Meeting Abstract
Desert and gopher tortoises (Gopherus) are the sole survivors of a diverse tortoise fauna from the Cenozoic of North American but now face multiple anthropogenic threats including habitat destruction and climate warming. Because models predicting biotic impacts of climate have not integrated other anthropogenic stressors, and range-shift predictions lack validation against hot conditions expected by century’s end, we develop ecophysiological-demographic models to identify populations at risk from simultaneous threats and predict range shifts under warming climates, past or future. Moreover, we use phylogenetic comparative methods to infer ancestral body temperatures and mode of thermoregulation. Tortoises evolved warmer body temperatures coincident with drying periods during the Miocene. Higher body temperatures coevolved with the invasion of grassland environments and an herbivorous diet. Models successfully recover distributions of extant Gopherus and even their Eocene ancestors – during the warmest period of the Cenozoic. Models forecast that Eocene-level warming by ~2080 may drive Gopherus extinct and that solar farms, which potentially limit warming globally, may paradoxically accelerate local extinctions. Nevertheless, widespread desertification of current agricultural areas by 2080 will create habitat – in regions where tortoise ancestors weathered previous hothouse episodes – into which tortoises can be translocated.
