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opencc-zeroDec 2017View details →

Data from: Heat tolerance is more variable than cold tolerance across species of Iberian lizards after controlling for intraspecific variation

<ol> <li>The widespread observation that heat tolerance is less variable than cold tolerance ('cold-tolerance asymmetry') leads to the prediction that species exposed to temperatures near their thermal maxima should have reduced evolutionary potential for adapting to climate warming. However, the prediction is largely supported by species-level global studies based on single estimates of both physiological metrics per taxon.</li> <li>We ask if cold-tolerance asymmetry holds for Iberian lizards after accounting for intraspecific variation in critical thermal maxima (CTmax) and minima (CTmin). To do so, we quantified CTmax and CTmin for 58 populations of 15 Iberian lizard species (299 individuals). Then, we randomly selected one population from each study species (population sample = 15 CTmax and CTmin values), tested for variance homoscedasticity across species, and repeated the test for thousands of population samples as if we had undertaken the same study thousands of times, each time sampling one different population per species.</li> <li>The ratio of variances in CTmax to CTmin across species varied up to 16-fold depending on the populations chosen. Variance ratios show how much CTmax departs from the cross-species mean compared to CTmin, with a unitary ratio indicating equal variance of both thermal limits. Sampling one population per species was six times more likely to result in the observation of greater CTmax variance ('heat-tolerance asymmetry') than cold-tolerance asymmetry. The null hypothesis of equal variance was twice as likely for cases of cold-tolerance asymmetry than for the opposite scenario.</li> <li>Range-wide, population-level studies that quantify heat and cold tolerance of individual species are urgently needed to ascertain the global prevalence of cold-tolerance asymmetry. While broad latitudinal clines of cold tolerance have been strongly supported, heat tolerance might respond to smaller-scale climatic and habitat factors hence go unnoticed in global studies. Studies investigating physiological responses to climate change should incorporate the extent to which thermal traits are characteristic of individuals, populations and/or species.</li> </ol>

opencc-zeroNov 2023View details →

Photosynthesis in newly-developed leaves of heat-tolerant wheat acclimates to long-term nocturnal warming

We examined photosynthetic capacity of newly-developed and pre-existing flag leaves of four wheat genotypes under three night temperatures (15, 20 and 25 °C) and common day temperature of 26 °C in two controlled environment experiments. In newly-developed leaves which acclimated (i.e. maintained or increased) the maximum rate of net CO2 assimilation (An) to long-term (9–13 weeks) nocturnal warming, acclimation was underpinned by greater capacity of Rubisco carboxylation (Vcmax) and photosynthetic electron transport (J). This indicates a night-dependent temperature sensitivity of the activation state of Rubisco. Metabolite profiling linked acclimation of An to greater accumulation of monosaccharides and saturated fatty acids in leaves, suggesting roles for osmotic adjustment of leaf turgor pressure and maintenance of cell membrane integrity. By contrast, warm night-induced inhibition of An was related to reductions in stomatal conductance of CO2 and J, despite higher basal electron transport thermal stability: Tcrit 51 of 45–46.5 °C in non-acclimated versus Tcrit of 43.8–45 °C in acclimated leaves. Pre-existing leaves exposed to short-term nocturnal warming (5–7 nights) showed no change in instantaneous temperature responses of An and photosynthetic capacity, except for an elite heat-tolerant genotype. These findings can be used to support strategies for developing climate-resilient wheat.

openmit-licenseNov 2023View details →

Paper data and code of manuscript: Intraspecific variation on heat tolerance in a model ectotherm: effects of body mass, cell size, oxygen and sex

When using the data or code from this manuscript, please cite it as:Leiva FP, Santos M, Rezende E, & Verberk WCEP. 2021. Paper data and code of manuscript: Intraspecific variation on heat tolerance in a model ectotherm: effects of body mass, cell size, oxygen and sex. Zenodo. <a href="https://doi.org/10.5281/zenodo.5120028">https://doi.org/10.5281/zenodo.5120028</a>.

opencc-zeroOct 2022View details →

Dataset and scripts from: Dietary sterol availability modulates heat tolerance of Daphnia

The increasing frequency and intensity of summer heat waves is pushing freshwater zooplankton towards their upper thermal tolerance limits. At the same time, higher temperatures and prolonged water column stratification can favor the dominance of cyanobacteria in phytoplankton. Even when not toxic or grazing resistant, these prokaryotes lack phytosterols as essential precursors for cholesterol, the main sterol in animal tissues. Cholesterol plays a crucial role in the physiological adaptation of ectotherms to high temperature. Therefore, the shift to cyanobacteria-dominated systems may increase the vulnerability of zooplankton to heatwaves by intensifying cholesterol limitation. Here, we used death time curves that take into consideration the intensity and duration of a thermal challenge and a dynamic model to study the effects of cholesterol limitation on the heat tolerance of the keystone species Daphnia magna and to simulate the cumulative mortality that could occur in a fluctuating environment over several days of heatwave. We show that increasing cholesterol limitation does not affect the slope between time-to-immobilization and temperature, but does decrease the maximal temperature that Daphnia can withstand by up to 0.74°C. This seemingly small difference is sufficient to halve the time individuals can survive heat stress. Our simulations predicted that, when facing heatwaves over several days, the differences in survival caused by cholesterol limitation build up rapidly. Considering the anticipated intensity and duration of future (2070-2099) heatwaves, cholesterol limitation could increase mortality by up to 45% and 72% under low- and medium-greenhouse-gas-emission scenarios, respectively. These results suggest that the increasing risk of cholesterol limitation due to more frequent cyanobacterial blooms could compromise the resistance of zooplankton populations to future heatwaves. More generally, this study shows the importance of considering the nutritional context in any attempt to predict ectotherm mortality with increasing temperatures in the field.

Fig. 4 in Vertical Zonation And Heat Tolerance Of Three Littorinid Gastropods On A Rocky Shore At Tanjung Chek Jawa, Singapore

Fig. 4. Mean glutamate oxaloacetate transaminase (GOT) activities (µmol NADH/min/g wet weight) of Littoraria sp., Echinolittorina malaccana and E. vidua from Tanjung Chek Jawa at four temperatures: 25 °C, 45 °C, 50 °C and 55 °C. (Vertical bars represent standard errors). Littoraria sp. ●––––●; Echinolittorina malaccana, ●........●; E. vidua ■-------■.

Fig. 2 in Vertical Zonation And Heat Tolerance Of Three Littorinid Gastropods On A Rocky Shore At Tanjung Chek Jawa, Singapore

Fig. 2. Kite diagrams showing the distributions of Littoraria spp. (LL), Echinolittorina malaccana (EM) and E. vidua (EV) on a sloping rock (angle of elevation of approximately 35.6°) at Tanjung Chek Jawa. (MHWS is represented by dashed line).

Fig. 1 in Vertical Zonation And Heat Tolerance Of Three Littorinid Gastropods On A Rocky Shore At Tanjung Chek Jawa, Singapore

Fig. 1. Kite diagrams showing the distributions of Littoraria spp. (LL) and Echinolittorina malaccana (EM) on a vertical rock at Tanjung Chek Jawa in (a) June/July, (b) September, and (c) December 2002. (MHWS is represented by dashed line).

Fig. 3 in Vertical Zonation And Heat Tolerance Of Three Littorinid Gastropods On A Rocky Shore At Tanjung Chek Jawa, Singapore

Fig. 3. Probit response curves of Littoraria sp. (●), Echinolittorina vidua (●) and E. malaccana (■), from which the 1h LT50 values are obtained.

opencc-zeroDec 2021View details →

Evolutionary responses of energy metabolism, development, and reproduction to artificial selection for increasing heat tolerance in Drosophila subobscura

Adaptation to warming conditions involves increased heat tolerance and metabolic changes to reduce maintenance costs and maximize biological functions close to fitness. Evidence shows that energy metabolism evolves in response to warming conditions, but we know little about how heat stress intensity determines the evolutionary responses of metabolism and life history traits. Here, we evaluated the evolutionary responses of energy metabolism and life-history traits to artificial selection for increasing heat tolerance in Drosophila subobscura, using two protocols to measure and select heat tolerance: slow and fast ramping protocols. We found that the increase in heat tolerance was associated with reduced activity of the enzymes involved in the glucose-6-phosphate branchpoint, but no changes in the metabolic rate in selected lines. We also found that the evolution of increased heat tolerance increased the early fecundity in selected lines and increased the egg-to-adult viability only in the slow-ramping selected lines. This work shows heat tolerance can evolve under different thermal scenarios but with different evolutionary outcomes on associated traits depending on the heat stress intensity. Therefore, spatial and temporal variability of thermal stress intensity should be taken into account to understand and predict the adaptive response to ongoing and future climatic conditions.

opencc-by-4.0May 2023View details →

GWAS analysis for tolerance to heat stress and milk production, in subtropical Egyptian goats

The conservation of local Egyptian goat genotypes has been a national program since 2009. Our study investigated different subtropical Egyptian goat populations (367 does) from different harsh ecological zones(hot Upper Egypt, Coastal Zone of Western Desert, and Wahati Desert Oasis) to identify genes associated with heat stress. We examined the physiological response of animals that were exposed to simulated summer grazing conditions, and physiological parameters including respiration rate, gas volume, rectal temperature, and skin temperature. Temperature Humidity Index ranged from 98.6 to 109.3, indicating that the animals were under severe heat stress. Results showed significant differences between the populations in their tolerance to heat stress, with Saidi goats being the most adapted to hot-dry conditions. Respiration rate was found to be the most reliable physiological trait for differentiating between animals in their tolerance to heat stress. The GWAS analysis involved 157 genotypes and 54,032 marker-SNPs, revealing 90 SNPs associated with heat stress and 70 SNPs associated with milk production. Chromosome 1 had the highest number of SNPs associated with heat-stress traits, while chromosome 4 exhibited the largest number of significant SNPs associated with milk production. Several genes were associated with heat stress response and tolerance in goats. These genes were categorized into three main groups: heat stress response, stress response, and reproduction, and feed intake. The first group includes USP54, KDM6A, and ETNPPL, which have multiple functions, such as steroid biosynthesis, metabolism, and stress response, and are also involved in key biological processes such as reproduction, immune response, and metabolism. The second group, which is mostly associated with immune response, includes GLTSCR2 and NAALADL2. Finally, a group of genes that may control animal feed intakes, including TRPM3 and ZBTB8A. Additionally, several genes, such as FHIT, GALNT18, RAPGEF5, and RBFOX1, linked to milk production, are known to be linked fertility, and fatty acid composition. These findings provide insights into the potential roles of these genes in heat stress response and tolerance in goats, and the genetic basis for improved milk production and animal welfare and can be used as selection markers in the ongoing breeding programs.