Insect herbivory and plant defense on ginkgoalean and bennettitalean leaves of the Middle Jurassic Daohugou Flora from Northeast China and their paleoclimatic implications

Interactions between terrestrial arthropods and plants play a significant role in terrestrial ecosystems. Research on plant–insect interactions through geologic time provides valuable information for studying insect behavior and plant structure, understanding their coevolution, as well as analyzing climate change. In this paper, we choose fossil ginkgoalean and bennettitalean leaves as the plant hosts to study insect herbivory in the Middle Jurassic Daohugou area. Seven damage types of four functional feeding groups have been identified. Of the four functional feeding groups, margin feeding is the most common, indicating an abundance of insects with chewing mouthparts. Ginkgoalean leaves, probably because of their chemical defense, suffered less severe insect damage than bennettitalean leaves. Physical defense has also been observed in various genera of the bennettitalean leaves. Significantly, leaves of Anomozamites had a shaggy indumentum on the abaxial leaf surface and long stiff hairs along the rachis protecting them from insect herbivory. Our results indicate that the climate in the Middle Jurassic of the Daohugou area was relatively warm and humid. This work contributes to the study of plant–insect coevolution in the Daohugou Biota and provides more proxy data for understanding the Middle Jurassic paleoclimate and paleoenvironment in Daohugou area.