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SFS Annual Meeting

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Organisms have optimal temperature ranges for physiological function. Climate change may push organisms beyond their optimal range, shifting community composition and potentially ecosystem function. The critical thermal maximum (CTmax)—the temperature at which an organism’s physical function is compromised—provides a relative measure of taxon sensitivity to increasing temperatures, and values have not been widely determined for tropical stream macroinvertebrates. We explored differences in thermal tolerance between tropical and temperate-zone stream insects from La Selva Biological Station (Costa Rica) and Missouri (USA). CTmax values were determined by placing individual insects in centrifuge tubes in a water bath while increasing the temperature 1°C per minute until loss of righting response. At the order level, CTmax values were significantly lower for tropical taxa than for temperate taxa. At the family level, CTmax values were significantly lower for tropical vs. temperate-zone Perlidae, but did not differ with ecoregion for Calopterygidae or Libellulidae. Related taxa had similar CTmax rankings in Missouri and La Selva, indicating that thermal tolerance is a phylogenetically conserved trait. Ephemeroptera and Plecoptera showed the highest thermal sensitivity, making them potential bioindicator taxa for changes in thermal regimes.

Rebecca Prest (Primary Presenter/Author), Missouri Western State University,;

Ben Allen (Co-Presenter/Co-Author), Missouri Western State University,;

Carissa Ganong (Co-Presenter/Co-Author), Missouri Western State University,;