Thermal Habitat Research Articles

Too Hot to Handle: A Meta-Analytical Review of the Thermal Tolerance and Adaptive Capacity of North American Sturgeon.

Understanding how ectotherms may fare with rising global temperatures and more frequent heatwaves is especially concerning for species already considered at-risk, such as long-lived, late-maturing sturgeon. There have been concerted efforts to collect data on the movement behavior and thermal physiology of North American sturgeon to enhance conservation efforts; thus, we sought to synthesize these data to understand how sturgeon respond to thermal stress and what capacity they have to acclimate and adapt to warming. Here, we combined a systematic literature review and meta-analysis, integrating field-based observations (distribution and spawning) and laboratory-based experiments (survival, activity, growth, metabolism, and upper thermal limits) for large-scale insights to understand the vulnerability of North American sturgeon to rising global temperatures. We summarized the preferred thermal habitat and thermal limits of sturgeon in their natural environment and using meta-analytical techniques, quantified the effect of prolonged temperature change on sturgeon whole-animal physiology and acute upper thermal limits. While acclimation did not have significant effects on physiological rates or survival overall, there were positive trends of activity and metabolism in young-of-the-year sturgeons, likely offset by negative trends of survival in early life. Notably, North American sturgeon have a greater capacity for thermal tolerance plasticity than other fishes, increasing upper thermal limits by 0.56°C per 1°C change in acclimation temperature. But with limited laboratory-based studies, more research is needed to understand if this is a sturgeon trait, or perhaps that of basal fishes in general. Importantly, with these data gaps, the fate of sturgeon remains uncertain as climate change intensifies, and physiological impacts across life stages likely limit ecological success.

A step in the deep evolution of Alvinellidae (Annelida: Polychaeta): A phylogenomic comparative approach based on transcriptomes

The Alvinellidae are a family of worms that are endemic to deep-sea hydrothermal vents in the Pacific and Indian Oceans. These annelid worms, a sister group to the Ampharetidae, occupy a wide range of thermal habitats. The family includes the most thermotolerant marine animals described to date such as the Pompeii worm Alvinella pompejana, and other species living at much lower temperatures such as Paralvinella grasslei or Paralvinella pandorae. The phylogeny of this family has not been studied extensively. It is, however, a complex case where molecular phylogenies have given conflicting results, especially concerning the monophyletic or polyphyletic nature of the genus Paralvinella.We carried out a comprehensive study of the phylogeny of this family using the best molecular data currently available from RNAseq datasets, leading to several hundred orthologous transcripts for 11 of the 14 species currently described or in description. The results obtained by the two most popular phylogenetic inference models (using either gene concatenation with maximum likelihood, or a coalescent-based model from gene trees) were compared using a series of ampharetid and terebellid outgroups.Our study shows that the global phylogenetic signal favors the hypothesis of paraphyly for the Paralvinella genus, with P. pandorae being sister species of the other Alvinellidae.However, a high number of gene trees also supports the hypothesis of alternative trees in which the monophyly of the Paralvinella genus, as initially proposed by Desbruyères and Laubier, is valid with the species P. pandorae and Paralvinella unidentata being sister species. According to molecular dating, the radiation of the Alvinellidae was rapid and took place in a short period of time between 80 and 110 million years ago. This is reflected at the genomic scale by gene trees equally separated between different phylogenetic hypothesis, showing high rates of incomplete lineage sorting between the first lineages of the Alvinellidae and probable gene transfers. Although different genomic regions seem to have different phylogenetic stories in the early step of the alvinellid radiation, our study supports the view that the two P. pandorae species can be grouped into a separate genus (possibly Nautalvinella) and that the Miralvinella subgenus, defined by Desbruyères and Laubier, is not valid anymore.

Marine migration, thermal habitat use and feeding habits of Arctic charr (Salvelinus alpinus (L. 1758)) in SW Greenland

Climate change is altering northern coastal aquatic habitats, especially in fjords. Data on current ecosystem structure and biodiversity in many northern fjord and coastal ecosystems, especially for Greenland, are lacking. We used acoustic telemetry combined with stable isotope analyses in a southwest Greenland fjord to investigate marine migrations, marine and freshwater thermal habitat use, and the marine feeding habits of 80 acoustically tagged Arctic charr over one year. During summer, most Arctic charr occupied the inner fjord. Models of Arctic charr thermal habitat use suggested higher experienced water temperatures in the inner compared to outer fjord (estimated 1.59ºC difference) during tagged charr mean 70-day (S.D.=14 days) residencies. During February and March, non-migratory individuals used warmer waters (+ 0.56ºC higher) than fish that ultimately migrated to sea, suggesting that over-wintering habitat use patterns influenced migration tactics. Stable isotope mixing model analysis indicated that Arctic charr fed mainly on capelin, marine gammarids and three-spine sticklebacks. The results provide a contemporary baseline for assessing predictions of potential changes in the ecology of Arctic charr in SW Greenland fjords.

Metabolite profiling and bioactivity assessment of cyanobacteria from the Azores reveals unique producers of cytotoxic and lipid reducing compounds

Cyanobacteria are a group of photosynthetic bacteria and a rich secondary metabolites source. The Bank of Algae and Cyanobacteria of the Azores (BACA) culture collection holds a significant number of strains, including many novel genera and species. 56 strains from freshwater, brackish, and thermal habitats were selected, and grown under standard conditions. Biomass was extracted with methanol, and cytotoxicity was assessed on two carcinoma cell lines, HepG2 and HCT116. The reduction of lipids was tested in zebrafish larvae, and in a steatosis model with fatty acid overloaded human liver cells. The cyanobacterial metabolome was analyzed by HR-ESI-LC-MS/MS and compared using CompareMS2. High similarities were observed in strains of the same genus when isolated from similar habitats, clustering in concordance to the taxonomical order, while no relation could be observed between strains from different genera originated from the same habitat. The extracts of Cyanobium sp. BACA0019, Pseudocalidococcus azoricus BACA0433 and Pegethrix atlantica BACA0077 reduced neutral lipids >40 % in zebrafish at 25 μg/mL, while from Symphyonema sp. BACA0090 and Aliinostoc sp. BACA0355 induced mortality. Lipid reduction in the steatosis model was observed in many strains, with significant results varying from 50 % to 100 %. Several strains reduced cell viability with the strongest effects from Scytonematopsis sp. BACA0005 (HepG2, 59.8 % and HCT116, 68.1 %), Aliinostoc sp. BACA0035 (HepG2, 43.3 %, and HCT116, 59.4 %) and Aliinostoc sp. BACA0355 (HepG2, 46.2 %, and HCT116, 75.5 %). The feature-based molecular networking identified several cluster of mass peaks related to the observed bioactivities. Chlorophyll derivatives and glycerolipids from Cyanobium sp. BACA0019, Pseudocalidococcus azoricus BACA0433 and Pegethrix atlantica BACA0077 were correlated with the reduction of lipids in zebrafish larvae, while several oligopeptides and fatty amides of Symphyonema sp. BACA0090 and Aliinostoc sp. BACA0355 with toxicity. Many clusters associated to the bioactivities remained unidentified, which may represent novel compounds, highlighting the chemodiversity of the BACA culture collection.

Thermal balance in Andean lizards: A perspective from the high mountains

AbstractHigh Andean lizards in the Andes face numerous challenges in high‐altitude environments characterized by significant temperature, spatial and temporal variations. These factors greatly influence their thermal characteristics and adaptive strategies for coping with temperature fluctuations. This study aims were to investigate the thermal biology of high mountain lizards (>2000 m) inhabiting the Andes Mountain range, using information from existing literature, and to identify the potential impacts of the original climate change scenarios developed in this study. Within the Andes, high‐altitude species are primarily found in families like Liolaemidae, Gymnophthalmidae, Tropiduridae, Anolidae and Leiourisauridae. Notably, we found in the literature that the higher body temperatures and maximum critical temperatures in southern species compared to those closer to the tropics. Typically, diurnal and seasonal temperature variations have a significant impact on the body temperature of these high‐altitude lizards, but their adaptive behaviours and physiological mechanisms enhance their resistance to extreme temperatures. Populations situated below the equator often exhibit higher body temperatures and maximum critical temperatures, largely due to their exposure to higher ambient temperatures during summer. With all global warming scenarios indicating temperature increases in latitudinal regions, tropical high‐altitude lizards, historically less thermally adaptable, may be particularly susceptible to these temperature rises. It is crucial to consider that additional factors, such as species activity patterns, thermal resource availability and diminishing suitable thermal habitats, will also play a pivotal role in shaping the future of these lizard species, making the situation even more complex and challenging.

Planning for green infrastructure by integrating multi-driver: Ranking priority based on accessibility equity

Green infrastructure provides multifarious benefits, improving urban resilience and sustainability amid increasing climate change and urbanization. Traditional green infrastructure planning studies were based on the spatial-equity principle, which usually neglected residents’ aggregation pattern, leading to the conflict with equitable green exposure. Using the sponge city of Zhengzhou as a case, this study proposes a novel priority ranking strategy, namely accessibility equity. We first spatially quantified the regional socioecological conditions on 0.25 km2 grids as green infrastructure planning drivers, including stormwater management, urban thermal environment, air quality, habitat maintenance and water purification. Subsequently we integrated these planning drivers with population density to conduct spatial autocorrelation analysis, priority ranking, and grid clustering. While most planning drivers are positively correlated with population density, except air quality, some areas show opposite trends in terms of local perspective, suggesting that the spatial equity may lead to mismatch between residents’ demand and GI priority. The priority order based on accessibility equity, rises in the city center and falls in suburbs and industrial zones. The study area is divided into four categories using k-means clustering, and we propose the corresponding adaptive green infrastructure development strategy. The framework can be a practical tool for guiding green infrastructure and sponge city projects.

Cold blood in warming waters: Effects of air temperature, precipitation, and groundwater on Gulf Sturgeon thermal habitats in a changing climate

AbstractObjectiveIn a changing climate, the effects of air temperature, precipitation, and groundwater on water temperature and thermal habitat suitability for Gulf Sturgeon Acipenser desotoi, listed as threatened under the U.S. Endangered Species Act, are not well understood. Hence, we incorporated these factors into thermal habitat models to forecast how Gulf Sturgeon may be affected by wide‐ranging climate change scenarios in 2024–2074.MethodsUsing data from the Choctawhatchee River, Florida, we developed precipitation‐ and groundwater‐corrected air–water temperature models, compared their accuracy with that of conventional air–water temperature models used in fisheries management, and projected future Gulf Sturgeon thermal habitat suitability for normal physiological functioning and fieldwork (i.e., population sampling and telemetry surgeries) in summer (May–August) under 16 climate change scenarios.ResultPrecipitation‐ and groundwater‐corrected models were more accurate than conventional air–water temperature models (mean improvement in adjusted R2 = +0.45; range = +0.09 to +0.75). Water temperature was projected to warm at widely variable rates across climate change scenarios encompassing different air temperature, precipitation, and groundwater regimes. Importantly, Gulf Sturgeon summer aggregation areas were cooler and influenced more by precipitation and groundwater and less by air temperature than were non‐aggregation areas. If precipitation and groundwater—as drivers of cooling—become warm in a changing climate, summer aggregation areas were projected to exhibit thermal habitat degradation equivalent to or greater than that of non‐aggregation areas.ConclusionOur results add hydrological context to the premise that aggregation areas provide cool water and energetic savings for Gulf Sturgeon during summer, underscoring the importance of protecting these habitats through groundwater conservation, water quality monitoring, and riparian/watershed habitat management. Our findings indicate that identifying thermally appropriate times for fieldwork activities will be increasingly important and time‐restricted as climate change intensifies. However, our research provides managers with a portfolio of water temperature models and an accurate, cost‐effective, management‐relevant approach to forecasting thermal habitat conditions for Gulf Sturgeon and other species in a changing climate.

Lake Superior fish community and fisheries, 2001–2022: An era of stability

Lake Superior is the least anthropogenically impacted of the Laurentian Great Lakes ecosystems, yet dramatic changes to the fish community are evident. Previous published works chronicled those changes and the efforts to rehabilitate the fish community through the year 2000. Here, we review through the year 2022, where post-rehabilitation stability was driven by lean lake trout (Salvelinus namaycush namaycush) as the most abundant piscivore in nearshore waters, siscowet lake trout (Salvelinus namaycush siscowet) as the most abundant piscivore in offshore waters, and a healthy, intact assemblage of native prey species, which created ecological redundancies and helped stabilize the food web. Stocking of non-native salmonines was reduced 74%, and populations of Chinook salmon (Oncorhynchus tshawytscha) and coho salmon (Oncorhynchus kisutch) were maintained through natural reproduction. Despite reduced stocking, yield from recreational fisheries was stable. Likewise, developments in population modeling led to evaluations and refinement of management strategies that helped create stability for lake trout, lake whitefish (Coregonus clupeaformis), and cisco (Coregonus artedi) fisheries. With lake trout rehabilitation achieved, focus shifted toward rehabilitation of native brook trout (Salvelinus fontinalis), lake sturgeon (Acipenser fulvescens), and walleye (Sander vitreus). Despite continued control efforts, sea lamprey (Petromyzon marinus) abundance increased considerably, and estimates of fish killed by lampreys averaged 2.65 million kg annually. Environmental changes have benefited sea lampreys and fostered thermal habitats more suitable to non-native organisms, posing new challenges for managers and researchers. Nevertheless, the post-rehabilitation stability in the contemporary fish community will help provide resilience to future perturbations in the ecosystem.

Seasonal and Daily Movement Patterns by Wels Catfish (Silurus glanis) at the Northern Fringe of Its Distribution Range

Fish behavior often varies across a species’ distribution range. Documenting how behaviors vary at fringes in comparison to core habitats is key to understanding the impact of environmental variation and the evolution of local adaptations. Here, we studied the behavior of Wels catfish (Silurus glanis) in Lake Möckeln, Sweden, which represent a European northern fringe population. Adult individuals (101–195 cm, N = 55) were caught and externally marked with data storage tags (DSTs). Fifteen DSTs were recovered a year after tagging, of which 11 tags contained long-term high-resolution behavioral data on the use of vertical (depth) and thermal habitats. This showed that the catfish already became active in late winter (<5 °C) and displayed nocturnal activity primarily during summer and late autumn. The latter included a transition from the bottom to the surface layer at dusk, continuous and high activity close to the surface during the night, and then descent back to deeper water at dawn. During the daytime, the catfish were mainly inactive in the bottom layer. These behaviors contrast with what is documented in conspecifics from the core distribution area, perhaps reflecting adaptive strategies to cope with lower temperatures and shorter summers.

The use of thermal performance analysis to improve conservation management: The case of the invasive Red Sea swimming blue crab Portunus segnis

The latest report from the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) expresses concern over the global proliferation of non-native species (NIS) driven by increasing temperatures. In 2023, the invasive blue crab Portunus segnis in the Mediterranean experienced a significant range expansion due to warmer waters in northern and western regions. Recognizing thermal tolerance as crucial for conservation, this study, using the blue crab as a model, emphasized the importance of considering thermal metabolic performance in conservation efforts. In this study, we experimentally measured the metabolic performance of P. segnis at different temperatures (from 7 to 42°C) using an oxygen consumption measurement system. The thermal performance curve (TPC) of P. segnis rose from 0.016 ± 0.011 mgO2 h−1 gWW−1 (12°C) to 0.238 ± 0.011 mgO2 h−1 gWW−1 (34°C), and decreased beyond. Organisms succumbed at 7°C and 42°C. The TPC obtained was compared with 24 TPC models and the O’Neill regression was the best fitting model determining the minimum critical thresholds (CTmin) at 11.33°C and CTmax at 41.13°C. Using the TPC curve equation, we applied the curve to satellite Mediterranean temperature data for the year 2022 and for the future (RCP 4.5 and 8.5) to determine the current and future monthly distribution of favorable thermal habitats for P. segnis. Results anticipated the future expansion of the species along the Spanish, French, Italian, and Greek coasts of the Aegean Sea, providing maps to prioritize high-risk invasion areas. Additionally, in the areas where the species in currently present, results predicted a long-term persistence of the species. Understanding species' responses to temperature changes appears crucial for anticipating and addressing the impending expansion of invasive species, underscoring the urgency of nature conservation measures.

Thermal tolerance plasticity and dynamics of thermal tolerance in Eublepharis macularius: Implications for future climate-driven heat stress

The intensity and duration of heat waves, as well as average global temperatures, are expected to increase due to climate change. Heat waves can cause physiological stress and reduce fitness in animals. Species can reduce overheating risk through phenotypic plasticity, which allows them to raise their thermal tolerance limits over time. This mechanism could be important for ectotherms whose body temperatures are directly influenced by available environmental temperatures. Geckos are a large, diverse group of ectotherms that vary in their thermal habitats and times of daily activity, which could affect how they physiologically adjust to heat waves. Data on thermal physiology are scarce for reptiles, with only one study in geckos. Understanding thermal tolerance and plasticity, and their relationship, is essential for understanding how some species are able to adjust or adapt to changing temperatures. In this study, we estimated thermal tolerance and plasticity, and their interaction, in the crepuscular gecko, Eublepharis macularius, a species that is emerging as a model for reptile biology. After estimating basal thermal tolerance for 28 geckos, thermal tolerance was measured for each individual a second time at several timepoints (3, 6, or 24 h) to determine thermal tolerance plasticity. We found that thermal tolerance plasticity (1) does not depend on the basal thermal tolerance of the organism, (2) was highest after 6 h from initial heat shock, and (3) was negatively influenced by individual body mass. Our findings contribute to the increasing body of work focused on understanding the influence of biological and environmental factors on thermal tolerance plasticity in organisms and provide phenotypic data to further investigate the molecular basis of thermal tolerance plasticity in organisms.

Hot, dry, and salty: The present and future of an Extremophile model lizard from Argentina

Global warming poses a threat to lizard populations by raising ambient temperatures above historical norms and reducing thermoregulation opportunities. Whereas the reptile fauna of desert systems is relatively well studied, the lizard fauna of saline environments has not received much attention and—to our knowledge—thermal ecology and the effects of global warming on lizards from saline environments have not been yet addressed. This pioneer study investigates the thermal ecology, locomotor performance and potential effects of climate warming on Liolaemus ditadai, a lizard endemic to one of the largest salt flats on Earth. We sampled L. ditadai using traps and active searches along its known distribution, as well as in other areas within Salinas Grandes and Salinas de Ambargasta, where the species had not been previously recorded. Using ensemble models (GAM, MARS, RandomForest), we modeled climatically suitable habitats for L. ditadai in the present and under a pessimistic future scenario (SSP585, 2070). L. ditadai emerges as an efficient thermoregulator, tolerating temperatures near its upper thermal limits. Our ecophysiological model suggests that available activity hours predict its distribution, and the projected temperature increase due to global climate change should minimally impact its persistence or may even have a positive effect on suitable thermal habitat. However, this theoretical increase in habitat could be linked to the distribution of halophilous scrub in the future. Our surveys reveal widespread distribution along the borders of Salinas Grandes and Salinas de Ambargasta, suggesting a potential presence along the entire border of both salt plains wherever halophytic vegetation exists. Optimistic model results, extended distribution, and no evidence of flood-related adverse effects offer insights into assessing the conservation status of L. ditadai, making it and the Salinas Grandes system suitable models for studying lizard ecophysiology in largely unknown saline environments.

Thermal sensitivity of metabolic performance in Squalus acanthias: efficacy of aerobic scope as a predictor of viable thermal habitat

Ocean warming due to climate change can affect the metabolism, performance, and survival of ectothermic marine species. On the US Northeast continental shelf (US NES), waters are warming faster than the global average, leading to elevated mean temperatures and an increased risk of marine heatwave exposure in the region. Thus, it is critical to understand the effects of warming on the region’s living marine resources. Here, we quantified the acute temperature sensitivity of metabolic traits to evaluate their role as possible drivers of acute thermal tolerance and viable habitat in the spiny dogfish shark Squalus acanthias on the US NES. From 10-23°C, the standard metabolic rate increased more rapidly than the maximum metabolic rate, resulting in a reduction in factorial aerobic scope at warmer temperatures. However, the oxygen supply capacity increased with temperature in proportion to maximum metabolic rate, and neither metric declined at the warmest temperatures, suggesting oxygen supply capacity does not limit performance within the tested range. Although behavioral observations revealed overt thermal stress via loss of equilibrium at ≥20°C and estimated lethal temperature at ∼24°C, sharks retained the ability to regulate their resting metabolic rate, achieve maximum activity, and peak absolute aerobic scope at warm temperatures. Results suggest that factors other than oxygen supply or aerobic scope are constraining thermal tolerance in S. acanthias and support the notion that aerobic scope cannot be universally applied to determine optimal or viable metabolic habitat.

Thermal habitat fragmentation in stratified lakes induces resource waves that brook charr track across seasons

The spatial configuration of thermal habitats constrains the thermoregulatory performance of ectotherms. Thermal landscapes also vary through time, which is particularly relevant in seasonal environments such as temperate lakes. Indeed, elevated temperatures in the epilimnion of dimictic lakes during summer could substantially reduce the use of this habitat by cold‐stenothermic fish during the stratified period. The main objective of this study was to evaluate whether thermal habitat fragmentation in stratified lakes modulates accessibility to resources that brook charr, Salvelinus fontinalis, which is a mobile consumer, can track across seasons. More specifically, we hypothesize that reduced access to the littoral habitat during summer enhances foraging opportunities in this habitat during winter. We used an automatic acoustic telemetry system offering full coverage of the lake to continuously record brook charr locations across seasons, and we estimated zoobenthos abundances in the littoral habitat using image processing and semi‐automatic classification. While brook charr concentrate in the metalimnion of the pelagic habitat in summer, most individuals in winter shift to a shallow bay that is unexploited in summer due to thermal constraints. In this habitat, zoobenthos abundance is more than twice as high at the end of the summer compared to littoral habitats close to the thermal refuge in the pelagic habitat. Surprisingly, brook charr showed strong within‐lake site fidelity between two consecutive summers, which suggests that spatial memory could be a key driver of seasonal habitat use in this lacustrine population. Overall, our results suggest that thermal barriers create fragmentation between littoral and pelagic habitats that in turn produces resource opportunities that brook charr can track across seasons.

Body length changes for Atlantic salmon (Salmo salar) over five decades exhibit weak spatial synchrony over a broad latitudinal gradient.

Understanding the factors that drive spatial synchrony among populations or species is important for management and recovery of populations. The range-wide declines in Atlantic salmon (Salmo salar) populations may be the result of broad-scale changes in the marine environment. Salmon undergo rapid growth in the ocean; therefore changing marine conditions may affect body size and fecundity estimates used to evaluate whether stock reference points are met. Using a dataset that spanned five decades, 172,268 individuals, and 19 rivers throughout Eastern Canada, we investigated the occurrence of spatial synchrony in changes in the body size of returning wild adult Atlantic salmon. Body size was then related to conditions in the marine environment (i.e., climate indices, thermal habitat availability, food availability, density-dependence, and fisheries exploitation rates) that may act on all populations during the ocean feeding phase of their life cycle. Body size increased during the 1980s and 1990s for salmon that returned to rivers after one (1SW) or two winters at sea (2SW); however, significant changes were only observed for 1SW and/or 2SW in some mid-latitude and northern rivers (10/13 rivers with 10 of more years of data during these decades) and not in southern rivers (0/2), suggesting weak spatial synchrony across Eastern Canada. For 1SW salmon in nine rivers, body size was longer when fisheries exploitation rates were lower. For 2SW salmon, body size was longer when suitable thermal habitat was more abundant (significant for 3/8 rivers) and the Atlantic Multidecadal Oscillation was higher (i.e., warmer sea surface temperatures; significant for 4/8 rivers). Overall, the weak spatial synchrony and variable effects of covariates on body size across rivers suggest that changes in Atlantic salmon body size may not be solely driven by shared conditions in the marine environment. Regardless, body size changes may have consequences for population management and recovery through the relationship between size and fecundity.

Physiological thermal niches, elevational ranges and thermal stress in dendrobatid frogs: An integrated approach

AbstractAimWe investigated the relationship between thermal physiology, elevational distribution and thermal stress among nine closely related dendrobatid frogs during their aquatic stage by employing an integrated approach, combining thermal physiology, environmental temperature modelling and predictive assessments of current and future exposure to thermal variation.LocationEcuador.TaxonAmphibians; Anura, Dendrobatidae, Epipedobates, Hyloxalus.MethodsWe determined the thermal performance curves (TPCs) of larval growth for each species and modelled the thermal variation in contrasting aquatic larval environments for both present and future times. This allowed us to estimate the expected elevational distributions and forecast periods of exposure to stressful temperatures that inhibit larval growth due to elevation and global warming.ResultsWe found significant correlations between optimum temperature (Topt), 50% maximum performance temperature (maxB50), 50% minimum performance temperature (minB50) and cold resistance (survival at 9°C) with the current elevational distributions. However, thermal physiology predicted lower than observed distributions for high‐elevation dendrobatids and higher than observed maximum elevations for lowland species. Nonetheless, our models predicted that low thermal variability habitats (i.e. streams and deep permanent ponds) can buffer the future temperature increase for all taxa, even when considering the most extreme scenario. In contrast, all species within high thermal variation habitats (open forest temporary ponds) are expected to experience stressful temperatures under present conditions.Main ConclusionsThe findings indicate that thermal physiology may not be a limiting factor for dendrobatid frog species' ranges in this equatorial mountain gradient. Highland species may need to adapt to suboptimal performance, while some lowland species could occupy higher elevations. This study emphasizes the importance of habitat buffering to mitigate thermal stress in the face of climate change for amphibians in tropical mountains.

Comparison of Hydric and Thermal Physiology in an Environmentally Diverse Clade of Caribbean Anoles.

As the world becomes warmer and precipitation patterns less predictable, organisms will experience greater heat and water stress. It is crucial to understand the factors that predict variation in thermal and hydric physiology among species. This study focuses on investigating the relationships between thermal and hydric diversity and their environmental predictors in a clade of Hispaniolan anole lizards, which are part of a broader Caribbean adaptive radiation. This clade, the "cybotoid" anoles, occupies a wide range of thermal habitats (from sea level to several kilometers above it) and hydric habitats (such as xeric scrub, broadleaf forest, and pine forest), setting up the possibility for ecophysiological specialization among species. Among the thermal traits, only cold tolerance is correlated with environmental temperature, and none of our climate variables are correlated with hydric physiology. Nevertheless, we found a negative relationship between heat tolerance (critical thermal maximum) and evaporative water loss at higher temperatures, such that more heat-tolerant lizards are also more desiccation-tolerant at higher temperatures. This finding hints at shared thermal and hydric specialization at higher temperatures, underscoring the importance of considering the interactive effects of temperature and water balance in ecophysiological studies. While ecophysiological differentiation is a core feature of the anole adaptive radiation, our results suggest that close relatives in this lineage do not diverge in hydric physiology and only diverge partially in thermal physiology.

Thermal scanners versus spotlighting: New opportunities for monitoring threatened small endotherms

AbstractThreatened species monitoring is challenging for small, cryptic endotherms that are most effectively detected at night. Low detectability is a challenge for monitoring programmes, resulting in low statistical power and sparse or zero‐inflated datasets. To advance conservation management programmes, efforts to address this are required. In recent years thermal scanners have emerged as an effective tool for detecting small endotherms, but the diversity of available thermal tools, focal habitats and target species mean that their applicability in many key scenarios remain untested. We directly compared vehicle‐mounted thermal surveys with vehicle‐based spotlighting targeting small endotherms in Australian native grasslands. Our targets included both common species that occur at high densities, and species that are notoriously difficult to detect with spotlights, which may occur at very low densities. We completed paired surveys of roosting grassland birds, and nocturnally active small mammals at 22 sites, once using thermal scanners and once using spotlights. Ultimately, distance sampling was conducted across 136 km of transects. Thermal scanners facilitated greater detection distances and higher total detections for small endotherms when compared with spotlighting. Species of greatest conservation concern, the Plains‐wanderer (Pedionomus torquatus—Pedionomidae) and Fat‐tailed Dunnart (Sminthopsis crassicaudata—Dasyuridae) were only detected using thermal scanners. Detection distances generated for thermal scanners were reduced by higher vegetation density; however, thermal scanners continued to outperform spotlights under this scenario. Observers also detected more stationary animals and fewer birds were flushed upon detection using thermal scanners when compared with spotlighting. Thermal scanners have the potential to improve the quality of monitoring datasets by increasing detection probabilities for small endotherms. We recommend the adoption of thermal scanners as a best‐practice tool for monitoring small endotherms in open grassland habitats at night, offering new opportunities to monitor endotherms where monitoring has historically been challenging, inadequate or impossible.

Unoccupied aerial vehicles as a tool to map lizard operative temperature in tropical environments

AbstractTo understand how ectotherms will respond to warming temperatures, we require information on thermal habitat quality at spatial resolutions and extents relevant to the organism. Measuring thermal habitat quality is either limited to small spatial extents, such as with ground‐based 3D operative temperature (Te) replicas, representing the temperature of the animal at equilibrium with its environment, or is based on microclimate derived from physical models that use land cover variables and downscale coarse climate data. We draw on aspects of both these approaches and test the ability of unoccupied aerial vehicle (UAV) data (optical RGB) to predict fine‐scale heterogeneity in sub‐canopy lizard (Anolis bicaorum) Te in tropical forest using random forest models. Anolis bicaorum is an endemic, critically endangered, species, facing significant threats of habitat loss and degradation, and work was conducted as part of a larger project. Our findings indicate that a model incorporating solely air temperature, measured at the centre of the 20 × 20 m plot, and ground‐based leaf area index (LAI) measurements, measured at directly above the 3D replica, predicted Te well. However, a model with air temperature and UAV‐derived canopy metrics performed slightly better with the added advantage of enabling the mapping of Te with continuous spatial extent at high spatial resolutions, across the whole of the UAV orthomosaic, allowing us to capture and map Te across the whole of the survey plot, rather than purely at 3D replica locations. Our work provides a feasible workflow to map sub‐canopy lizard Te in tropical environments at spatial scales relevant to the organism, and across continuous areas. This can be applied to other species and can represent species within the same community that have evolved a similar thermal niche. Such methods will be imperative in risk modelling of such species to anthropogenic land cover and climate change.

Molecular plasticity to ocean warming and habitat loss in a coral reef fish.

Sea surface temperatures are rising at unprecedented rates, leading to a progressive degradation of complex habitats formed by coral reefs. In parallel, acute thermal stress can lead to physiological challenges for ectotherms that inhabit coral reefs, including fishes. Warming and habitat simplification could push marine fishes beyond their physiological limits in the near future. Specifically, questions remain on how warming and habitat structure influence the brain of marine fishes. Here we evaluated how thermal stress and habitat loss are acting independently and synergistically as stressors in a damselfish of the Western Atlantic, Abudefduf saxatilis. For this experiment, 40 individuals were exposed to different combinations of temperature (27°C or 31°C) and habitat complexity (complex vs simple) for 10 days, and changes in brain gene expression and oxidative stress of liver and muscle were evaluated. The results indicate that warming resulted in increased oxidative damage in the liver (p=0.007) and changes in gene expression of the brain including genes associated with neurotransmission, immune function, and tissue repair. Individuals from simplified habitats showed higher numbers of differentially expressed genes, and changes for genes associated with synaptic plasticity and spatial memory. In addition, a reference transcriptome of A. saxatilis is presented here for the first time, serving as a resource for future molecular studies. This project enhances our understanding of how fishes are responding to the combination of coral reef degradation and thermal stress, while elucidating the plastic mechanisms that will enable generalists to persist in a changing world.