Evaporative water loss in insular populations of the Anolis cristatellus group (Reptilia : Sauria) in the British Virgin Islands II: The effects of drought

Previous work has shown that water loss in some populations of Anolis crist atellus from the British Virgin Islands is closely tied to the conditions a vailable on the islands they inhabit. This manifested itself in a strong co rrelation between habitat aridity and several water loss rate parameters. H ere we report on a similar study conducted in the same locations in 1994, a year of extreme drought. We hypothesized that lizards caught at the height of the drought will exper ience lower rates of water loss than those measured during a normal year. O ur findings show that in 1994, as in 1993, habitat aridity and water loss p arameters were strongly correlated. Also as before, the Guana Island popula tion of A. cristatellus displayed higher resistance to water loss than expe cted by the island's aridity. However, a striking change occurred within po pulations. All were at least as good at retaining water (measured as integu mentary resistance to water loss, R) as in 1993, and some were over 3.5 tim es better. Existing evidence is insufficient to determine whether these cha nges were the result of phenotypic plasticity or attributable to differenti al mortality of nonresistant individuals.