Meeting Abstract

3.4  Wednesday, Jan. 4  Comparison of upper thermal limits among geographically-distributed populations of the mosquito, Culex tarsalis VORHEES, Ashley*; GRAY, Emilie; BRADLEY, Timothy; University of California, Irvine avorhees@uci.edu

Thermal limits to activity play a central role in determining the abundance and geographic distribution of ecothermic animals. Therefore, understanding variation in thermal limits will be highly important for predicting species-level responses to climate change. While a variety of studies have examined large-scale patterns in thermal traits over geographic ranges, studies examining geographic variation in thermal tolerance limits within a single species are quite limited. To address this, we investigated the upper thermal limits of a widely distributed mosquito species, Culex tarsalis, across a climatic gradient. Our aim was to determine how the critical thermal maximum (CTMax) and metabolic rate vary with climate by comparing mosquitoes collected from several different sites. We captured and tested adult female C. tarsalis mosquitoes from three sites within California: 1) the northwest shore of the Salton Sea (Coachella, CA), 2) the San Joaquin Marsh Reserve (Irvine, CA), and the Sierra Nevada Aquatic Research Lab (Mammoth Lakes, CA). We determined the CTMax of individual mosquitoes using thermolimit respirometry, in which CO₂ release was measured from each animal as temperature increased, and CTMax was identified as the point of respiratory failure. Metabolic rate was measured using flow-through respirometry at 13, 23, and 33^oC. Our results showed that both CTMax and metabolic rate differed significantly among C. tarsalis from these different sites. Both variables appear to track environmental conditions, with CTMax being highest in mosquitoes from warm sites and metabolic rate being highest in mosquitoes from cold sites. These results contribute to our understanding of how certain traits can allow a widespread species such as C. tarsalis to inhabit such a wide variety of thermal environments.