Unexpected richness and distinct patterns of Morchella (Ascomycota) species diversity in Chongqing, a notable "Furnace City": unveiling rich diversity in hot regions.

Morchella species, commonly known as true morels and being cold-preferring fungi, are esteemed for their distinctive flavor as well as significant economic and prominent research value. Chongqing, located in southwestern China and renowned as the "Furnace City" due to its distinctive climate and extremely high summer temperatures, spans an area of 82,400 square kilometers with complex geographical topography, yet has lacked a comprehensive survey of true morels (Morchella) so far. From 2017 to 2024, we conducted extensive field surveys across 13 districts and counties within Chongqing, resulting in the collection of over 1,000 wild morel samples. Through a combination of multi-gene phylogenetic analysis and microscopic morphological observations, we uncovered a surprisingly high level of species richness of Morchella in Chongqing, identifying 13 species in the Esculenta clade (yellow morels) and three species in the Elata clade (black morels), including six newly described species: Morchellachinensis sp. nov., M.diversa sp. nov., M.eoa sp. nov., M.huoguo sp. nov., M.montana sp. nov., and M.universitatis sp. nov. Notably, M.nipponensis, previously documented only in Japan, is reported for the first time in China. Furthermore, significant divergence in species diversity between the Esculenta and Elata clades of Morchella has been observed in Chongqing, which is strongly influenced and shaped by the prevailing vegetation. The distribution pattern of Morchella species suggests that the impact of high summer temperatures on species diversity in Chongqing is partially mitigated by locally diverse mountainous habitats. In addition, the habitats of M.diversa and M.universitatis, the two most widely distributed species in Chongqing, exhibit higher vegetation diversity, suggesting that Morchella species with greater habitat adaptability tend to have broader geographic ranges. This study provides valuable insights into the species diversity and distribution pattern of Morchella, particularly in a region with unique climatic and ecological conditions, and highlights the need for further study into the correlation between vegetation and Morchella species.