Fossils reveal plant-insect interactions across the Triassic-Jurassic boundary in southern China

A recent study of fossil plants reveals plant-insect interactions across the Triassic-Jurassic boundary in the Sichuan Basin of southern China. This study was carried out by an international research team led by Professor Wang Yongdong from the Nanjing Institute of Geology and Paleontology of the Chinese Academy of Sciences (NIGPAS), in collaboration with Professor Stephen McLoughlin from the Swedish Museum of ‘natural History.

The study is published in Frontiers of ecology and evolution.

Plants and insects are the most diverse and ecologically important organisms in the terrestrial biosphere. Their interactions are also among the richest biotic relationships, providing important insights into the evolving complexity of terrestrial ecosystems across the geological record.

Fossil plants from the Upper Rhaetian Xujiahe Formation and early floral assemblages from the Jurassic Zhenzhuchong Formation provide the first data on foliar herbivory generated by terrestrial arthropods across the Triassic-Jurassic transition in the eastern Tethyan region (East Asia).

“The types of damage caused by the two fossil assemblages studied are collectively classified into seven functional categories of feeding and oviposition (i.e. hole feeding, margin feeding, surface feeding, skeletonization, drilling and sucking, oviposition and galls),” Xu Yuanyuan said. of the research team.

Most feeding strategies are widespread among major plant groups and persist across the Triassic-Jurassic boundary, with the exception of skeletonization (a category of external foliage feeding), which was restricted to the Late Triassic to within dipteridaceous ferns.

The researchers revealed that the respective frequency and diversity of plant-insect interactions before and after the end-Triassic mass extinction are almost the same, despite a substantial turnover of floral components. This suggests that insect herbivores were largely able to shift to alternative (but commonly related) plant groups during the dramatic floristic shift and environmental changes of the Late Triassic.

Sporadic occurrences of leaf modifications, such as marginal cusps on the pinnules of Pterophyllum and prominent ridges on the rachis of some ferns and bennettites, are interpreted as defense adaptations against insect herbivores.

“Some differences in taxonomic composition and herbivore representation between the later Triassic flora Xujiahe and the early Jurassic flora Zhenzhuchong are more likely to be related to collection and preservation biases rather than paleoecological changes,” Xu said.

This preliminary assessment of herbivory across the Triassic-Jurassic boundary calls for further studies in the Sichuan Basin of southern China to verify regional patterns of vegetation and herbivore changes in subtropical Asia. the East, and to encourage equivalent studies in other parts of the world. world to clarify global patterns of plant-insect interactions and floristic changes during this major event in Earth’s history.