Cryptostylis species (Orchidaceae) from a broad geographic and habitat range associate with a phylogenetically narrow lineage of Tulasnellaceae fungi

While many Australian terrestrial orchids have highly specialized mycorrhizal associations, we tested the hypothesis that the geographically widespread orchid genus Cryptostylis associates with a diversity of fungal species. Using fungal isolation and molecular approaches, we investigated the mycorrhizal as-sociations of five Australian Cryptostylis species (27 sites sampled) and included limited sampling from three Asiatic Cryptostylis species (two sites). Like related orchid genera, Tulasnellaceae formed the main fungal associations of the Cryptostylis species we sampled, although some ectomycorrhizal, ericoid and saprotrophic fungi were detected infrequently. Each species of Australian Cryptostylis associated with three to seven Tulasnella Operational Taxonomic Units (OTUs), except for C. hunteriana where only one Tulasnella OTU was detected. In total, eleven Tulasnella OTUs associated with Australian Cryptostylis. The Asiatic Cryptostylis associated with four different Tulasnella OTUs belonging to the same lineage as the Australian species. While five Tulasnella OTUs (T. australiensis, T. prima, T. warcupii, T. densa, and T. punctata) were used by multiple species of Australian Cryptostylis, the most commonly used OTU differed between orchid species. The association with different Tulasnella fungi by Cryptostylis species co-occurring at the same site suggests that in any given environmental condition, Cryptostylis species may intrinsically favour different fungal OTUs.(c) 2022 British Mycological Society. Published by Elsevier Ltd. All rights reserved.

Automated summary

While many Australian terrestrial orchids have specialized mycorrhizal associations, the Cryptostylis genus has been found to associate with a variety of fungal species. The main fungal associations for the sampled Cryptostylis species were Tulasnellaceae, with occasional detection of ectomycorrhizal, ericoid and saprotrophic fungi. Each Australian Cryptostylis species was associated with multiple Tulasnella OTUs, except for one species where only one Tulasnella OTU was detected. The Asiatic Cryptostylis species showed associations with Tulasnella OTUs belonging to the same lineage as the Australian species. Different Cryptostylis species at the same site were found to associate with different Tulasnella fungi, indicating a preference for specific fungal OTUs in different environmental conditions.