Abstract

An experimental approach was taken to evaluate the role of phenotypic plasticity in reptile coloration for three lizard species which exhibit dramatic variation in dorsal body darkness associated with different substrate environments. In southern New Mexico, blanched color morphs of Aspidoscelis inornata, Holbrookia maculata, and Sceloporus undulatus inhabit the gypsum dunes of White Sands, and a melanic color morph of S. undulatus is found on the Carrizozo lava flow. Temperature was manipulated to determine the extent of physiological (rapid) plasticity in coloration for all three species. Color change in response to short-term stimuli did not explain the variation among lizards from different habitats. Although lizards of all color morphs were slightly darker when colder, more melanic lizards displayed a diminished capacity for rapid color change. Common garden experiments were conducted to evaluate the potential for ontogenetic plasticity in coloration for H. maculata and S. undulatus. Offspring from mothers of different substrate environments were distinguishable by color despite identical developmental conditions. Hatchlings and adults exhibited similar coloration for H. maculata, but a developmental trajectory in coloration was observed in S. undulatus. Overall, environmental variation alone did not explain differences in dorsal coloration among lizards from distinctive habitats. Results from these experiments support the hypotheses that color morphology in Tularosa Basin lizards has a strong heritable component and that observed variation is likely adaptive.