DOI: 10.5061/dryad.840j728
title: Data from: How to assess Drosophila heat tolerance: unifying static and dynamic tolerance assays to predict heat distribution limits

description: 1. 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. 2. 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 &lt;10 minutes to
 &gt;12 hours and all species displayed the expected exponential
 relation between temperature and knockdown time (average R2=0.98). 3.
 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. 4. 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. 5.
 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 the
 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.
description: Drosophila_heat_tolerance_static_assaysKnockdown times for 11 species of Drosophila tested in static assays (constant temperature) covering knockdown times &lt;10 min to &gt;12 h.Jorgensen_Drosophila_heat_tolerance_static_assays.xlsxDrosophila_heat_tolerance_dynamic_assaysKnockdown temperatures from dynamic assays (0.05, 0.1 and 0.25 deg C/min) for 11 species of <i>Drosophila</i>.Jorgensen_Drosophila_heat_tolerance_dynamic_assays.xlsxDrosophila_distribution_climate_data<i>Drosophila</i> distribution data linked to climate variables.Jorgensen_Drosophila_distribution_climate_data.xlsx