Orchid diversity and distribution pattern in karst forests in eastern Yunnan Province, China

Global biodiversity loss and mass extinction of species have raised serious global concerns, especially in fragile ecosystems. Karst forest, a well-known fragile ecosystem, is served as a natural laboratory for biogeographical, ecological, evolutionary, and taxonomic research. However, species richness and distribution patterns in karst forests largely remain unclear. Orchidaceae has been regarded as the "flagship" group of plant diversity. In this study, we use Wanfengshan Nature Reserve in southeast Yunnan, China, as a model to determine the conservation status of orchids in the karst forest by conducting systematic field surveys in the past three years from 2019 to 2022. In total, we identified 78 orchid species in 35 genera in Wanfengshan Nature Reserve. The dominant species were Bulbophyllum andersonii, Eria coronaria, Nervilia mackinnonii and Paphiopedilum micranthum. Multiple life forms were also observed, including epiphyte (14.29%), facultative epiphyte (18.18%), lithophyte (23.38%), and terrestrial (44.15%). Orchid species richness showed a bimodal pattern varied with altitude, the higher richness was recorded at 1,500–1,600 and 1,200–1,300 ​m, while the minimum was below 1,100 ​m. Each independent hill is rich in orchid species including 'endemic' species. A total of 25 (33.8%) orchid species were considered threatened by the Redlist of Chinese Vascular Plants (Qin et al., 2017), including 3 CR species, 5 ​EN species and 17 VU species. We call for more research addressing the mechanisms of ecological adaption, mycorrhizal interactions, and pollination of orchids in karst forests, and effective ways for recovery and conservation of orchids.