Fungal community characteristics of the last remaining habitat of three paphiopedilum species in China.

Paphiopedilum armeniacum, Paphiopedilum wenshanense and Paphiopedilum emersonii are critically endangered wild orchids. Their populations are under severe threat, with a dramatic decline in the number of their natural distribution sites. Ex situ conservation and artificial breeding are the keys to maintaining the population to ensure the success of ex situ conservation and field return in the future. The habitat characteristics and soil nutrient information of the last remaining wild distribution sites of the three species were studied. ITS high-throughput sequencing was used to reveal the composition and structure of the soil fungal community, analyze its diversity and functional characteristics, and reveal its relationship with soil nutrients. The three species preferred to grow on low-lying, ventilated and shaded declivities with good water drainage. There were significant differences in soil alkali-hydrolyzed nitrogen and available phosphorus among the three species. There were 336 fungal species detected in the samples. On average, there were different dominant groups in the soil fungal communities of the three species. The functional groups of soil fungi within their habitats were dominated by saprophytic fungi and ectomycorrhizae, with significant differences in diversity and structure. The co-occurrence network of habitat soil fungi was mainly positive. Soil pH significantly affected soil fungal diversity within their habitats of the three paphiopedilum species. The study confirmed that the dominant groups of soil fungi were significantly correlated with soil nutrients. The three species exhibit comparable habitat inclinations, yet they display substantial variations in the composition, structure, and diversity of soil fungi. The fungal functional group is characterized by a rich presence of saprophytic fungi, a proliferation of ectomycorrhizae, and a modest occurrence of orchid mycorrhizae. The symbiotic interactions among the soil fungi associated with these three species are well-coordinated, enhancing their resilience against challenging environmental conditions. There is a significant correlation between soil environmental factors and the composition of soil fungal communities, with pH emerging as a pivotal factor regulating fungal diversity. Our research into the habitat traits and soil fungal ecosystems of the three wild Paphiopedilum species has established a cornerstone for prospective ex situ conservation measures and the eventual reestablishment of these species in their native landscapes.