Leafless epiphytic orchids share Ceratobasidiaceae mycorrhizal fungi

Some epiphytic orchids in the tribe Vandeae are characterized by extremely vestigial leaves (even leafless). Thus, their leaves provide only a small proportion of carbon required for their growth and development, while a large portion of carbon may need to be supplied by their roots and mycorrhizal fungi (MF). The MF richness and composition of leafless epiphytic orchids, which belong to numerous genera with diverse ecophysiologies and wide geographical ranges, remain poorly understood. In this study, we identified the MF communities of seven leafless epiphytic species from three orchid genera from up to 17 sites in China using high-throughput sequencing. Our analyses revealed that the leafless epiphytic orchids have a highly specialized association with Ceratobasidiaceae. Several fungal OTUs were found in three different orchid genera and have promoted germinations of Chiloschista and Phalaenopsis, which may have been caused by convergent evolution of leafless epiphytic orchids. Furthermore, the MF composition of Taeniophyllum glandulosum was significantly affected by collection site and host tree. Our study provides new insights into mycorrhizal associations of epiphytic orchids.

Automated summary

Some epiphytic orchids in the tribe Vandeae have extremely vestigial leaves or are even leafless, requiring a large portion of carbon from their roots and mycorrhizal fungi. This study identified highly specialized associations with Ceratobasidiaceae in leafless epiphytic orchids, as well as fungal OTUs promoting germinations in different orchid genera. The mycorrhizal composition of certain orchid species is significantly influenced by collection site and host tree, providing new insights into mycorrhizal associations in epiphytic orchids.