environmental conditions can explain colour signal variation by affecting processes such as signal efficacy, thermoregulation and camouflage. The relationships between colour signals, male quality traits and environmental factors have often been analysed in isolation, but simultaneous analyses are rare. Thus, the response of multiple colour signals to variation in all these factors in an integrative analysis remains to be investigated.Here, we investigated how multiple colour signals relate to their information content, examined the role of T as a potential mediator of these relationships and how environmental factors explain colour signal variation.We performed an integrative study to examine the covariation between three colour signals (melanin‐based black, carotenoid‐based yellow–orange and structural UV), physiological performance, parasitism, T levels and environmental factors (microclimate, forest cover) in male common lizards Zootoca vivipara from 13 populations.We found that the three colour signals conveyed information on different aspects of male condition, supporting a multiple message hypothesis. T influenced only parasitism, suggesting that T does not directly mediate the relationships between colour signals and their information content. Moreover, colour signals became more saturated in forested habitats, suggesting an adaptation to degraded light conditions, and became generally brighter in mesic conditions, in contradiction with the thermal melanism hypothesis.We show that distinct individual quality traits and environmental factors simultaneously explain variations of multiple colour signals with different production modes. Our study therefore highlights the complexity of colour signal evolution, involving various sets of selective pressures acting at the same time, but in different ways depending on colour production mechanism.

An Epistemic Analysis of Time Phenomenon

In this work we present an epistemic analysis of time phenomenon using the mathematical machinery of information theory and modular theory. By adopting limited commitment to the ontology of time evolution, and instead by mainly relying on the information that is in principle accessible to the observer, we find that the most primary aspect of the temporal experience, the perceived distinctiveness across the states of the world, emerges as a purely epistemic function. By analyzing the mathematical properties of this epistemic function, we interpret it to be in principle insensitive to any ontic state of the world, which leads to the conclusion that the observer is subject to temporal experience irrespective of whether the underlying state of the world is dynamical or invariant. On the ground of the presented analysis, we also provide a solution to the conceptual challenge of non-equilibrium phenomena that faces the thermal time hypothesis.

Microbial activity and temperature change affect growth of vesicular pores

Vesicular pores are observed in many different soil-forming environments. They can also be re-created in the lab through exposure to cyclic wetting and drying. However, little is known about the physical, chemical, and biological mechanisms involved in vesicular pore formation. This study was conducted to test the hypotheses that 1) microbial activity and 2) thermal expansion are important drivers of vesicular pore growth. These hypotheses were tested through laboratory experiments employing treatments to manipulate the biota (i.e., sterile, non-sterile, and glucose-amended treatments) and temperature change (i.e., wetting at 7 °C, 23 °C, and 40 °C before drying at 40 °C). The growth of vesicular pores, as well as vughs and planar voids, was compared among the treatments using bulk densities measured by three-dimensional laser scanning and pore analysis by computed tomography. Pore growth was found to be significantly greater in sterile soils compared to non-sterile and glucose-amended soils. Comparison among the temperature treatments showed the greatest pore growth in the samples that experienced the greatest temperature change between wetting and drying (7 °C to 40 °C). These results support the thermal expansion hypothesis of vesicular pore development, but contradict the microbial activity hypothesis.

Phenotypic plasticity in Acanthoscelides quadridentatus (Coleoptera: Chrysomelidae) and its effect on the seed fate of Mimosa setosa (Leguminosae: Mimosoideae)

In animals, changes in colour pigmentation in an intraspecific context are usually described as a polymorphism adaptive to environmental factors. According to the thermal melanism hypothesis (TMH), melanic individuals are more active because they may attain higher temperature and then benefit from higher size, foraging time and reproduction. The polymorphic seed-beetle Acanthoscelides quadridentatus (Coleoptera: Chrysomelidae) naturally attacks the seeds of two plant varieties, Mimosa setosa var. paludosa and M. setosa var. setosa, in the Brazilian savanna. The authors tested TMH in this system, predicting that melanic beetles would be larger, and infringe worst germination rate and higher seed mortality. Additionally, they tested whether seed weight plays a role in germination. The authors found two beetle morphs: a melanic/1.1-fold larger and another lighter/smaller. Seeds of M. setosa var. setosa are 1.9-fold heavier and its intact seeds germinate faster and with a higher amount than the seeds of M. setosa var. paludosa. There is no difference in the attack rate by beetle morphs. The attacked seeds of both plant varieties did not germinate. The authors evidence phenotypic plasticity in A. quadridentatus, highlighting that TMH is confirmed for the relationship between melanism and larger sizes, although there was no difference in foraging of melanic individuals. This study shed light on the importance of plant varieties in driving the morphology of seed-beetles.

Climatic conditions and prevalence of melanistic snakes-contrasting effects of warm springs and mild winters.

Climate change is one of the greatest challenges that wildlife is facing. Rapid shifts in climatic conditions may accelerate evolutionary changes in populations as a result of strong selective pressure. Most studies focus on the impact of climatic conditions on phenologies and annual cycles, whereas there are fewer reports of empirical support for climate-driven changes in the phenotypic variability of free-living populations. We investigated whether climatic variables explain the prevalence of colour polymorphism in a population of the grass snake (Natrix natrix) with two morphotypes, the melanistic and non-melanistic ones, in the period 1981-2013. We found that the prevalence of the black phenotype was negatively related to spring temperature and winter harshness, expressed as the number of snow days. According to the thermal melanism hypothesis, a high predation rate during warmer springs may override relaxed thermal benefits and vice versa, i.e. black individuals may perform better than typical ones when thermal conditions in spring are unfavourable. In turn, because they are smaller, melanistic individuals may be exposed to a higher risk of winter mortality, particularly during longer winters. We highlight the need for more studies on the effects of climatic conditions on temporal variation in melanism prevalence in other populations and species as well as in various geographic regions.

Does the thermal mismatch hypothesis predict disease outcomes in different morphs of a terrestrial salamander?

Many aspects of ectotherm physiology are temperature-dependent. The immune system of temperate-dwelling ectothermic host species is no exception and their immune function is often downregulated in cold temperatures. Likewise, species of ectothermic pathogens experience temperature-mediated effects on rates of transmission and/or virulence. Although seemingly straightforward, predicting the outcomes of ectothermic host-pathogen interactions is quite challenging. A recent hypothesis termed the thermal mismatch hypothesis posits that cool-adapted host species should be most susceptible to pathogen infection during warm temperature periods whereas warm-adapted host species should be most susceptible to pathogens during periods of cool temperatures. We explore this hypothesis using two ecologically and physiologically differentiated color morphs of the Eastern Red-backed Salamander (Plethodon cinereus) and a pathogenic chytrid fungus (Batrachochytrium dendrobatidis; hereafter "Bd") using a fully factorial laboratory experiment. At cool temperatures, unstriped salamanders (i.e., those that are tolerant of warm temperatures) had a significantly higher probability of Bd infection compared with cool-tolerant striped salamanders, consistent with the thermal mismatch hypothesis. However, we found no support for this hypothesis when salamanders were exposed to Bd at warm temperatures: the probability of Bd infection in the cool-tolerant striped salamanders was nearly identical in both cool and warm temperatures, opposite the predictions of the thermal mismatch hypothesis. Our results are most consistent with the fact that Bd grows poorly at warm temperatures. Alternatively, our data could indicate that the two color morphs do not differ in their tolerance to warm temperatures but that striped salamanders are more tolerant to cool temperatures than unstriped salamanders.

Ecogeographical patterns in owl plumage colouration: Climate and vegetation cover predict global colour variation

AbstractAimEcogeographical rules link animal colours, especially those produced by melanin pigments, with variation in environmental conditions over wide geographical scales. In particular, Gloger’s rule, coined for endothermic animals in two versions, suggests that tegument darkness should increase at high temperature, as well as in highly humid environments. On the other hand, the thermal melanism hypothesis predicts that darker colourations should be more frequent in colder areas given their thermoregulation benefits.LocationGlobal.Time periodContemporary.Major taxa studiedStrigiformes.MethodsHere, we provide a global comparative test of these contrasting expectations in all extant owls (n = 198 species), a group of nocturnal birds displaying huge variability in the degree of melanin‐based plumage colouration and environmental specialization. Combining analyses at both species and assemblage level, we assessed the climatic and environmental variables explaining variation in plumage lightness and redness across broad geographical gradients.ResultsDarker and redder owl phenotypes are more likely found near the equator. Species and assemblage level analyses reveal that owls have more frequently darker and redder plumages in warmer regions. In addition, owl species living in more vegetated areas are darker, and owl assemblages show darker colours in wetter areas.Main conclusionsGlobal patterns of colour variation in owls do not fit expectations from the thermal melanism hypothesis but support Gloger’s rule. Our findings also stress that several alternative selective forces may explain climatic effects on colouration over large geographical scales. Experimental work is urged to uncover the possible mechanisms behind the detected associations between owl colour and environmental variables.

Nine years of experimental warming did not influence the thermal sensitivity of metabolic rate in the medaka fish Oryzias latipes

Abstract A pressing challenge is to determine whether and how global‐change drivers influence species physiology and survival. Recently, researchers have proposed the metabolic theory of ecology, defending the hypothesis of a universal thermal dependence of metabolic rate or, alternatively, the metabolic cold adaptation theory, stating that local adaptation can influence the thermal sensitivity of metabolic rate. However, the long‐term (i.e. multigenerational) consequences of warming for the thermal sensitivity of metabolic rate remain largely unexplored although it determines energy use and is crucial for species response to climate change. In this study, we used an evolutionary experiment with medaka fishes Oryzias latipes maintained for more than 12 generations at warm and cold temperatures (30 and 20°C, respectively) to address this issue. Our objective was to investigate whether thermal adaptation influences the relationship between temperature and mass‐corrected metabolic rate and how this may occur. In agreement with the universal thermal dependence hypothesis, we found that warming did not significantly influence the thermal sensitivity of mass‐corrected metabolic rate: neither the intercept nor the slope of the temperature–metabolic rate relationship differed among fish lineages. Our small‐scale laboratory experiment thus indicated that there is limited potential for evolutionary change in medaka fish metabolic rate in response to warmer temperatures. Overall, we provide evidence that 9 years of experimental warming did not influence the thermal sensitivity of metabolic rate. Our results highlight the invariability of the thermal dependence of metabolic rate, which has important implications for adaptation to climate warming. This finding suggests a limited potential for metabolic adaptations in response to long‐term temperature changes, which may have negative consequences for the persistence of fish populations under climate change.

Disentangling drivers of thermal physiology: Community‐wide cold shock recovery of butterflies under natural conditions

AbstractPhysiological strategies of terrestrial ectotherms are a delicate interplay between species’ traits and their physical environment. Several theories and overarching hypotheses seek to explain strategies related to thermal physiology with respect to organisms and their environments. However, most of these have been investigated under controlled laboratory conditions with lab‐reared or otherwise acclimated individuals, removing the effect of environmental acclimation. This study examines an in‐situ physiological trait, cold shock recovery, across butterfly communities of the Colombian Andes from different environments, elevations, and ambient conditions. We explored four non‐mutually exclusive hypotheses—1) intrinsic (species) traits dictate response hypothesis; 2) extrinsic (environmental) traits dictate response hypothesis; 3) climate variability hypothesis; 4) thermal melanism hypothesis—to explain cold shock recovery of wild‐caught butterflies from high (1800 m.a.s.l) and low (600 m.a.s.l.) elevations in two habitat types (open and closed canopy). Cold shock recovery was measured as the time following a cold shock to full recovery, that is, flight. Ambient conditions and the thermal melanism hypothesis, which posits an interaction between pigmentation and solar intensity, best explained cold‐shock recovery. Higher temperatures and light exposure reduced recovery time. Dark butterflies under high solar intensity recovered from cold shock faster than light butterflies or those under low solar intensity regardless of species identity, morphology, or habitat characteristics. These results highlight the importance of ambient conditions and the interaction between pigmentation of tropical ectotherms and their physical thermal environments, patterns that may render populations vulnerable to the thermal impacts of climate change and development.Abstract in Spanish is available with online material.