Thermal Ecology Research Articles

Climate‐driven thermal opportunities and risks for leaf miners in aspen canopies

AbstractIn tree canopies, incoming solar radiation interacts with leaves and branches to generate temperature differences within and among leaves, presenting thermal opportunities and risks for leaf‐dwelling ectotherms. Although leaf biophysics and insect thermal ecology are well understood, few studies have examined them together in single systems. We examined temperature variability in aspen canopies, Populus tremuloides, and its consequences for a common herbivore, the leaf‐mining caterpillar Phyllocnistis populiella. We shaded leaves in the field and measured effects on leaf temperature and larval growth and survival. We also estimated larval thermal performance curves for feeding and growth and measured upper lethal temperatures. Sunlit leaves directly facing the incoming rays reached the highest temperatures, typically 3–8°C above ambient air temperature. Irradiance‐driven increases in temperature, however, were transient enough that they did not alter observed growth rates of leaf miners. Incubator and ramping experiments suggested that larval performance peaks between 25 and 32°C and declines to zero between 35 and 40°C, depending on the duration of temperature exposure. Upper lethal temperatures during 1‐h heat shocks were 42–43°C. When larvae were active in early spring, temperatures generally were low enough to depress rates of feeding and growth below their maxima, and only rarely did estimated mine temperatures rise beyond optimal temperatures. Observed leaf or mine temperatures never approached larval upper lethal temperatures. At this site during our experiments, larvae thus appeared to have a significant thermal safety margin; the more pressing problem was inadequate heat. Detailed information on mine temperatures and larval performance curves, however, allowed us to leverage long‐term data sets on air temperature to estimate potential future shifts in performance and longer‐term risks to larvae from lethally high temperatures. This analysis suggests that, in the past 20 years, larval performance has often been limited by cold and that the risk of heat stress has been low. Future warming will raise mean rates of feeding and growth but also the risk of exposure to injuriously or lethally high temperatures.

Temperature regulation in the Balkan spadefoot (Pelobates balcanicus Karaman, 1928) at the beginning of nocturnal activity.

On land, the amphibians interact with the environment in a complex way-even small changes in the physiological conditions may significantly impact the behaviour and vice versa. In ectothermic tetrapods, the transition from inactive to active phase may be related to important changes in their thermal status. We studied the thermal ecology of adult Balkan spadefoots (Pelobates balcanicus Karaman, 1928) in northeastern Bulgaria. These toads spend the daytime buried between 10 and 15 cm in sandy substrates, and emerge after sunset. On the substrate, their thermal energy exchange is defined by the absence of heat flow from the sun. Secondary heat sources, like stored heat and infrared radiation from the soil play an important role for the thermal balance of the active spadefoot toads. At the beginning of their daily activity, we measured substrate temperature (at a depth of 11–12 cm), toad’s surface body temperature, and also provided thermal profiles of the animals and the substrate surface in their microhabitats. In animals which recently emerged from the substrate, the temperature was comparatively higher and was closer to that of the subsoil on the spot. After that, body temperature decreased rapidly and continued to change slowly, in correlation with air temperature. We detected a temperature gradient on the dorsal surface of the toads. On the basis of our measurements and additional data, we discuss the eventual role of air humidity and the effects of surface and skin water evaporation on the water balance and activity of the investigated toads.

Evolutionary interactions between thermal ecology and sexual selection

Thermal ecology and mate competition are both pervasive features of ecological adaptation. A surge of recent work has uncovered the diversity of ways in which temperature affects mating interactions and sexual selection. However, the potential for thermal biology and reproductive ecology to evolve together as organisms adapt to their thermal environment has been underappreciated. Here, we develop a series of hypotheses regarding (1) not only how thermal ecology affects mating system dynamics, but also how mating dynamics can generate selection on thermal traits; and (2) how the thermal consequences of mate competition favour the reciprocal co-adaptation of thermal biology and sexual traits. We discuss our hypotheses in the context of both pre-copulatory and post-copulatory processes. We also call for future work integrating experimental and phylogenetic comparative approaches to understand evolutionary feedbacks between thermal ecology and sexual selection. Overall, studying reciprocal feedbacks between thermal ecology and sexual selection may be necessary to understand how organisms have adapted to the environments of the past and could persist in the environments of the future.

THERMAL BIOLOGY OF A POPULATION OF Xenosaurus newmanorum (SQUAMATA: XENOSAURIDAE) FROM XILITLA, SAN LUIS POTOSÍ, MEXICO: DO THEY ACTIVELY THERMOREGULATE?

The knob-scaled lizards (family Xenosauridae) comprise a clade of crevice-dwelling North American lizards with a trend towards low body temperature and high rates of water loss, and are often regarded as thermoconformers. However, there are few studies on their thermal ecology, most of them limited to documenting the body temperatures and their relation with environmental temperatures. Here, we documented the field body temperatures (Tb), selected temperatures (Tset), operative temperatures (Te), thermoregulatory effectiveness, and thermal tolerances of 10 individuals of the Newman’s Knob-scaled Lizard, Xenosaurus newmanorum, collected in the fall of 2017 in La Huasteca region of Mexico. Mean Tb was 22.75 °C and mean Tset 25.08 °C (1.64 °C and 3.97 °C above mean Te, respectively). The species had a relatively narrow thermal tolerance range (25.89 °C). Furthermore, based on two different thermoregulatory indexes, we found direct evidence of active thermoregulation in X. newmanorum. This constitutes the first record of active thermoregulation in a xenosaurid from a low-elevation environment and the second record of thermal tolerances. We discuss on the thermal strategies of other species of the genus and pose that active thermoregulation might be more widespread in Xenosaurus than previously thought.

Systematic evaluation of oxygen isotopes in cephalopod statoliths as thermal proxies

Abstract Temperature histories are critical for understanding and predicting ecological functioning in marine systems. Stable oxygen isotopes (δ18O) locked within calcified tissues can uncover experienced temperatures of marine animals, but have been little evaluated in the statoliths of cephalopods. As such, we investigated field applications of oxygen isotope ratios in statoliths (δ18Ostatoliths) for reconstructing the thermal histories of cuttlefish, octopus, and squid. In doing so, we collated measured (instrumental and modelled) temperature and salinity data, alongside δ18Ostatoliths data, of ocean-caught species from Taiwan and Australia. To navigate potential species-bias or “vital effects,” two aragonite-specific thermometry equations were compared, whilst simulation modelling evaluated variation and addressed uncertainties. Linear regressions identified environmental and biological influences on the differences between measured and reconstructed temperatures. Variable trends in temperature reconstructions were observed between taxa, which may be due to ecological traits. For squid, the relationship was highly aligned with no significant model predictors. For cuttlefish and octopus, differences between measured and reconstructed temperatures increased in warmer conditions, and may indicate thermoregulation behaviour. Here, we demonstrate that δ18Ostatoliths values can function as natural proxies of ocean temperature and are an invaluable tool for broadening the field of thermal ecology for the important, yet understudied, cephalopods.

Optimization of technological modes of heterogeneous systems at high turbulence

The phenomena of convective heat and mass transfer in turbulent flows, taking into account chemical reactions, are widespread and play an important role in natural phenomena and in various industries. Knowledge of the regularities of such flows is important in the formation of the theory of combustion physics, the development of new physical and chemical technologies, and the solution of problems of thermal power engineering and ecology. In the course of the study, complex combustion processes have been analyzed from the point of view of dependence on the influence of many physical and chemical parameters of the combustion reaction. In the study of phenomena in multiphase systems, the development of the theory of the formation of liquid droplets at high turbulence is of greatest interest. In this paper, the processes of atomization, ignition, and spatial distribution of droplets in heterogeneous two-phase flows have been studied by means of computer simulation methods. These studies were carried out on the basis of current environmental problems, including the problems of air pollution, consisting of harmful toxic metals, sulfuric, nitric acids, carbon oxides, and other harmful substances. The processes of dispersion and combustion of liquid fuels at high turbulence have been studied by using mathematical modeling methods based on the solution of partial differential equations and the optimal technological combustion mode taking into account the formation of carbon dioxide in the combustion chamber has been determined.

Food web consequences of thermal asymmetries

Abstract Understanding how food webs will respond to globally rising temperatures is a pressing issue. Temperature effects on food webs are likely underpinned by differences in the thermal sensitivity of consumers and resources, or thermal asymmetries. We identify three sources of asymmetry in the rising portion of thermal performance curves: inter‐thermy variation across thermoregulatory groups, intra‐thermy variation within a thermoregulatory group and rate‐dependent variation in how different ecological rates respond to temperature. We use a large empirical dataset on thermal sensitivities across thermoregulatory groups to explore how prevalent thermal asymmetries are in real consumer–resource interactions. We then develop theory to illustrate how food web temperature responses are mediated by the magnitude and direction of these thermal asymmetries. We use this model to show possible conditions under which food webs could respond to warming as currently expected, and when that may not be the case. Our results suggest that inter‐thermy, intra‐thermy and rate‐dependent asymmetries are likely common in natural food webs. We show how all thermal asymmetries have important effects on species abundances across trophic levels as well as the maximum trophic position in the food web. Both the direction of the asymmetries (i.e. which species respond more strongly) and their magnitude (the difference in thermal responses) determine the temperature response of the food web and, consistent with current expectations, top predator abundance almost always declines with temperature, even though maximum trophic position may increase. While our model shows that food web temperature responses can be varied, much of this variation can be explained by considering thermal asymmetries. Our study provides new data and theoretical insights into the widely varying food web effects of warming observed in laboratory, experimental and observational settings, and clarifies how predator and prey thermal ecology may influence overall food web responses in a changing world. Read the free Plain Language Summary for this article on the Journal blog.

Daily fluctuations in leaf temperature modulate the development of a foliar pathogen

Thermal ecology studies on the ecophysiological responses of organisms to temperature involve two paradigms: physiological rates are driven by body temperature and not directly by the environmental temperature, and they are largely influenced not only by its mean but also its variance. These paradigms together have been largely applied to macro invertebrates and vertebrates but rarely to microorganisms. According to these paradigms, foliar fungal pathogens are expected to respond directly to the fluctuations in leaf temperature, rather than in air temperature. We determined experimentally the impact of two patterns of leaf temperature variation of equal mean temperature, but differing in their daily amplitude, on the development of Zymoseptoria tritici, a fungus infecting wheat leaves. The highest daily thermal amplitude resulted in two detrimental effects for the pathogen fitness: an increase in the length of the latent period, i.e. the ‘generation time’ of the fungus when infecting its host plant, and a decrease in the density of fruiting bodies on the leaves. We discussed these empirical results, mainly the impact of both the daily thermal amplitude and the fluctuation frequency on the pathogen development in planta, in the light of the mathematical effect of the integration of non-linear functions. We concluded that it is necessary to take into account daily leaf temperature amplitudes to improve our understanding and prediction of the development of foliar fungal pathogens and other micro-organisms living in the phyllosphere in the climate change context.

The biogeography of warming tolerance in lizards

AbstractAimMany ectotherms are at risk from climate change as temperatures are increasingly exceeding their thermal limits. Many evaluations of the vulnerability of ectotherms to climate change have relied on statistical metrics derived from coarse‐scale climatic data, which may result in misleading predictions. By applying an integrative approach, we investigated geographical correlates of the vulnerability of lizards to climate change.LocationGlobally.TaxonLizards.MethodsWe combined data on lizard thermal physiology and ecology, with high‐resolution climate data and biophysical modelling to assess lizards’ vulnerability to climate change. We calculated warming tolerance (difference between their body temperatures and upper thermal limits) and number of hours of activity. We investigated associations between warming tolerance and activity time with latitude, altitude and biome types. We compared our approach with traditional methods to calculate warming tolerance (using solely macroclimatic data).ResultsWe found no latitudinal trend in the warming tolerance of lizards calculated from body temperature, but there was a weak negative correlation with altitude. We found associations between hours of activity and latitude and altitude. Desert species showed narrower warming tolerance than tropical and temperate species. Desert species and temperate species had reduced hours of activity when compared to tropical species. When warming tolerance was calculated from macroclimatic data, however, it was positively correlated with latitude and altitude, and species from tropical forested biomes showed narrow warming tolerances.Main ConclusionsVulnerability metrics calculated from macroclimatic data can produce divergent outcomes to those observed from fine‐scale climatic data. Our work indicates that the ability of desert and temperate lizard species to cope with heat stress by thermoregulating is more constrained than that of tropical species. Integrative assessments of ectotherms' vulnerability to climate change can highlight species and regions that should be prioritised for conservation management.

Behaviour broadens thermal safety margins on artificial coastal defences in the tropics

Tropical species are predicted to be among the most vulnerable to climate change as they often live close to their upper limits to thermal tolerance and in many cases, behavioural thermoregulation is required to persist in the thermal extremes of tropical latitudes. In concert with warming temperatures, near-shore species are faced with the additional threat of shoreline hardening, leading to a reduction in microhabitats that can provide thermal refuges. This situation is exemplified in Singapore, which lies almost on the equator and so experiences year-round hot temperatures, and much of its coastline is now seawall. To investigate the thermal ecology of a common intertidal gastropod, Nerita undata, on these artificial structures, we measured thermal conditions on two seawalls, the temperatures of habitats occupied by the snail, and compared these with the snail's thermal tolerance by measuring heart rate and behavioural thermoregulation (as preferred temperature, Tpref). At one of the two seawalls (Tanjong Rimau), temperatures experienced by N. undata exceeded all measures of thermal tolerance in the sun, while at the other (Palawan Beach), they did not. Temperatures in habitats occupied by the snails on the seawalls were similar to their measured Tpref in the laboratory and were lower than all measures of thermal tolerance. Behavioural thermoregulation by the snails, therefore, significantly increased the thermal safety margins of N. undata on the relatively homogenous seawalls in Singapore, and at one of the two seawalls were necessary to allow snails to survive. Accordingly, to facilitate motile species to maintain broad thermal safety margins through behavioural regulation, the provision of additional refuges from thermal stress is recommended on artificial coastal defences such as seawalls.

Impact of heat stress on the fitness outcomes of symbiotic infection in aphids: a meta-analysis.

Beneficial microorganisms shape the evolutionary trajectories of their hosts, facilitating or constraining the colonization of new ecological niches. One convincing example entails the responses of insect-microbe associations to rising temperatures. Indeed, insect resilience to stressful high temperatures depends on the genetic identity of the obligate symbiont and the presence of heat-protective facultative symbionts. As extensively studied organisms, aphids and their endosymbiotic bacteria represent valuable models to address eco-evolutionary questions about the thermal ecology of insect-microbe partnerships, with broad relevance to various biological systems and insect models. This meta-analysis aims to quantify the context-dependent impacts of symbionts on host phenotype in benign or stressful heat conditions, across fitness traits, types of heat stress and symbiont species. We found that warming lowered the benefits (resistance to parasitoids) and costs (development, fecundity) of infection by facultative symbionts, which was overall mostly beneficial to the hosts under short-term heat stress (heat shock) rather than extended warming. Heat-tolerant genotypes of the obligate symbiont Buchnera aphidicola and some facultative symbionts (Rickettsia sp., Serratia symbiotica) improved or maintained aphid fitness under heat stress. We discuss the implications of these findings for the general understanding of the cost-benefit balance of insect-microbe associations across multiple traits and their eco-evolutionary dynamics faced with climate change.

Wind of change: a diurnal skink thermoregulates between cooler set-points and for an increased amount of time in the presence of wind.

ABSTRACTWind has the potential to dramatically alter the thermal landscape of habitats, and consequently, to affect how ectotherms thermoregulate. However, few studies have directly assessed if wind alters thermoregulation by ectotherms. We compared the thermoregulation of a heliothermic New Zealand skink under three treatments: no wind, wind at 2 m s−1 and wind at 6 m s−1. We provided captive skinks with housing in which their preferred body temperature was only achievable inside a wind tunnel. During experimental treatments with wind, airflow was generated through the wind tunnel while the maximum available operative temperature remained consistent among treatments. Skinks were able to move in and out of the wind tunnel. Using thermal bio-loggers, we recorded near-continuous skin temperatures of skinks over 90 min. Contrary to our expectations, more skinks tended to thermoregulate in the two wind treatments compared with the treatments without wind (P=0.062) and of the skinks that did thermoregulate, those in the two wind treatments thermoregulated for significantly longer than those in the treatment without wind. The set-point temperatures that skinks thermoregulated between became significantly cooler as windspeed increased, despite skinks having access to the same operative temperatures. Overall, our study suggests that wind has the potential to significantly change the temperatures selected by lizards, even when comparable temperatures are available; wind is therefore an important environmental parameter to consider when studying the thermal ecology of ectotherms, including in the context of climate change.

Testing the reliability and ecological implications of ramping rates in the measurement of Critical Thermal maximum.

Critical Thermal maximum (CTmax) is often used to characterize the upper thermal limits of organisms and represents a key trait for evaluating the fitness of ectotherms. The lack of standardization in CTmax assays has, however, introduced methodological problems in its measurement, which can lead to questionable estimates of species’ upper thermal limits. Focusing on ants, which are model organisms for research on thermal ecology, we aim to obtain a reliable ramping rate that will yield the most rigorous measures of CTmax for the most species. After identifying three commonly used ramping rates (i.e., 0.2, 0.5 and 1.0°C min-1) in the literature, we experimentally determine their effects on the CTmax values of 27 species measured using dynamic assays. Next, we use static assays to evaluate the accuracy of these values in function of the time of exposure. Finally, we use field observations of species’ foraging activities across a wide range of ground temperatures to identify the most biologically relevant CTmax values and to develop a standardized method. Our results demonstrate that the use of a 1°C min-1 ramping rate in dynamic assays yields the most reliable CTmax values for comparing ant species’ upper thermal limits, which are further validated in static assays and field observations. We further illustrate how methodological biases in physiological trait measurements can affect subsequent analyses and conclusions on community comparisons between strata and habitats, and the detection of phylogenetic signal (Pagel’s λ and Bloomberg’s K). Overall, our study presents a methodological framework for identifying a reliable and standardized ramping rate to measure CTmax in ants, which can be applied to other ectotherms. Particular attention should be given to CTmax values obtained with less suitable ramping rates, and the potential biases they may introduce to trait-based research on global warming and habitat conversion, as well as inferences about phylogenetic conservatism.

Thermal ecology of Northern Water Snakes (Nerodia sipedon) in a northern wetland in central Michigan

Semi-aquatic north-temperate reptiles experience challenging environmental conditions for thermoregulation on both seasonal and daily bases. We studied the thermal biology of north-temperate Northern Water Snakes (Nerodia sipedon) in central Michigan by remote radiotelemetry monitoring of snake body temperature (Tb) using surgically implanted thermally-sensitive radio-transmitters and by measuring operative temperatures (Te) across a range of microhabitats using biophysical models. Our goals included evaluation of thermoregulatory capabilities at a locality that we viewed to be a fine-grained thermal environment, seasonal variations in patterns of thermoregulation, and the effects of sex on thermoregulation. During summer, snakes showed diel Tb cycling apparently using the open Sphagnum mat for late morning warming and shuttling among different microhabitats until early evening when a monotonic decline in Tb ensued and continued through the early morning hours. Snakes attained Tb within their laboratory-determined preferred body temperature range (Tset = 28–33 °C) mostly during late afternoon and with average percentages of Tb values for individual snakes within Tset range when permitted by operative temperatures (Ex) between 68 and 70% of the time depending on method of measurement. Relatively high investment in thermoregulation when thermal conditions were poor occurred only during September but declined thereafter as snakes prepared to overwinter. We did not detect differences in thermoregulation among reproductive females, non-reproductive females, and males. Relative to a population of N. sipedon at a higher latitude in Ontario our snakes showed a relatively high Tset range and thermoregulated more effectively, particularly during the daylight hours. It remains unclear how much inter-population variation in thermoregulation is due to potential adaptations to latitude, to habitat differences, or variations in methodologies.

VTMaxHerp: A data set of voluntary thermal maximum temperatures of amphibians and reptiles from two Brazilian hotspots.

Amphibians and reptiles are ectothermic animals and therefore depend on environmental temperatures to maintain their physiological functions. Despite being poorly documented, data on thermal behavioral thresholds to avoid overheating in their habitats are essential to improve the understanding of their thermal ecology and physiology. Here we provide a data set of 312 individual voluntary thermal maximum (VTMax ) values, the maximum temperature tolerated by individuals before actively moving to a colder place, for 53 species of amphibians and reptiles of the Atlantic Forest and Cerrado savannas of southeastern South America. Voluntary thermal maximum values were recorded as the body temperature at which the individuals exited a heating box experimental setup. This data set comprises 25 species of 15 genera and eight families of amphibians and 28 species of 24 genera and 12 families of reptiles. Of the total number of individual records, 67.9% derived from the Cerrado and 32.0% derived from the Atlantic Forest ecoregions. Overall, lizards had higher VTMax than amphibians and snakes, and individuals in the Atlantic Forest had overall higher VTMax values than the ones in Cerrado. This data set is the first to compile VTMax values for South American herpetofauna, along with detailed experimental information such as heating rates and time to reach VTMax . This data set provides a baseline for understanding thermal tolerances and requirements of Neotropical ectothermic vertebrate species, which might be useful for future research on the impact of climate change and to test novel ecological hypotheses. There are no copyright or proprietary restrictions except that this data paper should be cited when data are used for publications. In addition, the authors would appreciated being informed of research projects or teaching purposes when these data are used.

Parasites do not adapt to elevated temperature, as evidenced from experimental evolution of a phytoplankton-fungus system.

Global warming is predicted to impact the prevalence and severity of infectious diseases. However, empirical data supporting this statement usually stem from experiments in which parasite fitness and disease outcome are measured directly after temperature increase. This might exclude the possibility of parasite adaptation. To incorporate the adaptive response of parasites into predictions of disease severity in a warmer world, we undertook an experimental evolution assay in which a fungal parasite of phytoplankton was maintained at elevated or control temperatures for six months, corresponding to 100–200 parasite generations. Host cultures were maintained at the respective temperatures and provided as substrate, but were not under parasite pressure. A reciprocal infection experiment conducted after six-month serial passages revealed no evidence of parasite adaptation. In fact, parasite fitness at elevated temperatures was inferior in parasite populations reared at elevated temperatures compared with those maintained under control temperature. However, this effect was reversed after parasites were returned to control temperatures for a few (approx. 10) generations. The absence of parasite adaptation to elevated temperatures suggests that, in phytoplankton–fungus systems, disease outcome under global warming will be largely determined by both host and parasite thermal ecology.

Heterogeneous environmental seascape across a biogeographic break influences the thermal physiology and tolerances to ocean acidification in an ecosystem engineer

AbstractAimUnderstanding how spatio‐temporal environmental variability influences stress tolerance, local adaptation and phenotypic variation among populations is a key challenge for evolutionary ecology and climate change biology. Coastal biogeographic breaks are natural laboratories to explore this fundamental research question due to the contrasting environmental conditions experienced by natural populations across these regions.LocationIn the South East Pacific (SEP) coast, a major break (30º‐32ºS) is characterized by extreme natural variability in sea surface temperature (SST) and carbonate chemistry parameters related to temporal and spatial dynamics in upwelling events. Calcifying organisms inhibiting this zone are exposed to marked fluctuations and clines in SST that together with naturally acidified waters can impact their metabolism, calcification and fitness, making them particularly prone to the effects of climate change (e.g. ocean acidification, OA). We investigated to what extent the spatial and temporal environmental variability (in SST and seawater carbonate conditions) that characterizes the biogeographic break in the SEP influences intra‐specific differences in the thermal ecology and the tolerances to OA of the limpet Scurria araucana.MethodsDuring two years, we conducted field surveys of limpet populations at sites across the SEP break (27ºS, 30ºS and 32ºS). We collected individuals from each population to test for geographic differences in morphometric (e.g. total buoyancy weight, shell length) and physiological (e.g. oxygen consumption rate, cardiac activity and thermal performance curves; TPC) responses to local environmental conditions (Tº and pH/pCO2) and to simulated OA scenarios.ResultsPopulations of S. Araucana exhibit high tolerance to OA with no signal of geographic influence on this attribute. However, inter‐population differences in thermal physiology (metabolic rates and performances) were found across the biogeographic break in the SEP coast. Limpets from the central part of the break (30ºS) exhibit higher thermal performance compared to limpets from populations at both sides of the break.Main conclusionsVariation in SST has a greater effect shaping inter‐population differences in thermal physiology of the limpet S. araucana. These physiological differences are aligned the thermal heterogenous seascape along the biogeographic break in the SEP. Contrarily, temporal and spatial variation in seawater carbonate conditions does not influence inter‐population differences in phenotypic response populations, but an overall high tolerance to OA.

Sex-specific thermal tolerance limits in the ditch shrimp Palaemon varians: Eco-evolutionary implications under a warming ocean.

As global temperatures continue to rise due to global change, marine heatwaves are also becoming more frequent and intense, impacting marine biodiversity patterns worldwide. Organisms inhabiting shallow water environments, such as the commercially relevant ditch shrimp Palaemon varians, are expected to be the most affected by rising temperatures. Thus, addressing species' thermal ecology and climate extinction-risk is crucial to foster climate-smart conservation strategies for shallow water ecosystems. Here, we estimated sex-specific upper thermal tolerance limits for P. varians via the Critical Thermal Maximum method (CTmax), using loss of equilibrium as endpoint. We further calculated thermal safety margins for males and females and tested for correlations between upper thermal limits and shrimps' body size. To determine sex-biased variation in P. varians' traits (CTmax, weight and length), we compared trait variation between females and males through the coefficient of variation ratio (lnCVR). Females displayed an average CTmax value 1.8% lower than males (CTmaxfemales=37.0°C vs CTmaxmales=37.7°C). This finding may be related to the larger body size exhibited by females (156% heavier and 39% larger than males), as both length and weight had a significant effect on CTmax. The high energetic investment of females in offspring may also contribute to the differences recorded in thermal tolerance. Overall, organisms with a smaller body-size displayed a greater tolerance to elevated temperature, thus suggesting that smaller individuals may be positively selected in warmer environments. This selection may result in a reduction of size-at-maturity and shifts in sex ratio, given the sexual dimorphism in body size of shrimps. The thermal safety margin of P. varians was narrow (∼2.2°C for males and ∼1.5°C for females), revealing the vulnerability of this species to ocean warming and heatwaves.

A multi-layered approach uncovers overlooked taxonomic and physiological diversity in Alpine subterranean spiders (Araneae: Linyphiidae:

The integration of multiple lines of evidence in the delimitation of taxa is becoming the gold standard in modern taxonomy and systematics. However, multi-layered taxonomy is still incipient when it comes to species description within a mega-diverse group of organisms (e.g. arthropods), especially those inhabiting secluded environments such as caves. This may represent a significant shortcoming, because species in subterranean habitats generally show deep convergence in their somatic traits, perplexing our ability to delimit species by traditional approaches. The genus Troglohyphantes Joseph, 1882 (Araneae: Linyphiidae) is presently known to include 129 species and 5 subspecies, all of which are primarily distributed in subterranean habitats of the European mountain ranges. Recent studies on Italian alpine species covered taxonomy and faunistic, biogeography and ecology. However, our knowledge about the actual species diversity of Troglohyphantes spiders is far from complete, and it is expected that significant levels of overlooked diversity might exist within the genus. In this work, we combined morphological data with target gene molecular data, functional trait analysis and thermal physiology to explore overlooked diversity in Troglohyphantes vignai auct., a species of subterranean spider in the Western Italian Alps with an apparently broader distribution than its congeners. Our approach proved effective in uncovering overlooked diversity and further supporting the split of T. vignai auct. into three distinct species whose distribution ranges how striking resemblances with that of other subterranean spiders. We here describe the new species and discuss their origins in light of their geographical vicariance, niche convergence, thermal ecology and divergence time.

Predicting the growth of the amphibian chytrid fungus in varying temperature environments.

Environmental temperature is a crucial abiotic factor that influences the success of ectothermic organisms, including hosts and pathogens in disease systems. One example is the amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), which has led to widespread amphibian population declines. Understanding its thermal ecology is essential to effectively predict outbreaks. Studies that examine the impact of temperature on hosts and pathogens often do so in controlled constant temperatures. Although varying temperature experiments are becoming increasingly common, it is unrealistic to test every temperature scenario. Thus, reliable methods that use constant temperature data to predict performance in varying temperatures are needed. In this study, we tested whether we could accurately predict Bd growth in three varying temperature regimes, using a Bayesian hierarchical model fit with constant temperature Bd growth data. We fit the Bayesian hierarchical model five times, each time changing the thermal performance curve (TPC) used to constrain the logistic growth rate to determine how TPCs influence the predictions. We then validated the model predictions using Bd growth data collected from the three tested varying temperature regimes. Although all TPCs overpredicted Bd growth in the varying temperature regimes, some functional forms performed better than others. Varying temperature impacts on disease systems are still not well understood and improving our understanding and methodologies to predict these effects could provide insights into disease systems and help conservation efforts.