A new regime of herbivory from diverse plant–arthropod interactions from the Middle Jurassic of northeastern China

Abstract

Qualitative and quantitative evaluation of insect herbivory is important for understanding the complex and diverse plant–insect associations in terrestrial ecosystems during the mid Mesozoic. We examined 2503 plant specimens from the Mid-Jurassic (Callovian, 165 Ma) Jiulongshan Formation, a gymnosperm-dominant, fern subdominant plant assemblage at Daohugou, northeastern China, where 149 species/morphotypes from 11 plant groups were identified. Based on the functional feeding group–damage type (FFG-DT) system, we detected a richness of 11 FFGs and 78 DTs, frequency of 2329 DTs, 8045 feeding event occurrences, and herbivory index of 3.27 %. Major consumption occurred on broad-leaved of bennettitaleans, accounting for half of all herbivory indicated by multiple indices, and ginkgoaleans, less so for narrow-leaved of conifers. The top-four feeding groups were margin feeding, piercing and sucking, oviposition, and galling; all groups displayed a pattern of narrow DT functional-breadth (22.22 %) and twofold increase of broad DT functional-breadth (48.15 %). Physical plant defenses were found on the most herbivorized plant host implying trade-offs between host physiology and insect herbivory. Compared with other gymnosperm-dominated assemblages, the elevated richness and intensity of Daohugou herbivory indicates a new regime of resource consumption that occurred by late Middle Jurassic time associated with predator and especially parasitoid diversification.