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Annual Temperature Range Drives Thermal Breadth of Freshwater Insects Across Multiple Spatial Scales
Beatrice S Dewenter1, Darren P Giling1,2,3, Alisha A Shah4
1Centre for Applied Water Science, Institute for Applied Ecology, University of Canberra, Bruce ACT, Australia.
Ecology Letters
|December 11, 2025
Summary
Annual temperature range, not mean temperature or diel range, best explains freshwater insect thermal breadth (Tbr). This finding is crucial for understanding climate change impacts on aquatic ecosystems.
Area of Science:
- Ecology
- Climate Change Biology
- Zoology
Background:
- Thermal breadth (Tbr) is a key trait for predicting species' responses to climate change.
- Understanding variation in Tbr is essential for conservation efforts.
Purpose of the Study:
- To test three hypotheses explaining variation in Tbr: Climate Variability Hypothesis (CVH), Thermal Constraints Hypothesis (TCH), and Diel Narrowing Hypothesis (DNH).
- To investigate the drivers of Tbr in freshwater insects across elevational gradients.
Main Methods:
- Measured Tbr of Ephemeroptera, Plecoptera, and Trichoptera along elevational gradients in the Americas and Australia.
- Contrasted warm and cool-adapted species from tropical and temperate regions with differing climate variability.
Main Results:
- Found strong support for the CVH, indicating annual temperature range is a primary driver of Tbr.
- Observed limited support for the TCH in two of four regions.
- Found no support for the DNH.
Conclusions:
- Annual temperature variability is the most significant factor explaining Tbr in freshwater insects.
- Mean annual temperature and diel temperature range are less important drivers of Tbr for these organisms.
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