# Heat but Not Cold Tolerance Is Phylogenetically Constrained in Greenlandic Terrestrial Arthropods Under Future Global Warming

## TL;DR

This study shows that many Greenlandic arthropods may struggle to adapt to rising temperatures due to limited evolutionary flexibility, risking ecosystem changes.

## Contribution

The study provides new insights into the thermal limits and evolutionary constraints of Greenlandic arthropods under future climate change.

## Key findings

- 93 Greenlandic arthropod species showed significant variation in heat and cold tolerance.
- Over 25% of species may face stressful high temperatures in the future due to climate change.
- Phylogenetic signals indicate limited evolutionary potential for adapting to increasing temperatures.

## Abstract

The Arctic is currently warming at up to four times the global average. Likewise, climate variability within and across seasons is predicted to markedly increase in the future. This may challenge organisms in these pristine environments, making it critically important to understand their thermal biology and evolutionary potential. For Arctic ectotherms in particular, thermal tolerance limits and responses to climate change are mostly unknown. Knowledge on this is urgently needed to enable prediction of climate change impacts on future distributions of biodiversity in these rapidly changing environments. Here, we provide data on upper and lower thermal limits of 93 Greenlandic species of insects, arachnids, and collembolans caught and tested in the field and identified using barcode sequencing. This represents ~8% of described terrestrial Greenlandic arthropod species. We found pronounced differences in heat and cold tolerance among species and a strong phylogenetic signal for both heat tolerance and thermal scope (difference between upper and lower thermal limits). We argue that this indicates a limited capacity for coping with increasing and more variable future temperatures through evolutionary adaptation. Further, we modelled future increases in microhabitat temperatures in our sampling area. We found that > 25% of the investigated species may periodically experience stressful high temperatures in the future. These results suggest that climate change will likely result in substantial changes in distributions and abundances of terrestrial arthropods in Southern Greenland.

In this study we describe the temperature limits for almost 8% of the Greenlandic arthropod fauna (insects and spiders). By combining this with a DNA analysis and a projection of future climates inhabited by these species we reveal that upwards of 25% of the investigated species risk exposure to stressful temperatures by the end of the century and that they are potentially limited in their ability to adapt evolutionarily to higher temperatures. This suggests that the climatic changes predicted over the next century are likely to have pronounced effects on pristine Greenlandic ecosystems.