Responses of terrestrial polar arthropods to high and increasing temperatures

Abstract

Terrestrial arthropods in the Arctic and Antarctic are exposed to extreme and variable temperatures, and climate change is predicted to be especially pronounced in these regions. Available ecophysiological studies on terrestrial ectotherms from the Arctic and Antarctic typically focus on the ability of species to tolerate the extreme low temperatures that can occur in these regions, whereas studies investigating species plasticity and the importance of evolutionary adaptation to periodically high and increasing temperatures are limited. Here, we provide an overview of current knowledge on thermal adaptation to high temperatures of terrestrial arthropods in Arctic and Antarctic regions. Firstly, we summarize the literature on heat tolerance for terrestrial arthropods in these regions, and discuss variation in heat tolerance across species, habitats and polar regions. Secondly, we discuss the potential for species to cope with increasing and more variable temperatures through thermal plasticity and evolutionary adaptation. Thirdly, we summarize our current knowledge of the underlying physiological adjustments to heat stress in arthropods from polar regions. It is clear that very little data are available on the heat tolerance of arthropods in polar regions, but that large variation in arthropod thermal tolerance exists across polar regions, habitats and species. Further, the species investigated show unique physiological adjustments to heat stress, such as their ability to respond quickly to increasing or extreme temperatures. To understand the consequences of climate change on terrestrial arthropods in polar regions, we suggest that more studies on the ability of species to cope with stressful high and variable temperatures are needed.

Rapid Adjustments in Thermal Tolerance and the Metabolome to Daily Environmental Changes – A Field Study on the Arctic Seed Bug Nysius groenlandicus

“…In our study, we showed a linear relationship between ambient microhabitat temperature and measures of both cold and heat tolerance of field-collected specimens of N. groenlandicus . Given the temperatures observed in the field during summer in Narsarsuaq includes subzero night temperatures and peak day temperatures above 40°C ( Sørensen et al, 2019 ; Bahrndorff et al, 2021b ) we advocate that the ability to withstand and remain active at high temperatures and recover fast from low temperature coma is ecologically important, especially for a univoltine species such as N. groenlandicus . This allows the species to, e.g., forage and mate in a transient environment and short summer season.…”

“…The field work was conducted in July–August 2018 in Narsarsuaq (Southern Greenland, 61.160°N, 45.424°W). This region is characterized by cool temperatures, long winters and short and thermally variable summers ( Böcher and Nachman, 2001 ; Bahrndorff et al, 2021b ). The study site was a heath-like, grass-covered area, where adult N. groenlandicus were collected from the grasses using a sweep net ( Figure 1 ).…”

“…The glass vials containing the individuals were mounted to a rack and submerged into a glycol-water solution that was kept at −3 • C using a thermostat (LAUDA Proline Edition X RP 1845-C, LAUDA DR. R. WOBSER GMBH & CO., KG, Germany). This temperature was based on the lower critical temperature (CTmin) which induces a cold coma for the species (Bahrndorff et al, 2021b). Immediately after submersion, the temperature of the solution was increased at a rate of 0.2 • C/min.…”

“…In terrestrial ecosystems, daily changes in temperature can be substantial, and vary greatly with microhabitat characteristics such as topography and orientation, vegetation cover, shading and more ( Sears et al, 2019 ; Kearney et al, 2020 ; Lembrechts and Lenoir, 2020 ). Some of the most extreme environments are found in the polar regions where the winters are long and cold, and the summers short and periodically hot ( Bahrndorff et al, 2021b ). During the arctic summer, daily temperatures can vary by >30°C and reach subzero temperatures at night ( Convey et al, 2018 ; Davey et al, 2021 ).…”

“…The other form of more gradual acclimation includes seasonal acquisition of cold or heat tolerance that is induced by changes in temperature and photoperiod interacting with other abiotic factors (reviewed by Chown and Terblanche, 2006 ; Teets and Denlinger, 2013 ). There are several published examples of cold acclimation and rapid cold hardening in arctic arthropods (e.g., Bahrndorff et al, 2007 ; Everatt et al, 2013 ), but very few studies have investigated physiological acclimation of polar terrestrial arthropods to high temperatures ( Sørensen et al, 2019 ; Bahrndorff et al, 2021b ). Traditionally, thermal plasticity of insects has been investigated using model-organisms kept and hardened/acclimated to constant controlled temperatures in the laboratory ( Angilletta, 2009 ; Colinet et al, 2015 ; Javal et al, 2016 ; Ketola and Kristensen, 2017 ).…”