ABSTRACT
Elucidating the physiological mechanisms that underlie thermal stress and discovering how species differ in capacities for phenotypic acclimatization and evolutionary adaptation to this ...stress is critical for understanding current latitudinal and vertical distribution patterns of species and for predicting their future state in a warming world. Such mechanistic analyses require careful choice of study systems (species and temperature‐sensitive traits) and design of laboratory experiments that reflect the complexities of in situ conditions. Here, we critically review a wide range of studies of intertidal molluscs that provide mechanistic accounts of thermal effects across all levels of biological organization – behavioural, organismal, organ level, cellular, molecular, and genomic – and show how temperature‐sensitive traits govern distribution patterns and capacities for coping with thermal stress. Comparisons of congeners from different thermal habitats are especially effective means for identifying adaptive variation. We employ these mechanistic analyses to illustrate how species differ in the severity of threats posed by rising temperature. Counterintuitively, we show that some of the most heat‐tolerant species may be most threatened by increases in temperatures because of their small thermal safety margins and minimal abilities to acclimatize to higher temperatures. We discuss recent molecular biological and genomic studies that provide critical foundations for understanding the types of evolutionary changes in protein structure, RNA secondary structure, genome content, and gene expression capacities that underlie adaptation to temperature. Duplication of stress‐related genes, as found in heat‐tolerant molluscs, may provide enhanced capacity for coping with higher temperatures. We propose that the anatomical, behavioural, physiological, and genomic diversity found among intertidal molluscs, which commonly are of critical importance and high abundance in these ecosystems, makes this group of animals a highly appropriate study system for addressing questions about the mechanistic determinants of current and future distribution patterns of intertidal organisms.
Orthologous proteins of species adapted to different temperatures exhibit differences in stability and function that are interpreted to reflect adaptive variation in structural “flexibility.” ...However, quantifying flexibility and comparing flexibility across proteins has remained a challenge. To address this issue, we examined temperature effects on cytosolic malate dehydrogenase (cMDH) orthologs from differently thermally adapted congeners of five genera of marine molluscs whose field body temperatures span a range of ∼60 °C. We describe consistent patterns of convergent evolution in adaptation of function temperature effects on K
M of cofactor (NADH) and structural stability (rate of heat denaturation of activity). To determine how these differences depend on flexibilities of overall structure and of regions known to be important in binding and catalysis, we performed molecular dynamics simulation (MDS) analyses. MDS analyses revealed a significant negative correlation between adaptation temperature and heat-induced increase of backbone atom movements root mean square deviation (rmsd) of main-chain atoms. Root mean square fluctuations (RMSFs) of movement by individual amino acid residues varied across the sequence in a qualitatively similar pattern among orthologs. Regions of sequence involved in ligand binding and catalysis—termed mobile regions 1 and 2 (MR1 and MR2), respectively—showed the largest values for RMSF. Heat-induced changes in RMSF values across the sequence and, importantly, in MR1 and MR2 were greatest in cold-adapted species. MDS methods are shown to provide powerful tools for examining adaptation of enzymes by providing a quantitative index of protein flexibility and identifying sequence regions where adaptive change in flexibility occurs.
Summary
For rocky intertidal species that experience changes in a number of potential stressors seasonally and during the tidal cycle, sensing cellular energy status and modulating it adaptively may ...be crucial for responding to stressor effects. However, the responses of energy metabolism of intertidal species to multiple sublethal stressors are still unclear.
Here, we examined gene expression profiles of biomarkers related to sensing of cellular energy status and regulation of catabolism and energy expenditure in a mid‐intertidal limpet Cellana toreuma for elucidating the species’ cellular energy responses stresses from high temperature, desiccation and rainfall.
Expression levels of genes encoding metabolic regulators two subunits of AMP‐activated protein kinase, ampkα, ampkβ; Fu gene inhibition axis formation, axin; two sirtuins, NAD‐dependent deacetylase sirtuin‐1 (sirt1); NAD‐dependent deacetylase sirtuin‐5 (sirt5), metabolic enzymes (hexokinase, hk; pyruvate kinase, pk; isocitrate dehydrogenase, idh) and heat shock protein 70 (hsp70) were quantified in specimens exposed to different temperatures and aerial/freshwater spray conditions.
Based on the gene expression patterns, all individuals could be divided into three groups with divergent cellular energy status, indicating that the selected target genes are appropriate indicators of cellular metabolism. The divergent gene expression patterns indicated a sequence in which individuals from group 1, group 2 and group 3 were faced with increasing energy stress.
The frequency distributions of individuals in the three groups were different among different time points and treatments, indicating that high temperature, desiccation, and rainfall, singly or in combination, could cause energy stress.
Compared to the high percentage (100%) of individuals placed in the highest‐stress group (group 3), after 2 h of freshwater spray at 18 °C, the lower percentage (77·8%) of individuals in group 3 after 2 h of freshwater spray at 30 °C indicated the existence of interactive effects of high temperature and rain; high temperature resulted in a lower response of cellular energy metabolism to rainfall.
Sublethal environmental stresses from single stressors such as temperature or osmotic challenges can lead to cellular energy stress. Interactions among stressors may lead to a complex overall effect on cellular energy status in intertidal species.
Lay Summary
Coastal artificial structures on the former mudflats provide available habitats for the rocky intertidal species which can establish new populations in these emerging habitats over their former ...distribution range limits. As a former southern species, the oyster Crassostrea sikamea has become a pioneer and rapidly invaded the artificial shorelines in northern China. We used a seascape genomics approach to investigate the population structure and genetic sources of C. sikamea on the coastal artificial structures, which is crucial for understanding the genetic mechanisms driving species distribution range expansion and invasion pathway of intertidal species. Five C. sikamea populations, including two artificial substrate populations (WGZ and ZAP), one oyster reef population (LS), and two natural rocky shore populations (ZS and XM), were measured using single nucleotide polymorphism (SNPs) obtained from double digest restriction‐site associated DNA sequencing (ddRAD‐Seq). Redundancy analyses (RDA) were implemented for investigating the relationship between local temperature variables and the temperature adaptability of C. sikamea. Genetic diversity, direction and strength of gene flow, and population structure all revealed that the LS and ZS populations were the genetic sources for the oyster populations on the emerging northern coastal artificial structures. Results of RDA showed that there were different adaptive potentials for northern and southern populations to local temperature variables and the oyster reef population which frequently suffers from heat stress owned high heat adaptability. The ZS population as a genetic source nearby the Yangtze River estuary provided mass larvae for the northern populations, and the other genetic source, the heat‐tolerant LS population, in the oyster reef played an important role in the post‐settlement success by providing preadapted genotypes. These results highlight the importance of multiple sources with divergent adaptative capabilities for biological invasion, and also emphasize the importance of the oyster reef in coastal biodiversity and conservation.
摘要
潮滩上人工建筑物构建为潮间带岩相物种提供了适合的附着基质，使其能够跨越原有地理分布隔离，在新生境中建立种群。南方物种熊本牡蛎 (Crassostrea sikamea) 正迅速入侵中国北方人工海岸线，目前已成为江苏沿岸人工海岸线上的优势种。本研究采用景观基因组学 (seascape genomics) 方法对潮间带人工基质上熊本牡蛎种群结构和遗传来源进行了研究，以解析潮间带物种分布范围扩张的遗传机制和入侵途径。利用双酶切限制性位点测序 (ddRAD‐Seq) 获得2个人工基质种群 (WGZ和ZAP)、1个牡蛎礁种群 (LS) 和2个自然岩相种群 (ZS和XM) 的单核苷酸多态位点 (SNPs)，并采用冗余分析 (RDA) 研究了环境温度与熊本牡蛎种群温度适应性之间的关系。遗传多样性、基因流动方向和强度以及种群遗传结构等研究结果均表明，LS和ZS种群是北方沿岸新兴人工海岸线上牡蛎种群的遗传来源。RDA结果表明，长江口以北和以南种群对温度具有不同的适应能力，频繁遭受热浪事件的牡蛎礁种群 (LS) 具有较高的热适应性。长江口附近的ZS种群作为遗传来源为北方种群提供了大量的幼体，LS种群通过提供高温预适应基因型对新兴人工海岸线上种群的成功建立具有重要作用。这些结果强调了具有不同适应能力的多遗传来源会促进生物入侵，也强调了牡蛎礁在潮间带生物多样性保护中的重要性。.
Aim
Understanding the formation and maintenance of biogeographical breaks is fundamental for developing analyses related to biodiversity and conservation. Biogeographical patterns along China's coast ...are changing dramatically in the face of climate change and alterations in land‐use. In this paper, we sought to clarify the mechanisms responsible for the formation and maintenance of a biogeographical barrier on China's coast.
Location
Coastline of northern China.
Methods
We have reviewed literature of research related to biogeographical and phylogeographical patterns of intertidal macrobenthos along the coast of Jiangsu Province and adjacent areas, summarized the distribution patterns and biogeographical breakers. We have also reviewed literature about the processes and drivers on coastal biogeographical breaks, to clarify the mechanisms acting to the northward shift of the biogeographical break.
Results
The Yangtze (Changjiang) River Estuary Biogeographical Barrier (YREBB) at 30°–31°N, which serves as a coastal biogeographical boundary for the Cold Temperate Northwest Pacific Province and the Warm Temperate Northwest Pacific Province for marine species, has moved northward to ~33°–34°N due to the changes in habitat continuity, oceanographic circulation and climate factors. Consequently, a new biogeographic barrier for intertidal macrobenthos, the Subei Biogeographical Barrier (SBB) on the central coast of Jiangsu Province, has emerged.
Main conclusions
The formation and maintenance of the SBB are closely related to the larval dispersal potential, larval settlement success and post‐settlement population establishment, all of which have been profoundly influenced by anthropogenic environmental changes. The northward shift of the YREBB and the appearance of the SBB provide an excellent model system for investigating the impacts of climate change and land‐use change on coastal biogeographic patterning and for clarifying the mechanisms underlying the formation and maintenance of biogeographical barriers in the face of the unprecedented environmental changes.
The accretion-induced collapse (AIC) of a white dwarf in a binary with a nondegenerate companion can sometimes lead to the formation of a rapidly rotating and highly magnetized neutron star (NS). The ...spin-down of this NS can drive a powerful pulsar wind (PW) and bring out some detectable multi-wavelength emissions. On the one hand, the PW can evaporate the companion in a few days to form a torus surrounding the NS. Then, due to the blockage of the PW by the torus, a reverse shock can be formed in the wind to generate intense hard X-rays. This emission component disappears in a few weeks' time, after the torus is broken down at its inner boundary and scoured into a very thin disk. On the other hand, the interaction between the PW with an AIC ejecta can lead to a termination shock of the wind, which can produce a long-lasting soft X-ray emission component. In any case, the high-energy emissions from deep inside the system can be detected only after the AIC ejecta becomes transparent for X-rays. Meanwhile, by absorbing the X-rays, the AIC ejecta can be heated effectively and generate a fast-evolving and luminous ultraviolet (UV)/optical transient. Therefore, the predicted hard and soft X-ray emissions, associated by an UV/optical transient, provide a clear observational signature for identifying AIC events in current and future observations (e.g., AT 2018cow).
Predicting the effects of rising temperature entails measuring both habitat thermal characteristics and the physiological variation of the species as it relates to this microhabitat variation; these ...two types of measurements can generate what is termed a ‘physiological landscape’ for the species. Mapping the micro‐scale physiological landscape across space and time, rather than relying on large‐scale averages of temperature and means of thermal limits in a species, can allow more accurate estimates of an organism's sensitivity to temperature change and support development of more refined models of the impacts of anthropogenic climate change that have higher predictive power.
We thus continually monitored the body (operative) temperature of the intertidal mussel Mytilisepta virgata in both sun‐exposed and shaded microhabitats and determined the seasonal variations of cardiac performance of field‐acclimatized and laboratory‐acclimated mussels from different microhabitats for calculating the thermal sensitivity, as indicated by the difference between the maximum ambient temperature and an individual's upper thermal limit (thermal safety margin, TSM), in each microhabitat and each month.
The mussels experienced divergent thermal stress, in average temperature, acute and chronic thermal stress and thermal predictivity among different microhabitats, and presented high spatial–temporal variations of cardiac function as results of seasonal acclimatization and inter‐individual variations. Results of TSMs indicated that the thermal sensitivities of the mussels to high temperature were season‐ and microhabitat specific, and the mussels in the shaded microhabitats were predicted to survive the hottest summer temperatures; however, some individuals in the sun‐exposed microhabitats experienced temperatures above their sublethal temperature.
With the large, high‐resolution dataset of thermal environmental characteristics and the cardiac performances with high variations, we were able to integrate the effects of synchronized changes in microenvironmental temperatures and cardiac thermal responses and thereby characterize the physiological landscape of thermal sensitivity. The complex physiological landscape that exists in the intertidal zone must be taken into account when predicting the effects of changes in environmental temperature, such as those occurring with global climate change.
A free Plain Language Summary can be found within the Supporting Information of this article.
摘要
评估和预测气候变化的生态效应需要测定栖息地温度特征及生物生理耐受水平, 计算生物对环境温度变化的敏感性, 进而绘制 ‘生理景观’ 格局。通过分析小时空尺度生理景观的变化, 而不是单纯依赖于大尺度环境温度平均值和生物温度耐受能力的平均值, 可更为准确地预测生物对温度变化的敏感性及气候变化的生态效应。
本研究连续测定了潮间带条纹隔贻贝阴阳面不同微生境温度变化特征, 并分析了不同微环境生物贝类的心脏性能, 计算不同季节、不同微环境生物的温度安全区间 (Thermal safety margin, TSM), 以阐明小尺度生物温度敏感性的时空格局。
条纹隔贻贝在不同微生境面临着不同强度的温度胁迫, 呈现出高度的时空异质性。条纹隔贻贝心脏性能也表现出了高度的可塑性, 这主要与不同驯化温度和个体间差异有关。TSM结果表明, 贻贝对高温的敏感性是具有季节特异性和微生境特异性。在阴面微生境, 所有的条纹隔贻贝都可以在高温季节存活, 然后在阳面微生境, 部分个体可能会由于环境温度高于其亚致死温度而受到生理损害。
基于高清晰度的环境温度数据和生物心脏性能数据库, 可整合分析微生境温度与心脏性能曲线可塑性的生态效应, 评估生物对环境温度的敏感性。因此在评估和预测气候变化生态效应时, 需要充分考虑生理景观格局的复杂性及其时空变化格局。
A free Plain Language Summary can be found within the Supporting Information of this article.
Animal survival and species distribution in the face of global warming and increasing occurrences of heatwave largely depend on how heat tolerance shifts with plastic responses at different ...spatiotemporal scales, including long‐term acclimation/acclimatization and short‐term heat hardening. However, knowledge about the interaction of these plastic responses is still unclear.
To understand how plastic responses at different time‐scales work together to adjust heat tolerance of organisms, we examined the effect of heat hardening on the upper thermal limits of an intertidal mudflat bivalve, the razor clam Sinonovacula constricta, for different seasons using heart rate as a proxy.
We observed a stronger heat hardening response of S. constricta in warm seasons, implying that heat hardening worked synchronously with seasonal acclimatization to increase resistance of the clams to high temperatures in warm seasons. In warm seasons, heat hardening increased heat tolerance by 2–4°C and showed a 24‐hr temporal dependence, suggesting an adaptation to the diel fluctuation of thermal regimes in summer.
Furthermore, thermal stress resembling seasonal maximum environmental temperature induced stronger heat hardening effects, indicating that heat hardening is an essential plastic response to extreme hot weather, complementing seasonal acclimatization.
Our results suggest that high temperature risk can be alleviated jointly by seasonal acclimatization and heat hardening, and emphasize the importance of considering physiological plasticity on both long‐term and short‐term temporal scales in evaluating and forecasting vulnerability of organisms to climate change.
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.
Aim
Rapid anthropogenic warming coupled with changes in land use is altering the distributions of species, with consequences for ecosystem functioning and services. It is crucial to evaluate species ...range shifts based on understanding of the interaction of temperature with non‐climatic factors such as habitat availability and dispersal potential. Here, we aim to investigate roles of environmental temperature, habitat availability and population connectivity on the distributions of hard‐shore intertidal animals. We further examine potential roles of extensive artificial seawall construction in enabling poleward expansion of species in China, thus reshaping coastal biogeography.
Location
Chinese coast.
Time period
2013–2017.
Major taxa studied
Intertidal invertebrates.
Methods
We took an integrative approach encompassing distributional ecology, thermal physiology, molecular genetics, heat budget modelling and larval dispersal to elucidate how interacting multiple drivers, including temperature, habitat availability and larval dispersal, determine distributions of hard‐shore invertebrates, focusing on what sets their range edges at a boundary between biogeographic provinces.
Results
Our results untangle the complex interactions of global climate change with the impacts of regional scale coastal development. Temperature, larval transport and habitat availability are the major proximate factors controlling the range limits of coastal marine species. The artificial shorelines provide suitable habitats for hard‐shore species on the Yangtze River Delta, and minimum temperature in winter is an important factor setting the new northern range limit of these hard‐shore species along the Chinese coast.
Main conclusions
In the face of global warming and global sprawl of marine hard infrastructure, species distributions, community structures and biogeographic patterns are experiencing dramatic changes. The combined influence of multiple human stressors including climate change and artificial shorelines can be evaluated by using a multidisciplinary framework, including ecological distribution, physiological sensitivity of species to these stressors, and the role of dispersal in maintaining population connectivity.
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