97-MILLION YEARS OF ANGIOSPERM-INSECT ASSOCIATION - PALEOBIOLOGICAL INSIGHTS INTO THE MEANING OF COEVOLUTION

From well preserved leaf damage of the mid-Cretaceous Dakota Flora (97 million years ago), three distinctive, insect-mediated feeding traces have been identified and assigned to two extant genera and one subfam ily. These taxa are the leaf miners Stigmella and Ectoedemia of the Ne pticulidae and Phyllocnistinae of the Gracillariidae. These fossils in dicate that within 25 million years of early angiosperm radiation, the organs of woody dicots already were exploited in intricate and modern ways by insect herbivores, For Ectoedemia and its platanoid host, we document 97 million years of continuity for a plant-insect interaction . The early occurrence during the mid-Cretaceous of diverse and extens ive herbivory on woody angiosperms may be associated with the innovati on of deciduousness, in which a broadleafed angiosperm provided an eff icient, but disposable, photosynthetic organ that withstood the increa sed cost of additional insect herbivory. Moreover, the group represent ed in this study, the leaf-mining Lepidoptera, exhibits a wide range o f subordinal taxonomic differentiation and includes the Gracillariidae , a member of the most derived lepidopteran suborder, the Ditrysia. Di trysian presence during the mid-Cretaceous, in addition to lepidoptera n body-fossil evidence from Early Cretaceous and Late Jurassic deposit s, suggests that the radiation of major lepidopteran lineages probably occurred during the Late Jurassic on a gymnosperm-dominated flora.