Disparate patterns of thermal adaptation between life stages in temperate vs. tropical Drosophila melanogaster

Many terrestrial ectothermic species exhibit limited variation in upper thermal tolerance across latitude. However, these trends may not signify limited adaptive capacity to increase thermal tolerance in the face of climate change. Instead, thermal tolerance may be similar among populations because behavioural thermoregulation by mobile organisms or life stages may buffer natural selection for thermal tolerance. We compared thermal tolerance of adults and embryos among natural populations of Drosophila melanogaster from a broad range of thermal habitats around the globe to assess natural variation of thermal tolerance in mobile vs. immobile life stages. We found no variation among populations in adult thermal tolerance, but embryonic thermal tolerance was higher in tropical strains than in temperate strains. We further report that embryos live closer to their upper thermal limits than adults – that is, thermal safety margins are smaller for embryos than adults. F1 hybrid embryos from crosses between temperate and tropical populations had thermal tolerance that matched that of tropical embryos, suggesting the dominance of heat‐tolerant alleles. Together, our findings suggest that thermal selection has led to divergence in embryonic thermal tolerance but that selection for divergent thermal tolerance may be limited in adults. Further, our results suggest that thermal traits should be measured across life stages to better predict adaptive limits.     

热带季节雨林林窗边缘不同热力作用面热力效应的季节变化特征

通过对热带季节雨林雾凉季和湿热季昼间林窗区域不同热力作用面的热力效应初步分析,指出在西双版纳,不论是雾凉季还是湿热季,热带季节雨林林窗边缘壁面均具有不可忽视的热力作用,且由于受林缘树木的影响,热力效应较强的东侧,北侧林缘壁面最大区域出现位置高于次生林林窗,而强度小于次生林林窗,显示了林窗边缘壁面的热力效应除与太阳高度角,太阳辐射的时间长短和强度有关之外,林窗边缘树木高度也是不可忽视的因子,其结果可为进一步研究林窗小气候形成机制提供研究基础,为研究林窗更新及生物多样性问题提供科学参考。     

城市化进程中城市热岛景观格局演变的时空特征——以厦门市为例

热岛效应作为城市化过程中产生的特有环境问题,对其形成和演变规律的研究有助于人们提出有效的应对措施。以厦门市为研究对象,利用1987—2007年等时间间隔、同时相的5景Landsat TM/ETM+遥感影像数据进行地表温度反演,在此基础上使用景观格局指数分析厦门城市热岛景观格局随城市化进程演变的趋势。结果表明:随着厦门城市化进程加深,整个热岛景观在逐渐变得更加破碎化,高等级热岛景观斑块个数、类型面积和个体面积都增大;新的高等级热岛景观斑块都出现在原有高等级斑块附近,致使高等级类型的邻近度增加而各类型之间相互接触的程度也增加;景观总体的聚合度逐渐下降,而高等级热岛景观类型的聚合度则呈上升趋势;景观水平的蔓延度总体呈下降趋势,优势度高的低等级热岛景观所占的比重下降,优势度逐渐降低;多样性指数、均匀度指数总体呈上升趋势,各热岛景观面积在各类型间的分配逐渐趋于均匀;热岛景观斑块的转化方面,在20 a间低等级斑块类型(1、2、3级)向高等级斑块类型(4、5、6级)转化的面积总体上呈增加趋势,而高等级斑块类型向低等级斑块类型转化的面积总体上呈减小趋势,且等级升高的面积明显大于同期等级降低的面积;就高等级热岛景观斑块而言,他们与3级热岛景观斑块间的相互转化最容易发生,远比高等级斑块内部各类型之间的相互转化来得容易,尤其6类和5类的转化是最为困难的热岛景观变化之一;从空间上看,各高等级热岛景观斑块都经历了数量增加、面积扩大、等级升高三个方面的变化,形成了海沧、新阳、杏林、厦门岛西北港口区和机场5个高温组团。利用景观指数分析城市热环境,可探明热岛景观随城市化演变的趋势,并为有效的热岛效应减缓措施提供直接的理论依据。     

Correlated evolution of thermal niches and functional physiology in tropical freshwater fishes

The role of ecology in phenotypic and species diversification is widely documented. Nonetheless, numerous nonadaptive processes can shape realized niches and phenotypic variation in natural populations, complicating inferences about adaptive evolution at macroevolutionary scales. We tested for evolved differences in thermal tolerances and their association with the realized thermal niche (including metrics describing diurnal and seasonal patterns of temperature extremes and variability) across a genus of tropical freshwater fishes reared in a standardized environment. There was limited evolution along the thermal niche axis associated with variation in maximum temperature and in upper thermal limits. In contrast, there was considerable diversification along the first major axis of the thermal niche associated with minimum temperatures and in lower thermal limits. Across our adaptive landscape analyses, 70% of species exhibited evidence of divergence in thermal niches. Most importantly, the first two major axes of thermal niche variation were significantly correlated with variation in lower thermal limits. Our results indicate adaptation to divergent thermal niches and adaptive evolution of related functional traits, and highlight the importance of divergence in lower thermal limits for the evolution of tropical biodiversity.     

Hydroxylapatite thermal fractionation of chromatin and DNA

Chromatin and DNA from developing muscle cultures were fractionated by hydroxylapatite thermal chromatography on the basis of differential thermal stability. A thermal chromatography system was developed in which protein mediated thermal stability of chromatin DNA was maximally expressed. The resulting chromatin and DNA elution profiles were similar to thermal denaturation profiles in low ionic strength solution. Additional studies showed this system was able to detect protein stabilization of DNA in in vitro nucleohistone preparations. Although some protein remained bound to hydroxylapatite during chromatin thermal elution, it did not affect the denaturation or elution behavior of free DNA on the same column. These studies show that fragments of chromatin or DNA can be segregated on the basis of differential thermal stability by hydroxylapatite chromatography.     

Identification of local thermal conditions for sleeping comfort improvement in neutral to cold indoor thermal environments

The effect of the thermal environment on sleep quality has attracted considerable attention, as sleep forms one-third of human lifetime and the occupied space is largely constrained during sleep. With an increasing development of partial space regulation and task air conditioning systems and devices, thermal comfort demand concerning local thermal conditions has attracted more and more attention. In the present study, experiment was conducted and data mining technologies were performed to investigate correlations between local thermal conditions and whole body thermal comfort in sleeping state. The identification of local thermal condition included two steps: the first step was to clarify thermal sensation links between local and covered body, and the second step was to identify local thermal sensation inclination towards different thermal comfort levels. Thermal sensation correlations among local body parts and covered body were obtained. Back, face, and thigh were identified as three dominant linear-correlated local parts with weighting factors 0.488, 0.388, and 0.152, respectively; in addition, chest, arm, leg and foot were found as non-negligible local parts in the estimation of covered body thermal sensation. By dividing the sleeping human body into three parts as head, trunk and extremity, the proper local thermal sensations and their coupling relationships for whole body sleeping thermal comfort have been elaborated by three rules. The present study provides implications in sleeping thermal environment regulation in neutral to cold indoor conditions.     

Thermal freedom of Graomys griseoflavus in a seasonal environment

1. Thermal freedom, defined as the physiological potential to make full spatiotemporal use of the seasonal thermal macroclimate, was assessed in Graomys griseoflavus, a cricetid rodent inhabiting the Chaco Province in Argentina. 2. The extent of the physiological thermal range (58 degrees C) was larger than the seasonal thermal range (30-50 degrees C), favoring Graomys resistance to low winter temperatures. The upper physiological thermal limit was almost coincident with the highest extreme of summer temperatures. 3. Graomys thermal freedom is facilitated by a high evaporative water loss, high metabolic capability, wide thermal neutral zone and a 4 degrees C lability of body temperature. 4. Behavioral responses (thermal avoidance) are utilized by this species, but with no apparent loss in thermal freedom.     

Analysis of thermal stress in cryosurgery of kidneys

In this study, the thermal stress distribution in cryosurgery of kidney was investigated using a multiphysics finite element model developed in ANSYS (V8.1). The thermal portion of the model was verified using experimental data and the mechanics portion of the model (elastic) was verified using classic analytical solutions. Temperature dependent thermal and mechanical properties were used in the model. Moreover, the model accounts for thermal expansion due to both thermal expansion in single phase and volumetric expansion associated with phase change of tissue water to ice. For a clinical cylindrical cryoprobe inserted into the renal cortex from the top-middle renal capsule, it was found that the thermal stress distributions along the radial position are very different at different depths from the top renal capsule. The thermal stress is much higher at both ends than in the middle of the cryoprobe surface. It was found that there might be more tissue next to the top renal capsule than other region undergoing microcrack formation or plastic deformation. Furthermore, it was found that macrocrack formation is more likely to occur in tissue adjacent to the cryoprobe surface (especially on the sharp point tip) and during the thawing phase of cryosurgery. It was further found that the volumetric expansion associated with phase change induced much higher thermal stress than thermal expansion in a single phase and might therefore be the main cause of the frequently observed crack formation shortly after initiation of thawing in cryosurgery. Because the thermal stress adjacent to the cryoprobe is much higher than the yield stress of frozen renal tissue, a plastic stress model is required for better modeling of the thermal stress distribution in cryosurgery of kidney in future. However the computational effort will then be drastically increased due to the strong nonlinear nature of the plastic model and more experimental studies are indispensable for better understanding of the mechanical behavior of frozen tissue in cryosurgery.     

Effects of troponin on thermal unfolding of actin-bound tropomyosin

Differential scanning calorimetry (DSC) was used to study the effect of troponin (Tn) and its isolated components on the thermal unfolding of skeletal muscle tropomyosin (Tm) bound to F-actin. It is shown that in the absence of actin the thermal unfolding of Tm is expressed in two well-distinguished thermal transitions with maxima at 42.8 and 53.8°C. Interaction with F-actin affects the character of thermal unfolding of Tm leading to appearance of a new Tm transition with maximum at about 48°C, but it has no influence on the thermal denaturation of F-actin stabilized by aluminum fluoride, which occurs within the temperature region above 70°C. Addition of troponin leads to significant increase in the cooperativity and enthalpy of the thermal transition of the actin-bound Tm. The most pronounced effect of Tn was observed in the absence of calcium. To elucidate how troponin complex affects the properties of Tm, we studied the influence of its isolated components, troponin I (TnI) and troponin T (TnT), on the thermal unfolding of actin-bound Tm. Isolated TnT and TnI do not demonstrate cooperative thermal transitions on heating up to 100°C. However, addition of TnI, and especially of TnT, to the F-actin–Tm complex significantly increased the cooperativity of the thermal unfolding of actin-bound tropomyosin.     

Thermal ecology and physiology of an elongate and semi-fossorial arthropod,the bark centipede

Organismal performance is strongly linked to temperature because of the fundamental thermal dependence of chemical reaction rates. However, the relationship between the environment and body temperature can be altered by morphology and ecology. In particular, body size and body shape can impact thermal inertia, as high surface area to volume ratios will possess low thermal mass. Habitat type can also influence thermal physiology by altering the opportunity for thermoregulation. We studied the thermal ecology and physiology of an elongate invertebrate, the bark centipede (Scolopocryptops sexspinosus). We characterized field body temperature and environmental temperature distributions, measured thermal tolerance limits, and constructed thermal performance curves for a population in southern Georgia. We found evidence that bark centipedes behaviorally thermoregulate, despite living in sheltered microhabitats, and that performance was maintained over a broad range of temperatures (over 20 °C). However, both the thermal optimum for performance and upper thermal tolerance were much higher than mean body temperature in the field. Together, these results suggest that centipedes can thermoregulate and maintain performance over a broad range of temperatures but are sensitive to extreme temperatures. More broadly, our results suggest that wide performance breadth could be an adaptation to thermal heterogeneity in space and time for a species with low thermal inertia.     

绿量的城市热环境效应研究现状与展望

绿量对城市热环境的调控功能已成为目前研究热点。本文从绿量的概念与发展、绿量与城市热环境的调查方法、绿量与城市热环境的关联性以及其在城市规划方面的启示4方面进行论述,总结国内外研究进展,提出了未来该领域的4个发展方向,包括三维绿量调查方法的改善、城市热环境的监测与预测、城市绿量三维空间格局指标体系的构建以及关联绿量与城市热环境研究的三维空间格局分析方法的创建。本文为研究绿量调控城市热环境提供了一种三维空间分析的视角,以期更深入地探索城市绿量的三维空间格局、平衡城市热环境的适宜性和多方面生态效益,为城市绿色空间规划与设计提供科学依据,也为人类适应气候变化并科学调控城市热环境提供理论支持。     

Generalist grasshoppers from thermally variable sites do not have higher thermal tolerance than grasshoppers from thermally stable sites - A study of five populations

Thermal tolerance allows many organisms, including insects, to withstand stressful temperatures. Thermal generalists are expected to have higher thermal tolerance than specialists, but the environmental conditions leading to the evolution of a thermal generalist life history are not fully understood. Thermal variability has been put forth as an evolutionary driver of high thermal tolerance, but rarely has this been empirically tested. We used a generalist agricultural pest grasshopper, Melanoplus differentialis, to test upper and lower thermal limits of populations that experienced different levels of thermal variability.We quantified thermal heterogeneity at five sites in a longitudinal transect in the Midwestern U.S. by examining, over a 101-year period, 1) variance in daily thermal maxima and minima; and 2) daily range. Also, as a measure of a biologically relevant thermal extreme, we depicted days per month at each site that reached a stressfully high temperature for M. differentialis. We collected individuals from these sites and tested their upper and lower thermal limits. We found that most of our metrics of thermal heterogeneity differed among sites, while all sites experienced an average of at least two stressfully high temperature events per month. We found that heavier males from these sites were able to withstand both warmer and colder temperatures than smaller males, while heavier females had no thermal advantage over lighter females. However, site of origin had no effect on thermal tolerance.Our findings indicate three things: 1) there is no clear correlation between thermal variability and thermal tolerance in the populations we studied; 2) weight affects thermal tolerance range among sites for M. differentialis males, and 3) thermal extremes may be more important than thermal variability in determining CTMax in this species.     

A comparative analysis of the upper thermal tolerance limits of eastern Pacific porcelain crabs, genus Petrolisthes: influences of latitude, vertical zonation, acclimation, and phylogeny

Marine intertidal organisms are subjected to a variety of abiotic stresses, including aerial exposure and wide ranges of temperature. Intertidal species generally have higher thermal tolerance limits than do subtidal species, and tropical species have higher thermal tolerance limits than do temperate species. The adaptive significance of upper thermal tolerance limits of intertidal organisms, however, has not been examined within a comparative context. Here, we present a comparative analysis of the adaptive significance of upper thermal tolerance limits in 20 congeneric species of porcelain crabs, genus Petrolisthes, from intertidal and subtidal habitats throughout the eastern Pacific. Upper thermal tolerance limits are positively correlated with surface water temperatures and with maximal microhabitat temperatures. Analysis of phylogenetically independent contrasts (from a phylogenetic tree on the basis of the 16s rDNA gene sequence) suggests that upper thermal tolerance limits have evolved in response to maximal microhabitat temperatures. Upper thermal tolerance limits increased during thermal acclimation at elevated temperatures, the amount of increase being greater for subtidal than for intertidal species. This result suggests that the upper thermal tolerance limits of some intertidal species may be near current habitat temperature maxima, and global warming thus may affect the distribution limits of intertidal species to a greater extent than for subtidal species.     

Characterization of the thermal tolerances of forest ants of New England

Characterization of thermal tolerances of ants, which are both abundant and important in most terrestrial ecosystems, is needed since thermal constraints can inform how a species may respond to local climatic change. Here we identified the thermal tolerances of 16 common ant species of the Northeastern United States and determined relationships between body size, desiccation, and thermal tolerance among species. We hypothesized that maximum heat tolerances of these species would differ and be related to body size and capacity to resist desiccation. We identified four distinct groups of species belonging to one of three subfamilies, Dolichoderinae, Formicinae, or Myrmicinae, with different maximum thermal tolerances. Group “a” had a mean thermal tolerance of approximately 43°C (±1°C), group “b” had a mean thermal tolerance of 40°C (±1°C), group “c” had a mean thermal tolerance of 38°C (±0°C), and group “d” had a mean thermal tolerance of 36°C (±0°C). Groups “a” and “d” consisted of a single species (in the subfamilies Myrmicinae and Formicinae, respectively), while groups “b” and “c” were a mix of species in the subfamilies Myrmicinae, Formicinae, and Dolichoderinae. In the subfamily Formicinae, thermal tolerance increased with body size and critical water content, a metric of desiccation tolerance. In contrast, in the subfamily Myrmicinae, higher thermal tolerance was correlated with intermediate body size and lower critical water content. These findings suggest that the two dominant subfamilies in Northeastern deciduous forests have different relationships between body size, capacity to tolerate desiccation, and thermal tolerances across species. This variation in thermal tolerance suggests that climatic change may impact species differently.     

Thermal comfort of various building layouts with a proposed discomfort index range for tropical climate

Recent years have seen issues related to thermal comfort gaining more momentum in tropical countries. The thermal adaptation and thermal comfort index play a significant role in evaluating the outdoor thermal comfort. In this study, the aim is to capture the thermal sensation of respondents at outdoor environment through questionnaire survey and to determine the discomfort index (DI) to measure the thermal discomfort level. The results indicated that most respondents had thermally accepted the existing environment conditions although they felt slightly warm and hot. A strong correlation between thermal sensation and measured DI was also identified. As a result, a new discomfort index range had been proposed in association with local climate and thermal sensation of occupants to evaluate thermal comfort. The results had proved that the respondents can adapt to a wider range of thermal conditions.Validation of the questionnaire data at Putrajaya was done to prove that the thermal sensation in both Putrajaya and UTM was almost similar since they are located in the same tropical climate region. Hence, a quantitative field study on building layouts was done to facilitate the outdoor human discomfort level based on newly proposed discomfort index range. The results showed that slightly shaded building layouts of type- A and B exhibited higher temperature and discomfort index. The resultant adaptive thermal comfort theory was incorporated into the field studies as well. Finally, the study also showed that the DI values were highly dependent on ambient temperature and relative humidity but had fewer effects for solar radiation intensity.     

热带次生林林窗不同热力作用面特征分析

利用热带次生林林窗边缘树表温和林窗区域地表温的观测资料,探讨了昼间林窗各热力作用面的热力效应及其变化规律,通过分析林窗边缘树表温和林窗地表温的变化,指出在林窗区域林窗边缘墙面是林冠面,林窗地面,林内地面之外的亲的第4热力作用面;各个热力作用面的热力效应随季节,位置和时刻的不同有着明显差异,在受浓雾影响的上午,林窗地面热力作用较强,在中午和下午林窗东侧林缘壁面,林窗东侧－东北侧地面的热力作用显著,中乖以林窗地面作用较强;而下午则以林窄边缘墙面作用较强,各个较力作用面的热力特征和相互作用将制约林窗的热力变化,影响植物的生长。     

Influence of doped nitrogen and vacancy defects on the thermal conductivity of graphene nanoribbons

A systematic investigation of the thermal conductivity of zigzag graphene nanoribbons (ZGNRs) doped with nitrogen and containing a vacancy defect was performed using reverse nonequilibrium molecular dynamics (RNEMD). The investigation showed that the thermal conductivity of the ZGNRs was significantly reduced by nitrogen doping. The thermal conductivity dropped rapidly when the nitrogen doping concentration was low. Also, the presence of a vacancy defect was found to significantly decrease the thermal conductivity. Initially, as the vacancy moved from the heat sink to the heat source, the phonon frequency and the phonon energy increased, and the thermal conductivity decreased. When the distance between the vacancy in the ZGNR and the edge of the heat sink reached 2.214 nm, tunneling began to occur, allowing high-frequency phonons to pass through the vacancies and transfer some energy. The curve of the thermal conductivity of the ZGNRs versus the vacancy position was found to be pan-shaped, with the thermal conductivity of the ZGNRs controlled by the phonon. These findings could be useful when attempting to control heat transfer on the nanoscale using GNR-based thermal devices.     

Effect of volumetric water content on thermal properties of dairy cattle feces mixed with sawdust

This paper describes the thermal properties (effective thermal conductivity and thermal diffusivity) of an organic waste used to model the composting process in relation to volumetric water content at 20°C. The organic waste was a mixture of fresh dairy cattle feces and sawdust with a ratio of one-to-one on a dry weight basis. The thermal probe method was used to determine the effective thermal conductivity and diffusivity. The effective thermal conductivities were found to increase with volumetric water content, and ranged from 0.0500 to 0.202 W m⁻¹ K⁻¹ at volumetric water contents of 0% and 44.2%, respectively. The thermal diffusivity was not affected by the volumetric water content, and was found to have a mean value of 1.08 × 10⁻⁷ m² s⁻¹.     

Thermal fluctuation spectroscopy of DNA thermal denaturation

We have developed the technique of thermal fluctuation spectroscopy to measure the thermal fluctuations in a system. This technique is particularly useful to study the denaturation dynamics of biomolecules like DNA. Here we present a study of the thermal fluctuations during the thermal denaturation (or melting) of double-stranded DNA. We find that the thermal denaturation of heteropolymeric DNA is accompanied by large, non-Gaussian thermal fluctuations. The thermal fluctuations show a two-peak structure as a function of temperature. Calculations of enthalpy exchanged show that the first peak comes from the denaturation of AT rich regions and the second peak from denaturation of GC rich regions. The large fluctuations are almost absent in homopolymeric DNA. We suggest that bubble formation and cooperative opening and closing dynamics of basepairs causes the additional fluctuation at the first peak and a large cooperative transition from a partially molten DNA to a completely denatured state causes the additional fluctuation at the second peak.     

Disentangling thermal preference and the thermal dependence of movement in ectotherms

Many ectotherms thermoregulate by choosing environmental temperatures that maximize diverse performance traits, including fitness. For this reason, physiological ecologists have measured preferred temperatures of diverse ectotherms for nearly a century. Thermal preference is usually measured by observing organism distributions on laboratory thermal gradients. This approach is appropriate for large ectotherms which have sufficient thermal inertia to decouple body temperatures from gradient temperatures. However, body temperatures and therefore speeds of movement of small ectotherms will closely track gradient temperature, making it difficult to distinguish between thermal preference and thermal dependence of movement. Here we develop and demonstrate the use of a patch model to derive the expected thermal gradient distribution given only the thermal dependence of movement. Comparison of this null distribution with the observed gradient distribution reveals thermal preference of small ectotherms.