Thermal Ecology Research Articles

Flexible simulation of animal thermoregulatory behavior in three-dimensional synthetic environments from thermal and optical images

Several animals have low metabolism and show body temperatures that are in accordance with environmental temperatures. The relationship between environmental temperature and body temperature is influenced by body size and behavior, in which that some animals accept thermal variation whereas others regulate temperature through behavior. Three-dimensional (3D) environments based on thermal imaging represent a solid tool to elucidate this thermoregulatory behavior to help understand important topics in thermal ecology such as estimating cost of thermoregulation under realistic field conditions, as well as compute the risk of overheating and thermal damage under different ecological scenarios. Although in some studies the proposed models simulate thermoregulation, the connection between thermal and optical image is not explored. This junction can offer a more useful 3D visualization, where topological structures of the landscape can be observed together with thermal information. In this article we present a computational system that is not only capable of generating 3D models by using both thermal and optical images, but is also capable of simulating the thermoregulation behaviors of several animals by means of parameter adjustments made by the user. Our system was analyzed by 22 experts in the biology area – most of them with teaching experience –, who answered objective questions based on their knowledge about the topic, as well as questions about their perception on the simulation provided by our proposal. We used a technology acceptance questionnaire and asked for their contributions through their suggestions. The objective questions reached a hit rate of 68%, which suggests that is relatively easy to use the environment, providing clear comprehension about the simulation, although there is the possibility for improvements. We also found that the hit rate is not related to the experts' level of experience nor with the volunteers' familiarity with 3D environments. Also, 95% of the volunteers indicate a high degree of perceived usefulness, suggesting a potential for using our proposal in teaching and research activities.

How seasonality influences the thermal biology of lizards with different thermoregulatory strategies: a meta-analysis.

Ectotherms that maintain thermal balance in the face of varying climates should be able to colonise a wide range of habitats. In lizards, thermoregulation usually appears as a variety of behaviours that buffer external influences over physiology. Basking species rely on solar radiation to raise body temperatures and usually show high thermoregulatory precision. By contrast, species that do not bask are often constrained by climatic conditions in their habitats, thus having lower thermoregulatory precision. While much focus has been given to the effects of mean habitat temperatures, relatively less is known about how seasonality affects the thermal biology of lizards on a macroecological scale. Considering the current climate crisis, assessing how lizards cope with temporal variations in environmental temperature is essential to understand better how these organisms will fare under climate change. Activity body temperatures (Tb ) represent the internal temperature of an animal measured in nature during its active period (i.e. realised thermal niche), and preferred body temperatures (Tpref ) are those selected by an animal in a laboratory thermal gradient that lacks thermoregulatory costs (i.e. fundamental thermal niche). Both traits form the bulk of thermal ecology research and are often studied in the context of seasonality. In this study, we used a meta-analysis to test how environmental temperature seasonality influences the seasonal variation in the Tb and Tpref of lizards that differ in thermoregulatory strategy (basking versus non-basking). Based on 333 effect sizes from 137 species, we found that Tb varied over a greater magnitude than Tpref across seasons. Variations in Tb were not influenced by environmental temperature seasonality; however, body size and thermoregulatory strategy mediated Tb responses. Specifically, larger species were subjected to greater seasonal variations in Tb , and basking species endured greater seasonal variations in Tb compared to non-basking species. On the other hand, the seasonal variation in Tpref increased with environmental temperature seasonality regardless of body size. Thermoregulatory strategy also influenced Tpref , suggesting that behaviour has an important role in mediating Tpref responses to seasonal variations in the thermal landscape. After controlling for phylogenetic effects, we showed that Tb and Tpref varied significantly across lizard families. Taken together, our results support the notion that the relationship between thermal biology responses and climatic parameters can be taxon and trait dependent. Our results also showcase the importance of considering ecological and behavioural aspects in macroecological studies. We further highlight current systematic, geographical, and knowledge gaps in thermal ecology research. Our work should benefit those who aim to understand more fully how seasonality shapes thermal biology in lizards, ultimately contributing to the goal of elucidating the evolution of temperature-sensitive traits in ectotherms.

A neurophysiological limit and its biogeographic correlations: Cold-induced spreading depolarization in tropical butterflies.

The physiology of insects is directly influenced by environmental temperature, and thermal tolerance is therefore intrinsically linked to their thermal niche and distribution. Understanding the mechanisms that limit insect thermal tolerance is crucial to predicting biogeography and range shifts. Recent studies on locusts and flies suggest that the critical thermal minimum (CTmin) follows from a loss of CNS function via a spreading depolarization. We hypothesized that other insect taxa share this phenomenon. Here we investigate whether spreading depolarization events occur in butterflies exposed to cold. Supporting our hypothesis, we find that exposure to stressful cold induced spreading depolarization in all 12 species tested. This reinforces the idea that spreading depolarization is a common mechanism underlying the insect CTmin. Furthermore, our results highlight how CNS function is tuned to match species' environments. Further research into the physiology underlying spreading depolarization will likely elucidate key mechanisms determining insect thermal tolerance and ecology.

Functional responses in a lizard along a 3.5‐km altitudinal gradient

AbstractAimPhysiological and metabolic performance are key mediators of the functional response of species to environmental change. Few environments offer such a multifaceted array of stressors as high‐altitude habitats, which differ markedly in temperature, water availability, UV radiation and oxygen pressure compared to low‐altitude habitats. Species that inhabit large altitudinal gradients are thus excellent models to study how organisms respond to environmental variation.LocationTenerife island, Canary Islands archipelago (Spain).TaxonTenerife lizard (Gallotia galloti, Lacertidae).MethodsWe integrated data on age structure, thermal and hydric regulatory behaviour and four metabolic and stress‐related biomarkers for an insular lizard that inhabits an extreme altitudinal range (sea level to 3700 m a.s.l.), to understand how an ectotherms' age, ecophysiology and metabolism can be affected by extreme environmental variation.ResultsWe found marked differences in metabolic stress markers associated with altitude (particularly in the abundance of carbonyl metabolites and relative telomere length), but without a linear pattern along the altitudinal cline. Contrary to expectations, longer telomeres and lower carbonyl content were detected at the highest altitude, suggesting reduced stress in these populations. Evaporative water loss differed between populations but did not follow a linear altitudinal gradient. Lizard age structure or thermal physiological performance did not markedly change across different altitudes. Mixed signals in life‐history and thermal ecology across populations and altitude suggest complex responses to variable conditions across altitude in this species.Main ConclusionsOur integrative study of multiple functional traits demonstrated that adaptation to highly divergent environmental conditions in this lizard is potentially linked to an interplay between plasticity and local adaptation variably associated with different functional traits.

Living in the mountains: Thermal ecology and freezing tolerance of the lizard Abronia taeniata (Squamata: Anguidae)

The impact of daily and seasonal variation in environmental temperature on lizards is important, since their physiological processes are body temperature dependent. Lizards that occupy mountainous areas must have been favoured to colonize such habitats through selection on thermal biology traits to thermoregulate effectively. Moreover, mountain lizards may be able to maintain their activity near their minimum critical temperature and even have antifreeze mechanisms. Tolerance of freezing is related to the biosynthesis of cryoprotective molecules, such as glucose, whose concentration may increase after freezing. The aims of the present work were: (1) study the thermoregulation of the viviparous lizard Abronia taeniata, and (2) determine its survival and/or tolerance to freezing. This species occurs in pine forests, pine-oak forests, and mountain mesophilic forests in areas that reach freezing temperatures. In the field, we recorded air, substrate, and body temperatures at capture time of the lizards, and registered operative temperatures at the study area. In the laboratory, we determined thermal preferences, crystallization point, and blood glucose levels of individuals before and after freezing. We found out that A. taeniata sustains activity in a wide range of temperatures, actively avoids thermally favourable microhabitats in spring, and is a moderate thermoregulator during autumn and winter. In A. taeniata, the body temperatures are tightly linked to air and substrate temperatures. Seasonality had an effect over body temperature, preferred temperatures and thermoregulatory effectiveness indices. When exposed to temperatures below zero, A. taeniata showed an increase in blood glucose levels, which aided them in surviving freezing. Taken together, our results suggest that A. taeniata may sustain activity at low environmental temperatures, due to an effective behavioural thermoregulation, and in case temperatures of its habitat go below zero, is also capable of tolerate freezing.

Assessing thermal ecology of herpetofauna across a heterogeneous microhabitat mosaic in a changing aridland riparian system

Species–environmental relationships, including drivers of body temperature (T B), are important for understanding thermal ecology and physiological needs of species during climate change. This is especially important among ectotherms, including amphibians and reptiles (i.e., herpetofauna), in aridland riparian systems. Infrared thermography (IRT) can reliably and noninvasively estimate T B of ectothermic herpetofauna while simultaneously assessing thermal heterogeneity across a mosaic of microhabitats. We used IRT at a semi-arid riparian zone in Tucson, Arizona to assess herpetofauna–environmental relationships during early-season activity periods in 2020 and 2022. From mixed-effect modeling of desert riparian herpetofauna (n = 81), we found complex environmental relationships influencing T B. Microhabitat perch surface temperature (T S) best explained T B; many ambient conditions were inadequate at capturing T B. Herpetofauna were as warm by mid-morning than in the early afternoon, with T B approaching equilibrium with T S as mornings progressed. Less T B–T S variation was detected for anurans (e.g., canyon treefrogs, Hyla arenicolor) than with lizards, supporting that desert amphibians are sensitive to the thermal landscape. There was also complex environmental variation among thermally heterogeneous microhabitats used and available to herpetofauna. As perch T S increased, shade became more important, though shade sources may be less relevant. The methods and data obtained in this study can serve to establish baselines during seasonally and ecologically important periods and be used to monitor thermal ecology changes across time for herpetofauna or taxa with similar life history in aridland riparian systems. Although ectotherm thermoregulatory functions are undeniably complex, we recommend IRT as a rapid, noninvasive, and complementary tool to monitor cryptic thermal ecology in heterogeneous systems. Understanding species–environmental relationships and monitoring responses of wildlife across time can help guide more effective biodiversity conservation management strategies in a warming and drying world.

Mutualisms in a warming world.

Predicting the impacts of global warming on mutualisms poses a significant challenge given the functional and life history differences that usually exist among interacting species. However, this is a critical endeavour since virtually all species on Earth depend on other species for survival and/or reproduction. The field of thermal ecology can provide physiological and mechanistic insights, as well as quantitative tools, for addressing this challenge. Here, we develop a conceptual and quantitative framework that connects thermal physiology to species' traits, species' traits to interacting mutualists' traits and interacting traits to the mutualism. We first identify the functioning of reciprocal mutualism-relevant traits in diverse systems as the key temperature-dependent mechanisms driving the interaction. We then develop metrics that measure the thermal performance of interacting mutualists' traits and that approximate the thermal performance of the mutualism itself. This integrated approach allows us to additionally examine how warming might interact with resource/nutrient availability and affect mutualistic species' associations across space and time. We offer this framework as a synthesis of convergent and critical issues in mutualism science in a changing world, and as a baseline to which other ecological complexities and scales might be added.

Thermal mismatches explain consumer-resource dynamics in response to environmental warming.

Changing temperatures will impact food webs in ways we yet to fully understand. The thermal sensitivities of various physiological and ecological processes differ across organisms and study systems, hindering the generation of accurate predictions. One step towards improving this picture is to acquire a mechanistic understanding of how temperature change impacts trophic interactions before we can scale these insights up to food webs and ecosystems. Here, we implement a mechanistic approach centered on the thermal sensitivity of energetic balances in pairwise consumer-resource interactions, measuring the thermal dependence of energetic gain and loss for two resource and one consumer freshwater species. Quantifying the balance between energy gain and loss, we determined the temperature ranges where the balance decreased for each species in isolation (intraspecific thermal mismatch) and where a mismatch in the balance between consumer and resource species emerged (interspecific thermal mismatch). The latter reveals the temperatures for which consumer and resource energetic balances respond either differently or in the same way, which in turn informs us of the strength of top-down control. We found that warming improved the energetic balance for both resources, but reduces it for the consumer, due to the stronger thermal sensitivity of respiration compared to ingestion. The interspecific thermal mismatch yielded different patterns between the two consumer-resource pairs. In one case, the consumer-resource energetic balance became weaker throughout the temperature gradient, and in the other case it produced a U-shaped response. By also measuring interaction strength for these interaction pairs, we demonstrated the correspondence of interspecific thermal mismatches and interaction strength. Our approach accounts for the energetic traits of both consumer and resource species, which combined produce a good indication of the thermal sensitivity of interaction strength. Thus, this novel approach links thermal ecology with parameters typically explored in food-web studies.

Developed black beaches - too hot to emerge? Factors affecting sand temperatures at nesting grounds of olive ridley sea turtles (Lepidochelys olivacea)

Climate change research on sea turtles has focused on the impact of rising temperatures on sex ratios, while the thermal ecology of natural nesting grounds has received less attention. Many nesting beaches are highly affected by vegetation loss and urbanization which in turn may affect their thermal profile, particularly at beaches with dark volcanic sand. We studied the sand temperatures on two urban-developed volcanic sea turtle nesting beaches in Guatemala for two years, and their potential effect on the thermal ecology of sea turtle nests by using the olive ridley as model species. We hypothesized that local weather, type of cover at surface, and season (dry vs rainy) will have a pronounced effect on sand temperatures, potentially affecting the hatching success of sea turtles. Average sand temperatures at nesting beaches were almost always above the pivotal temperature (87% of days), and either close to or above the thermal maximum tolerance of sea turtle embryos over longer periods (78% of days). We found that higher air temperatures led to higher sand temperatures, and high relative humidity and precipitation led to lower sand temperatures. As expected, sand temperatures in plots covered by vegetation were lower (32.5 ± 2.8°C) than those without vegetation cover (33.1 ± 2.6°C). Plots close to concrete structures showed the highest sand temperatures (34.0 ± 3.2°C). Our results highlight the relevance of vegetation in buffering the effects of high sand temperatures, which will have profound implications for the resilience of olive ridleys to global warming.

The time course of acclimation of critical thermal maxima is modulated by the magnitude of temperature change and thermal daily fluctuations

Plasticity in the critical thermal maximum (CTmax) helps ectotherms survive in variable thermal conditions. Yet, little is known about the environmental mechanisms modulating its time course. We used the larvae of three neotropical anurans (Boana platanera, Engystomops pustulosus and Rhinella horribilis) to test whether the magnitude of temperature changes and the existence of fluctuations in the thermal environment affected both the amount of change in CTmax and its acclimation rate (i.e., its time course). For that, we transferred tadpoles from a pre-treatment temperature (23 °C, constant) to two different water temperatures: mean (28 °C) and hot (33 °C), crossed with constant and daily fluctuating thermal regimes, and recorded CTmax values, daily during six days. We modeled changes in CTmax as an asymptotic function of time, temperature, and the daily thermal fluctuation. The fitted function provided the asymptotic CTmax value (CTmax∞) and CTmax acclimation rate (k). Tadpoles achieved their CTmax∞ between one and three days. Transferring tadpoles to the hot treatment generated higher CTmax∞ at earlier times, inducing faster acclimation rates in tadpoles. In contrast, thermal fluctuations equally led to higher CTmax∞ values but tadpoles required longer times to achieve CTmax∞ (i.e., slower acclimation rates). These thermal treatments interacted differently with the studied species. In general, the thermal generalist Rhinella horribilis showed the most plastic acclimation rates whereas the ephemeral-pond breeder Engystomops pustulosus, more exposed to heat peaks during larval development, showed less plastic (i.e., canalized) acclimation rates. Further comparative studies of the time course of CTmax acclimation should help to disentangle the complex interplay between the thermal environment and species ecology, to understand how tadpoles acclimate to heat stress.

Automated observation of physical snowpack properties in Ny-Ålesund

The snow season in the Svalbard archipelago generally lasts 6–10 months a year and significantly impacts the regional climate, glaciers mass balance, permafrost thermal regime and ecology. Due to the lack of long-term continuous snowpack physical data, it is still challenging for the numerical snow physics models to simulate multi-layer snowpack evolution, especially for remote Arctic areas. To fill this gap, in November 2020, an automated nivometric station (ANS) was installed ∼1 km Southwest from the settlement of Ny-Ålesund (Spitzbergen, Svalbard), in a flat area over the lowland tundra. It automatically provides continuous snow data, including NIR images of the fractional snow-cover area (fSCA), snow depth (SD), internal snow temperature and liquid water content (LWC) profiles at different depths with a 10 min time resolution. Here we present the first-year record of automatic snow preliminary measurements collected between November 2020 and July 2021 together with weekly manual observations for comparison. The snow season at the ANS site lasted for 225 days with an annual net accumulation of 117 cm (392 mm of water equivalent). The LWC in the snowpack was generally low (<4%) during wintertime, nevertheless, we observed three snow-melting events between November and February 2021 and one in June 2021, connected with positive temperature and rain on snow events (ROS). In view of the foreseen future developments, the ANS is the first automated, comprehensive snowpack monitoring system in Ny-Ålesund measuring key essential climate variables needed to understand the seasonal evolution of the snow cover on land.

Effects of Prairie Degradation and Restoration on Box Turtle Thermal Ecology

Prairie habitat loss in the United States has led to population declines in many prairie-associated species, including Ornate Box Turtles (Terrapene ornata). Northwest Arkansas is an intergrade zone between the prairie-dwelling T. ornata and the more forest-associated Three-Toed Box Turtle (Terrapene carolina). As such, limited information exists on the potential differences in physiology and thermal ecology between the two box turtle species and how those differences might influence their habitat use. We addressed gaps in our knowledge of the thermal and spatial ecology of T. ornata and T. carolina with a three-part study. First, we compared the thermal profiles of refugia, open, and vegetated microhabitats across degraded prairie, restored prairie, and adjacent forest macrohabitats using operative temperature models and a linear mixed effect model. Second, we measured total evaporative water loss of both species across a range of body sizes. Finally, we fitted a subset of turtles with iButton data loggers and monitored them in the field to examine carapace temperatures and habitat use. Operative temperature models recorded high, largely homogeneous temperatures across microhabitats in degraded prairie and heterogeneous temperatures across restored prairie microhabitats, while forest habitat maintained stable, cool temperatures. Both species exhibited similar evaporative water loss rates; however, T. ornata experienced a broader range of temperatures in the field. Terrapene ornata were exclusively found in prairie habitat, whereas T. carolina was often found in forested habitats and subsurface refugia. Our results demonstrate key differences in box turtle thermal biology and highlight suboptimal thermal characteristics in degraded prairie and forest habitat that should be considered in prairie restoration and management for T. ornata conservation.

Cool‐Blooded Bees for Cool‐Weather Flowers

Photo 1. The Sierra de Cazorla mountains in southeastern Spain, where the study was carried out. The area is characterized by rugged topography, high habitat and species diversity, and outstanding degree of preservation of natural vegetation. Photo credit: Carlos M. Herrera. Photo 2. As in many other mountain areas from mid-latitudes of the Holarctic realm, the flowering season in plant communities of the Sierra de Cazorla starts well before the end of winter, when ambient temperatures are still cool even in the clearest, sunniest days. Some plants living at high elevations, as the daffodil Narcissus longispathus (Amaryllidaceae) shown in the picture, sometimes have to face the latest snowfalls of the winter while already bearing open flowers. Photo credit: Carlos M. Herrera. Photo 3. A sampler of early-blooming plants from the Sierra de Cazorla area having mining bees of the genus Andrena as their main pollinators. Clockwise from the top left (percentage of bee pollinators contributed by species of Andrena shown in parentheses): Iberis carnosa (Brassicaceae, 100%); Hepatica nobilis (Ranunculaceae, 80%); Crocus nevadensis (Iridaceae, 79%); Draba hispanica (Brassicaceae, 71%); Narcissus hedraeanthus (Amaryllidaceae, 67%); and Fritillaria lusitanica (Liliaceae, 63%). Photo credit: Carlos M. Herrera. Photo 4. The genus Andrena is the second largest genus of bees, with ~1,600 described species worldwide. They pollinate many wild plants in boreal and temperate habitats of Eurasia and North America, particularly species flowering in winter and early spring. Out of the nearly 100 Andrena species recorded to date from the Sierra de Cazorla region, 30 were included in our study on their thermal ecology. Some of these are featured in these pictures. Clockwise from the top left: Andrena baetica (on Ornithogalum umbellatum, Asparagaceae); Andrena bicolor (on Primula acaulis, Primulaceae); Andrena congruens (on Eryngium campestre, Apiaceae); Andrena fulva (on Rosmarinus officinalis, Lamiaceae); Andrena lagopus (on Diplotaxis catholica, Brassicaceae); Andrena nigroaenea (on Erodium cheilanthifolium, Geraniaceae); Andrena sardoa (on Asphodelus cerasiferus, Xanthorrhoeaceae); and Andrena trimmerana (on Berberis hispanica, Berberidaceae). Photo credit: Carlos M. Herrera. These photographs illustrate the article “Seasonality of pollinators in Mediterranean montane habitats: cool-blooded bees for early-blooming plants” by Carlos M. Herrera, Alejandro Núñez, Luis O. Aguado and Conchita Alonso published in Ecological Monographs. https://doi.org/10.1002/ecm.1570

Some considerations of measuring temperature sensitivity in thermal ecology

Some considerations of measuring temperature sensitivity in thermal ecology

How to generate accurate continuous thermal regimes from sparse but regular temperature measurements

Abstract In ecology, there is an emerging emphasis on the importance of capturing temperature variation at relevant scales. Temperature fluctuates continuously in nature but is sampled at discrete time points, so how often should ecologists measure temperature to capture its variation? A recent development in thermal ecology is the use of spectral analysis of temperature time series to determine at what frequencies important temperature fluctuations occur. Building on this, I borrow from signal processing theory to show how continuous thermal regimes can be effectively reconstructed from discrete, regular, measurements, and provide a rule of thumb for designing temperature sampling schemes that capture ecologically relevant temporal variation. I introduce sinc interpolation, a method for reconstructing continuous waveforms from discrete samples. Furthermore, I introduce the Nyquist–Shannon sampling theorem, which states that continuous complex waveforms can be perfectly sinc‐interpolated from discrete, regular, samples if sampling intervals are sufficiently short. To demonstrate the power of these concepts in an ecological context, I apply them to several published high‐resolved (15‐min intervals) temperature time series used for ecological predictions of insect development times. First, I use spectral analysis to illuminate the fluctuation frequencies that dominate the temperature data. Second, I employ sinc interpolation over artificially thinned versions of the temperature time series. Third, I compare interpolated temperatures with observed temperatures to demonstrate the Nyquist–Shannon sampling theorem and its relation to spectral analysis. Last, I repeat the ecological predictions using sinc‐interpolated temperatures. Daily, and less frequent, fluctuations dominated the variation in all the temperature time series. Therefore, in accordance with the Nyquist–Shannon sampling theorem, 11‐h measurement intervals consistently retrieved most 15‐min temperature variation. Moreover, previous predictions of insect development times were improved by using sinc‐interpolated, rather than averaged, temperatures. By identifying the highest frequency at which ecologically (or otherwise) relevant temperature fluctuations occur and applying the Nyquist–Shannon sampling theorem, ecologists (or others doing climate‐related research) can use sinc interpolation to produce remarkably accurate continuous thermal regimes from sparse but regular temperature measurements. Surprisingly, these concepts have remained largely unexplored in ecology despite their applicability, not least in thermal ecology.

Initial insights on the thermal ecology of lake whitefish in northwestern Lake Michigan

Lake whitefish Coregonus clupeaformisare a native coldwater species supporting important recreational and commercial fisheries in the Laurentian Great Lakes. Climate-related changes in water temperature may have important implications for the future sustainability of these fisheries. However, projecting future habitat availability is difficult because limited information is available on lake whitefish thermal ecology in the region. In this study, archival temperature loggers were implanted into 400 lake whitefish from northwestern Lake Michigan, including Green Bay, during October–November 2017. Loggers recorded temperature for 11 months at 4-hr intervals. Thirteen recovered temperature loggers were used in analyses. In winter (1 December–31 March), temperatures occupied by lake whitefish ranged from 0 to 8.0 °C, while in spring (1 April–31 May) temperatures ranged from 0 to 20.0 °C. In summer (1 June–15 September) and fall (16 September–7 November), lake whitefish occupied temperatures of 4–21.5 and 4–21.0 °C, respectively. Average temperatures in summer (10.8 °C) were within the previously proposed optimal temperature range (10–14 °C) and broad thermal niche (7–17 °C); however, 58% of observations were outside the optimal temperature range and 11% of observations were outside the broad thermal niche. Our results suggest that lake whitefish from northwestern Lake Michigan inhabit temperatures both above and below previously reported expected temperature ranges. This study provides initial insights on lake whitefish thermal ecology in Lake Michigan and can be used as a baseline for future work aimed at determining how lake whitefish habitat availability may change in the future.

Disturbance of primary producer communities disrupts the thermal limits of the associated aquatic fauna

Environmental fluctuation forms a framework of variability within which species have evolved. Environmental fluctuation includes predictability, such as diel cycles of aquatic oxygen fluctuation driven by primary producers. Oxygen availability and fluctuation shape the physiological responses of aquatic animals to warming, so that, in theory, oxygen fluctuation could influence their thermal ecology. We describe annual oxygen variability in agricultural drainage channels and show that disruption of oxygen fluctuation through dredging of plants reduces the thermal tolerance of freshwater animals. We compared the temperature responses of snails, amphipods, leeches and mussels exposed to either natural oxygen fluctuation or constant oxygen in situ under different acclimation periods. Oxygen saturation in channel water ranged from c. 0 % saturation at night to >300 % during the day. Temperature showed normal seasonal variation and was almost synchronous with daily oxygen fluctuation. A dredging event in 2020 dramatically reduced dissolved oxygen variability and the correlation between oxygen and temperature was lost. The tolerance of invertebrates to thermal stress was significantly lower when natural fluctuation in oxygen availability was reduced and decoupled from temperature. This highlights the importance of natural cycles of variability and the need to include finer scale effects, including indirect biological effects, in modelling the ecosystem-level consequences of climate change. Furthermore, restoration and management of primary producers in aquatic habitats could be important to improve the thermal protection of aquatic invertebrates and their resistance to environmental variation imposed by climate change.

Seasonal and elevational variation in thermal ecology of the crevice-dwelling knob-scaled lizard Xenosaurus fractus from central-eastern Mexico

There is strong covariation between the thermal physiology of ectothermic animals and their thermal environment. Spatial and temporal differences in the thermal environment across a species' range may result in changes in thermal preferences between populations of that species. Alternatively, thermoregulatory-based microhabitat selection can allow individuals to maintain similar body temperatures across a broad thermal gradient. Which strategy a species adopts is often dependent on taxon-specific levels of physiological conservatism or ecological context. Identifying which strategies species use in response to spatial and temporal variation in environmental temperatures requires empirical evidence, which then can support predictions as to how a species might respond to a changing climate. Here we present findings of our analyses of the thermal quality, thermoregulatory accuracy and efficiency for the lizard, Xenosaurus fractus, across an elevation-thermal gradient and over the temporal thermal variation associated with seasonal changes. Xenosaurus fractus is a strict crevice-dweller, a habitat that can buffer this lizard from extreme temperatures and is a thermal conformer (body temperatures reflect air and substrate temperatures). We found populations of this species differed in their thermal preferences along an elevation gradient and between seasons. Specifically, we found that habitat thermal quality, thermoregulatory accuracy and efficiency (all measures of how well the lizards' body temperatures compared to their preferred body temperatures) varied along thermal gradients and with season. Our findings indicate that this species has adapted to local conditions and shows seasonal flexibility in those spatial adaptations. Along with their strict crevice-dwelling habitat, these adaptations may provide some protection against a warming climate.

Dry-season variability in near-surface temperature measurements and landsat-based land surface temperature in Kenyatta University, Kenya

Understanding thermal gradients is essential for sustainability of built-up ecosystems, biodiversity conservation, and human health. Urbanized environments in the tropics have received little attention on underlying factors and processes governing thermal variability as compared to temperate environments, despite the worsening heat stress exposure from global warming. This study characterized near surface air temperature (NST) and land surface temperature (LST) profiles across Kenyatta University, main campus, located in the peri-urban using in situ traverse temperature measurements and satellite remote sensing methods respectively. The study sought to; (i) find out if the use of fixed and mobile temperature sensors in time-synchronized in situ traverses can yield statistically significant temperature gradients (ΔT) attributable to landscape features, (ii) find out how time of the day influences NST gradients, (iii) determine how NST clusters compare to LST values derived from analysis of ‘cloud-free’ Landsat 8 OLI (Operational Land Imager) satellite image, and (iv) determine how NST and LST values are related to biophysical properties of land cover features.. The Getis–Ord Gi* statistics of ΔT values indicate statistically significant clustering hot and cold spots, especially in the afternoon (3–5 PM). NST ‘hot spots’ and ‘cold spots’ coincide with hot and cold regions of Landsat-based LST map. Ordinary Least Square Regression (OLS) indicate statistically significant (p < 0.01) coefficients of MNDWI and NDBI explaining 15% of ΔT variation, and albedo, MNDWI, and NDBI explaining 46% of the variations in LST patterns. These findings demonstrate that under clear sky, late afternoon walking traverses records spatial variability in NST within tropical peri-urban environments during dry season. This study approach may be enhanced through collecting biophysical attributes and NST records simultaneously to improve reliability of regression models for urban thermal ecology.

Thermal tolerance of western corn rootworm: Critical thermal limits, knock-down resistance, and chill coma recovery

Western corn rootworm, Diabrotica virgifera virgifera, is one of the most economically important crop pests in the world with estimates of damage and control approximating over $1 billion USD annually. Despite an abundance of research devoted to studying rootworm biology in the central Corn Belt of the United States, key aspects on their thermal ecology are still lacking. Here we address this knowledge gap by measuring critical thermal limits, knock-down resistance, and chill coma recovery. In doing so, we also address methodological questions surrounding measurements of thermal tolerance using a variety of dynamic and static assays. The average critical thermal maxima across all trials was 43.0 °C, while the average critical thermal minima was 2.5 °C. Critical thermal limits were relatively invariant across all treatments except at faster ramping rates. Knock-down resistance decreased with increasing temperature as survival dropped from 100% at 39 °C to 0% within 10 min at 44 °C. Recovery from chill coma increased by 1.62 min for each hour of exposure at 0 °C, while survival decreased by 50% after only 24 h. Combined, our results present the first composite picture of different thermal traits for western corn rootworm, which will be vital for predicting their survival and potential spread under future climate change scenarios.