Quantifying Potentially Suitable Geographical Habitat Changes in Chinese Caterpillar Fungus with Enhanced MaxEnt Model

Chinese Caterpillar Fungus (CCF) is a fungal–insect complex formed by the underground larvae of certain species in the family Hepialidae parasitized by Ophiocordyceps sinensis (Berk.) (G.H.Sung, J.M.Sung, Hywel-Jones & Spatafora). It is a precious Chinese herbal medicine with significant medicinal value. This study aimed to identify the key environmental factors influencing the distribution of CCFs using the MaxEnt model. First, in the MaxEnt model optimized using the ENMeval package, the most suitable combinations of feature classes and regularization parameters were selected. Second, 22 environmental variables were used to construct distribution models for O. sinensis, host insects, and CCFs. Then, the distribution areas of O. sinensis and host insects were overlapped to identify highly suitable habitats where both coexist. Finally, these highly suitable habitats were compared to analyze the differences in the distribution areas of O. sinensis and host insects and their contributions to the formation of the CCF distribution area. The results showed that elevation, bio18, and bio09 were the primary environmental factors influencing the distributions of O. sinensis, host insects, and CCFs. Considering the present, 2050s, and 2070s, the highly suitable areas for all three entities overlapped to a large extent. When we superimposed the high-suitability zones of O. sinensis and host insects, the overlapping area was found to be 56.87 × 104 km2, which accounted for 5.92% of China’s total land area. The high-suitability area for CCFs was 64.06 × 104 km2, accounting for 6.67% of China’s total land area. The findings of this study provide valuable insights into the mechanisms behind the combination of O. sinensis and host insects in forming CCFs.