Meeting Abstract
Phenotypic plasticity is commonly observed in organisms responding to climate change, and might buffer populations from decline. However, the potential of phenotypic plasticity to counter climate change-induced stressors has rarely been examined experimentally. We experimentally assessed behavioral nesting plasticity in lizards (Sceloporus tristichus). Exposure to temperatures > 44C causes instant death of embryos. While below ground nests rarely reach such high temperatures currently, biophysical modeling predicts that S. tristichus nests will rise above 44C for brief periods annually by 2100. Modeling also indicates that females could fully buffer their offspring by subtly altering nesting sites: increasing nest depth or shade cover. To test the capacity for females to sufficiently adjust their nesting, we exposed gravid females to an optimal or stressful (temperatures hotter than preferred 3hrs/d) thermal regime for the majority of egg development. We then released the lizards immediately prior to oviposition in individual outdoor enclosures that provided three shade environments (30, 60, and 90%) and 30cm-deep soil within which to nest. The temperature regime that females experienced while gravid did not affect nesting. By contrast, temperature at the time of nesting affected nest depth, although not in the direction expected: females dug shallower nests when exposed to warmer temperatures. We suggest that females failed to adaptively adjust their nest-sites because, throughout their evolutionary history, critical high nest temperatures were so rare and unpredictable as to not select for an avoidance mechanism. Similar failures of plasticity will likely be common whenever climate change is predicted to induce novel stressful conditions, such as an increased incidence of critically high temperatures.
