Physical leaf defenses - altered by Zea life-history evolution, domestication, and breeding - mediate oviposition preference of a specialist leafhopper

Plant anti-herbivore defenses are known to be affected by life-history evolution, as well as by domestication and breeding in the case of crop species. A suite of plants from the maize genus Zea (Poaceae) and the specialist herbivore Dalbulus maidis (DeLong & Wolcott) (Hemiptera: Cicadellidae) were used to test the hypothesis that anti-herbivore defenses are affected by plant life-history evolution and human intervention through domestication and breeding for high yield. The suite of plants included a maize (Zea mays ssp. mays L.) commercial hybrid, a maize landrace, two populations of the annual Balsas teosinte (Z.mays ssp. parviglumis Iltis & Doebley), and perennial teosinte (Z.diploperennis Iltis, Doebley & Guzman). Leaf toughness, pubescence, and oviposition preference were compared among the suite of host plants looking for effects of transitions in life history (i.e., from perennial to annual life cycle), domestication (i.e., from wild annual to domesticated annual), and breeding (i.e., from landrace to hybrid maize) on defense against D.maidis. Results on leaf toughness suggested that the life-history and domestication transitions weakened the plant's resistance to penetration by the mouthparts and ovipositor of D.maidis, whereas results on pubescence suggested that this putative defense was strengthened with the breeding transition, contrary to expectations. Results on oviposition preference of D.maidis coincided with the expectation that life-history and domestication transitions would lead to preference for Balsas teosinte over perennial teosinte, and of landrace maize over Balsas teosinte. Also, a negative correlation suggested that oviposition preference is significantly influenced by leaf toughness. Overall, the results suggested that Zea defenses against the specialist herbivore D.maidis were variably affected by plant life-history evolution, domestication, and breeding, and that chemical defense may play a role in Zea defense against D.maidis because leaf toughness and pubescence only partially explained its host preferences.