PATTERNS OF HERBIVORY FROM THE MIDDLE JURASSIC AND EARLY CRETACEOUS CHINA

Climate in China from the Middle Jurassic (ca. 160 mya) to Early Cretaceous (ca. 120 mya) shifted toward a warmer and more humid regime, accompanied by seasonally arid and semiarid microenvironments. This change occurred during an earlier phase of gymnosperm diversification, followed by early angiosperm expansion in concert with co-radiation of numerous insect lineages. Our study focuses on insect herbivory from these late Middle Jurassic and mid Early Cretaceous intervals, where we compare patterns of autecological associations between plants and phytophagous insects at multiple temporal and spatial scales. The first of two superlocalities is the late Middle Jurassic Jiulongshan Formation that forms the Daohugou Biota of Ningcheng County, Inner Mongolia. The second superlocality is the Yixian Formation of Early Cretaceous age, and includes two localities from the Jehol Biota, Liaoning, a locality from Ningcheng County, and another from Duolun County, both from Inner Mongolia. The host plants principally are Lycopodiales, Selaginellales, Equisetales, Filicales, Bennettiales, Cycadales, Ginkgoales, Gnetales, coniferophytes, and various pteridosperms. Damaged plants organs from these biotas were classified based on membership in a functional feeding group and assignment to a diagnosable damage type (DT), listed in the Guide to Insect (and other) Damage Types on Compressed Plant Fossils (Labandeira et al., 2007). We recorded foliar hole feeding, margin feeding, skeletonization, and surface feeding. Consumption of inner plant tissues was done by insects involved in galling, mining, oviposition, piercing-and-sucking and seed predation. Each censused plant organ was tabulated and scored for the presence or absence of particular insect DTs, and then statistically analyzed to reveal the diversity, frequency, abundances and host-species distributions of insect damage at specific intervals, localities, habitats and plant hosts. Preliminary results show that the Daohugou Biota has more plant species and associated herbivore DT diversity than the Jehol Biota. This contrast ultimately may reflect changing microclimate within the immediate region as well as the extinction of earlier plant and insect taxa during early angiosperm expansion.