Meeting Abstract
The effects of climate change on plants and animals are pervasive. Importantly, climate change is expected to increase the thermal variation experienced by organisms, in addition to an overall increase in mean temperature. Because their body temperatures are heavily influenced by environmental temperatures, ectotherms are highly vulnerable to the effects of climate change. To investigate the effects of increased temperature and increased thermal variation on survival, emergence phenology, and developmental rates of an ectotherm with a complex life cycle (the dragonfly Erythemis collocata), we manipulated the temperatures experienced by developing larval dragonflies. In our first experiment, we elevated mean temperature by either 2.5 or 5° C, simulating predicted temperatures in 50 and 100 years, respectively. In our second experiment, we exposed dragonfly larvae to temperatures that were constantly 3.5° C above ambient, or to an “increased variation” treatment in which a mean increase of 3.5° C was achieved by alternating between 1° and 6° C above ambient. When mean temperatures were elevated but tracked ambient variation, we found that dragonflies emerged earlier, but did not experience differential survival. Similarly, when we manipulated thermal variability, larvae in both warmed treatments developed more rapidly than controls. However, larval survival decreased for animals that experienced increased thermal variability. Taken together, our results suggest that the effects of increased thermal variability may have negative effects on organisms that go beyond the effects of increased mean temperatures alone.
