Chameleons have a long tongue used to catch insects. The five toes on each foot are bound in two separate groups: one group of two toes and one group of three toes. This allows chameleons to grasp onto branches. Chameleons also have a flexible tail they use to hold onto branches, and they can change the color of their skin to communicate with other chameleons and for camouflage. Which statement about chameleons refers to the expression of a trait that is most influenced by the environment?