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Introduction: Flower color polymorphism is often attributed to selection pressures from Q9 pollinators or other non-pollinator stress factors. Generally, flower color polymorphism demonstrates effective acclimatization linked to either pollinator-mediated selection or pleiotropic effects. Methods: To test these hypotheses in Ophiorrhiza japonica, we compared pollinator visitation frequencies and plant traits between pink and white morphs in Shibing, a dolomite Karst region recognized as a World Natural Heritage Site. We also assessed the ratio of flower morphs and the reproductive success of the two morphs during spring and winter. Additionally, we examined the effects of temperature shifts on the two morphs under various temperature treatments. Results and discussion: Our results revealed no significant difference in visitation frequencies between the morphs. However, the ratio of pink to white morph differed significantly between spring and winter. The temperature of pink morph was higher than that of white morph at temperatures ranging from 0-24°C, while white morph had higher temperatures than pink morph at -4°C. Based on the aforementioned results, pollinators are not the primary factor influencing the distribution of flower colors in spring and winter. Furthermore, the response of different flower colors to temperature suggests that temperature is more likely the factor driving changes in flower coloration. Our study provides further evidence supporting the pleiotropic effect hypothesis, which posits that flower color polymorphism can be maintained by fluctuating temperatures in the dolomite Karst region. This study offers a potential model for explaining flower color polymorphism in Karst regions. [ABSTRACT FROM AUTHOR]

Phenology models are widely used in Decision Support Systems to predict the phenology of pests. Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a polyphagous pest, has a high prevalence in apple trees (Malus domestica Borkh.) (Rosales: Rosaceae) in certain areas, despite the fact that apple trees are considered secondary hosts. Its natural behavior of feeding inside plant tissue at the larval stage makes monitoring and planning methods of control critical for Integrated Pest Management. The development times and survival rates of two field populations of G. molesta larvae on apple cultivars 'Gala', 'Golden', and 'Fuji' were determined under different temperature (constant versus field fluctuation) and feeding conditions (diet versus apples attached to the tree and detached from the tree). The results showed that G. molesta fitness in apples is affected by fluctuating temperature regimes in the field, the condition of the fruit, whether or not the fruit is attached to the tree, and the cultivar. The temperature was the main cause of the differences in the studied parameters. Larvae developme–nt time was delayed due to fluctuating field temperatures. Larvae had a shorter development time in fruits detached from the tree compared to attached fruits, and apple cultivars influenced development time in both laboratory and field conditions, with the 'Golden' cultivar having better fitness and a higher rate of larvae survival in the fruits attached to the tree. These factors need to be considered to properly adjust the phenology models and improve the Integrated Pest Management system of apples. [ABSTRACT FROM AUTHOR]

IntroductionFlower color polymorphism is often attributed to selection pressures from Q9 pollinators or other non-pollinator stress factors. Generally, flower color polymorphism demonstrates effective acclimatization linked to either pollinator-mediated selection or pleiotropic effects.MethodsTo test these hypotheses in Ophiorrhiza japonica, we compared pollinator visitation frequencies and plant traits between pink and white morphs in Shibing, a dolomite Karst region recognized as a World Natural Heritage Site. We also assessed the ratio of flower morphs and the reproductive success of the two morphs during spring and winter. Additionally, we examined the effects of temperature shifts on the two morphs under various temperature treatments.Results and discussionOur results revealed no significant difference in visitation frequencies between the morphs. However, the ratio of pink to white morph differed significantly between spring and winter. The temperature of pink morph was higher than that of white morph at temperatures ranging from 0-24°C, while white morph had higher temperatures than pink morph at -4°C. Based on the aforementioned results, pollinators are not the primary factor influencing the distribution of flower colors in spring and winter. Furthermore, the response of different flower colors to temperature suggests that temperature is more likely the factor driving changes in flower coloration. Our study provides further evidence supporting the pleiotropic effect hypothesis, which posits that flower color polymorphism can be maintained by fluctuating temperatures in the dolomite Karst region. This study offers a potential model for explaining flower color polymorphism in Karst regions.

Postbiotics are metabolites derived from living probiotic bacteria like Lactobacillus strains, during the fermentation process and/or produced in pure form on laboratory scales. These compounds, depending on the type of probiotic from which they are prepared, have specific antibacterial agents such as: organic acids, bacteriocins, short‐chain fatty acids, and peptides. The objective of this study was to investigate the effect of Lactobacillus acidophilus supernatant (LAS) on the growth pattern of Salmonella enteritidis at fluctuating temperatures and the sensory evaluation of milk that contains this probiotic. Baranyi and Roberts's model determined the best‐fit curve for the microbial growth. According to mathematical equations, the highest and lowest specific growth (μmax) rates of S. enteritidis were obtained at 0.055 h−1 and 0.0059 h−1 and also highest and lowest maximum generation time (MGT) values were obtained at 20.06 h and 8.85 h, respectively. Sensory evaluation by the Triangel test reveals that LAS could not establish a significant (p >.05) adverse effect on milk perceptible. Regarding the results obtained in the present study, LAS, without causing adverse sensory change, could act as a safe food additive for the control of bacterial pathogens and reducing food waste, particularly in milk and milk‐containing food products. [ABSTRACT FROM AUTHOR]

Phenology models are widely used in Decision Support Systems to predict the phenology of pests. Grapholita molesta (Busck) (Lepidoptera: Tortricidae), a polyphagous pest, has a high prevalence in apple trees (Malus domestica Borkh.) (Rosales: Rosaceae) in certain areas, despite the fact that apple trees are considered secondary hosts. Its natural behavior of feeding inside plant tissue at the larval stage makes monitoring and planning methods of control critical for Integrated Pest Management. The development times and survival rates of two field populations of G. molesta larvae on apple cultivars ‘Gala’, ‘Golden’, and ‘Fuji’ were determined under different temperature (constant versus field fluctuation) and feeding conditions (diet versus apples attached to the tree and detached from the tree). The results showed that G. molesta fitness in apples is affected by fluctuating temperature regimes in the field, the condition of the fruit, whether or not the fruit is attached to the tree, and the cultivar. The temperature was the main cause of the differences in the studied parameters. Larvae developme–nt time was delayed due to fluctuating field temperatures. Larvae had a shorter development time in fruits detached from the tree compared to attached fruits, and apple cultivars influenced development time in both laboratory and field conditions, with the ‘Golden’ cultivar having better fitness and a higher rate of larvae survival in the fruits attached to the tree. These factors need to be considered to properly adjust the phenology models and improve the Integrated Pest Management system of apples.

Climate change is associated with the increase in both the mean and variability of thermal conditions. Therefore, the use of more realistic fluctuating thermal regimes is the most appropriate laboratory method for predicting population responses to thermal heterogeneity. However, the long- and short-term implications of evolving under such conditions are not well understood. Here, we examined differences in key life-history traits among populations of seed beetles (Callosobruchus maculatus) that evolved under either constant control conditions or in an environment with fluctuating daily temperatures. Specifically, individuals from two distinct genetic backgrounds were kept for 19 generations at one of two temperatures, a constant temperature (T  = 29 °C) or a fluctuating daily cycle (T mean = 33 °C, T max = 40 °C, and T min = 26 °C), and were assayed either in their evolved environment or in the other environment. We found that beetles that evolved in fluctuating environments but were then switched to constant 29 °C conditions had far greater lifetime reproductive success compared with beetles that were kept in their evolved environments. This increase in reproductive success suggests that beetles raised in fluctuating environments may have evolved greater thermal breadth than control condition beetles. In addition, the degree of sexual dimorphism in body size and development varied as a function of genetic background, evolved thermal environment, and current temperature conditions. These results not only highlight the value of incorporating diel fluctuations into climate research but also suggest that populations that experience variability in temperature may be better able to respond to both short- and long-term changes in environmental conditions. [ABSTRACT FROM AUTHOR]

Using Pyriproxyfen in controlling Aedes aegypti shows great potential considering its high competence in low dosages. As an endocrine disruptor, temperature can interfere with its efficiency, related to a decrease in larval emergence inhibition in hotter environments. However, previous studies have been performed at constant temperatures in the laboratory, which may not precisely reflect the environmental conditions in the field. The aim of this study was to assess the effect of the fluctuating temperatures in Pyriproxyfen efficiency on controlling Aedes aegypti larvae. We selected maximum and minimum temperatures from the Brazilian Meteorological Institute database from September to April for cities grouped by five regions. Five fluctuating temperatures (17–26; 20–28.5; 23–32.5; 23–30.5; 19.5–31 °C) were applied to bioassays assessing Pyriproxyfen efficiency in preventing adult emergence in Aedes aegypti larvae in five concentrations. In the lowest temperatures, the most diluted Pyriproxyfen treatment (0.0025 mg/L) was efficient in preventing the emergence of almost thrice the larvae than in the hottest temperatures (61% and 21%, respectively, p value = 0.00015). The concentration that inhibits the emergence of 50% of the population was lower than that preconized by the World Health Organization (0.01 mg/L) in all treatments, except for the hottest temperatures, for which we estimated 0.010 mg/L. We concluded that fluctuating temperatures in laboratory bioassays can provide a more realistic result to integrate the strategies in vector surveillance. For a country with continental proportions such as Brazil, considering regionalities is crucial to the rational use of insecticides. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the effectiveness of A. oryzae in inhibiting aflatoxin B1 (AFB1) and ochratoxin A (OTA) production by A. flavus and A. carbonarius, respectively, under shifting temperatures. A. oryzae was tested on different agar, namely coconut cream agar (CCA) and chili-based agar to figure out the variation in the effectiveness of A. oryzae on the most appropriate medium for A. flavus and A. carbonarius to produce mycotoxin and under natural condition where they are predominantly found. On CCA, the temperatures applied were 20, 30, 35, 40, 20/30, 20/35, and 20/40 °C, while on chili-based agar, the temperatures imposed were 20, 40, and 20/40 °C, at varied water activity of 0.92 and 0.97aw. The findings indicated that A. oryzae was much more effective in inhibiting the growth of A. flavus rather than A. carbonarius, yet it was able to inhibit higher OTA concentration than AFB1 at fluctuating temperatures on CCA as the most appropriate medium for A. flavus and A. carbonarius. A. oryzae effectively inhibited AFB1 and OTA at static temperature of 20 °C and water activity of 0.97aw on chili-based agar. Under fluctuating temperatures (20/40 °C), A. oryzae was also able to control mycotoxin, particularly OTA at high water activity (0.97aw).

Abstract Environmental temperature is a crucial abiotic factor that influences the success of ectothermic organisms, including hosts and pathogens in disease systems. One example is the amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), which has led to widespread amphibian population declines. Understanding its thermal ecology is essential to effectively predict outbreaks. Studies that examine the impact of temperature on hosts and pathogens often do so in controlled constant temperatures. Although varying temperature experiments are becoming increasingly common, it is unrealistic to test every temperature scenario. Thus, reliable methods that use constant temperature data to predict performance in varying temperatures are needed. In this study, we tested whether we could accurately predict Bd growth in three varying temperature regimes, using a Bayesian hierarchical model fit with constant temperature Bd growth data. We fit the Bayesian hierarchical model five times, each time changing the thermal performance curve (TPC) used to constrain the logistic growth rate to determine how TPCs influence the predictions. We then validated the model predictions using Bd growth data collected from the three tested varying temperature regimes. Although all TPCs overpredicted Bd growth in the varying temperature regimes, some functional forms performed better than others. Varying temperature impacts on disease systems are still not well understood and improving our understanding and methodologies to predict these effects could provide insights into disease systems and help conservation efforts.

With climate change, the occurrence of extreme weather events such as heatwaves is expected to increase. Extreme temperature events are short periods of high temperature (i.e., >95th percentile of temperature distribution), and their occurrences are difficult to predict. These extreme temperature events pose great challenges to living organisms, especially ectotherms such as insects whose body temperature is greatly influenced by environmental temperature. Temperature is known to play an essential role in driving insect performance as well as inducing behavioral changes. Exposure to extreme temperatures causes physiological damage leading to potential long‐lasting effects on insect performance. We aimed at assessing the impact of direct (i.e., current) and indirect (previously experienced) exposure to extreme temperature on the oviposition success of Diadegma semiclausum Hellén (Hymenoptera: Ichneumonidae). Diadegma semiclausum is a larval endoparasitoid of Plutella xylostella L. (Lepidoptera: Plutellidae), a worldwide pest of brassicaceous crops. Oviposition success, measured as the percentage of parasitized P. xylostella, was significantly lower at 33 °C than at 25 °C. However, previous exposure to 33 °C did not significantly impact the egg‐laying performance of D. semiclausum, indicating that, after a heatwave, the egg‐laying performance can recover. Neither the direct nor indirect exposure to extreme temperature altered D. semiclausum host‐instar preference. These results indicate that temperature directly impacts D. semiclausum parasitism performance, although more detailed research is needed to disentangle direct physiological mechanisms from behavioral responses. Overall, these study results confirm others, suggesting that control of P. xylostella by D. semiclausum is likely to be impaired by more frequent heatwaves predicted under climate change scenarios. [ABSTRACT FROM AUTHOR]

Abstract Overwintering is a challenging period in the life of temperate insects. A limited energy budget characteristic of this period can result in reduced investment in immune system. Here, we investigated selected physiological and immunological parameters in laboratory‐reared and field‐collected harlequin ladybirds (Harmonia axyridis). For laboratory‐reared beetles, we focused on the effects of winter temperature regime (cold, average, or warm winter) on total haemocyte concentration aiming to investigate potential effects of ongoing climate change on immune system in overwintering insects. We recorded strong reduction in haemocyte concentration during winter; however, there were only limited effects of winter temperature regime on changes in haemocyte concentration in the course of overwintering. For field‐collected beetles, we measured additional parameters, specifically: total protein concentration, antimicrobial activity against Escherichia coli, and haemocyte concentration before and after overwintering. The field experiment did not investigate effects of winter temperature, but focused on changes in inducibility of insect immune system during overwintering, that is, measured parameters were compared between naïve beetles and those challenged by Escherichia coli. Haemocyte concentration decreased during overwintering, but only in individuals challenged by Escherichia coli. Prior to overwintering, the challenged beetles had a significantly higher haemocyte concentration compared to naïve beetles, whereas no difference was observed after overwintering. A similar pattern was observed also for antimicrobial activity against Escherichia coli as challenged beetles outperformed naïve beetles before overwintering, but not after winter. In both sexes, total protein concentration increased in the course of overwintering, but females had a significantly higher total protein concentration in their hemolymph compared to males. In general, our results revealed that insect’s ability to respond to an immune challenge is significantly reduced in the course of overwintering.

This study aimed to evaluate the effectiveness of A. oryzae in inhibiting aflatoxin B1 (AFB1) and ochratoxin A (OTA) production by A. flavus and A. carbonarius, respectively, under shifting temperatures. A. oryzae was tested on different agar, namely coconut cream agar (CCA) and chili-based agar to figure out the variation in the effectiveness of A. oryzae on the most appropriate medium for A. flavus and A. carbonarius to produce mycotoxin and under natural condition where they are predominantly found. On CCA, the temperatures applied were 20, 30, 35, 40, 20/30, 20/35, and 20/40 °C, while on chili-based agar, the temperatures imposed were 20, 40, and 20/40 °C, at varied water activity of 0.92 and 0.97aw. The findings indicated that A. oryzae was much more effective in inhibiting the growth of A. flavus rather than A. carbonarius, yet it was able to inhibit higher OTA concentration than AFB1 at fluctuating temperatures on CCA as the most appropriate medium for A. flavus and A. carbonarius. A. oryzae effectively inhibited AFB1 and OTA at static temperature of 20 °C and water activity of 0.97aw on chili-based agar. Under fluctuating temperatures (20/40 °C), A. oryzae was also able to control mycotoxin, particularly OTA at high water activity (0.97aw). [ABSTRACT FROM AUTHOR]

Abstract Diurnal fluctuations in temperature are ubiquitous in terrestrial environments, and insects and other ectotherms have evolved to tolerate or acclimate to such fluctuations. Few studies have examined whether ectotherms acclimate to diurnal temperature fluctuations, or how natural and domesticated populations differ in their responses to diurnal fluctuations. We examine how diurnally fluctuating temperatures during development affect growth, acclimation, and stress responses for two populations of Manduca sexta: a field population that typically experiences wide variation in mean and fluctuations in temperature, and a laboratory population that has been domesticated in nearly constant temperatures for more than 300 generations. Laboratory experiments showed that diurnal fluctuations throughout larval development reduced pupal mass for the laboratory but not the field population. The differing effects of diurnal fluctuations were greatest at higher mean temperature (30°C): Here diurnal fluctuations reduced pupal mass and increased pupal development time for the laboratory population, but had little effect for the field population. We also evaluated how mean and fluctuations in temperature during early larval development affected growth rate during the final larval instar as a function of test temperature. At an intermediate (25°C) mean temperature, both the laboratory and field population showed a positive acclimation response to diurnal fluctuations, in which subsequent growth rate was significantly higher at most test temperatures. In contrast at higher mean temperature (30°C), diurnal fluctuations significantly reduced subsequent growth rate at most test temperatures for the laboratory population, but not for the field population. These results suggest that during domestication in constant temperatures, the laboratory population has lost the capacity to tolerate or acclimate to high and fluctuating temperatures. Population differences in acclimation capacity in response to temperature fluctuations have not been previously demonstrated, but they may be important for understanding the evolution of reaction norms and performance curves.

Environmental temperature is a crucial abiotic factor that influences the success of ectothermic organisms, including hosts and pathogens in disease systems. One example is the amphibian chytrid fungus, Batrachochytrium dendrobatidis (Bd), which has led to widespread amphibian population declines. Understanding its thermal ecology is essential to effectively predict outbreaks. Studies that examine the impact of temperature on hosts and pathogens often do so in controlled constant temperatures. Although varying temperature experiments are becoming increasingly common, it is unrealistic to test every temperature scenario. Thus, reliable methods that use constant temperature data to predict performance in varying temperatures are needed. In this study, we tested whether we could accurately predict Bd growth in three varying temperature regimes, using a Bayesian hierarchical model fit with constant temperature Bd growth data. We fit the Bayesian hierarchical model five times, each time changing the thermal performance curve (TPC) used to constrain the logistic growth rate to determine how TPCs influence the predictions. We then validated the model predictions using Bd growth data collected from the three tested varying temperature regimes. Although all TPCs overpredicted Bd growth in the varying temperature regimes, some functional forms performed better than others. Varying temperature impacts on disease systems are still not well understood and improving our understanding and methodologies to predict these effects could provide insights into disease systems and help conservation efforts. [ABSTRACT FROM AUTHOR]

Physiological dormancy in wild cardoon (Cynara cardunculus var. sylvestris) can be terminated by achenes exposure to alternating temperatures, likely with the participation of reactive oxygen species (ROS). Cyanide is a natural compound that mediates seed dormancy removal in some plant species in association with oxidative signalling exerted by ROS. To date, no study has been conducted on the cyanide effect on ROS homeostasis during the germination of cardoon. Here, we showed that the addition of cyanide at low concentrations in dormant cardoon achenes promotes dormancy breakage at a constant temperature, speeds up germination to alternating temperatures and promotes ROS accumulation in embryonic axes of dormant achenes. The in-silico transcriptome analysis showed that the expression levels of transcripts of genes associated with ROS signalling and production, calcium signalling, gibberellins biosynthesis and cell wall loosening were significantly up-regulated at the alternating temperatures imbibition condition. In contrast, the expression of gene transcripts associated with the inhibition of germination, ABA biosynthesis and signalling were up-regulated at the constant temperature imbibition. However, no significant difference in lipid peroxidation or protein carbonylation levels was observed when achenes were imbibed at constant or alternating temperature conditions. These results suggest that dormancy termination triggered by alternating temperatures or cyanide could be mediated by ROS production and signalling in the cardoon embryonic axis, but this does not determine extensive protein carbonylation.

• Alternating temperature enhanced seed germination in four cultivars of aubergine. • The most effective treatment tested was a temperature regime of 35/20°C at 16/8 h. • Endogenous hormone analysis showed decreased ABA in seeds with higher germination. • Increased germination and emergence correlated well with increase lipase levels. • There was a corresponding increase observed in SOD with increased germination. High seed quality is important for obtaining high quality seedlings for commercial vegetable production. The rate of seed germination affects seedling quality since seeds which tend to germinate more slowly generally result in low-quality seedlings, especially in aubergine seeds. Alternating temperatures play a crucial role in determining the rate of seed germination in many plant species. This study investigated the effect of alternating temperatures on aubergine seed germination, emergence rates, and physiological changes regulating dormancy. Seeds from four open-pollinated aubergine cultivars were incubated for 14 days under the following temperature regimes: 35/20°C-24/24h, 35/20°C-16/8h, 35/20°C-8/16h, 30/20°C-24/24h, 30/20°C-16/8h, 30/20°C-8/16h, or at constant 25°C. The highest mean germination was 92%, with a corresponding highest mean emergence of 88%, which was found with the 35/20°C-16/8h treatment. All alternating temperature treatments displayed faster germination and emergence compared to the control (25°C), as well as high catalase, superoxide dismutase and ascorbate peroxidase antioxidant enzyme activities, and high auxin and salicylic acid levels. In contrast, lipase enzyme activity, abscisic acid and jasmonic acid content decreased. In conclusion, these findings showed that alternating temperatures improved aubergine seed germination rate, and seedling emergence, and also demonstrated positive correlations with enzymatic and hormonal fluctuations within the seeds. [ABSTRACT FROM AUTHOR]

Overwintering is a challenging period in the life of temperate insects. A limited energy budget characteristic of this period can result in reduced investment in immune system. Here, we investigated selected physiological and immunological parameters in laboratory‐reared and field‐collected harlequin ladybirds (Harmonia axyridis). For laboratory‐reared beetles, we focused on the effects of winter temperature regime (cold, average, or warm winter) on total haemocyte concentration aiming to investigate potential effects of ongoing climate change on immune system in overwintering insects. We recorded strong reduction in haemocyte concentration during winter; however, there were only limited effects of winter temperature regime on changes in haemocyte concentration in the course of overwintering. For field‐collected beetles, we measured additional parameters, specifically: total protein concentration, antimicrobial activity against Escherichia coli, and haemocyte concentration before and after overwintering. The field experiment did not investigate effects of winter temperature, but focused on changes in inducibility of insect immune system during overwintering, that is, measured parameters were compared between naïve beetles and those challenged by Escherichia coli. Haemocyte concentration decreased during overwintering, but only in individuals challenged by Escherichia coli. Prior to overwintering, the challenged beetles had a significantly higher haemocyte concentration compared to naïve beetles, whereas no difference was observed after overwintering. A similar pattern was observed also for antimicrobial activity against Escherichia coli as challenged beetles outperformed naïve beetles before overwintering, but not after winter. In both sexes, total protein concentration increased in the course of overwintering, but females had a significantly higher total protein concentration in their hemolymph compared to males. In general, our results revealed that insect's ability to respond to an immune challenge is significantly reduced in the course of overwintering. [ABSTRACT FROM AUTHOR]

In species with temperature-dependent sex determination (TSD), incubation temperatures regulate the expression of genes involved in gonadal differentiation and determine whether the gonads develop into ovaries or testes. For most species, natural incubation conditions result in transient exposure to thermal cues for both ovarian and testis development, but how individuals respond to this transient exposure varies and can drive variation in the resulting sex ratios. Here, we argue that variation in the timing to respond to temperature cues, or thermal responsiveness, is a trait needing further study. Recent work in the red-eared slider turtle (Trachemys scripta) has found that when embryos experience transient exposure to warm conditions (i.e., heatwaves), some embryos show high responsiveness, requiring only short exposures to commit to ovarian development, while others show low responsiveness, developing testes even after more extended exposures to warm conditions. We discuss how maternal estrogens might influence thermal responsiveness for organisms that develop under thermal fluctuations. Examining the interplay of molecular responses to more subtle thermal and endocrine environments may reveal significant insights into the process of sex determination in species with TSD. [ABSTRACT FROM AUTHOR]

Diurnal fluctuations in temperature are ubiquitous in terrestrial environments, and insects and other ectotherms have evolved to tolerate or acclimate to such fluctuations. Few studies have examined whether ectotherms acclimate to diurnal temperature fluctuations, or how natural and domesticated populations differ in their responses to diurnal fluctuations. We examine how diurnally fluctuating temperatures during development affect growth, acclimation, and stress responses for two populations of Manduca sexta: a field population that typically experiences wide variation in mean and fluctuations in temperature, and a laboratory population that has been domesticated in nearly constant temperatures for more than 300 generations. Laboratory experiments showed that diurnal fluctuations throughout larval development reduced pupal mass for the laboratory but not the field population. The differing effects of diurnal fluctuations were greatest at higher mean temperature (30°C): Here diurnal fluctuations reduced pupal mass and increased pupal development time for the laboratory population, but had little effect for the field population. We also evaluated how mean and fluctuations in temperature during early larval development affected growth rate during the final larval instar as a function of test temperature. At an intermediate (25°C) mean temperature, both the laboratory and field population showed a positive acclimation response to diurnal fluctuations, in which subsequent growth rate was significantly higher at most test temperatures. In contrast at higher mean temperature (30°C), diurnal fluctuations significantly reduced subsequent growth rate at most test temperatures for the laboratory population, but not for the field population. These results suggest that during domestication in constant temperatures, the laboratory population has lost the capacity to tolerate or acclimate to high and fluctuating temperatures. Population differences in acclimation capacity in response to temperature fluctuations have not been previously demonstrated, but they may be important for understanding the evolution of reaction norms and performance curves. [ABSTRACT FROM AUTHOR]

The debate about behavioral thermoregulation inside reptile eggs centers on the frequency (and hence, biological significance) of the phenomenon, not about its validity. Both sides of the debate agree that large eggs in shallow nests laid in sun‐exposed soil will experience clines in mean temperature and (especially) diel thermal variance; that embryos in the middle phase of development have the ability to reposition themselves, and room to do so; and that small changes in developmental temperatures can influence offspring fitness. Equally, all protagonists agree that thermal clines will be too low in some other kinds of nests, and that embryonic repositioning is impossible very early and very late in development. Based on an array of other fitness‐enhancing behaviors exhibited by tetrapod embryos, and general principles for recognizing adaptation, we conclude that behavioral thermoregulation inside the egg likely is adaptive in some but not all reptile species. We identify productive directions for empirical research to resolve points of contention. Reptile embryos affect their temperatures by moving around in the egg. Contrary to recent criticisms, embryos during mid‐development are capable of moving and have adequate space in which to do so. [ABSTRACT FROM AUTHOR]

Drosophila suzukii Matsumura ( Diptera) is a polyphagous herbivore native to East Asia that develops in cultivated and wild fruits. In 2011, it appeared in Germany. In 2012, economic damage was recorded and, in 2014, the harvest of stone and soft fruits was lost in some regions. By contrast, during 2015, populations remained lower. Record temperatures and dryness might have impeded population growth during that year., To test this hypothesis, flies were exposed to a 4-day simulation. We evaluated the effect of fluctuating temperature and humidity on mortality and reproduction of D. suzukii from three age classes (average age: class 1: 3 days; class 2: 11 days; class 3: 20 days). Maximum temperatures were 27, 33 and 39 °C. Relative humidity oscillated between 18% and 85%., Fly mortality through heat stress ranged from 50% to 80%. Higher rates died of oldest flies and females. Offspring per female did not differ between heat stressed and control groups., Flies of both sexes were not sterilized through heat and dryness. Prior acclimation reduced any negative effects., We concluded that heat waves and extreme dryness during 2015 were one cause of the low population densities of D. suzukii observed under field conditions. [ABSTRACT FROM AUTHOR]

Necrophagous fly species are commonly used as forensic tools to estimate the minimum postmortem interval (PMImin). Many researchers raised necrophagous flies under constant temperature regimes to collect their developmental data. However, in most forensic cases, the ambient temperature fluctuates. In order to investigate a forensically important fly developmental mode (the Isomegalen diagram, Isomorphen diagram and Thermal summation models) and make comparisons of the developmental rate between constant temperatures and fluctuating temperatures, we used Aldrichina grahami (Diptera: Calliphoridae) to investigate the life history parameters at eight constant temperatures ranging from 8 to 36 °C. We also compared developmental rate of A. grahami in three groups of constant versus fluctuating temperatures: 8 °C vs. 6−12 °C, 12 °C vs. 10−16 °C, and 16 °C vs. 14−20 °C. Our data showed that A. grahami is cold tolerant with a mean (±SE) development threshold temperature (D0) of 3.41 ± 0.48 °C and a thermal summation constant (K) of 8125.2 ± 288.4-degree hours. The three groups subjected to fluctuating temperatures took longer to develop compared to those developing in constant temperatures when simulated in a model. These results not only provide detailed developmental data for the use of A. grahami in the estimation of the PMI, but also indicate that ambient temperature fluctuation must be taken into consideration for the use of all necrophagous fly species.

Physiological ecologists have long assumed that thermoregulatory behaviour will evolve to optimise physiological performance. The coadaptation hypothesis predicts that an animal’s preferred body temperature will correspond to the temperature at which its performance is optimal. Here we use a strong inference approach to examine the relationship between thermal preference and locomotor performance in the caterpillars of a wingless sub-Antarctic moth, Pringleophaga marioni Viette (Tineidae). The coadaptation hypothesis and its alternatives (suboptimal is optimal, thermodynamic effect, trait variation) are tested. Compared to the optimal movement temperature (22.5 °C for field-fresh caterpillars and 25, 20, 22.5, 25 and 20 °C following seven day acclimations to 0, 5, 10, 15 and 5–15 °C respectively), caterpillar thermal preference was significantly lower (9.2 °C for field-fresh individuals and 9.4, 8.8, 8.1, 5.2 and 4.6 °C following acclimation to 0, 5, 10, 15 and 5–15 °C, respectively). Together with the low degree of asymmetry observed in the performance curves, and the finding that acclimation to high temperatures did not result in maximal performance, all, but one of the above hypotheses (i.e. ‘trait variation’) was rejected. The thermal preference of P. marioni caterpillars more closely resembles temperatures at which survival is high (5–10 °C), or where feeding is optimal (10 °C), than where locomotion speed is maximal, suggesting that thermal preference may be optimised for overall fitness rather than for a given trait. [ABSTRACT FROM AUTHOR]

Ecotoxicological studies considerably improved realism by assessing the toxicity of pollutants at different temperatures. Nevertheless, they may miss key interaction patterns between pollutants and temperature by typically considering only part of the natural thermal gradient experienced by species and ignoring daily temperature fluctuations (DTF). We therefore tested in a common garden laboratory experiment the effects of the pesticide chlorpyrifos across a range of mean temperatures and DTF on physiological traits (related to oxidative stress and bioenergetics) in low- and high-latitude populations of Ischnura elegans damselfly larvae. As expected, the impact of chlorpyrifos varied along the wide range of mean temperatures (12–34 °C). None of the physiological traits (except the superoxide anion levels) were affected by chlorpyrifos at the intermediate mean temperatures (20–24 °C). Instead, most of them were negatively affected by chlorpyrifos (reduced activity levels of the antioxidant defense enzymes superoxide dismutase [SOD], catalase [CAT] and peroxidase [PER], and a reduced energy budget) at the very high (≥28 °C) or extreme high temperatures (≥32 °C), and to lesser extent at the lower mean temperatures (≤16 °C). Notably, at the lower mean temperatures the negative impact of chlorpyrifos was often only present or stronger under DTF. Although the chlorpyrifos effects on the physiological traits greatly depended on the experimentally imposed thermal gradient, patterns were mainly consistent across the natural latitude-associated thermal gradient, indicating the generality of our results. The thermal patterns in chlorpyrifos-induced physiological responses contributed to the observed toxicity patterns in life history (reduced survival and growth at low and high mean temperatures). Taken together, our results underscore the importance of evaluating pesticide toxicity along a temperature gradient and of taking a mechanistic approach with a focus on physiology, to improve our understanding of the combined effects of pollutants and temperature in natural populations. [Display omitted] • Chlorpyrifos effects on physiology varied along a wide range of temperatures. • Chlorpyrifos had adverse effects at low and especially at high mean temperatures. • However, at intermediate temperatures, chlorpyrifos did not affect the physiology. • Patterns in physiological traits were strongly correlated with life history traits. [ABSTRACT FROM AUTHOR]

Seed germination of the kiwifruit (Actinidia deliciosa A. Chev. C.F. Liang and A.R. Ferguson), a deciduous, perennial vine, is low because of seed dormancy. The main purpose of this study was to characterize kiwifruit seed dormancy and germination in response to environmental factors such as temperature and light. Dormancy of hydrated seeds is alleviated by the perception of a period at low temperatures (stratification) of at least 3 weeks at 2 or 5°C. Alleviation of dormancy is accomplished by incubation at fluctuating temperatures (20/30°C). A red light pulse did not affect germination, whereas a far-red light pulse strongly inhibited germination. This inhibition was readily reverted by a second pulse of red light, indicating that phytochromes are also involved in dormancy alleviation. Although seed germination was inhibited by the fruit pulp, the latter prevented neither perception of low temperature nor changes in the light sensitivity of the seeds. Therefore, it can be advanced that kiwifruit seeds will only germinate after dispersal if the time–temperature requirement for dormancy alleviation and fluctuating temperatures for dormancy termination are fulfilled. Perception of a closed canopy might interfere with dormancy termination. [ABSTRACT FROM PUBLISHER]

Temperature compensation in whole-animal metabolic rate is one of the responses thought, controversially, to characterize insects from low temperature environments. Temperature compensation may either involve a change in absolute values of metabolic rates or a change in the slope of the metabolic rate – temperature relationship. Moreover, assessments of compensation may be complicated by animal responses to fluctuating temperatures. Here we examined whole animal metabolic rates, at 0 °C, 5 °C, 10 °C and 15 °C, in caterpillars of the sub-Antarctic moth, Pringleophaga marioni Viette (Tineidae), following one week acclimations to 5 °C, 10 °C and 15 °C, and fluctuating temperatures of 0–10 °C, 5–15 °C, and 10–20 °C. Over the short term, temperature compensation was found following acclimation to 5 °C, but the effect size was small (3–14%). By comparison with caterpillars of 13 other lepidopteran species, no effect of temperature compensation was present, with the relationship between metabolic rate and temperature having a Q 10 of 2 among species, and no effect of latitude on temperature-corrected metabolic rate. Fluctuating temperature acclimations for the most part had little effect compared with constant temperatures of the same mean value. Nonetheless, fluctuating temperatures of 5–15 °C resulted in lower metabolic rates at all test temperatures compared with constant 10 °C acclimation, in keeping with expectations from the literature. Absence of significant responses, or those of large effect, in metabolic rates in response to acclimation, may be a consequence of the unpredictable temperature variation over the short-term on sub-Antarctic Marion Island, to which P. marioni is endemic. [ABSTRACT FROM AUTHOR]

Temperature and ultraviolet radiation (UVR) are key environmental drivers that are linked in their effects on cellular damage. Exposure to both high temperatures and UVR can cause cellular damage that result in the up-regulation of common protective mechanisms, such as the induction of heat shock proteins (Hsps) and antioxidants. As such, the interactive effects of these stressors at the cellular level may determine physiological limits, such as thermal tolerance. Furthermore, antioxidant activity is often thermally sensitive, which may lead to temperature dependent effects of UVR exposure. Here we examined the interactive effects of temperature and UVR on upper thermal limits, Hsp70 abundance, oxidative damage and antioxidant (catalase) activity. We exposed Limnodynastes peronii tadpoles to one of three temperature treatments (constant 18 °C, constant 28 °C and daily fluctuations between 18 and 28 °C) in the presence or absence of UVR. Tadpoles were tested for upper thermal limits (CTmax), induction of Hsp70, oxidative damage and catalase activity. Our results show that CTmax was influenced by an interactive effect between temperature and UVR treatment. For tadpoles kept in cold temperatures, exposure to UVR led to cross-tolerance to high temperatures, increasing CTmax. Plasticity in this trait was not fully explained by changes in the lower level mechanistic traits examined. These results highlight the difficulty in predicting the mechanistic basis for the interactive effects of multiple stressors on whole animal traits. Multifactorial studies may therefore be required to understand how complex mechanistic processes shape physiological tolerances, and determine responses to environmental variation. [ABSTRACT FROM AUTHOR]

Coping with cold winter conditions is a major challenge for many insects. In early spring we observed newly emerged Drosophila subobscura , which had overwintered as larvae and pupae. As temperatures increase during spring these flies are faced with higher minimum and maximum temperatures in their natural microhabitat. Thus, there is a potential costly mismatch between winter and early spring acclimatization and the increased ambient temperatures later in adult life. We obtained individuals from a natural Danish population of D. subobscura and acclimated them in the laboratory to 20 °C for one generation, and compared critical thermal maximum (CTmax) and minimum (CTmin) to that of individuals collected directly from their natural microhabitat. The two populations (laboratory and field) were subsequently both held in the laboratory at 20 °C and tested for their CTmax and CTmin every third day for 28 days. At the first day of testing, field acclimatized D. subobscura had both higher heat and cold resistance compared to laboratory flies, and thereby a considerable larger thermal scope. Following transfer to the laboratory, cold and heat resistance of the field flies decreased over time relative to the laboratory flies. Despite the substantial decrease in thermal tolerances the thermal scope remained larger for field acclimatized individuals for the duration of the experiment. We conclude that flies acclimatized to their natural microhabitat had increased cold resistance, without a loss in heat tolerance. Thus while a negative correlation between cold and heat tolerance is typically observed in laboratory studies in Drosophila sp., this was not observed for field acclimatized D. subobscura in this study. We suggest that this is an adaptation to juvenile overwintering in temperate cold environments, where developmental (winter) temperatures can be much lower than temperatures experienced by reproducing adults after emergence (spring). The ability to gain cold tolerance through acclimatization without a parallel loss of heat tolerance affects thermal scope and suggests that high and low thermal tolerance act through mechanisms with different dynamics and reversibility. [ABSTRACT FROM AUTHOR]

Temperature is a key factor affecting both dormancy and germination. In non-dormant seeds, when temperature is within the thermal range permissive for germination, it just regulates germination velocity, while in seeds presenting dormancy it can also be affecting dormancy level, dormancy termination and the expression of dormancy itself. This dual effect of temperature on dormancy and germination often leads to misinterpretation of obtained germination results and confounds the analysis of temperature effects in seed populations presenting some degree of dormancy. In the present paper we discuss the effect of temperature in the regulation of dormancy level and its implications in dormancy expression, as an attempt to construct a conceptual framework that allows distinguishing between the effects of temperature on dormancy and germination. Finally, we present examples of how a better understanding of these effects could help us to interpret the mixed effects of temperature on both processes during incubation of seeds presenting dormancy. [ABSTRACT FROM AUTHOR]

Laboratory studies were conducted to assess the effect of temperature on the survival, development, longevity and fecundity of Helicoverpa armigera (Lepidoptera: Noctuidae) at eight different fluctuating temperatures with an amplitude ±9 °C under constant photoperiodic conditions of 16:8 h (L:D). H. armigera achieved complete development from egg to adult emergence between mean 17.5 and 32.5 °C. At mean 35 °C, all newly hatched larvae died and at mean 15 °C entered diapause at pupal stage. The lower developmental thresholds of the immature stages were estimated by a linear model and ranged from 4.63 °C (pupal stage) to 7.69 °C (egg stage). The developmental thresholds estimated by a nonlinear model were slightly higher than those estimated by the linear model. Adult longevity and fecundity were reduced at mean fluctuating temperatures 17.5 and 32.5 °C, but tended to be independent of the pattern of temperature change at moderate temperatures. The maximum reproductive performance, 1130 eggs per female, was observed at mean 25 °C. The intrinsic rates of increase were positive, meaning that H. armigera could be expected to persist or increase in number between mean 17.5 and 32.5 °C, with the maximum value at mean 27.5 °C. H. armigera survives, develops and reproduces within a wide range of fluctuating temperatures, while it completes the above functions with different levels of success at different mean temperatures of diurnal variation. Comparison of our results with similar data from the literature involving constant conditions is discussed. This information will provide a better understanding of H. armigera phenology and population dynamics under natural conditions and is essential to understanding the ecological and evolutionary consequences of climate change on this important species. [ABSTRACT FROM AUTHOR]

Cold storage is one means of preserving parasitoids prior to release in augmentation biological control programs. This study examined the feasibility of storing larval and pupal stages of a sexual population of Lysiphlebus fabarum Marshall (Hymenoptera: Braconidae: Aphidiinae) at 6 ± 1 and 8 ± 1 °C, 50-60% r.h., and L14:D10 photoperiod. These life stages were stored for periods of 1, 2, and 3 weeks under fluctuating thermal regimes (2 h daily at 21 ± 1 °C). Generally, pupae gave better results than larvae, and 6 °C was better than 8 °C, considering wasp survival, wasp size (tibial and antennal lengths), egg load, and egg size. The best results were obtained with pupae stored for 2 weeks under a fluctuating temperature regime at 6 °C. Females emerging from this treatment did not differ from controls (developing directly at 21 °C) in body size, egg size, or progeny sex ratio, and suffered less than 20% mortality. Egg loads were reduced in these wasps, but the reductions were substantially less than occurred in other 2-week-storage treatments. Wasps stored in this manner successfully parasitized similar numbers of aphids as controls and produced similar progeny sex ratios. These results reveal a suitable set of low-temperature conditions that can be used to delay the development of L. fabarum for 2 weeks with minimal impact on wasp fitness. [ABSTRACT FROM AUTHOR]

The adaptability of organisms to novel environmental conditions depends on the amount of genetic variance present in the population as well as on the ability of individuals to adjust their phenotype through phenotypic plasticity. Here, we investigated the phenotypic plasticity induced by a single generation's exposure to three different temperature regimes with respect to several life-history and stress-resistance traits in a natural population of Drosophila simulans. We studied a constant as well as a predictably and an unpredictably fluctuating temperature regime. We found high levels of phenotypic plasticity among all temperature regimes, suggesting a strong influence of both temperature fluctuations and their predictability. Increased heat tolerance was observed for flies developed in both types of fluctuating thermal environments compared with flies developed in a constant environment. We suggest that this was due to beneficial hardening when developing in either fluctuating temperature environment. To our surprise, flies that developed in constant and predictably changing environments were similar to each other in most traits when compared to flies from the unpredictably fluctuating environment. The unpredictably changing thermal environment imposed the most stressful condition, resulting in the lowest performance for stress-related traits, even though the absolute temperature changes never exceeded that of the predictably fluctuating environment. The overall decreased stress resistance of flies in the unpredictably fluctuating environment may be the consequence of maladaptive phenotypic plasticity in this setting, indicating that the adaptive value of plasticity depends on the predictability of the environment. [ABSTRACT FROM AUTHOR]

Fluctuating temperatures terminate seed dormancy in many species, including Cynara cardunculus (L.) var. sylvestris. Termination of physiological dormancy requires low ratios of abscisic acid (ABA)/gibberellins (GA). In a previous paper we have shown that physiological responses to fluctuating temperatures comprise a reduction of abscisic acid (ABA) content and sensitivity. However, a possible stimulation of GA synthesis was also suggested as part of the mechanism. That possible stimulation, as well as the identification of potential regulatory sites for ABA and GA metabolism and signalling involved in the termination of dormancy by fluctuating temperatures, are yet to be determined. In this study, we measured GA content and sensitivity in seeds incubated under constant and fluctuating temperatures. We also assessed the expression of several genes involved in ABA and GA metabolism and signalling. Our results show that fluctuating temperatures reduce ABA/GA ratios through a reduction in ABA accumulation during incubation but without altering GA synthesis as compared to that observed under constant temperatures. On the other hand, fluctuating temperatures did not increase sensitivity to GA. Fluctuating temperatures reduced the expression of CycaNCED and CycaABI5 (ABA synthesis and signalling genes) with a temporal pattern that coincides with the interruption of ABA accumulation that precedes germination of seeds incubated under fluctuating temperatures. However, fluctuating temperatures did not modify the expression of CycaCYP707A2 (ABA inactivation) as compared to that observed under constant temperatures. Consistent with our determinations of GA content and sensitivity, fluctuating temperatures did not modify the expression of GA synthesis (CycaGA3ox) and signalling genes (CycaRGL2 and CycaGAI) in relation to that observed at constant temperatures. These results show that fluctuating temperatures terminate dormancy in Cynara cardunculus seeds through an interruption in ABA accumulation and a reduction in ABA signalling exerted at the level of CycaNCED and CycaABI5 expression. [ABSTRACT FROM AUTHOR]

An increasing intensity of stress is expected to affect the fitness traits of an organism more and more negatively, but in particular cases, extremely resistant individuals have been observed. The present study was undertaken to determine the effects of different stress intensities on fitness traits of the parasitoid wasp Aphidius ervi Haliday., We exposed 1-day-old mummies (dead aphids containing the parasitoid pupa) for 4 weeks to combinations of two low temperatures (4 and 0 °C, 0 °C being the most stressful) and two thermal regimes (constant and fluctuating, constant being the most stressful), representing four stress levels., The present results showed that resistant individuals occurred only in the most stressful treatment (0 °C, constant temperature), which induced a higher mortality rate. These resistant individuals performed almost as well as those of the control, but showed a reduction in their size. The fluctuating regimes, at both temperatures, presented a high emergence rate, but at the expense of higher lipid consumption. Unexpectedly, the fluctuating regime associated with the presumably more stressful temperature (0 °C) produced individuals without any decrease in the measured fitness traits, in contrast to the treatment expected to be less stressful (4 °C, fluctuating temperature)., This result opens a new area of research in stress ecology and could modify the practice of cold storage in biological control. [ABSTRACT FROM AUTHOR]

Experiments were conducted to compare the immature development of Protophormia terraenovae (Robineau-Desvoidy) at fluctuating temperatures of 4-28 and 9-23°C to their mean constant temperature, 16°C. Overall development was fastest at the greater fluctuation and slowest at the constant temperature but showed similar percentages of development time in each stage. The rate summation effect is suspected to have caused this difference in development rate because fluctuations above the mean increase the rate relatively more than temperatures below the mean can lower the rate. [ABSTRACT FROM AUTHOR]

Abstract: Based on the enthalpy-porosity technique, a model of thermal conduction accompanied with solidification and melting processes is developed and numerically analyzed to investigate the thermal response of the brick wall filled with phase change materials (PCM). The thermal response, which is represented by indoor wall surface temperature response, of brick wall filled with PCM is evaluated and compared with that of solid brick wall. The effects of PCM filling and its filling amount on thermal response of brick wall are investigated and discussed. It is indicated that, compared to the common solid brick wall, the thermal storage of brick wall filled with PCM is elevated by the alternate process of melting and solidification under fluctuating outdoor temperatures. The use of PCM in the brick walls is beneficial for the thermal insulation, temperature hysteresis and thermal comfort for occupancy. In addition, with the increasing filling amount of PCM, the fluctuation of indoor wall surface temperature is significantly smoothed. Correspondingly, the hysteresis in response to the outdoor temperature fluctuation is enhanced. Moreover, the present model is verified by experimental data available in the literature. [Copyright &y& Elsevier]

Abstract: Development of larvae of different forensically important flies under constant low, medium and high temperatures as well as under daily fluctuating temperatures in a climatic chamber was investigated and compared. Results suggest faster development under fluctuating temperatures for Sarcophaga argyrostoma and Lucilia illustris but slower development for Calliphora vicina and Calliphora vomitoria. Fluctuating temperatures had a higher impact on larvae in feeding stages than in post-feeding stages. Moreover an ability to develop at constant low temperatures was noted for some species. Negligence of fluctuating temperatures in legal cases can lead to distinctly wrong estimates of the post-mortem interval (PMI). [Copyright &y& Elsevier]

Cynara cardunculus (L.) seeds require incubation at fluctuating temperatures to terminate dormancy. In this study, we analysed the physiological mechanisms underlying such a requirement, focusing on the role of abscisic acid (ABA) and gibberellin (GA). As a conceptual framework, we considered the possibility that fluctuating temperatures and light trigger a similar set of hormonal processes after stimulus perception. To test this possibility, we (1) carried out hydrotime analysis of germination in seeds exposed to fluctuating temperatures (25/15°C) and constant temperature (20°C) with or without gibberellin (GA3) or red light; (2) determined the responses of seeds incubated at fluctuating or constant temperature to ABA, GA3, fluridone, an inhibitor of ABA biosynthesis, and paclobutrazol, an inhibitor of GA biosynthesis; and (3) determined the ABA content of seeds incubated at fluctuating or constant temperature. Incubation at 25/15°C or 20°C in the presence of GA3 reduced the mean base water potential [Ψ(50)] of the population to a similar extent, compared to that observed with seeds incubated at 20°C without GA3. Irradiation with red light also reduced cb(50) to a lesser extent than incubation in the presence of GA3. At all concentrations tested, exogenously applied GA3 did not promote germination of seeds incubated at 25/15°C. However, paclobutrazol inhibited germination, suggesting that fluctuating temperatures terminate dormancy through de novo GA biosynthesis. Fluctuating temperatures enhanced seed germination in the presence of ABA, but ABA content did not differ between seeds incubated at fluctuating and constant temperatures. This study provides clear evidence for the involvement of hormonal regulation in dormancy termination by fluctuating temperatures. [ABSTRACT FROM AUTHOR]

Seed germination and seedling emergence are key processes for population recruitment. Flooding and grazing are disturbances forming gaps that may strongly influence recruitment patterns in space and time, but their combined effects and action mechanisms have rarely been addressed. In this study we analysed the effects of microhabitat conditions associated with winter flooding and spring-summer defoliation on seed germination and seedling establishment of Paspalum dilatatum, a dominant perennial C4 grass in native grasslands of the Flooding Pampa, Argentina. The dynamics of seedling emergence from natural seed banks and buried seeds was studied in a factorial experiment with flooding and defoliation treatments applied to soil monoliths (mesocosms) collected from natural grassland. Additional laboratory experiments were applied to investigate seed germination under different combinations of temperature, light quality and simulated flooding. Seed germination and seedling emergence of P. dilatatum were promoted by flooding and high intensity defoliation. Gaps generated by flooding were maintained by high intensity defoliation exercising a synergistic effect on survival seedlings. Flooding resulted in the breaking of seed dormancy and higher germination rates associated with alternating temperature and the activation of the phytochrome system. Our results indicate that microhabitat conditions associated with the disturbances forming gaps, such as flooding and heavy grazing, synergistically promote the recruitment process of this dominant grass species. [ABSTRACT FROM AUTHOR]

Picris hieracioides var. japonica (Asteraceae), which grows in occasionally disturbed habitats such as riverbanks, is rarely observed under dense vegetation. We examined the effect of the experience and timing of receiving leaf-transmitted light in gap-detecting seed germination in this plant. Seeds under unfiltered light, which simulated the light conditions of seeds on the soil surface in a canopy gap, germinated at a constant temperature of 20°C. However, most seeds in darkness, which simulated the light conditions of seeds buried in the soil without receiving leaf-transmitted light, germinated under temperature fluctuations of over 4°C. Seeds in darkness after receiving leaf-transmitted light for 1 week, which simulated the light conditions of seeds buried in the soil after receiving leaf-transmitted light, germinated under temperature fluctuations of over 8°C. Finally, seeds under continuous leaf-transmitted light, which simulated the light conditions of seeds on the soil surface below preexisting vegetation, germinated under temperature fluctuations of over 12°C. Seeds that experience unfiltered light, which suggests that they are in a gap, should not delay germination. In contrast, seeds that have received leaf-transmitted light should delay germination until the vegetation above is removed. Seeds exposed to leaf-transmitted light required larger temperature fluctuations in darkness than did untreated seeds, and seeds under continuous leaf-transmitted light required the largest temperature fluctuations. The various germination reactions to each gap signal in P. hieracioides var. japonica seeds allow the more reliable detection of gaps for subsequent seedling establishment. The requirement for gap signals that created high precision of timing in the germination process results in the germination of this species only in gaps. Therefore, P. hieracioides var. japonica is rarely found under dense vegetation. [ABSTRACT FROM AUTHOR]

Fluctuating Thermal Regimes (FTR), where organisms are held at low temperatures with a brief, daily warm pulse, have been shown to increase longevity in adult insects and improve pupa survival while reducing sublethal effects. We used FTR to extend the longevity and thus generation time of the fly species Themira biloba (Diptera: Sepsidae). T. biloba can be maintained in continuous culture and requires an insecticide-free dung substrate for larval growth and development. Our objective was to decrease labor and consumable materials required to maintain insect species in critical scientific collections using FTR. We extended pupation time from 4 days up to 8 weeks with no increase in mortality, and mean adult longevity was increased from 12 days to 50 days. FTR is a valuable tool for reducing the investment required to maintain rare and exotic insects. • Fluctuating temperatures extended pupa development from 4 days to 8 weeks. • Mean adult longevity increased from 12 ± 0.29 days to 50 ± 1.79 days. • This protocol may be used to extend generation time and reduce resource consumption in some non-model species. [ABSTRACT FROM AUTHOR]

[Display omitted] • Temperature fluctuations affect the biology and cold tolerance of insects. • We tested the effects of temperature changes on the survival of SWD. • At mild temperatures (5 °C), increasing warm-up frequency was harmful. • At freezing temperatures (0 °C), daily warm-ups improved survival outcomes. • Fluctuating temperatures during cold acclimation similarly improved survival. • We conclude temperature fluctuations may affect overwintering survival of SWD. Among overwintering Drosophila suzukii , discrete environmental changes in temperature and photoperiod induce a suite of biochemical changes conferring cold tolerance. However, little is known regarding how temperature fluctuations, which can influence metabolic and cellular repair activity, affect survival outcomes in this species. For that reason, we designed three experiments to test the effects of intermittent warm-up periods and the degree of temperature fluctuation on winter-morphotype (WM) D. suzukii survival. We found that at 5 °C, a temperature sufficient to induce reproductive diapause, but warm enough to allow foraging, increasing warm-up frequency (warmed to 25 °C at various interval schedules) was associated with decreased survival. In contrast, when the nightly low temperature was 0 °C, daily fluctuations that warmed the environment to temperatures above freezing (5, or 15 °C) appeared beneficial and resulted in improved survival compared to flies held at 0 °C during day and night. When we next evaluated cold tolerance using a 24-hour stress test assay (-5 °C), we found that again, thermal fluctuations improved survival compared to static freezing conditions. However, we also found that WM D. suzukii exposed to freezing temperatures during acclimation were less cold tolerant, regardless of the thermal fluctuation schedule, indicating that there may be tradeoffs between adequate acclimation temperature, which is required to induce cold tolerance, and the ensuing effects of incidental chill injury. Moving forward, these data, which account for the nuanced interactions between the thermal environment and in the internal physiology of D. suzukii , may help refine seasonal populations models, which aim to forecast pest pressure based on conditions the previous winter. [ABSTRACT FROM AUTHOR]

• Kiwi seeds present dormancy which impairs seedling production in nursery. • Seeds stratified at low temperatures gradually gained the ability to germinate. • After stratification dormancy must be terminated by fluctuating temperatures. • We propose a mathematical model to optimize in time dormancy overcoming. • This constitutes a tool to optimize kiwi seedling production in nursery. Kiwifruit (Actinidia deliciosa A. Chev. C.F. Liang and A.R. Ferguson) seedling production in the nursery is usually impaired because of low seed germination resulting from primary dormancy. Dormancy of hydrated seeds is alleviated by the perception of a period at low temperatures (stratification), but further incubation under fluctuating temperatures (20/30 °C) is a requirement for dormancy termination. The aim of this study was to establish functional relationships between changes in the sensitivity of the seed population to different cycle-doses of fluctuating temperature and dormancy alleviation under different times and stratification temperatures. We propose a model based on the concept of stratification thermal time to predict changes in the fraction of the seed population that would germinate as a function of the number of fluctuating temperature cycle-doses. Results showed that stratification at cool temperatures produced higher rates of change than stratification at warmer temperatures. Construction of response curves with a thermal time scale was possible because seeds that had accumulated similar stratification thermal time achieved similar germination percentages in response to cycle-doses of fluctuating temperatures. The model was tested against independent experimental data yielding good agreement between predicted and observed data. Overall, this constitutes an important tool to overcome dormancy in a way that should result in a more efficient and faster production of kiwifruit seedlings or rootstocks. [ABSTRACT FROM AUTHOR]

Much interest exists in the extent to which constant versus fluctuating temperatures affect thermal performance traits and their phenotypic plasticity. Theory suggests that effects should vary with temperature, being especially pronounced at more extreme low (because of thermal respite) and high (because of Jensen's inequality) temperatures. Here we tested this idea by examining the effects of constant temperatures (10 to 30 °C in 5 °C increments) and fluctuating temperatures (means equal to the constant temperatures, but with fluctuations of ±5 °C) temperatures on the adult (F2) phenotypic plasticity of three thermal performance traits – critical thermal minimum (CT min), critical thermal maximum (CT max), and upper lethal temperature (ULT 50) in ten species of springtails (Collembola) from three families (Isotomidae 7 spp.; Entomobryidae 2 spp.; Onychiuridae 1 sp.). The lowest mean CT min value recorded here was -3.56 ± 1.0 °C for Paristoma notabilis and the highest mean CT max was 43.1 ± 0.8 °C for Hemisotoma thermophila. The Acclimation Response Ratio for CT min was on average 0.12 °C/°C (range: 0.04 to 0.21 °C/°C), but was much lower for CT max (mean: 0.017 °C/°C, range: -0.015 to 0.047 °C/°C) and lower also for ULT 50 (mean: 0.05 °C/°C, range: -0.007 to 0.14 °C/°C). Fluctuating versus constant temperatures typically had little effect on adult phenotypic plasticity, with effect sizes either no different from zero, or inconsistent in the direction of difference. Previous work assessing adult phenotypic plasticity of these thermal performance traits across a range of constant temperatures can thus be applied to a broader range of circumstances in springtails. • Adult springtails exhibit similar thermal tolerance plasticity when exposed to constant versus fluctuating temperatures. • Thermal tolerance trait values increase as acclimation temperature increases. • Previous work using constant temperatures to estimate critical thermal limits can be considered reliable. [ABSTRACT FROM AUTHOR]

Necrophagous fly species are commonly used as forensic tools to estimate the minimum postmortem interval (PMImin). Many researchers raised necrophagous flies under constant temperature regimes to collect their developmental data. However, in most forensic cases, the ambient temperature fluctuates. In order to investigate a forensically important fly developmental mode (the Isomegalen diagram, Isomorphen diagram and Thermal summation models) and make comparisons of the developmental rate between constant temperatures and fluctuating temperatures, we used Aldrichina grahami (Diptera: Calliphoridae) to investigate the life history parameters at eight constant temperatures ranging from 8 to 36 °C. We also compared developmental rate of A. grahami in three groups of constant versus fluctuating temperatures: 8 °C vs. 6–12 °C, 12 °C vs. 10–16 °C, and 16 °C vs. 14–20 °C. Our data showed that A. grahami is cold tolerant with a mean (±SE) development threshold temperature (D0) of 3.41 ± 0.48 °C and a thermal summation constant (K) of 8125.2 ± 288.4-degree hours. The three groups subjected to fluctuating temperatures took longer to develop compared to those developing in constant temperatures when simulated in a model. These results not only provide detailed developmental data for the use of A. grahami in the estimation of the PMI, but also indicate that ambient temperature fluctuation must be taken into consideration for the use of all necrophagous fly species. [ABSTRACT FROM AUTHOR]