Differences in cold tolerance, desiccation resistance, and cryoprotectant production between three populations of...

Possible links between cold-tolerance and desiccation resistance were examined between larvae of the goldenrod gall fly collected from Michigan, southern Ohio, and Alabama locations as their host plant senesced. After acclimation to 5 degrees C, Michigan-collected larvae were more cold-tolerant (25% survival after a 96 h exposure to -40 degrees C) than larvae from Ohio (10% survival) and Alabama (0% survival). Increased cold-tolerance was partially linked to higher concentrations of the cryoprotectant glycerol (Michigan: 500 +/- 30 mmol; Ohio: 270 +/- 20; Alabama: 220 +/- 20). Moreover, cryoprotectants may have functioned to reduce rates of overall and cuticular water loss for Michigan larvae, 0.10 +/- 0.01 and 0.037 +/- 0.003 microg mm(-2) h(-1), respectively, values that were 40-44% lower than those for Ohio and Alabama larvae and may represent a link between desiccation resistance and cold-tolerance. After acclimation to 20 degrees C, Alabama-collected larvae had metabolic rates that were 40% lower than those from Ohio and Michigan that averaged 0.100 +/- 0.006 microl of CO(2) produced g(-1) h(-1). The lower metabolic rate of Alabama-collected larvae at 20 degrees C likely resulted in reduced respiratory transpiration that may represent a mechanism to maintain water balance at the higher overwintering temperatures they typically experience.