Mycorrhizal Fungal Diversity and Community Composition in Two Closely Related Platanthera (Orchidaceae) Species

Abstract

While it is generally acknowledged that orchid species rely on mycorrhizal fungi for completion of their life cycle, little is yet known about how mycorrhizal fungal diversity and community composition vary within and between closely related orchid taxa. In this study, we used 454 amplicon pyrosequencing to investigate variation in mycorrhizal communities between pure (allopatric) and mixed (sympatric) populations of two closely related Platanthera species (Platanthera bifolia and P. chlorantha) and putative hybrids. Consistent with previous research, the two species primarily associated primarily with members of the Ceratobasidiaceae and, to a lesser extent, with members of the Sebacinales and Tulasnellaceae. In addition, a large number of ectomycorrhizal fungi belonging to various families were observed. Although a considerable number of mycorrhizal fungi were common to both species, the fungal communities were significantly different between the two species. Individuals with intermediate morphology showed communities similar to P. bifolia, confirming previous results based on the genetic architecture and fragrance composition that putative hybrids essentially belonged to one of the parental species (P. bifolia). Differences in mycorrhizal communities between species were smaller in mixed populations than between pure populations, suggesting that variation in mycorrhizal communities was largely controlled by local environmental conditions. The small differences in mycorrhizal communities in mixed populations suggests that mycorrhizal fungi are most likely not directly involved in maintaining species boundaries between the two Platanthera species. However, seed germination experiments are needed to unambiguously assess the contribution of mycorrhizal divergence to reproductive isolation.

Stable isotope signatures of underground seedlings reveal the organic matter gained by adult orchids from mycorrhizal fungi

“…Roots of Platanthera bifolia were colonised by the Ceratobasidiaceae Thanatephorus fusisporus as in Esposito et al. (), and the germination mycobionts of P. bifolia overlapped with Thanatephorus but also hosted Ceratobasidiaceae and Tulasnellaceae.…”

“…Seven orchid species known to be associated with rhizoctonia fungi as adults (Bidartondo et al., ; Esposito, Jacquemyn, Waud, & Tyteca, ; Jacquemyn, Brys, Cammue, Honnay, & Lievens, ; Jacquemyn et al., ; Oja, Kohout, Tedersoo, Kull, & Kõljalg, ; Stark, Babik, & Durka, ; Těšitelová et al., ) were chosen for the in situ seed sowing experiment and sampled together with autotrophic references at four sites in North‐East Bavaria for stable isotope natural abundance analysis (Table ): Dactylorhiza majalis (Rchb.) P.F.Hunt & Summerh.…”

Noctuid moths as potential hybridization agents for Platanthera orchids

“…Within the framework of our research devoted to Platanthera in Belgium (Esposito, Jacquemyn, Waud & Tyteca 2016), we here focus on the observation of moth visitors of two Platanthera species, namely P. bifolia (L.) Rich. and P. chlorantha (Custer) Rchb.…”

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“…388 Population clustering showed a consistent pattern indicating two independent genetic clusters: P. bifolia 498 Bateman et al 2014), in a previous study (Esposito et al 2016), we showed that in our studied sympatric 499 populations, mycorrhizal fungi were most likely not directly involved in maintaining species boundaries.…”