Further evidence of Ceratobasidium D.P. Rogers (Basidiomycota) serving as the ubiquitous fungal associate of Platanthera leucophaea (Orchidaceae) in the North American tallgrass prairie

Hana L Thixton,Elizabeth J Esselman,Laura L Corey,Lawrence W Zettler

doi:10.1186/s40529-020-00289-z

Abstract

BackgroundIn the United States and Canada, ca. one-half of native orchid species are now threatened with extinction. A number of these species are restricted to tallgrass prairies of central North America, such as the Eastern Prairie Fringed Orchid, Platanthera leucophaea (Nutt.) Lindl.—a U.S. Federally threatened species.ResultsWe provide new records of fungi recovered from roots of P. leucophaea and five other orchid species inhabiting prairie sites in Illinois and neighboring states during a 10-year period (2008–2017). A total of 39 fungal endophytes were isolated from Cypripedium candidum (1), Platanthera lacera (1), P. leucophaea (32), P. peramoena (3), Spiranthes lacera (1), and S. magnicamporum (1), 31 (79%) of which were assignable to Ceratobasidium and the remainder to Tulasnella. These fungi were acquired from 16 different sites, 13 of which are new records including two new state records (Iowa, Wisconsin). Molecular analysis revealed that some Ceratobasidium strains were virtually identical despite being geographically isolated by > 300 km.ConclusionsThis study, encompassing a decade of work, confirms that Platanthera leucophaea is a mycorrhizal specialist with heavy reliance on Ceratobasidium with the tallgrass prairie ecosystem of North America. Our isolation of Ceratobasidium from P. leucophaea spanning additional sites suggests that the association is widespread. Such information should provide conservationists and land managers with more confidence in developing protocols that facilitate the long-term conservation of this prairie orchid.

Highlights

In the United States and Canada, ca. one-half of native orchid species are threatened with extinction
We provide new records of fungi recovered from P. leucophaea and five other orchid species inhabiting prairie sites in Illinois
During the 10-year period (2008–2017), a total of 39 new records of fungal endophytes were recovered from six native orchid species from tallgrass prairies in the United States in Illinois, Iowa, Michigan, and Wisconsin, mostly from roots of Platanthera leucophaea in Illinois where the species is most abundant (Table 1, Fig. 2)

Summary

Introduction

In the United States and Canada, ca. one-half of native orchid species are threatened with extinction. In the United States and Canada, about one-half of native orchid species are threatened with extinction (Krupnick et al 2013). A number of these species are restricted to tallgrass prairies of central North America (Bowles 1983) including the Eastern Prairie Fringed Orchid, Platanthera leucophaea (Nutt.) Lindl. 0.1% of original tallgrass prairie habitat remains (Samson and Knopf 1994; Leach and Givnish 1996), primarily in areas that were never tilled (e.g., cemeteries, railroad tracks), and occasionally in abandoned agricultural fields. These areas currently serve as ‘refugia’ for rare orchids and their associated biotic agents (e.g., pollinators, mycorrhizal fungi). Molecular methods (ITS amplification and sequencing) were used to confirm identification of select strains, and to detect genetic variation of Ceratobasidium strains within and between orchid populations

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