Search

Copyright of Conservation Biology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The climate variable hypothesis predicts low-latitude organisms have limited physiological acclimation to thermal variations. We experimentally manipulated thermal environments for I Takydromus i lizards from three latitudinal species and determined their physiological responses at multiple levels, including metabolic rates, growth, organ sizes, mitochondrial respiration, and proteomic and metabolomic regulations. [Extracted from the article]

Copyright of Functional Ecology is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Heat tolerance at the immobile embryonic stage is expected to be critical in determining species vulnerability to climate change. However, how the mean and developmental plasticity of embryonic heat tolerance vary geographically, and how these geographic variations affect species' vulnerability under climate change remain unknown. We experimentally determined the mean and developmental plasticity of embryonic acute heat tolerance (EAHT, i.e., heat shock temperature at which embryonic heartbeats ceased) for three latitudinally distributed populations of an oviparous lacertid lizard. The experimental results suggested that the mean EAHT decreased with decreasing latitude and that the reaction norms of EAHT in relation to developmental temperatures showed "flat," "bell‐shaped," and "decreasing" patterns at high, medium, and low latitudes, respectively. Based on the means and plasticity of EAHT and weather data across China, we project that the heat stress frequency would increase from the present to the future and increase toward low latitudes. Furthermore, heat stress becomes more extensive with the incorporation of developmental plasticity. Incorporating the mean EAHT during the embryonic development season, heat stress frequency, and climate variables in a species distribution model projects that suitable habitats could move northward in response to ongoing climate change and shrink due to the loss of southern habitat. Moreover, even lizards within the areas that are predicted to remain highly suitable are expected to experience increases in heat stress over time, particularly at medium and low latitudes. Our study reveals geographic variation in the mean and developmental plasticity of EAHT and highlights its importance for predicting species vulnerability and range shifts in response to climate change. [ABSTRACT FROM AUTHOR]

Our results show embryos from the low-latitudinal population had low EAHT and decreased developmental plasticity of EAHT against incubation temperatures. Under ongoing climate warming, how embryos of oviparous species tolerate the extreme heat events geographically is critical to predict the vulnerabilities of organisms. [Extracted from the article]

Aspects of global change result in warming temperatures that threaten biodiversity across the planet. Eggs of non‐avian, oviparous reptiles (henceforth "reptiles") are particularly vulnerable to warming due to a lack of parental care during incubation and limited ability to behaviorally thermoregulate. Because warming temperatures will cause increases in both mean and variance of nest temperatures, it is crucial to consider embryo responses to both chronic and acute heat stress. Although many studies have considered embryo survival across constant incubation temperatures (i.e., chronic stress) and in response to brief exposure to extreme temperatures (i.e., acute stress), there are no standard metrics or terminology for determining heat stress of embryos. This impedes comparisons across studies and species and hinders our ability to predict how species will respond to global change. In this review, we compare various methods that have been used to assess embryonic heat tolerance in reptiles and provide new terminology and metrics for quantifying embryo responses to both chronic and acute heat stress. We apply these recommendations to data from the literature to assess chronic heat tolerance in 16 squamates, 16 turtles, five crocodilians, and the tuatara and acute heat tolerance for nine squamates and one turtle. Our results indicate that there is relatively large variation in chronic and acute heat tolerance across species, and we outline directions for future research, calling for more studies that assess embryo responses to acute thermal stress, integrate embryo responses to chronic and acute temperatures in predictive models, and identify mechanisms that determine heat tolerance. Highlights: We propose metrics for reptile embryo heat tolerance with respect to chronic and acute temperatures and describe how future studies can incorporate these metrics to advance our understanding of embryo thermal physiology. [ABSTRACT FROM AUTHOR]

Research on the thermal ecology and physiology of free‐living organisms is accelerating as scientists and managers recognize the urgency of the global biodiversity crisis brought on by climate change. As ectotherms, temperature fundamentally affects most aspects of the lives of amphibians and reptiles, making them excellent models for studying how animals are impacted by changing temperatures. As research on this group of organisms accelerates, it is essential to maintain consistent and optimal methodology so that results can be compared across groups and over time. This review addresses the utility of reptiles and amphibians as model organisms for thermal studies by reviewing the best practices for research on their thermal ecology and physiology, and by highlighting key studies that have advanced the field with new and improved methods. We end by presenting several areas where reptiles and amphibians show great promise for further advancing our understanding of how temperature relations between organisms and their environments are impacted by global climate change. Highlights: we provide a useful "how to" guide for studying the thermal ecology of reptiles and amphibians.We highlight key studies on reptiles and amphibians that help us understand the impacts of the climate crisis on biodiversity. [ABSTRACT FROM AUTHOR]

Flight of nocturnal insects may be limited by cool nighttime environmental temperatures. We used laboratory and field experiments to explore the thermal basis of nocturnal flight in wing‐polymorphic Gryllus lineaticeps crickets consisting of long‐winged (LW), flight‐capable morphs and short‐winged (SW), flight‐incapable morphs. These crickets are a model for life history evolution and loss of flight, but their thermal requirements for flight have been unknown. We hypothesized that LW crickets achieve warm body temperatures required for flight through a combination of behavioural thermoregulation, producing heat endogenously (either by initiating muscular thermogenesis or increasing resting metabolic rate) and minimizing heat loss (by circulatory adjustments or insulation).Summer evening air temperatures in the field gradually declined from 25 to 18°C during the hours of nighttime cricket activity. Laboratory LW crickets did not fly at a body temperature of 18°C, and 60% flew at 25°C. In an experimental thermal gradient, spontaneous flight did not occur until body temperature exceeded 35°C, confirming that nocturnal field air temperature limits flight in this species.In a thermal gradient, LW crickets preferred higher temperatures (~36°C) than SW crickets (~32.5°C). In the field, all crickets were warmer than air temperature but considerably cooler than their preferred temperatures. LW crickets had higher field body temperatures (24.3°C) than SW crickets (22.3°C). LW crickets spontaneously initiated muscular thermogenesis through wing vibrations, increasing body temperature to a pre‐flight maximum of 35°C. Muscular thermogenesis was limited below 25°C. LW crickets cooled more slowly and had higher metabolic rates than SW crickets.We conclude that LW crickets prepare to fly on cool nights by gaining heat from warm substrates, activating endogenous muscular thermogenesis and reducing their cooling rate. These mechanisms are absent or less pronounced in SW crickets. The overall thermoregulatory strategy we report represents a previously unrecognized component of insect dispersal polymorphism. We suggest that thermal constraints on nocturnal flight may have contributed to evolutionary loss of flight in other insect groups. A free Plain Language Summary can be found within the Supporting Information of this article. [ABSTRACT FROM AUTHOR]

A major goal of seasonal biology is to understand how selection on phenology and the physiological niche interact. In oviparous species, fitness variation across the growing season suggests that phenological shifts will alter selective environments experienced by embryos. We hypothesize that physiology could become co‐adapted with phenology; such that embryos perform better in the environmental conditions they are adapted to compared to embryos adapted to other environments (temporal matching).Here, we tested for temporal matching to seasonal changes in the environmental temperatures with toad‐headed lizard, Phrynocephalus przewalskii, which inhabits the temperate desert steppe of China. We used a split‐clutch reciprocal experiment, by incubating eggs from early‐ and late‐breeding females at rising and falling temperature regimes, respectively, to separate the influence of intrinsic (genetic and parental) vs. extrinsic factors (developmental plasticity or acclimatization) on the performance and fitness of offspring.Eggs from early‐breeding females were with higher quality than those from late‐breeding females, likely due to better maternal provisioning. Offspring from early‐breeding females had higher selected body temperatures and metabolic rates than those from late‐breeding females.Falling temperatures that may indicate the end of the growing season, reduced incubation duration and increased metabolic rates for both early and late eggs, compared to rising temperatures. Late hatchlings had higher growth rates when incubated at falling compared to rising temperatures, while growth rates of early hatchlings were not sensitive to incubation temperature. Thus, growth and survival rates of late embryos were similar to early embryos under falling temperatures, despite early embryos being of generally higher quality.Overall, our study confirms that "early is higher quality." Intrinsic factors dominate offspring performance and fitness, with a general advantage for early embryos throughout the season. We found some support for temporal matching, demonstrating that late embryos with lower quality have physiological strategies that are specialized to late‐season environments, allowing them to attain similar fitness in late‐season environments to that of early embryos. A plain language summary is available for this article. Plain Language Summary [ABSTRACT FROM AUTHOR]

The vulnerability of species to climate warming varies along latitudinal and elevational clines, but how sympatric species vary in vulnerability to climate warming remains largely unknown. We experimentally simulated nest temperatures of two sympatric lizards with divergent microhabitat preferences (Phrynocephalus przewalskii and Eremias argus), under climate warming senarios, to determine the response of embryos to increased mean temperatures and heat waves. Our study demonstrated that simulated climate warming reduced hatching success and hatchling size and growth in E. argus (that prefers closed microhabitats), but had less effect in P. przewalskii (that occupies open microhabitats). The reduced growth rate of E. argus hatchlings was associated with a decrease in metabolic rate, which was more evident in hatchling E. argus than in P. przewalskii. Our results suggest lizards that prefer closed microhabitats may be more vulnerable to climate warming than those that prefer open microhabitats; further studies are needed to test this hypothesis. More generally, the divergent responses of sympatric species to climate warming highlights the importance of distinguishing the thermal sensitivity of behavior and physiology for each species of a community, in order to make predictions about the impacts of climate warming at regional scales. Our study reveals divergent responses between sympatric species to climate warming (including heat waves). And we highlight the importance of distinguishing the thermal sensitivity of behavior and physiology in each species of a community, and of considering the response of each species as a unit of interest rather than simply the response of the community as a whole. We provide a more detailed picture of the impact of climate warming on organisms, allowing us to predict outcomes and develop more effective conservation strategies. [ABSTRACT FROM AUTHOR]

Abstract: The fitness consequence of maternal nest‐site choice has attracted increasing scientific attention, but field studies identifying the long‐term effects of nest‐site choice on offspring survival and reproductive success are still rare in vertebrates. To investigate the consequences of nest‐site choice in lizards, we quantified the thermal and hydric conditions of nest sites that were chosen by female toad‐headed agama (Phrynocephalus przewalskii) in the desert steppe of northern China. We also determined the effect of nest‐site choice on embryonic development and survival and on offspring growth, survival and maturity by comparing the embryos and offspring from maternally and randomly chosen nest sites. We found that female toad‐headed agama chose warm and moist nest sites that improved the developmental rate and survivorship of embryos and promoted the post‐hatching growth, sexual maturity, reproduction and fitness of offspring, thereby improving their reproductive success. Such studies on short‐lived lizards across multiple stages of embryonic and postembryonic ontogeny are critical for fully understanding the fitness consequences of nest‐site choice. A plain language summary is available for this article. [ABSTRACT FROM AUTHOR]