Plant-insect interaction from the Middle Jurassic Haifanggou Formaton in Huludao, western Liaoning and its geological implications

Abstract

Abstract Numerous well-preserved fossil plants have been discovered from the Middle Jurassic Haifanggou Formation in Baimashi Village, Lianshan District, Huludao, Liaoning. To gain insights into the plant-insect interaction during the Middle Jurassic in western Liaoning, this paper aimed to identify and quantitatively analyze evidence of insect damage on fossil plant leaves from the Haifanggou Formation based on the previous systematic research. Seven insect damage types (DTs) assigned to three functional feeding groups (FFGs) were identified. Margin feeding was the most prevalent FFG, followed by hole feeding and surface feeding. It suggests that Orthoptera and Hymenoptera with chewing mouthparts were dominant during the Middle Jurassic in this area, with Hemiptera and Coleoptera also playing a significant role. The primary plant taxa targeted by insects was Ginkgophytes, followed by Pteridophytes, Cycadophytes and Czekanowskiales, while Cycadophytes exhibited the highest average percentage of damaged leaf perimeter and area. This could be attributed to the physical insect resistance mechanism of conifers, as well as the chemical defense capabilities of Pteridophytes and Ginkgophytes during the Middle Jurassic. Approximately 17.54% of the observed fossil plants showed traces of insect damage, indicating the active presence of insects in the area and a close relationship between plants and insects during the Middle Jurassic. Considering the climate-indicative insect damage types and the flora composition, it can be inferred that the climate in the Middle Jurassic northwestern Huludao was warm and humid, potentially accompanied by intermittent droughts.