Meeting Abstract

P1.68  Sunday, Jan. 4  The evolution of insect cold tolerance: A Drosophila model STRACHAN, L.A.*; TARNOWSKI, H.E.; SINCLAIR, B.J.; University of Western Ontario, London, ON; University of Western Ontario, London, ON; University of Western Ontario, London, ON lstrach3@uwo.ca

Insects survive subzero environments using cold tolerance strategies generally divided into two categories: freeze tolerant and freeze avoiding. In spite of extensive research on insect cold tolerance, the evolutionary influences on the choice of strategy remain unclear. Most freeze tolerant dipteran species survive freezing as larvae; however, previous Drosophila studies have focused primarily on the adult fly. We hypothesise that both freeze avoiding and freeze tolerant strategies will be present in Drosophila larvae, and use a comparative approach to examine cold tolerance attributes among species. Low temperature survival, supercooling points (SCPs) and cold tolerance strategies were determined in larvae of 27 Drosophila species. In addition, the relationship between body size, water content and SCP was studied, and acclimation regimes and inoculative freezing were used to mimic natural environmental conditions. A Drosophila phylogeny was developed using the COI, COII, and 28s sequences of all species in stock. We then examined the factors influencing cold tolerance in a phylogenetically-independent context in an effort to map how strategies have evolved within the genus. Thus far no freeze tolerant larvae have been observed. Among species, lower lethal temperatures span a range of ten degrees; and freeze avoiding species are distinct from chill susceptible species. Additionally, we found body mass and absolute water content are stronger determinants of SCP than phylogeny, and species differ in hardening capacity during acclimation regimes.