Meeting Abstract

P3.25  Jan. 6  Altitudinal Clines in Insect Body Size: Physiological Interpretations of Mixed Patterns FRAZIER, M.R.**; DILLON, M.E.; CRANE, S.; Univ. of Washington, Seattle; Univ. of Washington, Seattle; City College of New York, NY mfrazier@u.washington.edu

Chown and Gaston hypothesized that the probability of an insect species expressing an increasing or decreasing body size cline along a latitudinal gradient depends on the length of its generation time relative to the length of its growing season. An insect with a long generation time relative to its growing season is more likely to evolve smaller body sizes across a latitudinal gradient. This evolutionary tactic sacrifices body size to speed development, allowing completion of a generation within the growing season. Conversely, insects with short generation times relative to their growing season are less time limited; therefore, they should become larger along a latitudinal gradient due to the developmental and evolutionary effects of cold temperatures on ectothermic body size. We studied the body size clines of insects along altitudinal gradients to test this hypothesis. We compiled published data on the body size trends of 51 insect species (males and females were counted individually when possible because they often showed different trends, so N = 81). In 31 cases, insect body size increased with altitude. However, in 50 cases, body size decreased with altitude. If Chown and Gaston are correct, insect species with longer development times and shorter growing seasons (i.e. insect species at high latitudes) would be more likely to have negative body size clines across altitude. A comparative analysis supported this hypothesis, and hopefully an analysis corrected for phylogenetic history will concur with the interesting results of this preliminary analysis!