Heat tolerance and thermal scope are evolutionarily constrained in Greenlandic terrestrial arthropods

Temperatures in the Arctic currently rise at four times the global average, making it of utmost importance to understand the thermal biology of species in these sensitive environments. For arctic ectotherms in particular, thermal tolerance limits and adaptive potential are mostly unknown. Such knowledge is urgently needed to predict climate change impacts on future distributions of biodiversity in these rapidly changing environments. Here, we provide new data on upper and lower thermal limits of 93 Greenlandic species of insects, arachnids, and collembolans identified using barcode sequencing representing ~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), suggesting that terrestrial Greenlandic arthropods are evolutionarily constrained in their capacity to cope with increasing and more variable future temperatures. Further, with projected future increases in microclimatic temperatures induced by climate change, we reveal a marked increase in the number of species that will experience potentially stressful temperatures for prolonged periods of time. Together, our results suggest that climate change will likely result in substantial changes in distributions and abundances of Greenlandic terrestrial arthropods.