Meeting Abstract

102-7  Saturday, Jan. 6 15:00 - 15:15  City limits: Determinants of thermal maxima in an urban ant community JOHNSON, D.*; STAHLSCHMIDT, Z.R.; Univ. of the Pacific; Univ. of the Pacific

Examining the thermal responses of urban animals is critical because cities are rapidly expanding, and temperatures are increasing globally—particularly in urban environments. Although cities tend to be warmer due to the heat island effect, this thermal hazard may be offset by increased availability of water in urban ecosystems (e.g., irrigation). The sensitivity of animals (including those in urban environments) to high temperatures can be determined by the critical thermal maximum (Tmax), and variation in Tmax may be driven by a range of factors. For example, animals that are larger, adapted to warmer microclimates, or well-hydrated may have relatively high Tmax values. Alternatively, Tmax may be phylogenetically constrained wherein closely related species exhibit similar Tmax values, regardless of differences in morphology or physiological state. Thus, we manipulated water access and determined Tmax (knockdown temperature) for ants common to cities in California’s Central Valley. We determined Tmax (range: 29-61°C) for 688 individuals spanning 11 species. We will discuss the effects of body size, hydration state, and adaptation to local environments (active temperatures of ants in the field) on Tmax after controlling for phylogeny. Together, our results will inform the abiotic and biotic factors influencing animals’ sensitivity to high temperatures in an increasingly warm world.