Thermal adaptations of adults and eggs in the Arctic seed bug Nysius groenlandicus (Insecta: Hemiptera) from South Greenland

Abstract

Temperatures in Arctic and sub-Arctic regions are highly variable, with long, and cold winters, and short summers. Studies on thermal biology of ectotherms from these latitudes have mostly focused on how organisms cope with cold temperatures. However, temperatures in microhabitats such as south-facing slopes can occasionally reach high and potentially stressful temperatures. Such microclimatic conditions are challenging for organisms, since they need to time their development to coincide with the short summer, while coping with thermal extremes during summer and winter. In the present study, we investigate upper and lower thermal limits of adults and eggs in Nysius groenlandicus, a univoltine seed bug widely distributed in Greenland and alpine areas of Scandinavia and with preference for dry and sunny habitats. Secondly, we investigate the survival strategy of the overwintering egg stage during cold exposure. We found a clear association between the microhabitat temperatures experienced by each specific life stage and their heat and cold tolerance. Thus, adults and eggs, which are both exposed to high summer temperatures, showed a high heat tolerance. Adults which do not overwinter had very poor cold tolerance, whereas eggs produced in autumn were very cold hardy (with some survival at − 21 °C). Cold tolerance of the eggs of N. groenlandicus was based on freeze avoidance through extensive supercooling and by conserving water. These results suggest life stage-specific adaptation to heat and cold stress in Arctic and sub-Arctic insects, and highlight new research avenues addressing adaptation to higher and more variable temperatures in Arctic and sub-Arctic regions.

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

“…Conversely, heat stress is often countered by behavioral thermoregulation in ectotherms, for instance by seeking shadow or migrating below-ground ( Huey and Tewksbury, 2009 ; Kearney et al, 2009 ). The higher heat tolerance and plasticity for this trait in females could be explained by the univoltine life history and the short arctic summers requiring females to seek out warm temperatures to rapidly complete their life cycle ( Bahrndorff et al, 2021a ). Further, our results indicate a trade-off between heat and cold tolerance.…”

“…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 ). Organisms, including insects, living in these environments must therefore be able to survive and reproduce over a wide range of temperatures ( Deere et al, 2006 ; Bahrndorff et al, 2021a ). This can be achieved by evolutionary adaptation to the local thermal conditions across generations, or by fast adjustments of the physiology within the lifetime of an organism via phenotypic plasticity ( Scheiner, 1993 ; Fusco and Minelli, 2010 ; Kristensen et al, 2020 ).…”

Responses of terrestrial polar arthropods to high and increasing temperatures

“…The largest daily temperature span reached 39 and 26.5°C in the sun and shade, respectively. The seed bug is well adapted to these changes in temperature; the adult life stage of the species has a critical thermal minimum (CT min ; see Glossary) of −3.2 to 3.4°C and a critical thermal maximum (CT max ) of 49.4 to 52°C (Bahrndorff et al, 2021a;Böcher and Nachman, 2001;Sørensen et al, 2019). Adult N. groenlandicus have a strong preference for high temperatures (above 30°C), which is thought to enable rapid growth, development and reproduction in the short and warm summers (Böcher and Nachman, 2001).…”