New discovery of rare insect damage in the Pliocene of India reinforces the biogeographic history of Eurasian ecosystems

Abstract

Plant–insect interactions in the fossil record are, as yet, sparsely known and understudied. Here, we document evidence of a new type of insect skeletonization on Abroma augustum (L.) L. f. (Malvaceae) leaf remains from the latest Neogene (Pliocene) sediments of Chotanagpur plateau, Jharkhand, eastern India. This unique skeletonization feeding trace attributable to herbivorous insects occurs all over the surfaces of our recovered Pliocene leaf remains. In the skeletonized area, the interveinal tissues are completely removed leaving behind only the tough leaf veins. This type of insect feeding behaviour is documented for the first time on Indian Cenozoic leaf remains. Based on published data, as well as our survey of modern forests adjacent to the fossil locality, we suggest that probable damage inducers of this skeletonization on Abroma Jacq. fossil leaves might be Chrysomelid (Coleopteran) beetles. This finding also reveals that specific insect feeding damage, such as the one presented here, can reveal similarity of environments despite the difference of plant species observed. Such results strengthen the importance of using plant–insect interactions on leaves as a complementary proxy to others revealing paleoenvironmental conditions.