3.9 Wednesday, Jan. 4 Ecologically-relevant stresses hurt differently: the response of Eurosta solidaginis to repeated freeze-thaw cycles. MARSHALL, Katie E*; SINCLAIR, Brent J; University of Western Ontario email@example.com
Repeated freeze-thaw cycles are common in temperate latitudes, and are predicted to change in frequency in future climates. The goldenrod gall fly Eurosta solidaginis overwinters through a broad geographical range as a freeze tolerant prepupa in goldenrod stems above the snow and experiences the full range of air temperatures, which causes repeated freeze-thaw events for this species in the field. Locally-collected flies were subjected to one of three experimental conditions: control (maintained at 0C), sustained freezing (a single 120h exposure to -20C), or repeated freezing (ten 12h exposures to -20C). We characterized both immediate as well as long-term effects of repeated freezing in this species to unravel some of the costs and benefits of repeated freezing. We found that responses to repeated freezing were consistently distinct from the sustained freeze exposure (although the total amount of time spent frozen was equal), and included a depressed freezing point, decreased survival, and increase in development time. We also found that neutral lipid pools in this species are characterized by a large accumulation of free fatty acid as well as the presence of a large quantity of an unknown lipid. Repeated freezing increased the quantity of this unknown lipid at the expense of free fatty acid and triacylglyceride. Taken together, these results indicate that the effects of repeated freezing are not predictable from a single freezing event, and that responses to repeated freeze-thaws are likely more relevant to field conditions.