Meeting Abstract

24.5  Friday, Jan. 4  Thermal sensitivity of metabolic rates explains range properties: towards a cause-and-effect understanding of climate change vulnerability BERNARDO, J.*; SPOTILA, J.R.; AGOSTA, S.; Texas A&M Univ.; Drexel Univ.; VA Commonwealth Univ. jbernardo@tamu.edu

Understanding causes of species distributions has been a central goal of ecology for more than a century, but our current understanding is surprisingly unsophisticated. Most current evidence is based on correlations between abiotic factors and range properties (limits, extents) but does not examine species biology directly. Macroecological, and macrophysiological approaches do consider correlations between species traits and range properties, but they are often weak and lack a concrete mechanistic, cause-and-effect explanation. Here we test macro-scale predictions of The Oxygen- and Capacity-Limitation of Thermal Tolerance Model (OCLM), a mechanistic model based on detailed analysis of cellular and sub-cellular processes assayed in vivo as organisms are thermally challenged. The OCLM, developed using marine animals, finds that deterioration of whole organism performance with increasing temperature past optimal performance reflects an inability to satisfy oxygen demands of metabolism, and the concomitant onset of anaerobisis. Using a salamander model system, we show that the rate at which metabolic performance deteriorates with increasing temperature explains a substantial amount of interspecific variance in lower elevational limits and in the latitudinal extent of geographic ranges. These results provide (1) one of the strongest empirical explanations of interspecific variance in range properties in any system, (2) the first interspecific comparative support of the predictions of the OCLM, and (3) the first demonstration of the relevance of the OCLM to terrestrial organisms. Our results also have important implications for evolutionary models of species range determination.