Meeting Abstract
Most organisms live in thermally variable environments and climate change stands to increase this variation. However, studies often utilize constant temperatures and focus on a single life stage, which may undermine the accuracy of climate change predictions. One hypothesis that has been utilized to help predict organismal responses to temperature fluctuation is the climate variability hypothesis (CVH), which posits that increased temperature variation selects for increased thermal plasticity. Though the CVH has been tested along natural temperature gradients (e.g. latitude), it may also predict thermal plasticity across discrete life stages that experience varying degrees of thermal fluctuation. Here, we test the CVH across life stages of Onthophagus taurus dung beetles; pupa develop underground buffered from temperature extremes, whereas adults also inhabit open fields and dung pats with substantial temperature fluctuation. We reared F2 full-siblings in either high (24 ± 8°C) or low (24 ± 4°C) temperature fluctuation treatments and quantified thermal plasticity at pupal and adult life stages. We compared shifts in thermal sensitivity of metabolism among treatments and life stages by measuring CO2 production at 15, 20, 25, and 30 °C in pupae and adults. We found that adults exhibited thermal plasticity and pupae did not, supporting the CVH. In response to thermal variability, adults exhibited metabolic depression, which should conserve energy in fluctuating temperatures. This novel application of the CVH underscores the importance of considering stage-dependent thermal responses in climate change forecasting; predictions that are not based on the most critical life stage may overestimate the likelihood of persistence.
