Insects struggle to adapt to extreme temperatures, making them vulnerable to climate change

Insects have a poor ability to adjust their thermal limits at high temperatures and are therefore more sensitive to global warming than previously thought.

As more frequent and intense heat waves expose animals to temperatures outside their normal limits, an international team led by researchers from the University of Bristol studied more than 100 species of insects to better understand how these changes will likely affect them.

Insects – which are as important as pollinators, crop pests and vectors of disease – are particularly vulnerable to temperature extremes. One of the ways insects can cope with such extremes is through acclimatization, where prior thermal exposure extends their critical thermal limits. Acclimatization can trigger physiological changes such as the upregulation of heat shock proteins and lead to changes in the composition of phospholipids in the cell membrane.

The team found that the insects struggled to do this effectively, revealing that acclimatization of the upper and lower critical thermal limits was low — for every 1°C change in exposure, the limits were only adjusted of 0.092°C and 0.147°C respectively (i.e. only a small offset of 10 or 15%).

They did, however, find that juvenile insects have a greater ability to acclimate, pointing out that there may be critical periods of life during a heat wave that can improve later resilience.

Lead author Hester Weaving, from Bristol’s School of Biological Sciences, said: “As temperature extremes become more intense and frequent in our warming world, many insects will have to rely on the shift to new ranges or on modifying their behavior to cope, rather than being able to physiologically tolerate wider temperatures.

“Our comparative study has identified some major gaps in understanding insect responses to climate change and we urge more studies of species in underrepresented groups and locations.”

The team is currently investigating how insect reproduction is affected by exposure to temperature extremes, as this may be more important in predicting future distributions than measures of performance or survival.

Financial support was provided by the Royal Society, BBSRC and a pump priming grant from Bristol University’s GCRF.

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Materials provided by University of Bristol. Note: Content may be edited for style and length.