Cold hardiness and deacclimation of overwintering Papilio zelicaon pupae

Seasonally-acquired cold tolerance can be reversed at warm temperatures, leaving temperate ectotherms vulnerable to cold snaps. However, deacclimation, and its underlying mechanisms, has not been well-explored in insects. Swallowtail butterflies are widely distributed but in some cases their range is limited by low temperature and their cold tolerance is seasonally acquired, implying that they experience mortality resulting from deacclimation. We investigated cold tolerance and hemolymph composition of Anise swallowtail (Papilio zelicaon) pupae during overwintering in the laboratory, and after four days exposure to warm temperatures in spring. Overwintering pupae had supercooling points around − 20.5 °C and survived brief exposures to − 30 °C, suggesting partial freeze tolerance. Overwintering pupae had hemolymph osmolality of approximately 920 mOsm, imparted by high concentrations of glycerol, K+ and Na+. After exposure to spring warming, supercooling points increased to approximately − 17 °C, and survival of a 1 h exposure to − 20 °C decreased from 100% to 0%. This deacclimation was associated with decreased hemolymph osmolality and reduced glycerol, trehalose, Na+ and Ca2 + concentrations. We compared cold tolerance of pupae to weather conditions at and beyond the species\u27 northern range boundary. Minimum temperatures at the range boundary approached the lower lethal temperature of pupae, and were colder north of the range, suggesting that cold hardiness may set northern range limits. Minimum temperatures following warm snaps were likely to cause mortality in at least one of the past three years. Cold snaps in the spring are increasing in frequency as a result of global climate change, so are likely to be a significant source of mortality for this species, and other temperate ectotherms

Cold truths: how winter drives responses of terrestrial organisms to climate change

Winter is a key driver of individual performance, community composition, and ecological interactions in terrestrial habitats. Although climate change research tends to focus on performance in the growing season, climate change is also modifying winter conditions rapidly. Changes to winter temperatures, the variability of winter conditions, and winter snow cover can interact to induce cold injury, alter energy and water balance, advance or retard phenology, and modify community interactions. Species vary in their susceptibility to these winter drivers, hampering efforts to predict biological responses to climate change. Existing frameworks for predicting the impacts of climate change do not incorporate the complexity of organismal responses to winter. Here, we synthesise organismal responses to winter climate change, and use this synthesis to build a framework to predict exposure and sensitivity to negative impacts. This framework can be used to estimate the vulnerability of species to winter climate change. We describe the importance of relationships between winter conditions and performance during the growing season in determining fitness, and demonstrate how summer and winter processes are linked. Incorporating winter into current models will require concerted effort from theoreticians and empiricists, and the expansion of current growing-season studies to incorporate winter

Biodiversity inventories in high gear: DNA barcoding facilitates a rapid biotic survey of a temperate nature reserve

Comprehensive biotic surveys, or ‘all taxon biodiversity inventories’ (ATBI), have traditionally been limited in scale or scope due to the complications surrounding specimen sorting and species identification. To circumvent these issues, several ATBI projects have successfully integrated DNA barcoding into their identification procedures and witnessed acceleration in their surveys and subsequent increase in project scope and scale. The Biodiversity Institute of Ontario partnered with the rare Charitable Research Reserve and delegates of the 6th International Barcode of Life Conference to complete its own rapid, barcode-assisted ATBI of an established land trust in Cambridge, Ontario, Canada