Limited plasticity of low temperature tolerance in an Australian cantharid beetle 'Chauliognathus lugubris'

Spatial and/or taxonomic bias in thermal tolerance and plasticity data can severely impact projections of climate change responses and limit the understanding of the evolution of thermal performance curves. Thus, further data from under-represented groups and geographical locations are important for synthesizing and predicting the physiological responses of insects to climate variability. For example, the magnitude of rapid cold-hardening (RCH) and seasonal acclimatization of low temperature tolerance are typically poorly documented for nondipteran species from the southern Hemisphere. Moreover, few studies assess RCH responses under different acclimation regimes. To address this paucity of data, the low temperature survival, RCH and acclimation ability of 'Chauliognathus lugubris' (F.) are assessed from an adult aggregation collected in Armidale, New South Wales, Australia. Beetles are acclimated to either 27 or 20 °C for 1 week and then tested for their ability to survive cold shock or rapidly cold-harden. There is no effect of acclimation on low temperature survival (mean survival range at -5.4 °C for 2 h: 4-52% in 27 and 20 °C acclimation groups). In addition, beetles show no significant improvement in survival after acute thermal pretreatments. In conclusion, these data suggest a generally poor acclimation potential of low temperature survival and no RCH responses in adult Australian cantharid beetles, which is accordance with what might be expected given the microclimate experienced, their ability for behavioural regulation and the life history of the species.