SD01: Are phenological syndromes associated with critical thermal limits in bees?

Critical thermal limits—defined as the temperatures at which individuals lose motor control—are physiological traits generally associated with the lowest and highest temperatures where individuals can persist. Empirical studies in a wide range of ectotherms have demonstrated that species that live in areas with lower temperature variation (e.g., tropical or low elevation environments) tolerate less extreme critical thermal limits than species that inhabit areas with broader thermal variation (e.g., high altitude and temperate regions). In contrast, studies characterizing differences in critical thermal limits between species that experience different temperature variation due to seasonality in temperate areas (e.g., spring, summer and fall) are limited. In this study, we aim to test the hypothesis that critical thermal tolerance is associated with when organisms are active (a.k.a. phenological syndromes). We predict that species active during colder periods of the year exhibit lower minimum thermal tolerances than species exclusively active during warmer periods. We collected data on the critical thermal minima and maxima of 8 species that are active across the year (broad phenology) or are exclusively active spring, summer, or fall. We discuss our results in the context of the existing literature and the association between animal thermal limits and occurrence.