The Bogert effect and environmental heterogeneity

A classic question in evolutionary biology is whether behavioural flexibility hastens or hinders evolutionary change. The latter idea, that behavior reduces the number of environmental states experienced by an organism and therefore buffers that organism against selection, has been dubbed the “Bogert Effect” after Charles Bogert, the biologist who first popularized the phenomenon using data from lizards. The Bogert Effect is pervasive when traits like mean body temperature, which tend to be invariant across space in species that behaviourally thermoregulate, are considered. Nevertheless, behavioural thermoregulation decreases or stops when spatial variation in operative temperature is low. We compared environmental temperatures, thermoregulatory behavior, and a suite of physiological and morphological traits between two populations of the southern rock agama (Agama atra) in South Africa that experience different climatic regimes. Individuals from both populations thermoregulated efficie...