Impacts of environmental variability on desiccation rate,plastic responses and population dynamics of Glossina pallidipes

Physiological responses to transient conditions may result in costly responses with little fitness benefits, and therefore, a trade‐off must exist between the speed of response and the duration of exposure to new conditions. Here, using the puparia of an important insect disease vector, Glossina pallidipes, we examine this potential trade‐off using a novel combination of an experimental approach and a population dynamics model. Specifically, we explore and dissect the interactions between plastic physiological responses, treatment‐duration and ‐intensity using an experimental approach. We then integrate these experimental results from organismal water‐balance data and their plastic responses into a population dynamics model to examine the potential relative fitness effects of simulated transient weather conditions on population growth rates. The results show evidence for the predicted trade‐off for plasticity of water loss rate (WLR) and the duration of new environmental conditions. When altered environmental conditions lasted for longer durations, physiological responses could match the new environmental conditions, and this resulted in a lower WLR and lower rates of population decline. At shorter time‐scales however, a mismatch between acclimation duration and physiological responses was reflected by reduced overall population growth rates. This may indicate a potential fitness cost due to insufficient time for physiological adjustments to take place. The outcomes of this work therefore suggest plastic water balance responses have both costs and benefits, and these depend on the time‐scale and magnitude of variation in environmental conditions. These results are significant for understanding the evolution of plastic physiological responses and changes in population abundance in the context of environmental variability.     

Evolutionary rescue in randomly mating,selfing, and clonal populations

Severe environmental change can drive a population extinct unless the population adapts in time to the new conditions (“evolutionary rescue”). How does biparental sexual reproduction influence the chances of population persistence compared to clonal reproduction or selfing? In this article, we set up a one‐locus two‐allele model for adaptation in diploid species, where rescue is contingent on the establishment of the mutant homozygote. Reproduction can occur by random mating, selfing, or clonally. Random mating generates and destroys the rescue mutant; selfing is efficient at generating it but at the same time depletes the heterozygote, which can lead to a low mutant frequency in the standing genetic variation. Due to these (and other) antagonistic effects, we find a nontrivial dependence of population survival on the rate of sex/selfing, which is strongly influenced by the dominance coefficient of the mutation before and after the environmental change. Importantly, since mating with the wild‐type breaks the mutant homozygote up, a slow decay of the wild‐type population size can impede rescue in randomly mating populations.     

556例多发伤患者的急诊救治临床分析

目的探讨多发伤患者的救治策略。方法回顾分析我科2000年1月至2008年5月急诊抢救的556例多发伤患者的临床资料。结果 16例患者经抢救无效死亡,死亡率2.88%;其余患者均经紧急抢救及行必要实验室检查,病情稳定,好转率达97.12%。平均抢救时间为(1.37±1.05)h。结论强化多发伤的急诊科早期救治,树立创伤急救"黄金1 h"观念,是提高多发伤患者生存率及降低死亡率的关键。     

EVOLUTIONARY RESCUE OF SEXUAL AND ASEXUAL POPULATIONS IN A DETERIORATING ENVIRONMENT

The environmental change experienced by many contemporary populations of organisms poses a serious risk to their survival. From the theory of evolutionary rescue, we predict that the combination of sex and genetic diversity should increase the probability of survival by increasing variation and thereby the probability of generating a type that can tolerate the stressful environment. We tested this prediction by comparing experimental populations of Chlamydomonas reinhardtii that differ in sexuality and in the initial amount of genetic diversity. The lines were serially propagated in an environment where the level of stress caused by salt increased over time from fresh water to the limits of marine conditions. In the long term, the combination of high diversity and obligate sexuality was most effective in supporting evolutionary rescue. Most of the adaptation to high‐salt environments in the obligate sexual‐high diversity lines had occurred by midway through the experiment, indicating that positive genetic correlations of adaptation to lethal stress with adaptation to sublethal stress greatly increased the probability of evolutionary rescue. The evolutionary rescue events observed in this study provide evidence that major shifts in ways of life can arise within short time frames through the action of natural selection in sexual populations.     

Experimental climate warming decreases photosynthetic efficiency of lichens in an arid South African ecosystem

Modest increases in global temperature have been implicated in causing population extirpations and range shifts in taxa inhabiting colder environs and in ectotherms whose thermoregulation is more closely tied to environmental conditions. Many arid-adapted endotherms already experience conditions at their physiological limits, so it is conceivable that they could be similarly affected by warming temperatures. We explored how climatic variables might influence the apparent survival of the banner-tailed kangaroo rat (Dipodomys spectabilis), a rodent endemic to the Chihuahuan Desert of North America and renowned for its behavioral and physiological adaptations to arid environments. Relative variable weight, strength of variable relationships, and other criteria indicated that summer, diurnal land surface temperature (SD_LST) was the primary environmental driver of apparent survival in these arid-adapted rodents. Higher temperatures had a negative effect on apparent survival, which ranged from 0.15 (SE = 0.04) for subadults to 0.50 (SE = 0.07) for adults. Elevated SD_LST may negatively influence survival through multiple pathways, including increased water loss and energy expenditure that could lead to chronic stress and/or hyperthermia that could cause direct mortality. Land surface temperatures are predicted to increase by as much 6.5°C by 2099, reducing apparent survival of adults to ~0.15 in some regions of the species’ range, possibly causing a shift in their distribution. The relationship between SD_LST and survival suggests a mechanism whereby physiological tolerances are exceeded resulting in a reduction to individual fitness that may ultimately cause a shift in the species’ range over time.     

Relictual physiological ecology in the threatened land snail Codringtonia helenae: A cause for decline in a changing environment?

Land snails often exhibit intra-annual cycles of activity interspersed by periods of dormancy (hibernation/aestivation), accompanied by a range of behavioural and physiological adaptations to ensure their survival under adverse environmental conditions. These adaptations are useful to understand species-specific habitat requirements and to predict their response to environmental changes. We examined the seasonal physiological and biochemical composition patterns of the threatened land snail Codringtonia helenae, endemic to Greece, in relation to its behavioural ecology and climatic conditions. Fuel reserves (glycogen, lipids, proteins) and water were accumulated prior to aestivation, but subsequently were rapidly depleted. LDH exhibited substantial rise during aestivation, suggesting that anaerobic pathways may provide additional energy. The major outcome of our study was the unambiguous discrimination of the four life-cycle periods. Most remarkable was the clear distinction of the aestivation period, with hibernation, the other dormancy period, showing similarity with the two active periods but not with aestivation. We observed disassociation between behavioural and physiological responses and climatic conditions. The physiological responses of C. helenae were effective during hibernation, but only partly compensate the effect of adverse conditions during aestivation, since its aestivating behaviour is occasional and time limited. Perhaps, the behavioural ecology of Codringtonia is relictual and shaped during past environmental conditions. This constitutes an important extinction threat considering the current climatic trends and the deterioration of the habitat of that species due to human activities.     

Evolutionary rescue can be impeded by temporary environmental amelioration

Rapid evolutionary adaptation has the potential to rescue from extinction populations experiencing environmental changes. Little is known, however, about the impact of short‐term environmental fluctuations during long‐term environmental deterioration, an intrinsic property of realistic environmental changes. Temporary environmental amelioration arising from such fluctuations could either facilitate evolutionary rescue by allowing population recovery (a positive demographic effect) or impede it by relaxing selection for beneficial mutations required for future survival (a negative population genetic effect). We address this uncertainty in an experiment with populations of a bacteriophage virus that evolved under deteriorating conditions (gradually increasing temperature). Periodic environmental amelioration (short periods of reduced temperature) caused demographic recovery during the early phase of the experiment, but ultimately reduced the frequency of evolutionary rescue. These experimental results suggest that environmental fluctuations could reduce the potential of evolutionary rescue.     

Model of human/liquid cooling garment interaction for space suit automatic thermal control

The Wissler human thermoregulation model was augmented to incorporate simulation of a space suit thermal control system that includes interaction with a liquid cooled garment (LCG) and ventilation gas flow through the suit. The model was utilized in the design process of an automatic controller intended to maintain thermal neutrality of an exercising subject wearing a liquid cooling garment. An experimental apparatus was designed and built to test the efficacy of specific physiological state measurements to provide feedback data for input to the automatic control algorithm. Control of the coolant inlet temperature to the LCG was based on evaluation of transient physiological parameters that describe the thermal state of the subject, including metabolic rate, skin temperatures, and core temperature. Experimental evaluation of the control algorithm function was accomplished in an environmental chamber under conditions that simulated the thermal environment of a space suit and transient metabolic work loads typical of astronaut extravehicular activity (EVA). The model was also applied to analyze experiments to evaluate performance of the automatic control system in maintaining thermal comfort during extensive transient metabolic profiles for a range of environmental temperatures. Finally, the model was used to predict the efficacy of the LCG thermal controller for providing thermal comfort for a variety of regiments that may be encountered in future space missions. Simulations with the Wissler model accurately predicted the thermal interaction between the subject and LCG for a wide range of metabolic profiles and environmental conditions and matched the function of the automatic temperature controller for inlet cooling water to the LCG.     

Ecophysiological and morphological parameters related to survival in grass species exposed to an extreme climatic event

An experiment was performed to elucidate interspecific differences in survival time of grass species subjected to an extreme climatic event. We exposed eight grass species to a simulated heat wave in the field ('free air' temperature increase at 11°C above ambient) combined with drought. We determined whether interspecific differences in survival time were related to the responses of the species to the imposed stress or could be explained by their ecophysiological or morphological characteristics in unstressed conditions. Surprisingly, there was no effect of specific leaf area, but species with a higher total leaf area survived longer. This may arise from a greater water reserve in the plant as a whole, which could delay the desiccation of the meristem, or from reduced evaporation due to a higher leaf area index. Species in which the decrease in light-saturated stomatal conductance ( g _s ) and photosynthetic CO₂ uptake rate ( A _max ) was strongly related to the decrease in soil water availability (measured as soil relative water content and stress duration) survived longer than species in which g _s and A _max likewise declined but responded more to daily fluctuations in irradiance, temperature, and vapor pressure deficit during the heat wave. We, therefore, hypothesize that interspecific differences in stress survival time might be related to the extent to which stomata react to changes in soil water conditions relatively to changes in other environmental and physiological factors. The results suggest that resistance to extremes is governed by other mechanisms than resistance to moderate drought.     

Survival analysis of three clones of Brachionus plicatilis (Rotifera)

Age-specific survival schedules of females from three genetically different clones of Brachionus plicatilis were analyzed at several environmental conditions in the laboratory.Lifespan showed the expected decrease with increasing temperature, but a general trend with salinity or genotype was not observed. Probability of death increased with age, as tested by polynomial regression analysis of the survival curve and using theoretical mortality distributions. Three two-parameter models (linear-exponential model, Weibull model, and Gompertz model) were fitted to the survival data. Fitting of these models to data was rather poor, but the Gompertz model and, to a lesser extent, the Weibull model fitted the data better than the linear-exponential model. Parameters obtained from the survival curve analyses were related to other demographic parameters. A significant relationship between the shape parameter of the Gompertz model and the cohort generation time was detected, suggesting, but not proving, an effect of reproductive effort on aging.     

Validation of the Fiala multi-node thermophysiological model for UTCI application

The important requirement that COST Action 730 demanded of the physiological model to be used for the Universal Thermal Climate Index (UTCI) was its capability of accurate simulation of human thermophysiological responses across a wide range of relevant environmental conditions, such as conditions corresponding to the selection of all habitable climates and their seasonal changes, and transient conditions representing the temporal variation of outdoor conditions. In the first part of this study, available heat budget/two-node models and multi-node thermophysiological models were evaluated by direct comparison over a wide spectrum of climatic conditions. The UTCI-Fiala model predicted most reliably the average human thermal response, as shown by least deviations from physiologically plausible responses when compared to other models. In the second part of the study, this model was subjected to extensive validation using the results of human subject experiments for a range of relevant (steady-state and transient) environmental conditions. The UTCI-Fiala multi-node model proved its ability to predict adequately the human physiological response for a variety of moderate and extreme conditions represented in the COST 730 database. The mean skin and core temperatures were predicted with average root-mean-square deviations of 1.35 ± 1.00°C and 0.32 ± 0.20°C, respectively.     

Variation in juvenile survival and related physiological traits among dipterocarp species co‐existing in a Bornean forest

Question: What environmental factors and physiological traits determine the juvenile survival rates of 11 dipterocarp species (Dipterocarpaceae) co-occurring in a Bornean tropical rain forest? Location: Tropical northwestern Borneo. Methods: In 248 quadrats, distributed over 12 ha, the juvenile (height< 2.0 m) survival of 11 shade-tolerant dipterocarp species was monitored for one year. The probability of survival for each species was expressed as a logistic function of plant height and three environmental factors: canopy openness, soil water potential and conspecific individual density. The correlation between survival under shaded conditions and several physiological traits of juveniles was tested by normal Pearson correlation and a phylogeny based manner using independent contrasts. Results: Seven species had increased survival under more open canopies, one species had increased and two species had decreased survival at drier sites. Six species had higher survival as the density of conspecifics increased, whereas two species had lower survival. The magnitudes of the effects for the three environmental factors were similar. However, the interspecific difference in survival was largely determined by a dependence of small seedlings on the light environment. Survival under low light was correlated positively with root dry mass and negatively with total leaf area of juveniles. Conclusions: Responses of seedlings to the fine-scale gradient of light availability were considerably different among the 11 species. Species that suffered increased mortality under low light had a set of structural traits that would potentially allow rapid growth under bright conditions. Differential performance along the light gradient may contribute to the stable coexistence of these species.     

Large-Scale Modelling of the Environmentally-Driven Population Dynamics of Temperate Aedes albopictus (Skuse)

The Asian tiger mosquito, Aedes albopictus, is a highly invasive vector species. It is a proven vector of dengue and chikungunya viruses, with the potential to host a further 24 arboviruses. It has recently expanded its geographical range, threatening many countries in the Middle East, Mediterranean, Europe and North America. Here, we investigate the theoretical limitations of its range expansion by developing an environmentally-driven mathematical model of its population dynamics. We focus on the temperate strain of Ae. albopictus and compile a comprehensive literature-based database of physiological parameters. As a novel approach, we link its population dynamics to globally-available environmental datasets by performing inference on all parameters. We adopt a Bayesian approach using experimental data as prior knowledge and the surveillance dataset of Emilia-Romagna, Italy, as evidence. The model accounts for temperature, precipitation, human population density and photoperiod as the main environmental drivers, and, in addition, incorporates the mechanism of diapause and a simple breeding site model. The model demonstrates high predictive skill over the reference region and beyond, confirming most of the current reports of vector presence in Europe. One of the main hypotheses derived from the model is the survival of Ae. albopictus populations through harsh winter conditions. The model, constrained by the environmental datasets, requires that either diapausing eggs or adult vectors have increased cold resistance. The model also suggests that temperature and photoperiod control diapause initiation and termination differentially. We demonstrate that it is possible to account for unobserved properties and constraints, such as differences between laboratory and field conditions, to derive reliable inferences on the environmental dependence of Ae. albopictus populations.     

Analyzing the ecosystem carbon and hydrologic characteristics of forested wetland using a biogeochemical process model

A comprehensive biogeochemical model, Wetland‐DNDC, was applied to analyze the carbon and hydrologic characteristics of forested wetland ecosystem at Minnesota (MN) and Florida (FL) sites. The model simulates the flows of carbon, energy, and water in forested wetlands. Modeled carbon dynamics depends on physiological plant factors, the size of plant pools, environmental factors, and the total amount and turnover rates of soil organic matter. The model realistically simulated water level fluctuation, forest production, carbon pools change, and CO₂ and CH₄ emission under natural variations in different environmental factors at two sites. Analyses were focused on parameters and inputs potentially cause the greatest uncertainty in calculated change in plant and soil C and water levels fluctuation and shows that it was important to obtain accurate input data for initial C content, climatic conditions, and allocation of net primary production to various forested wetland components. The magnitude of the forest responses was dependent not only on the rate of changes in environmental factors, but also on site‐specific conditions such as climate and soil. This paper explores the ability of using the biogeochemical process model Wetland‐DNDC to estimate the carbon and hydrologic dynamics of forested wetlands and shifts in these dynamics in response to changing environmental conditions.     

Functional aquaporin diversity in plants

Due to the fact that most plants are immobile, a rapid response of physiological processes to changing environmental conditions is essential for their survival. Thus, in comparison to many other organisms, plants might need a more sophisticated tuning of water balance. Among others, this is reflected by the comparable large amount of aquaporin genes in plant genomes. So far, aquaporins were shown to be involved in many physiological processes like root water uptake, reproduction or photosynthesis. Their classification as simple water pores has changed according to their molecular function into channels permeable for water, small solutes and/or gases. An adjustment of the corresponding physiological process could be achieved by regulation mechanisms. Concerning aquaporins these range from posttranslational modification, molecular trafficking to heteromerization of aquaporin isoforms. The aim of this review is to underline the function of the four plant aquaporin family subclasses with regard to the substrate specificity, regulation and physiological relevance.     

Coral chimerism as an evolutionary rescue mechanism to mitigate global climate change impacts

Climate change and anthropogenic pressures inflict a wide range of profound damages on coral reef ecosystems, reshaping coral reef communities due to their physiological and ecological intolerance to the newly developing environmental conditions. Here, I present coral chimerism as an evolutionary rescue tool for accelerating adaptive responses to global climate change impacts. The “evolutionary rescue” power is contingent on the premise that coral chimerism counters the erosion of genetic and phenotypic diversity. Further benefits are gained when flexible chimeric entities alter their somatic constituents following changes in environmental conditions, synergistically presenting the best‐fitting combination of their genetic components to endure in a capricious environment, exhibiting always their environmentally matched physiological characteristics. Chimerism should be considered as an integral part of the ecological engineering toolbox being developed for active reef restoration.     

Functional aquaporin diversity in plants

Due to the fact that most plants are immobile, a rapid response of physiological processes to changing environmental conditions is essential for their survival. Thus, in comparison to many other organisms, plants might need a more sophisticated tuning of water balance. Among others, this is reflected by the comparable large amount of aquaporin genes in plant genomes. So far, aquaporins were shown to be involved in many physiological processes like root water uptake, reproduction or photosynthesis. Their classification as simple water pores has changed according to their molecular function into channels permeable for water, small solutes and/or gases. An adjustment of the corresponding physiological process could be achieved by regulation mechanisms. Concerning aquaporins these range from posttranslational modification, molecular trafficking to heteromerization of aquaporin isoforms. The aim of this review is to underline the function of the four plant aquaporin family subclasses with regard to the substrate specificity, regulation and physiological relevance.     

Survival adaptations of threeEuphorbia spp. in arid ecosystem

Three species ofEuphorbia (E. granulata, E. prostrata andE. hirta) exhibited both morphological and physiological adaptations in dry environmental conditions. High bound water, thick cuticle, dense hair covering and low stomatal index are some of the survival adaptations they developed under water stress conditions of the Indian arid zone.     

Cytoprotective Effect of Short-Term Pretreatment with Proanthocyanidin on Human Gingival Fibroblasts Exposed to Harsh Environmental Conditions

Our previous study showed that exposing mouse fibroblasts to proanthocyanidin (PA) for only 1 min accelerated cell proliferation in a concentration-dependent manner. In this study, exposing human gingival fibroblasts (HGFs) to PA for 1 min similarly accelerated the proliferative response of the cells. Besides the accelerated proliferative response, PA showed a cytoprotective effect on HGFs exposed to harsh environmental conditions; short-term exposure of HGFs in the mitotic phase to pure water or physiological saline resulted in a lower recovery of viable cells. Pretreatment and concomitant treatment with PA improved the low recovery of cells exposed to pure water or physiological saline. In addition, HGFs exposed to PA for 1 min proliferated well even after being cultured in serum-free medium. In 100% confluent HGFs, being cultured in serum-free medium resulted in a high intracellular reactive oxygen species (ROS) level, but pretreatment with PA prevented the cells from increasing intracellular ROS. Thus, the results suggest that a short-term PA treatment exerts cytoprotective effects on HGFs exposed to harsh environmental conditions by improving the intracellular oxidative stress response.