Changes in host plant use favor divergence of vibrational signals in treehoppers (Membracidae: Enchenopa binotata)

Abstract

Shifts to novel host plants can have dramatic consequences for a wide range of traits in plant-feeding insects. If the traits affected are mating signals, host shifts can provide a direct source of reproductive isolation. Mating signal evolution will be affected when changes in host use, either by use of a different plant species or plant part, lead to communication in a different signal environment. The sensory drive hypothesis predicts that signals should adapt to transmit efficiently in their local environment. Signal divergence, therefore, can occur where closely related insect species occur on host plants with different signal transmission properties. These predictions were tested in two closely related species in the Enchenopa binotata species complex (Hemiptera: Membracidae), host-specific plant-feeding insects that communicate using plant-borne vibrations. Their mating signals are relatively pure tones that vary among species in frequency (pitch), the most important signal trait for mate recognition. As predicted by sensory drive, it is shown that two closely related E. binotata species have evolved signals that transmit most efficiently in their contrasting communication environments. Changes in host use thus favor divergence of the signal trait most important for behavioral isolation. [Work supported by NSF.]