Meeting Abstract

S9.6  Friday, Jan. 7  Physiological adaptation to climate change in a montane insect DAHLHOFF, EP*; RANK, NE; Santa Clara University; Sonoma State University edahlhoff@scu.edu

The willow beetle Chrysomela aeneicollis is an ideal model system for investigating physiological mechanisms by which climate change impacts natural systems. Beetles are found at high elevation in California’s Sierra Nevada, and are exposed to elevated and subzero temperatures during summer that cause physiological stress. A unique feature of Sierra populations is that the glycolytic enzyme locus phosphoglucose isomerase (PGI) is under temperature selection. PGI-1 is common in cool, northern regions and PGI-4 in warmer, southern regions; alleles 1 and 4 are in relatively equal frequency in populations intermediate in geography and climate. Seasonal and decadal changes in climate have caused shifts in PGI allele frequency; they have also caused beetles to colonize high elevations, become extinct at lower elevations, and populations to change in size. To identify mechanisms causing these shifts, we have measured effects of temperature variation on survival, physiology and reproductive activity of beetles in lab and in nature. We have found consistent differences among PGI genotypes in thermal tolerance, larval growth and survival, metabolic rate, running speed, fecundity and mating frequency suggesting that PGI 1-1 and 1-4 individuals perform best under mild conditions, 4-4 homozygotes under extreme conditions. Heat shock protein expression varies among PGI genotypes and is positively related to measures of survival, performance and reproductive success. If hot summers and dry winters become more common in the Sierra Nevada, as is predicted by many climate models, low elevation populations of willow beetles may become extinct; populations where PGI-1 is most common may be most vulnerable.