The Two Marked Treehopper species complex, Genus Enchenopa is a complex of approximately 8 species of Treehoppers (Membracidae). Enchenopa colonize several species of trees that differ in host plant chemistry, physiology and structure. Each host tree species has a species of Enchenopa that is similar in appearance to other species with only slight differences in morphological characters. The Enchenopa species have greater differences in physiology, biochemistry and genetics.
Enchenopa is an example of speciation driven by adaptation to host plants. At one time, all Enchenopa were a single species. As they expanded their range from their original host plant, to new hosts, their physical characters were well adapted but their physiology and biochemistry were not. Those Enchenopa populations on walnut evolved behavioral, physiological and biochemical adaptations to walnut. Those Enchenopa populations on redbud evolved behavioral, physiological and biochemical adaptations to redbud. Adaptations for walnut are not suited for redbud and vice-versa.
The host plant is selected by the female and the female possesses behaviors that lead to laying eggs on a suitable host plant. The immature has limited mobility and is confined to the plant where it hatched. Thus, Enchenopa on redbud develop independently of Enchenopa on walnut. Other behaviors reinforce mating such that redbud males only mate with redbud females and not females from other plants. Over time, these populations acquired enough unique adaptations that they have become separate species.