CANCELLED - Giving RFID-tags a piggyback ride: Tracking activity of terrestrial insects under heat stress and varying microhabitats

Background/Question/Methods

Global warming causes not only generally higher average temperatures but also more frequent extreme heat events. Such changes in temperature have substantial effects on the physiology of mobile terrestrial ectotherms. To maintain performance at high temperatures, organisms have to adjust their thermoregulatory behavior by either reducing their mobility or moving to preferable microhabitats. However, tracking data on invertebrate movement and activity is scarce, since most tracking systems incorporate too big and heavy transmitters to be applicable to insects. Here, we developed a new experimental approach for gathering movement tracking data of ground-dwelling insects using Radio Frequency Identification (RFID). In fully-controlled mesocosms, we assessed the movement activity of insects in response to heat stress under different microhabitat variabilities, comprising leaf litter of different species being either separated (high microhabitat variability, MV) or well mixed (low MV). To simulate extreme heat events over 14-day periods, we increased the ambient temperature along a gradient up to 39°C.

Results/Conclusions

Our results indicate that the effect of extreme heat on movement activity is highly dependent on the respective microhabitat variability (MV). While the high MV (separated litter) provides an environment where activity is still maintainable for insects, we find a strong decrease in activity within low MV (mixed litter) under heat stress. The microhabitat variability characterizes how flexible organisms can cope with heat stress and adjust their behavior to save energy and to maintain performance. Thus, habitat variability may buffer the consequences of extreme temperatures on individual performance and survival, and thereby determining how terrestrial ectotherms will respond to heat stress under climate change.