As the most diverse creatures on earth today, insects have prospered since the Carboniferous, and have become an important role in the terrestrial ecosystem in the Permian. At the end of the Permian, the largest biological extinction event in geological history occurred, leading to the collapse of terrestrial ecosystems. So far, the evolutionary process of insects during this period is quite controversial in the academic community, which has led to our poor knowledge of insect response mechanisms to the mass extinction.
Scientists have established a global beetle (Insecta: Coleoptera) fossil morphology database at the Big Data Center of the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences. On this basis, a variety of mathematical models are used to classify the diversity of beetles from the Early Permian to the Middle Triassic. , Morphological divergence, phylogeny and ecological habits were comprehensively analyzed, and the early evolution history of beetles was reconstructed. The study found that mass extinction events (especially deforestation) significantly affected the early evolution of beetles.
Studies have shown that with the radiation of the early and middle Permian beetle stem populations, their diversity and morphological divergence increased simultaneously. After the mass extinction event at the end of the Permian, the early Triassic beetle-eating stem populations were almost completely extinct, and their diversity and morphological divergence were significantly reduced. The gap in the fossil record of predatory beetles in the Early Triassic roughly coincides with the collapse of the forest ecosystem (ie, the coal-free period), indicating that the extinction of predatory beetles may be due to the disappearance of the habitat caused by deforestation. During the Middle Triassic, the beetle group recovered significantly, and new carnivorous beetle groups reappeared widely, which also coincided with the recovery time of the forest ecosystem.
In modern nature, insects play an important role in the terrestrial carbon cycle. Forests are the largest carbon storage in terrestrial ecosystems. Phytophagous insects decompose wood tissue to return the carbon fixed by photosynthesis to the atmosphere in the form of carbon dioxide. At present, the contribution rate of insects to the decomposition of forest dead wood is 29% on average. Even in a short period of time, the outbreak of herbivorous beetles is enough to transform the forest from a carbon sink to a carbon source.
The large radiation of paleozoic terrestrial plants was accompanied by huge carbon storage and oxygen release, which is considered to be the leading factor in the increase in atmospheric oxygen content during the same period. In the Permian, eating beetles became important wood decomposers. These beetles significantly increase the degradation rate of wood by interacting with microorganisms. Therefore, the radiation of the permian eater beetles may be a major driving force for the decline of atmospheric oxygen content in the Permian.
Today, human-induced global warming and deforestation events have led to a continuous decline in the diversity of forest insects, which is very similar to the extinction event at the end of the Permian. This research may help us better understand how insects will respond to global climate changes in the future.