Temperate insects with narrow seasonal activity periods can be as vulnerable to climate change as tropical insect\xa0 species

Frank Johansson,Viktor Nilsson-Örtman,Germán Orizaola

doi:10.1038/s41598-020-65608-7

Frank Johansson, Viktor Nilsson-Örtman + Show 1 more

Open Access

https://doi.org/10.1038/s41598-020-65608-7

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Abstract

The magnitude and ecological impact of climate change varies with latitude. Several recent models have shown that tropical ectotherms face the greatest risk from warming because they currently experience temperatures much closer to their physiological optimum than temperate taxa. Even a small increase in temperature may thus result in steep fitness declines in tropical species but increased fitness in temperate species. This prediction, however, is based on a model that does not account for latitudinal differences in activity periods. Temperate species in particular may often experience considerably higher temperatures than expected during the active season. Here, we integrate data on insect warming tolerance and temperature-dependent development to re-evaluate latitudinal trends in thermal safety margins after accounting for latitudinal trends in insect seasonal activity. Our analyses suggest that temperate and tropical species differ far less in thermal safety margins than commonly assumed, and add to the recent number of studies suggesting that tropical and temperate species might face similar levels of threat from climate change.

Highlights

The magnitude and ecological impact of climate change varies with latitude
warming tolerances (WT) and thermal safety margins (TSM) showed a considerably flatter latitudinal trend when we accounted for latitudinal differences in insect activity periods by calculating these metrics using the mean temperature during the active season ThabA (Fig. 2C,D,)
We find that previous analyses that have compared thermal optima and maxima (Topt and thermal maximum (Tmax)) with the annual mean habitat temperature (Thab) have greatly overestimated the warming tolerances (WT) and thermal safety margins (TSM) of temperate species (Fig. 2A,B), but not those of tropical species

Summary

Introduction

The magnitude and ecological impact of climate change varies with latitude. Several recent models have shown that tropical ectotherms face the greatest risk from warming because they currently experience temperatures much closer to their physiological optimum than temperate taxa. In the last decade several studies have synthesized and analyzed ectotherm TPC data on a global scale Most strikingly, these studies have brought widespread attention to the fact that tropical species appear to be more vulnerable to climate change than temperate species. The results revealed that tropical species have considerably narrower thermal safety margins and warming tolerances than temperate species[11] This suggests that even a small increase in global mean temperatures will result in precipitous declines in the fitness and performance of tropical species – as they become pushed toward or beyond their thermal maxima – whereas temperate species will benefit from an increase in mean temperatures, as they currently experience temperatures well below their thermal optimum[14,15,16]). One strength of this data set is that it uses intrinsic rates of population growth (r), a direct measure of Darwinian fitness

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