Herbivory, pollination and mimicry during the preangiospermous Mesozoic

The preangiospermous part of the Mesozoic Era was a time when the terrestrial realm became modern, particularly for associations between insects and plants. After the ecological readjustments following the end-Permian crisis 252 million years (m.y.) ago, a spectacular diversification of insect herbivores on a multitude of vascular plant lineages began in Gondwana during the Late Triassic, around 225 m.y. ago. Signaling this modernization of associational diversity was the appearance of extensive external foliage feeding, piercing-and-sucking, leaf mining, galling, seed predation, wood boring, ovipositional damage and other feeding interactions that are abundantly recorded from the varied habitats in deposits of the Molteno Formation, South Africa. In contrast to herbivory, evidence for pollination is sparse during the Late Triassic, but a variety of mutualism modes is evident during the late Middle Jurassic (165 m.y. ago) to the mid Early Cretaceous (125 m.y. ago) of Eurasia, particularly from lake deposits in China. A variety of evidence indicates that at least ten major lineages of long-proboscid insects were present throughout this interval: brachyceran flies, aneuretopsychine scorpionflies, kalligrammatid lacewings, and possibly the earliest glossate moths. Plant hosts for these pollinators included a variety of ginkgophytes, cheirolepidiaceous conifers, seedferns, bennettitaleans, and gnetaleans which bore various tubular structures often accompanied by fluid rewards to effect insect mediated transfer of pollen. As well, evidence for mandibulate insects, including plant damage patterns, indicate that bennettitaleans and cycads were accessed by a different pollination strategy. Also documented from eastern Eurasian biotas is herbivory that indicate insect herbivore targeting of particular seed plant clades, particularly bennettitaleans and seedferns. These deposits also harbor evidence for advanced mimicry involving, for example, scorpionflies and co-occurring ginkgoalean leaves. While it was angiosperms and more derived lineages of mostly holometabolous insects that structured the biota during the past 125 million years, nevertheless it was the 100 m.y. period from 225 to 125 m.y. ago that the plant-insect associational world became modernized. The difference was that this earlier interval involved ferns and gymnospermous seed plants and mostly insect lineages ancestral to modern holometabolous clades.