Unifying indices of heat tolerance in ectotherms

Cooper, Brandon S.; Williams, Benjamin H.; Angilletta, Michael J.

doi:10.1016/j.jtherbio.2008.04.001

Cited by 38 publications

(45 citation statements)

References 20 publications

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“…It is likely that our estimates of heat tolerance are close to lethal limits (Hoffmann et al 2003a;Cooper et al 2008), whereas our estimates of cold tolerance may be far from lethal limits, because drosophilids can survive and recover from extended periods of cold coma (Sinclair and Roberts 2005 and references therein). The thermal limits reported here are therefore beyond those where normal activity is maintained, but for cold in particular the limits are much narrower than the limits estimated for cold survival (cf.…”

Section: Discussionmentioning

confidence: 87%

Thermal Tolerance in Widespread and TropicalDrosophilaSpecies: Does Phenotypic Plasticity Increase with Latitude?

Overgaard¹,

Kristensen²,

Mitchell³

et al. 2011

The American Naturalist

223

248

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The distribution of insects can often be related to variation in their response to thermal extremes, which in turn may reflect differences in plastic responses or innate variation in resistance. Species with widespread distributions are expected to have evolved higher levels of plasticity than those from restricted tropical areas. This study compares adult thermal limits across five widespread species and five restricted tropical species of Drosophila from eastern Australia and investigates how these limits are affected by developmental acclimation and hardening after controlling for environmental variation and phylogeny. Irrespective of acclimation, cold resistance was higher in the widespread species. Developmental cold acclimation simulating temperate conditions extended cold limits by 2°-4°C, whereas developmental heat acclimation under simulated tropical conditions increased upper thermal limits by <1°C. The response to adult heat-hardening was weak, whereas widespread species tended to have a larger cold-hardening response that increased cold tolerance by 2°-5°C. These patterns persisted after phylogenetic correction and when flies were reared under high and low constant temperatures. The results do not support the hypothesis that widely distributed species have larger phenotypic plasticity for thermal tolerance limits, and Drosophila species distributions are therefore more closely linked to differences in innate thermal tolerance limits.

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Section: Discussionmentioning

confidence: 87%

Thermal Tolerance in Widespread and TropicalDrosophilaSpecies: Does Phenotypic Plasticity Increase with Latitude?

Overgaard¹,

Kristensen²,

Mitchell³

et al. 2011

The American Naturalist

223

248

View full text Add to dashboard Cite

show abstract

“…Likewise, it is clear that the critical temperature measured by dynamic methods depends on the rate at which temperature is increased (Overgaard, Kristensen, & Sørensen, ; Sørensen, Loeschcke, & Kristensen, ; Terblanche, Deere, Clusella‐Trullas, Janion, & Chown, ). It has also been discussed if static and dynamic assays impose the same form of heat stress on the animal (Castañeda, Rezende, & Santos, ; Cooper, Williams, & Angilletta, ; Kilgour & McCauley, ; Mitchell & Hoffmann, ; Rezende et al, ; Santos, Castañeda, & Rezende, ; Sgrò et al, ; Terblanche et al, ), and several studies have therefore highlighted the apparent problem of comparing results across the two assays. Finally, both assays have been questioned for their aptness in describing thermal tolerance in ecologically relevant settings (Chown, Jumbam, Sørensen, & Terblanche, ; Lutterschmidt & Hutchison, ; Mitchell & Hoffmann, ; Ribeiro, Camacho, & Navas, ; Terblanche et al, ).…”

Section: Introductionmentioning

confidence: 99%

How to assess Drosophila heat tolerance: Unifying static and dynamic tolerance assays to predict heat distribution limits

2019

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Thermal tolerance is a critical determinant of ectotherm distribution, which is likely to be influenced by future climate change. To predict such distributional changes, simple and comparable measures of heat tolerance are needed and these measures should ideally correlate with the characteristics of the species current thermal environments. A recent model (thermal tolerance landscapes—TTLs) uses the exponential relation between temperature and knockdown time to describe the thermal tolerance of ectotherms across time/temperature scales. Here, we established TTLs for 11 Drosophila species representing different thermal ecotypes by measuring knockdown time at 9–17 stressful temperatures (0.5°C intervals). These temperatures caused knockdown times ranging from <10 min to >12 hrs and all species displayed the expected exponential relation between temperature and knockdown time (average R2 = 0.98). Previous studies using TTLs have reported a trade‐off between tolerance to acute and chronic heat stress in ectotherms. The present study did not find evidence to support this trade‐off in drosophilids. Instead, we show how this “trade‐off” can arise as an analytical artefact caused by insufficient data collection and excessive data extrapolation. Dynamic assays represent an alternative method to describe heat tolerance of ectotherms, where animals are exposed to gradually increasing temperatures until knockdown. The comparability of static and dynamic assays has previously been questioned, but here we show that static and dynamic assays give comparable information on heat tolerance. Using the constants derived from static TTLs, we mathematically model the expected dynamic knockdown temperature and subsequently confirm this model by comparison to empirically obtained knockdown temperatures from all 11 species. Characterisation of heat tolerance in laboratory settings is an important tool in thermal biology, but more so if the measures correlate with the environmental gradients that characterise the fundamental niche of species. Here, we show that both static and dynamic assays were characterised by strong correlations to precipitation of the driest month and maximum temperature of the warmest month combined (R2 = 0.68–0.71). This demonstrates that both assay types offer simple measures of heat tolerance that are ecologically relevant for the tested drosophilids. A plain language summary is available for this article.

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“…Previous studies concerning behavior-related upper thermal tolerance for insects mainly focused on ''critical thermal maximum (CT max )'', ''knockdown temperature/time'' and ''heat coma''. Those indices were defined as the temperatures at which test insects began to lose muscle control, stop walking or move their legs/antennae for the last time (Cooper et al, 2008;Hazell et al, 2010;Mitchell and Hoffmann, 2010;Terblanche et al, 2007). Most of those behaviors occur when the insects become physiologically and/or physically impaired due to heat stress.…”

Section: Introductionmentioning

confidence: 99%

Climate warming may increase aphids’ dropping probabilities in response to high temperatures

2012

Journal of Insect Physiology

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Unifying indices of heat tolerance in ectotherms

Cited by 38 publications

References 20 publications

Thermal Tolerance in Widespread and TropicalDrosophilaSpecies: Does Phenotypic Plasticity Increase with Latitude?

Thermal Tolerance in Widespread and TropicalDrosophilaSpecies: Does Phenotypic Plasticity Increase with Latitude?

How to assess Drosophila heat tolerance: Unifying static and dynamic tolerance assays to predict heat distribution limits

Climate warming may increase aphids’ dropping probabilities in response to high temperatures

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