Signals of host plant domestication in the morphological and genetic structuring of a specialist herbivore

Plant domestication is believed to lead to crops that are poorly defended against herbivores, compared to crop wild ancestors. If the difference in plant defense levels between crop wild ancestors and crops is sufficiently large, then populations of specialist herbivores may adapt to exploit the lesser-defended and increasingly abundant host represented by the crop plant. Moreover, the increased abundance of a plant following domestication may lead to an increased abundance of crop plant-adapted herbivores, and a decrease in their genetic variability. In contrast, isolated populations of crop wild ancestors may represent refugia where herbivores not adapted to crop plants may persist as small populations. Our studies have focused on Corn leafhopper (Dalbulus maidis) a specialist phloem-feeder on Zea, in the context of maize (Zea mays mays) domestication in western Mexico. Our molecular genetic (AFLP, mtDNA) and morphometric (body and wing shape) studies revealed overlapping population structuring in Corn leafhopper into discrete, “Wild” and “Pestiferous” populations. Overall, our results suggest that maize domestication is signaled in the marked genetic and morphological differentiation evident between Wild and Pestiferous Corn leafhoppers.