Erroneous Arrhenius: modified arrhenius model best explains the temperature dependence of ectotherm fitness

The interaction between warming and enrichment accelerates food-web simplification in freshwater systems

Nutrient enrichment and climate warming threaten freshwater systems. Metabolic theory and the paradox of enrichment predict that both stressors independently can lead to simpler food-webs having fewer nodes, shorter food-chains and lower connectance, but cancel each other's effects when simultaneously present. Yet, these theoretical predictions remain untested in complex natural systems. We inferred the food-web structure of 256 lakes and 373 streams from standardized fish community samplings in France. Contrary to theoretical predictions, we found that warming shortens fish food-chain length and that this effect was magnified in enriched streams and lakes. Additionally, lakes experiencing enrichment exhibit lower connectance in their fish food-webs. Our study suggests that warming and enrichment interact to magnify food-web simplification in nature, raising further concerns about the fate of freshwater systems as climate change effects will dramatically increase in the coming decades.

Predicting the dispersal and invasion dynamics of ambrosia beetles through demographic reconstruction and process-explicit modeling

Evaluating potential routes of invasion of pathogens and vectors of sanitary importance is essential for planning and decision-making at multiple scales. An effective tool are process-explicit models that allow coupling environmental, demographic and dispersal information to evaluate population growth and range dynamics as a function of the abiotic conditions in a region. In this work we simulate multiple dispersal/invasion routes in Mexico that could be taken by ambrosia beetles and a specific symbiont, Harringtonia lauricola, responsible for a severe epiphytic of Lauraceae in North America. We used Xyleborus bispinatus Eichhoff 1868 as a study subject and estimated its demography in the laboratory in a temperature gradient (17, 20, 26, 29, 35 °C), which we then used to parameterize a process-based model to estimate its metapopulation dynamics. The maximum intrinsic growth rate of X. bispinatus is 0.13 with a thermal optimum of 26.2 °C. The models suggest important regions for the establishment and dispersal the states of Veracruz, Chiapas and Oaxaca (high host and secondary vectors diversity), the Isthmus of Tehuantepec (connectivity region), and Michoacán and Jalisco (important avocado plantations). The use of hybrid process-based models is a promising tool to refine the predictions applied to the study of biological invasions and species distributions.

Hotter is not (always) better: Embracing unimodal scaling of biological rates with temperature

Rate-temperature scaling relationships have fascinated biologists for nearly two centuries and are increasingly important in our era of global climate change. These relationships are hypothesized to originate from the temperature-dependent kinetics of rate-limiting biochemical reactions of metabolism. Several prominent theories have formalized this hypothesis using the Arrhenius model, which characterizes a monotonic temperature dependence using an activation energy E. However, the ubiquitous unimodal nature of biological temperature responses presents important theoretical, methodological, and conceptual challenges that restrict the promise for insight, prediction, and progress. Here we review the development of key hypotheses and methods for the temperature-scaling of biological rates. Using simulations, we examine the constraints of monotonic models, illustrating their sensitivity to data nuances such as temperature range and noise, and their tendency to yield variable and underestimated E, with critical consequences for climate change predictions. We also evaluate the behaviour of two prominent unimodal models when applied to incomplete and noisy datasets. We conclude with recommendations for resolving these challenges in future research, and advocate for a shift to unimodal models that better characterize the full range of biological temperature responses.

Fast Assimilation-Temperature Response: a FAsTeR method for measuring the temperature dependence of leaf-level photosynthesis

We present the Fast Assimilation-Temperature Response (FAsTeR) method, a new method for measuring plant assimilation-temperature (AT) response that reduces measurement time and increases data density compared with conventional methods. The FAsTeR method subjects plant leaves to a linearly increasing temperature ramp while taking rapid, nonequilibrium measurements of gas exchange variables. Two postprocessing steps are employed to correct measured assimilation rates for nonequilibrium effects and sensor calibration drift. Results obtained with the new method are compared with those from two conventional stepwise methods. Our new method accurately reproduces results obtained from conventional methods, reduces measurement time by a factor of c. 3.3 (from c. 90 to 27 min), and increases data density by a factor of c. 55 (from c. 10 to c. 550 observations). Simulation results demonstrate that increased data density substantially improves confidence in parameter estimates and drastically reduces the influence of noise. By improving measurement speed and data density, the FAsTeR method enables users to ask fundamentally new kinds of ecological and physiological questions, expediting data collection in short-field campaigns, and improving the representativeness of data across species in the literature.

Shrinking body size of European anchovy in the Bay of Biscay

Decreased body size is often cited as a major response to ocean warming. Available evidence, however, questions the actual emergence of shrinking trends and the prevalence of temperature-driven changes in size over alternative drivers. In marine fish, changes in food availability or fluctuations in abundance, including those due to size-selective fishing, provide compelling mechanisms to explain changes in body size. Here, based on three decades of scientific survey data (1990-2021), we report a decline in the average body size-length and weight-of anchovy, Engraulis encrasicolus L., in the Bay of Biscay. Shrinking was evident in all age classes, from juveniles to adults. Allometric adjustment indicated slightly more pronounced declines in weight than in total length, which is consistent with a change toward a slender body shape. Trends in adult weight were nonlinear, with rates accelerating to an average decline of up to 25% decade-1 during the last two decades. We found a strong association between higher anchovy abundance and reduced juvenile size. The effect of density dependence was less clear later in life, and temperature became the best predictor of declines in adult size. Theoretical analyses based on a strategic model further suggested that observed patterns are consistent with a simultaneous, opposing effect of rising temperatures on accelerating early growth and decreasing adult size as predicted by the temperature-size rule. Macroecological assessment of ecogeographical-Bergmann's and James'-rules in anchovy size suggested that the observed decline largely exceeds intraspecific variation and might be the result of selection. Limitations inherent in the observational nature of the study recommend caution and a continued assessment and exploration of alternative drivers. Additional evidence of a climate-driven regime shift in the region suggests, however, that shrinking anchovy sizes may signal a long-lasting change in the structure and functioning of the Bay of Biscay ecosystem.

Thermal dependence of Daphnia life history reveals asymmetries between key vital rates

Temperature variation affects virtually every aspect of ectotherms' ecological performance, such as their foraging rate, reproduction, and survival. Although these changes influence what happens at higher levels of organizations, such as populations and communities, qualitative changes in dynamics usually require some degree of asymmetry between key vital rates, i.e. that different vital rates, such as growth, development, fecundity and mortality rates, respond differently to temperature. In order to identify possible asymmetries among vital rates and/or life stages, we characterized the thermal response of individuals a clone of Daphnia sinensis, drawn from a high-mountain environment in Taiwan, and examined the temperature dependence of growth, maturation, reproduction, and mortality rates, as well as fitness measures (r and R₀) at eight temperatures. Daphnia sinensis was able to maintain reproductive success over a broad range of temperatures, much wider than the one experienced in its environment. However, negative effects of temperature were perceptible at temperatures much lower than the highest one at which they can achieve reproductive success. Adult mortality greatly increased for temperatures above 23 °C, and other vital rates started to decelerate, resulting in a large drop in lifetime reproductive success. This finding implies that D. sinensis may be able to persist over a wide range of temperatures, but also that it may become more sensitive to the detrimental effect of species interactions at increased temperatures. Different vital rates responded relatively similarly at low temperatures, but the degree of asymmetry among these rates was much more pronounced at higher temperatures. In particular, rates associated with adult performance decelerated more strongly than juveniles' rates. These findings indicate that elevated temperatures affect the balance between juvenile and adult performance, which is known to have a crucial role in Daphnia population dynamics. We discuss the implications of these results for the dynamics of structured populations.

Mutualisms in a warming world

Predicting the impacts of global warming on mutualisms poses a significant challenge given the functional and life history differences that usually exist among interacting species. However, this is a critical endeavour since virtually all species on Earth depend on other species for survival and/or reproduction. The field of thermal ecology can provide physiological and mechanistic insights, as well as quantitative tools, for addressing this challenge. Here, we develop a conceptual and quantitative framework that connects thermal physiology to species' traits, species' traits to interacting mutualists' traits and interacting traits to the mutualism. We first identify the functioning of reciprocal mutualism-relevant traits in diverse systems as the key temperature-dependent mechanisms driving the interaction. We then develop metrics that measure the thermal performance of interacting mutualists' traits and that approximate the thermal performance of the mutualism itself. This integrated approach allows us to additionally examine how warming might interact with resource/nutrient availability and affect mutualistic species' associations across space and time. We offer this framework as a synthesis of convergent and critical issues in mutualism science in a changing world, and as a baseline to which other ecological complexities and scales might be added.

Temperature-dependent development and reproduction of Tarsonemus confusus (Acari: Tarsonemidae): an important pest mite of horticulture

The tarsonemid mite Tarsonemus confusus Ewing has become an economically important pest in orchards in China. This study investigated the temperature-dependent development and reproduction of T. confusus at 15, 20, 25, 30, 33 and 35 °C. Eggs failed to hatch at 35 °C. When temperature increased from 15 to 30 °C, the developmental rate of eggs, larvae and quiescent larvae and that from egg to adulthood of both sexes significantly increased, and the time period required by females to commence oviposition significantly decreased. The lower temperature threshold (T₀) for the development of eggs, larvae and quiescent larvae was between 9.3 and 12.0 °C and both sexes required about 60 degree days (DD) to complete a life cycle. Females were expected to start oviposition at 12.9 °C. The number of eggs laid, the number of female offspring produced and the egg hatch rate were significantly higher at 20, 25 and 30 °C than at 15 and 33 °C. Increasing temperature shortened the longevity of both sexes but increased the intrinsic rate of increase (r_m) and finite capacity for increase (λ) with significantly shorter generation time (T) and doubling time (DT) within a temperature range of 15-30 °C. The net reproductive rate (R₀) was highest at 25 °C. Results of this study may improve our knowledge of fundamental biology and ecology in genus Tarsonemus in general and in T. confusus in particular. Based on the local climate conditions, the applications of these results in predicting the seasonal population dynamics of T. confusus and timing the pest management are discussed.

Key infection stages defending heat stress in high-temperature-resistant Blumeria graminis f. sp. tritici isolates

With the increase of temperature in the winter wheat-growing regions in China, the high-temperature-resistant Blumeria graminis f. sp. tritici (Bgt) isolates developed in the fields. To clarify the key infection stages and the roles of heat shock protein (HSP) genes of high-temperature-resistant Bgt isolates defending high temperature, 3 high-temperature-resistant and 3 sensitive Bgt isolates were selected from 55 isolates after determination of temperature sensitivity. And then they were used to investigate the infection stages and the expression levels of HSP genes, including Bgthsp60, Bgthsp70, Bgthsp90, and Bgthsp104, at 18°C and 25°C. The formation frequency of abnormal appressoria and inhibition rate of haustoria formation of high-temperature-resistant isolates at 25°C were lower than those of high-temperature-sensitive isolates, while major axis of microcolonies of high-temperature-resistant isolates was higher than those of high-temperature-sensitive isolates at 25°C. The results indicated that haustoria formation and hyphal expansion were the key infection stages of defense against heat stress in high-temperature-resistant isolates. Further analyses of HSP genes found the expression levels of Bgthsp60 and Bgthsp70c were upregulated at 24 and 72 h post-inoculation in high-temperature-resistant isolates, while no significant difference was observed for Bgthsp90 and Bgthsp104 genes. Taken together, the basis of high-temperature-resistant Bgt isolates is associated with induced expression of Bgthsp60 and Bgthsp70c response to heat stress in haustoria formation and hyphal expansion stages.

Coevolution of the Ess1-CTD axis in polar fungi suggests a role for phase separation in cold tolerance

Most of the world's biodiversity lives in cold (-2° to 4°C) and hypersaline environments. To understand how cells adapt to such conditions, we isolated two key components of the transcription machinery from fungal species that live in extreme polar environments: the Ess1 prolyl isomerase and its target, the carboxy-terminal domain (CTD) of RNA polymerase II. Polar Ess1 enzymes are conserved and functional in the model yeast, Saccharomyces cerevisiae. By contrast, polar CTDs diverge from the consensus (YSPTSPS)26 and are not fully functional in S. cerevisiae. These CTDs retain the critical Ess1 Ser-Pro target motifs, but substitutions at Y1, T4, and S7 profoundly affected their ability to undergo phase separation in vitro and localize in vivo. We propose that environmentally tuned phase separation by the CTD and other intrinsically disordered regions plays an adaptive role in cold tolerance by concentrating enzymes and substrates to overcome energetic barriers to metabolic activity.

A general theory for temperature dependence in biology

At present, there is no simple, first principles-based, and general model for quantitatively describing the full range of observed biological temperature responses. Here we derive a general theory for temperature dependence in biology based on Eyring-Evans-Polanyi's theory for chemical reaction rates. Assuming only that the conformational entropy of molecules changes with temperature, we derive a theory for the temperature dependence of enzyme reaction rates which takes the form of an exponential function modified by a power law and that describes the characteristic asymmetric curved temperature response. Based on a few additional principles, our model can be used to predict the temperature response above the enzyme level, thus spanning quantum to classical scales. Our theory provides an analytical description for the shape of temperature response curves and demonstrates its generality by showing the convergence of all temperature dependence responses onto universal relationships-a universal data collapse-under appropriate normalization and by identifying a general optimal temperature, around 25 ^∘C, characterizing all temperature response curves. The model provides a good fit to empirical data for a wide variety of biological rates, times, and steady-state quantities, from molecular to ecological scales and across multiple taxonomic groups (from viruses to mammals). This theory provides a simple framework to understand and predict the impact of temperature on biological quantities based on the first principles of thermodynamics, bridging quantum to classical scales.

Processes of the Reliability and Degradation Mechanism of High-Power Semiconductor Lasers

High-power semiconductor lasers have attracted widespread attention because of their small size, easy modulation, and high conversion efficiency. They play an important role in national economic construction and national defense construction, including free-space communication; industrial processing; and the medical, aerospace, and military fields, as well as other fields. The reliability of high-power semiconductor lasers is the key point of the application system. Higher reliability is sought in the military defense and aerospace fields in particular. Reliability testing and failure analysis help to improve the performance of high-power semiconductor lasers. This article provides a basis for understanding the reliability issues of semiconductor lasers across the whole supply chain. Firstly, it explains the failure modes and causes of failure in high-power semiconductor lasers; this article also summarizes the principles and application status of accelerated aging experiments and lifetime evaluation; it also introduces common techniques used for high-power semiconductor laser failure analysis, such as the electron beam-induced current (EBIC) technique and the optical beam-induced current (OBIC) technique, etc. Finally, methods used to improve the reliability of high-power semiconductor lasers are proposed in terms of the preparation process, reliability screening, and method application.

The Possible Role of Body Temperature in Modulating Brain and Body Sizes in Hominin Evolution

Many models have posited that the concomitant evolution of large brains and body sizes in hominins was constrained by metabolic costs. In such studies, the impact of body temperature has arguably not been sufficiently addressed despite the well-established fact that the rates of most physiological processes are manifestly temperature-dependent. Hence, the potential role of body temperature in regulating the number of neurons and body size is investigated by means of a heuristic quantitative model. It is suggested that modest deviations in body temperature (i.e., by a couple of degrees Celsius) might allow for substantive changes in brain and body parameters. In particular, a higher body temperature may prove amenable to an increased number of neurons, a higher brain-to-body mass ratio and fewer hours expended on feeding activities, while the converse could apply when the temperature is lowered. Future studies should, therefore, endeavor to explore and incorporate the effects of body temperature in metabolic theories of hominin evolution, while also integrating other factors such as foraging efficiency, diet, and fire control in tandem.

Are ectotherm brains vulnerable to global warming?

Elevated temperatures during development affect a wide range of traits in ectotherms. Less well understood is the impact of global warming on brain development, which has only rarely been studied experimentally. Here, we evaluate current progress in the field and search for common response patterns among ectotherm groups. Evidence suggests that temperature may have a positive effect on neuronal activity and growth in developing brains, but only up to a threshold, above which temperature is detrimental to neuron development. These responses appear to be taxon dependent but this assumption may be due to a paucity of data for some taxonomic groups. We provide a framework with which to advance this highly promising field in the future.

Universal rules of life: metabolic rates, biological times and the equal fitness paradigm

Here we review and extend the equal fitness paradigm (EFP) as an important step in developing and testing a synthetic theory of ecology and evolution based on energy and metabolism. The EFP states that all organisms are equally fit at steady state, because they allocate the same quantity of energy, ~ 22.4 kJ/g/generation to the production of offspring. On the one hand, the EFP may seem tautological, because equal fitness is necessary for the origin and persistence of biodiversity. On the other hand, the EFP reflects universal laws of life: how biological metabolism - the uptake, transformation and allocation of energy - links ecological and evolutionary patterns and processes across levels of organisation from: (1) structure and function of individual organisms, (2) life history and dynamics of populations, and (3) interactions and coevolution of species in ecosystems. The physics and biology of metabolism have facilitated the evolution of millions of species with idiosyncratic anatomy, physiology, behaviour and ecology but also with many shared traits and tradeoffs that reflect the single origin and universal rules of life.

Diversity of Dominant Soil Bacteria Increases with Warming Velocity at the Global Scale

Understanding global soil bacterial diversity is important because of its role in maintaining a healthy global ecosystem. Given the effects of environmental changes (e.g., warming and human impact) on the diversity of animals and plants, effects on soil bacterial diversity are expected; however, they have been poorly evaluated at the global scale to date. Thus, in this study, we focused on the dominant soil bacteria, which are likely critical drivers of key soil processes worldwide, and investigated the effects of warming velocity and human activities on their diversity. Using a global dataset of bacteria, we performed spatial analysis to evaluate the effects of warming velocity and human activities, while statistically controlling for the potentially confounding effects of current climate and geographic parameters with global climate and geographic data. We demonstrated that the diversity of the dominant soil bacteria was influenced globally, not only by the aridity index (dryness) and pH but also by warming velocity from the Last Glacial Maximum (21,000 years ago) to the present, showing significant increases. The increase in bacterial diversity with warming velocity was particularly significant in forests and grasslands. An effect of human activity was also observed, but it was secondary to warming velocity. These findings provide robust evidence and advance our understanding of the effects of environmental changes (particularly global warming) on soil bacterial diversity at the global scale.

Natural selection drives population divergence for local adaptation in a wheat pathogen

Evolution favors the emergence of locally-adapted optimum phenotypes that are likely to differ across a wide array of environmental conditions. The emergence of favorable adaptive characteristics is accelerated in agricultural pathogens due to the unique properties of agro-ecosystems. We performed a Q_ST - F_ST comparison using 164 strains of Parastagonospora nodorum sampled from eight global field populations to disentangle the predominant evolutionary forces driving population divergence in a wheat pathogen. We used digital image analysis to obtain quantitative measurements of growth rate and melanization at different temperatures and under different fungicide concentrations in a common garden experiment. F_ST measures were based on complete genome sequences obtained for all 164 isolates. Our analyses indicated that all measured traits were under selection. Growth rates at 18 °C and 24 °C were under stabilizing selection (Q_ST < F_ST), while diversifying selection (Q_ST > F_ST) was the predominant evolutionary force affecting growth under fungicide and high temperature stress. Stabilizing selection (Q_ST < F_ST) was the predominant force affecting melanization across the different environments. Melanin production increased at 30 °C but was negatively correlated with higher growth rates, consistent with a trade-off under heat stress. Our results demonstrate that global populations of P. nodorum possess significant evolutionary potential to adapt to changing local conditions, including warmer temperatures and applications of fungicides.

Effects of Constant and Fluctuating Low Temperatures on the Development of Aedes aegypti (Diptera: Culicidae) from a Temperate Region

Most studies of the effects of low temperature on the development of immature stages of Aedes aegypti (L.) have been performed at constant temperatures in the laboratory, which may not accurately reflect the variable environmental conditions in the field. Thus, the aim of this study was to assess the effect of constant temperatures (CT) and fluctuating low temperatures (FT) on the fitness of Ae. aegypti of Buenos Aires, Argentina. Three CT treatments (12, 14, and 16°C) and three FT treatments (12, 14, and 16°C ± 4°C) were performed and then survival, development time, and size of adults analyzed for each treatment. The immature stages completed development in all the treatments, with an average survival of 88% at 16°C, 85% at 14°C, and 22% at 12°C, and showed no differences between the CT and FT treatments. Development times were similar between the CT and FT treatments at 16°C (average ± SD: 22.7 ± 2.0 d) and at 14°C (average ± SD: 30.5 ± 2.5 d), whereas at 12°C, they lasted longer under CT (average ± SD: 46.6 ± 5.1 d) than under FT (average ± SD: 37 ± 6.5 d). The sizes of the adults at 12 and 14°C were similar but larger than those at 16°C, and showed no differences between the CT and FT treatments. Compared to populations of other geographical regions assessed in previous studies, the shorter development times and the high survival at 14 and 16°C, and the ability to complete development at 12°C, a fact not previously reported, suggest that the Ae. aegypti population of Buenos Aires city has a higher tolerance to these conditions.

Performance in a variable world: using Jensen's inequality to scale up from individuals to populations

Body temperature affects plants' and animals' performance, but these effects are complicated by thermal variation through time within an individual and variation through space among individuals in a population. This review and synthesis describes how the effects of thermal variation-in both time and space-can be estimated by applying a simple, nonlinear averaging scheme. The method is first applied to the temporal variation experienced by an individual, providing an estimate of the individual's average performance. The method is then applied to the scale-dependent thermal variation among individuals, which is modelled as a 1/f-noise phenomenon. For an individual, thermal variation reduces average performance, lowers the temperature of maximum performance (Topt ) and contracts the range of viable temperatures. Thermal variation among individuals similarly reduces performance and lowers Topt , but increases the viable range of average temperatures. These results must be viewed with caution, however, because they do not take into account the time-dependent interaction between body temperature and physiological plasticity. Quantifying these interactions is perhaps the largest challenge for ecological and conservation physiologists as they attempt to predict the effects of climate change.

Morphology-based differences in the thermal response of freshwater phytoplankton

The thermal response of maximum growth rate in morphology-based functional groups (MBFG) of freshwater phytoplankton is analysed. Contrasting an exponential Boltzmann-Arrhenius with a unimodal model, three main features were evaluated: (i) the activation energy of the rise (E_r), (ii) the presence of a break in the thermal response and (iii) the activation energy of the fall (E_f). The whole dataset (N = 563) showed an exponential increase (E_r ∼ 0.5), a break around 24°C and no temperature dependence after the breakpoint (E_f = 0). Contrasting thermal responses among MBFG were found. All groups showed positive activation energy (E_r > 0), four showed no evidence of decline in growth rate (temperature range = 0-35°C) and two presented a breakpoint followed by a sharp decrease in growth rate. Our results evidenced systematic differences between MBFG in the thermal response and a coherent response significantly related to morphological traits other than size (i.e. within MBFG). These results provide relevant information for water quality modelling and climate change predictions.

The Biokinetic Spectrum for Temperature and optimal Darwinian fitness

Darwinian fitness is maximised at a temperature below T_opt, but what this temperature is remains unclear. By linking our previous work on the Biokinetic Spectrum for Temperature with a model for temperature-dependent biological growth rate we obtain a plausible value for such a temperature. We find this approach reveals considerable commonalities in how life responds to temperature with implications that follow in evolution, physiology and ecology. We described a data set consisting of 17,021 observations of temperature-dependent population growth rates from 2411 bacterial, archaeal and eukaryal strains. We fitted a thermodynamic model to describe the strains' temperature-dependent growth rate curves that assumed growth was limited by a single rate-limiting enzyme. We defined U_mes as an empirical measure of the temperature at which strains grew as fast and also as efficiently as possible. We propose that Darwinian fitness is optimised at U_mes by trading-off growth rate and physiological efficiency. Using the full data set we calculated the Biokinetic Spectrum for Temperature (BKST): the distribution of temperature-dependent growth rates for each temperature. We used quantile regression to fit alternative models to the BKST to obtain quantile curves. A quantile is a value that contains a particular proportion of the data. The quantile curves suggested commonalities in temperature-dependencies spanning taxa and ecotype, consistent with the single rate-limiting enzyme concept. We showed that on the log scale, the slopes of the quantile curves were the same as the slopes of the thermodynamic model growth curves at U_mes. This was true for Bacteria, Archaea, and Eukarya, and across other conditions (pH, water activity, metabolic type and trophic type). We showed that the quantile curves were the loci of the temperatures and growth rates that optimised Darwinian fitness for each strain at a given temperature-dependence and independently of other conditions. The quantile curves for Archaea and Bacteria shared a number of similarities attributable to the influence of the properties of water on protein folding. Other implications have impact on evolutionary biology, ecology, and physiology. The model predicts the existence of eurythermic strains that grow with about equal efficiency over a broad temperature range. These strains will have higher evolutionary rates with lower mutational costs that are independent of environmental conditions, a factor likely to have been significant during the Precambrian if the early Earth was warmer than today. The model predicts that random mutations are likely to result in shifts along the quantile curves and not across them. It predicts that some psychrophiles will be capable of performing well under climate change, and that selection will favour faster growth rates as the temperature increases. Last, it predicts trade-offs between growth rate and soma production, so that temperature-dependence, and possibly Darwinian fitness, remain constant over a broad temperature range and growth rates.

From conceptual to computational: Cost and benefits of lizard thermoregulation revisited

A classic paper detailed conceptual analyses of behavioral thermoregulation (Huey and Slatkin, 1976) and has served as the theoretical foundation for hundreds of investigative studies. Most recently, investigators have revisited this theoretical presentation to offer additional interpretation for both heterogeneity and spatial structure of temperature and how it may influence energetic costs (Sears and Angilletta, 2015). Interestingly, this foundational presentation by Huey and Slatkin, over 40 years ago, has never received formal computational analyses to address mathematically the postulates of this conceptual model. Here we use functions that closely mimic those that were described by Huey and Slatkin to provide both a theoretical and computational analysis for the cost and benefits of lizard thermoregulation. We demonstrate both the utility and inherent accuracy of their analyses using a model that was developed conceptually without the use of now readily available computational tools. But contrary to Huey and Slatkin's analyses, we provide a mathematical proof that perfect thermoregulation is never an optimal strategy and show by computational analysis that thermoregulatory strategy (k ) may decrease, not increase, with increasing cost.

Evaluating the kinetic basis of plant growth from organs to ecosystems

Contents Summary 37 I. Introduction 37 II. Predictions for metabolic kinetics 38 III. Kinetics of net photosynthesis 38 IV. Kinetics of plant growth 40 V. Hypotheses for higher-level kinetic decoupling 41 VI. Conclusions 42 Acknowledgements 42 References 42 SUMMARY: Understanding how temperature influences the scaling of physiological rates through levels of biological organization is critical for predicting plant responses to climate. Metabolic theory predicts that many rates increase exponentially with temperature following an activation energy (E) of 0.32 eV for photosynthesis. Here, I evaluate this prediction for net photosynthesis and organ, individual, and ecosystem growth. Observed E for photosynthesis varied widely but was not statistically different from predictions, while E for organs was greater than predicted, and E for individuals and ecosystems only weakly characterized temperature responses. I review several hypotheses that may underlie these results. Understanding how multiple rate-limiting processes coalesce into a single E that characterizes metabolic responses to temperature, and how to best estimate E from unimodal data, remain important challenges.

Decomposing the effects of ocean environments on predator-prey body-size relationships in food webs

Body-size relationships between predators and their prey are important in ecological studies because they reflect the structure and function of food webs. Inspired by studies on the impact of global warming on food webs, the effects of temperature on body-size relationships have been widely investigated; however, the impact of environmental factors on body-size relationships has not been fully evaluated because climate warming affects various ocean environments. Thus, here, we comprehensively investigated the effects of ocean environments and predator-prey body-size relationships by integrating a large-scale dataset of predator-prey body-size relationships in marine food webs with global oceanographic data. We showed that various oceanographic parameters influence prey size selection. In particular, oxygen concentration, primary production and salinity, in addition to temperature, significantly alter body-size relationships. Furthermore, we demonstrated that variability (seasonality) of ocean environments significantly affects body-size relationships. The effects of ocean environments on body-size relationships were generally remarkable for small body sizes, but were also significant for large body sizes and were relatively weak for intermediate body sizes, in the cases of temperature seasonality, oxygen concentration and salinity variability. These findings break down the complex effects of ocean environments on body-size relationships, advancing our understanding of how ocean environments influence the structure and functioning of food webs.

Slow and temperature-mediated pathogen adaptation to a nonspecific fungicide in agricultural ecosystem

The spread of antimicrobial resistance and global change in air temperature represent two major phenomena that are exerting a disastrous impact on natural and social issues but investigation of the interaction between these phenomena in an evolutionary context is limited. In this study, a statistical genetic approach was used to investigate the evolution of antimicrobial resistance in agricultural ecosystem and its association with local air temperature, precipitation, and UV radiation. We found no resistance to mancozeb, a nonspecific fungicide widely used in agriculture for more than half a century, in 215 Alternaria alternata isolates sampled from geographic locations along a climatic gradient and cropping system representing diverse ecotypes in China, consistent with low resistance risk in many nonspecific fungicides. Genetic variance accounts for ~35% of phenotypic variation, while genotype-environment interaction is negligible, suggesting that heritability plays a more important role in the evolution of resistance to mancozeb in plant pathogens than phenotypic plasticity. We also found that tolerance to mancozeb in agricultural ecosystem is under constraining selection and significantly associated with local air temperature, possibly resulting from a pleiotropic effect of resistance with thermal and other ecological adaptations. The implication of these results for fungicide and other antimicrobial management in the context of global warming is discussed.

Predictions of response to temperature are contingent on model choice and data quality

The equations used to account for the temperature dependence of biological processes, including growth and metabolic rates, are the foundations of our predictions of how global biogeochemistry and biogeography change in response to global climate change. We review and test the use of 12 equations used to model the temperature dependence of biological processes across the full range of their temperature response, including supra- and suboptimal temperatures. We focus on fitting these equations to thermal response curves for phytoplankton growth but also tested the equations on a variety of traits across a wide diversity of organisms. We found that many of the surveyed equations have comparable abilities to fit data and equally high requirements for data quality (number of test temperatures and range of response captured) but lead to different estimates of cardinal temperatures and of the biological rates at these temperatures. When these rate estimates are used for biogeographic predictions, differences between the estimates of even the best-fitting models can exceed the global biological change predicted for a decade of global warming. As a result, studies of the biological response to global changes in temperature must make careful consideration of model selection and of the quality of the data used for parametrizing these models.

Process-Based Models of Phenology for Plants and Animals

Phenology is a key aspect of plant and animal life strategies that determines the ability to capture seasonally variable resources. It defines the season and duration of growth and reproduction and paces ecological interactions and ecosystem functions. Phenology models have become a key component of models in agronomy, forestry, ecology, and biogeosciences. Plant and animal process-based phenology models have taken different paths that have so far not crossed. Yet, they share many features because plant and animal annual cycles also share many characteristics, from their stepwise progression, including a resting period, to their dependence on similar environmental factors. We review the strengths and shortcomings of these models and the divergences in modeling approaches for plants and animals, which are mostly due to specificities of the questions they tackle. Finally, we discuss the most promising avenues and the challenges phenology modeling needs to address in the upcoming years.

The combined effects of reactant kinetics and enzyme stability explain the temperature dependence of metabolic rates

A mechanistic understanding of the response of metabolic rate to temperature is essential for understanding thermal ecology and metabolic adaptation. Although the Arrhenius equation has been used to describe the effects of temperature on reaction rates and metabolic traits, it does not adequately describe two aspects of the thermal performance curve (TPC) for metabolic rate—that metabolic rate is a unimodal function of temperature often with maximal values in the biologically relevant temperature range and that activation energies are temperature dependent. We show that the temperature dependence of metabolic rate in ectotherms is well described by an enzyme‐assisted Arrhenius (EAAR) model that accounts for the temperature‐dependent contribution of enzymes to decreasing the activation energy required for reactions to occur. The model is mechanistically derived using the thermodynamic rules that govern protein stability. We contrast our model with other unimodal functions that also can be used to describe the temperature dependence of metabolic rate to show how the EAAR model provides an important advance over previous work. We fit the EAAR model to metabolic rate data for a variety of taxa to demonstrate the model's utility in describing metabolic rate TPCs while revealing significant differences in thermodynamic properties across species and acclimation temperatures. Our model advances our ability to understand the metabolic and ecological consequences of increases in the mean and variance of temperature associated with global climate change. In addition, the model suggests avenues by which organisms can acclimate and adapt to changing thermal environments. Furthermore, the parameters in the EAAR model generate links between organismal level performance and underlying molecular processes that can be tested for in future work.

Trade-offs and evolution of thermal adaptation in the Irish potato famine pathogen Phytophthora infestans

Temperature is one of the most important environmental parameters with crucial impacts on nearly all biological processes. Due to anthropogenic activity, average air temperatures are expected to increase by a few degrees in coming decades, accompanied by an increased occurrence of extreme temperature events. Such global trends are likely to have various major impacts on human society through their influence on natural ecosystems, food production and biotic interactions, including diseases. In this study, we used a combination of statistical genetics, experimental evolution and common garden experiments to investigate the evolutionary potential for thermal adaptation in the potato late blight pathogen, Phytophthora infestans, and infer its likely response to changing temperatures. We found a trade-off associated with thermal adaptation to heterogeneous environments in P. infestans, with the degree of the trade-off peaking approximately at the pathogen's optimum growth temperature. A genetic trade-off in thermal adaptation was also evidenced by the negative association between a strain's growth rate and its thermal range for growth, and warm climates selecting for a low pathogen growth rate. We also found a mirror effect of phenotypic plasticity and genetic adaptation on growth rate. At below the optimum, phenotypic plasticity enhances pathogen's growth rate but nature selects for slower growing genotypes when temperature increases. At above the optimum, phenotypic plasticity reduces pathogen's growth rate but natural selection favours for faster growing genotypes when temperature increases further. We conclude from these findings that the growth rate of P. infestans will only be marginally affected by global warming.

Crossing regimes of temperature dependence in animal movement

A pressing challenge in ecology is to understand the effects of changing global temperatures on food web structure and dynamics. The stability of these complex ecological networks largely depends on how predator-prey interactions may respond to temperature changes. Because predators and prey rely on their velocities to catch food or avoid being eaten, understanding how temperatures may affect animal movement is central to this quest. Despite our efforts, we still lack a mechanistic understanding of how the effect of temperature on metabolic processes scales up to animal movement and beyond. Here, we merge a biomechanical approach, the Metabolic Theory of Ecology and empirical data to show that animal movement displays multiple regimes of temperature dependence. We also show that crossing these regimes has important consequences for population dynamics and stability, which depend on the parameters controlling predator-prey interactions. We argue that this dependence upon interaction parameters may help explain why experimental work on the temperature dependence of interaction strengths has so far yielded conflicting results. More importantly, these changes in the temperature dependence of animal movement can have consequences that go well beyond ecological interactions and affect, for example, animal communication, mating, sensory detection, and any behavioral modality dependent on the movement of limbs. Finally, by not taking into account the changes in temperature dependence reported here we might not be able to properly forecast the impact of global warming on ecological processes and propose appropriate mitigation action when needed.

Feet, heat and scallops: what is the cost of anthropogenic disturbance in bivalve aquaculture?

The effects of unnatural disturbances on the behaviour and energetics of animals are an important issue for conservation and commercial animal production. Biologging enables estimation of the energy costs of these disturbances, but not specifically the effect these costs have on growth; a key outcome measure for animal farming enterprises. We looked at how natural and anthropogenically induced activity and energy expenditure of king scallops Pecten maximus varies with temperature. These data were then used to model growth time of king scallops reared in an aquaculture facility under different temperatures and anthropogenic disturbance levels. The scallops exhibited a typical total metabolic rate (MR)-temperature curve, with a peak reached at a middling temperature. The percentage of their total MR associated with spinning and swimming, behavioural responses to disturbance, was considerable. Interestingly, as temperature increased, the activity MR associated with a given level of activity decreased; a hitherto unreported relationship in any species. The model results suggest there is a trade-off in the ambient temperature that should be set by hatcheries between the optimal for scallop growth if completely undisturbed versus mitigating against the energy costs elicited by anthropogenic disturbance. Furthermore, the model indicates that this trade-off is affected by scallop size. Aquaculture facilities typically have controls to limit the impact of human activities, yet the present data indicate that hatcheries may be advised to consider whether more controls could further decrease extraneous scallop behaviours, resulting in enhanced scallop yields and improved financial margins.

Real versus Artificial Variation in the Thermal Sensitivity of Biological Traits

Whether the thermal sensitivity of an organism's traits follows the simple Boltzmann-Arrhenius model remains a contentious issue that centers around consideration of its operational temperature range and whether the sensitivity corresponds to one or a few underlying rate-limiting enzymes. Resolving this issue is crucial, because mechanistic models for temperature dependence of traits are required to predict the biological effects of climate change. Here, by combining theory with data on 1,085 thermal responses from a wide range of traits and organisms, we show that substantial variation in thermal sensitivity (activation energy) estimates can arise simply because of variation in the range of measured temperatures. Furthermore, when thermal responses deviate systematically from the Boltzmann-Arrhenius model, variation in measured temperature ranges across studies can bias estimated activation energy distributions toward higher mean, median, variance, and skewness. Remarkably, this bias alone can yield activation energies that encompass the range expected from biochemical reactions (from ~0.2 to 1.2 eV), making it difficult to establish whether a single activation energy appropriately captures thermal sensitivity. We provide guidelines and a simple equation for partially correcting for such artifacts. Our results have important implications for understanding the mechanistic basis of thermal responses of biological traits and for accurately modeling effects of variation in thermal sensitivity on responses of individuals, populations, and ecological communities to changing climatic temperatures.

An evidence-based framework for predicting the impact of differing autotroph-heterotroph thermal sensitivities on consumer-prey dynamics

Increased temperature accelerates vital rates, influencing microbial population and wider ecosystem dynamics, for example, the predicted increases in cyanobacterial blooms associated with global warming. However, heterotrophic and mixotrophic protists, which are dominant grazers of microalgae, may be more thermally sensitive than autotrophs, and thus prey could be suppressed as temperature rises. Theoretical and meta-analyses have begun to address this issue, but an appropriate framework linking experimental data with theory is lacking. Using ecophysiological data to develop a novel model structure, we provide the first validation of this thermal sensitivity hypothesis: increased temperature improves the consumer's ability to control the autotrophic prey. Specifically, the model accounts for temperature effects on auto- and mixotrophs and ingestion, growth and mortality rates, using an ecologically and economically important system (cyanobacteria grazed by a mixotrophic flagellate). Once established, we show the model to be a good predictor of temperature impacts on consumer–prey dynamics by comparing simulations with microcosm observations. Then, through simulations, we indicate our conclusions remain valid, even with large changes in bottom-up factors (prey growth and carrying capacity). In conclusion, we show that rising temperature could, counterintuitively, reduce the propensity for microalgal blooms to occur and, critically, provide a novel model framework for needed, continued assessment.

Thermal variation, thermal extremes and the physiological performance of individuals

In this review we consider how small-scale temporal and spatial variation in body temperature, and biochemical/physiological variation among individuals, affect the prediction of organisms' performance in nature. For ‘normal’ body temperatures – benign temperatures near the species' mean – thermal biology traditionally uses performance curves to describe how physiological capabilities vary with temperature. However, these curves, which are typically measured under static laboratory conditions, can yield incomplete or inaccurate predictions of how organisms respond to natural patterns of temperature variation. For example, scale transition theory predicts that, in a variable environment, peak average performance is lower and occurs at a lower mean temperature than the peak of statically measured performance. We also demonstrate that temporal variation in performance is minimized near this new ‘optimal’ temperature. These factors add complexity to predictions of the consequences of climate change. We then move beyond the performance curve approach to consider the effects of rare, extreme temperatures. A statistical procedure (the environmental bootstrap) allows for long-term simulations that capture the temporal pattern of extremes (a Poisson interval distribution), which is characterized by clusters of events interspersed with long intervals of benign conditions. The bootstrap can be combined with biophysical models to incorporate temporal, spatial and physiological variation into evolutionary models of thermal tolerance. We conclude with several challenges that must be overcome to more fully develop our understanding of thermal performance in the context of a changing climate by explicitly considering different forms of small-scale variation. These challenges highlight the need to empirically and rigorously test existing theories.

The effects of temperature on aerobic metabolism: towards a mechanistic understanding of the responses of ectotherms to a changing environment

Because of its profound effects on the rates of biological processes such as aerobic metabolism, environmental temperature plays an important role in shaping the distribution and abundance of species. As temperature increases, the rate of metabolism increases and then rapidly declines at higher temperatures – a response that can be described using a thermal performance curve (TPC). Although the shape of the TPC for aerobic metabolism is often attributed to the competing effects of thermodynamics, which can be described using the Arrhenius equation, and the effects of temperature on protein stability, this account represents an over-simplification of the factors acting even at the level of single proteins. In addition, it cannot adequately account for the effects of temperature on complex multistep processes, such as aerobic metabolism, that rely on mechanisms acting across multiple levels of biological organization. The purpose of this review is to explore our current understanding of the factors that shape the TPC for aerobic metabolism in response to acute changes in temperature, and to highlight areas where this understanding is weak or insufficient. Developing a more strongly grounded mechanistic model to account for the shape of the TPC for aerobic metabolism is crucial because these TPCs are the foundation of several recent attempts to predict the responses of species to climate change, including the metabolic theory of ecology and the hypothesis of oxygen and capacity-limited thermal tolerance.

Interactions between temperature and nutrients across levels of ecological organization

Temperature and nutrient availability play key roles in controlling the pathways and rates at which energy and materials move through ecosystems. These factors have also changed dramatically on Earth over the past century as human activities have intensified. Although significant effort has been devoted to understanding the role of temperature and nutrients in isolation, less is known about how these two factors interact to influence ecological processes. Recent advances in ecological stoichiometry and metabolic ecology provide a useful framework for making progress in this area, but conceptual synthesis and review are needed to help catalyze additional research. Here, we examine known and potential interactions between temperature and nutrients from a variety of physiological, community, and ecosystem perspectives. We first review patterns at the level of the individual, focusing on four traits--growth, respiration, body size, and elemental content--that should theoretically govern how temperature and nutrients interact to influence higher levels of biological organization. We next explore the interactive effects of temperature and nutrients on populations, communities, and food webs by synthesizing information related to community size spectra, biomass distributions, and elemental composition. We use metabolic theory to make predictions about how population-level secondary production should respond to interactions between temperature and resource supply, setting up qualitative predictions about the flows of energy and materials through metazoan food webs. Last, we examine how temperature-nutrient interactions influence processes at the whole-ecosystem level, focusing on apparent vs. intrinsic activation energies of ecosystem processes, how to represent temperature-nutrient interactions in ecosystem models, and patterns with respect to nutrient uptake and organic matter decomposition. We conclude that a better understanding of interactions between temperature and nutrients will be critical for developing realistic predictions about ecological responses to multiple, simultaneous drivers of global change, including climate warming and elevated nutrient supply.

Inferring the temperature dependence of population parameters: the effects of experimental design and inference algorithm

Understanding and quantifying the temperature dependence of population parameters, such as intrinsic growth rate and carrying capacity, is critical for predicting the ecological responses to environmental change. Many studies provide empirical estimates of such temperature dependencies, but a thorough investigation of the methods used to infer them has not been performed yet. We created artificial population time series using a stochastic logistic model parameterized with the Arrhenius equation, so that activation energy drives the temperature dependence of population parameters. We simulated different experimental designs and used different inference methods, varying the likelihood functions and other aspects of the parameter estimation methods. Finally, we applied the best performing inference methods to real data for the species Paramecium caudatum. The relative error of the estimates of activation energy varied between 5% and 30%. The fraction of habitat sampled played the most important role in determining the relative error; sampling at least 1% of the habitat kept it below 50%. We found that methods that simultaneously use all time series data (direct methods) and methods that estimate population parameters separately for each temperature (indirect methods) are complementary. Indirect methods provide a clearer insight into the shape of the functional form describing the temperature dependence of population parameters; direct methods enable a more accurate estimation of the parameters of such functional forms. Using both methods, we found that growth rate and carrying capacity of Paramecium caudatum scale with temperature according to different activation energies. Our study shows how careful choice of experimental design and inference methods can increase the accuracy of the inferred relationships between temperature and population parameters. The comparison of estimation methods provided here can increase the accuracy of model predictions, with important implications in understanding and predicting the effects of temperature on the dynamics of populations.

Comparing temperature effects on Escherichia coli, Salmonella, and Enterococcus survival in surface waters

The objective of this study was to compare dependency of survival rates on temperature for indicator organisms Escherichia coli and Enterococcus and the pathogen Salmonella in surface waters. A database of 86 survival datasets from peer-reviewed papers on inactivation of E. coli, Salmonella and Enterococcus in marine waters and of E. coli and Salmonella in lake waters was assembled. The Q10 model was used to express temperature effect on survival rates obtained from linear sections of semi-logarithmic survival graphs. Available data were insufficient to establish differences in survival rates and temperature dependencies for marine waters where values of Q10  = 3 and a survival rate of 0·7 day(-1) could be applied. The Q10 values in lake waters were substantially lower in marine waters, and Salmonella inactivation in lake water was, on average, twice as fast as E. coli; data on E. coli substantially outnumber data on Enterococcus and Salmonella. The relative increase in inactivation with increase in temperature is higher in marine waters than lake water, and differences in inactivation between Salmonella and E. coli at a given temperature were significant in lake water but not in marine waters.

SIGNIFICANCE AND IMPACT OF THE STUDY

Microbiological quality of surface waters is of paramount importance for public health. The novelty of this work is using a large compendium of published data to develop the first comparison of temperature effects on survival of the pathogen Salmonella and water quality indicator micro-organisms Escherichia coli and Enterococcus in natural waters. The existing relatively large body of knowledge on E. coli survival appears to be useful to assess the effect of temperature on survival of Salmonella. Moreover, results of this work constitute an essential input in models to support environmental management decisions on the use of surface water sources in agriculture, aquaculture and recreation.