Heat-wave tolerance in tropical intertidal animals: accounting for thermal and desiccation tolerances

Abstract

Abstract We investigated whether thermal tolerance is useful in predicting the responses of tropical snails to heat-waves - unusually warm periods of weather. Studying four sympatric high-rocky-shore species, we assessed thermal tolerance from the lethal limit following a constant rate of acute warming, as well as from an ecologically-relevant heat tolerance measure accounting for midday thermal exposure times. These thermal tolerance assessments were then compared with the survival of snails under three laboratory-simulated heat-wave treatments, each constituting four days of cycling temperatures but varying in daily maximum temperature (45, 48 and 50 °C). Additionally, water loss of individual snails was measured daily to assess the effect of desiccation due to heat-wave exposure. We found that responses to heat-wave exposure are complex and are not always predictable from thermal tolerance traits. This arises from a mismatch in thermal tolerance and desiccation tolerance, such that variation in daily thermal maximum and duration of the heat-waves produced different survival responses for each species. This study highlights the need to consider both thermal and desiccation tolerance traits when building frameworks to predicting heat-wave vulnerability in benthic intertidal ectotherms.