Plant–insect interaction patterns in the late Neogene palaeoforest of Chotanagpur Plateau, eastern India

Abstract

Plants and insects are essential components of terrestrial ecosystems and insect herbivory is the most important type of biotic interaction in these ecosystems alongside the role of insects as pollinators. Insect damaged fossil leaves are the only direct sources documenting the historical effect of folivorous arthropods on once living foliar tissue. The present study focuses on the patterns of plant–insect association for the Pliocene locality of the Chotanagpur Plateau, Jharkhand, eastern India. Out of 1500 fossil angiosperm leaves that were studied, 1080 leaves (72%) were damaged. About 37 damage types (DTs) representing six functional feeding groups (FFGs) were identified, i.e., galling (50.74%), margin feeding (23.24%), hole feeding (17.04%), skeletonization (1.94%), mining (2.22%), surface feeding (3.33%) and others (1.49%). Galling is the prevalent form of damage here. The host plant taxa bearing the damage types belonged to Fabaceae, Malvaceae, Anacardiaceae, Moraceae, Rhamnaceae, Rubiaceae, Myrtaceae, etc.. On the basis of comparison with extant taxa, possible culprits could have belonged to the insect orders Orthoptera, Coleoptera, Lepidoptera, Diptera, Hemiptera, and Hymenoptera. The evidence of numerous body fossils of Lepidoptera (caterpillar), Diptera (gall midge), and Hemiptera from our studied sedimentary section provides direct clues to the plant–insect interactions. It seems the tropical, predominantly humid, Pliocene climate favored large-scale herbivory in the palaeoforest of Jharkhand, eastern India.