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. More-over, 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.
Warming temperatures caused by climate change are predicted to vary temporally and spatially. For mid‐ and high‐latitude reptiles, the seasonal variation in warming temperatures experienced by ...embryos and hatchlings may determine offspring fitness, yet this has remained largely unexplored.
To evaluate the independent and interactive influence of seasonal variation in warming temperatures on embryonic and hatchling development, we incubated eggs and reared hatchlings of a cold‐climate oviparous ectothermic species, the Heilongjiang grass lizard (Takydromus amurensis), following a 2 × 2 factorial design (present climate versus warming climate for embryos × present climate versus warming climate for hatchlings). We then evaluated embryonic and hatchling development, including hatching success, incubation period, initial hatchling body size, hatchling metabolic rate, growth rate and survival in the mesocosms.
We found that warming temperatures shortened the incubation period and produced hatchlings with higher survival rates than those incubated under the present climate conditions. Similarly, hatchlings reared under a warming climate had similar growth rates and resting metabolic rates, but higher survival rates than those reared under the present climate. Hatchlings that experienced both warming incubation and warming growth conditions had the highest survival rates.
This study revealed that moderate warming temperatures (Representative Concentration Pathway, RCP 4.5, 1.1–2.6°C) experienced by embryos and hatchlings interact to benefit hatchling fitness in cold‐climate oviparous ectotherms. Our study also highlighted the importance of integrating seasonal variation in warming temperatures when evaluating the responses to climate warming in multiple developmental stages in oviparous ectotherms.
摘要
气候变暖导致的温度升高存在着时空变异。对于中高纬度的爬行动物而言, 胚胎发育和后代生长经历的变暖温度可能存在季节间差异。而此种季节间差异的变暖温度如何影响后代的适合度, 目前仍然知之甚少。
为了评估季节间差异的变暖温度对胚胎发育和后代发育的独立或交互的影响, 我们以一种寒冷气候区分布的卵生外温物种黑龙江草蜥 (Takydromus amurensis) 为研究对象, 利用2 × 2因子控制的实验方案开展胚胎孵化和幼体饲养等工作 (当前气候与变暖气候胚胎孵化 × 当前气候与变暖气候幼体饲养)。并且, 我们检测了胚胎和幼体发育的指标, 包括孵化成功率、孵化期和幼体初始体长和体重、幼体代谢率、生长率和存活率等。
我们发现, 模拟气候变暖的孵化环境缩短了胚胎的孵化期, 并且孵出的幼体具有更高的存活率。此外, 尽管与当前气候下饲养的幼体在生长率和代谢率上并无差异, 但是在模拟变暖气候下饲养的幼体的存活率得到了显著地提升。从胚胎发育到后代生长阶段均经历变暖温度的幼体, 具有最高的存活率。
本研究揭示了胚胎和幼体均经历中等程度的气候变暖 (RCP 4.5, 1.1–2.6°C) 交互地提升了幼体的适合度, 证明了中等程度的气候变暖可能有益于寒冷气候的卵生外温动物。不仅如此, 本研究也强调了在评估具有多生活史阶段的卵生外温动物对气候变暖的响应时, 考虑季节间温度变暖差异的重要性。
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Read the free Plain Language Summary for this article on the Journal blog.
Diamonds were brazed on the substrate with nickel‑chromium (NiCr) filler alloy at a certain temperature for three different mesh belt speeds in the mesh belt continuous tunnel furnace, respectively. ...In this study, a different perspective involving the exploration of the new processes was used that could allow for the mass production of brazed diamond tools. The interfacial microstructure between the diamonds and filler alloy was analyzed by scanning electron microscopy, energy dispersive spectrometry, and X-ray diffraction. The residual stresses and mechanical properties of the brazed diamonds were determined through the laser Raman spectrum and the compressive strength or impact toughness testing equipment for superabrasives, respectively. The results illustrated the occurrence of chemical reaction at the interface of the filler alloy-diamond followed by the formation of the CrC compound. Moreover, the thickness of the interfacial reaction layer increased with the decrease in the mesh belt speed. The brazing high temperature and development of the CrC layer were found to be responsible for the residual stresses in the diamonds. The mechanical properties of the brazed diamond grits strongly depended on the resultant thickness of the diamond surface and the residual stresses produced during brazing.
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•The diamond was successfully brazed in tunnel furnace, which can heat continuously and carry out a large-scale production.•Effects of process parameters on microstructure, residual stresses and properties of brazed diamonds were investigated.•Correlations among microstructure, residual stresses and properties of tunnel furnace brazed diamond were identified.
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.
A free Plain Language Summary can be found within the Supporting Information of this article
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Natural nests of egg-laying birds and reptiles exhibit substantial thermal variation, at a range of spatial and temporal scales. Rates and trajectories of embryonic development are highly sensitive ...to temperature, favouring an ability of embryos to respond adaptively (i.e. match their developmental biology to local thermal regimes). Spatially, thermal variation can be significant within a single nest (top to bottom), among adjacent nests (as a function of shading, nest depth etc.), across populations that inhabit areas with different weather conditions, and across species that differ in climates occupied and/or nest characteristics. Thermal regimes also vary temporally, in ways that generate differences among nests within a single population (e.g. due to seasonal timing of laying), among populations and across species. Anthropogenic activities (e.g. habitat clearing, climate change) add to this spatial and temporal diversity in thermal regimes. We review published literature on embryonic adaptations to spatio-temporal heterogeneity in nest temperatures. Although relatively few taxa have been studied in detail, and proximate mechanisms remain unclear, our review identifies many cases in which natural selection appears to have fine-tuned embryogenesis to match local thermal regimes. Developmental rates have been reported to differ between uppermost versus lower eggs within a single nest, between eggs laid early versus late in the season, and between populations from cooler versus warmer climates. We identify gaps in our understanding of thermal adaptations of early (embryonic) phases of the life history, and suggest fruitful opportunities for future research.
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.
Research on the thermal ecology of reptiles and amphibians has facilitated hypothesis testing about how climate change will impact biodiversity. This review article discusses the best practices in thermal research to help unite research toward the common goal of better understanding how temperature impacts organisms.
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.
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.
Plain Language Summary
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
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.
We review methods for calculating heat tolerance of non‐avian reptile embryos and define new metrics that can be used to better compare embryo thermal physiology across studies and species.
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.
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