What a pest looks like: Morphological differentiation between wild and pestiferous corn leafhoppers, Dalbulus maidis

Corn leafhopper (Dalbulus maidis) is genetically differentiated across populations on its Zea hosts. Our recent studies showed genetic population structuring in corn leafhopper samples from Mexico, such that an isolated subpopulation occurs on perennial teosinte (Zea diploperennis) in upland, cloud forest habitat, while a widespread subpopulation occurs extensively on maize (Zea mays mays) and Balsas teosinte (Zea mays parviglumis). Balsas teosinte is the progenitor of maize, and presumably corn leafhopper’s ancestral host. Those studies suggested that the corn leafhopper subpopulation on perennial teosinte represents ancient genetic diversity, present when maize cultivation spread from its area of domestication in the lowlands, while the subpopulation on maize represents the narrow genetic diversity of corn leafhoppers adapted for exploitation and dominance of maize as a host plant: These two subpopulations thus represent “wild” and “pestiferous” corn leafhoppers, respectively. We present results of a large morphometrics study (involving >200 specimens from 7 field sites and one lab population; two host plants, and; 20 body and 24 wing measurements, and dry mass) showing clear morphological differentiation between the perennial teosinte and maize subpopulations of corn leafhopper. Our results are relevant to questions concerning the emergence of agricultural pests and their independent morphological evolution following domestication of crop plants.