Print PageWe sought to determine whether host-associated differentiation (HAD) is prevalent among populations of corn leafhopper (Dalbulus maidis) occurring on three of its host plants in central Mexico: perennial teosinte (Zea diploperennis), Balsas teosinte (Zea mays ssp. parviglumis), and maize (Z. mays ssp. mays). Corn leafhopper is a specialist herbivore on the maize genus Zea, and both Dalbulus and Zea evolved in central Mexico. We used amplified fragment length polymorphisms (AFLPs) to assess HAD by measuring gene flow among corn leafhoppers on the three host plants in central and northwestern Mexico.
Results/Conclusions
Our results showed that corn leafhopper in Mexico is composed of at least two reproductively discrete populations: An “itinerant” population associated with maize and Balsas teosinte, and widely distributed in Mexico, and a “Las Joyas” population restricted to perennial teosinte, and confined to a small mountain range (Sierra de Manantlán) in central Mexico. Our results further showed that the genetic distinctiveness of the two corn leafhopper populations is not due to geographic spread or barriers: Las Joyas population corn leafhoppers are genetically distinct despite their geographical proximity (~5Km) to itinerant corn leafhoppers, while itinerant corn leafhoppers are genetically uniform even when sampled at locations separated by hundreds of kilometers (>800Km), mountain ranges, and a maritime corridor (Gulf of Cortez). On the basis of our results we proposed prehistoric and modern scenarios, including likely ecological and anthropogenic influences, in which the observed patterns of gene flow among corn leafhoppers on the three host plants could have originated and could be maintained. Also, we hypothesized that after evolving on wild, annual species of Zea in central Mexico, corn leafhopper expanded its host range to include perennial teosinte, and that this expansion was facilitated by maize cultivation by native inhabitants within the last ~9,000 years.
