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Habitat-driven variation in mycorrhizal communities in the terrestrial orchid genus Dactylorhiza

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ABSTRACT

Orchid species are critically dependent on mycorrhizal fungi for completion of their life cycle, particularly during the early stages of their development when nutritional resources are scarce. As such, orchid mycorrhizal fungi play an important role in the population dynamics, abundance, and spatial distribution of orchid species. However, less is known about the ecology and distribution of orchid mycorrhizal fungi. In this study, we used 454 amplicon pyrosequencing to investigate ecological and geographic variation in mycorrhizal associations in fourteen species of the orchid genus Dactylorhiza. More specifically, we tested the hypothesis that variation in orchid mycorrhizal communities resulted primarily from differences in habitat conditions where the species were growing. The results showed that all investigated Dactylorhiza species associated with a large number of fungal OTUs, the majority belonging to the Tulasnellaceae, Ceratobasidiaceae and Sebacinales. Mycorrhizal specificity was low, but significant variation in mycorrhizal community composition was observed between species inhabiting different ecological habitats. Although several fungi had a broad geographic distribution, Species Indicator Analysis revealed some fungi that were characteristic for specific habitats. Overall, these results indicate that orchid mycorrhizal fungi may have a broad geographic distribution, but that their occurrence is bounded by specific habitat conditions.

No MeSH data available.


Diversity of putative orchid mycorrhizal fungi detected in the roots of fourteen Dactylorhiza species sampled in 35 populations across Europe.(a) The number of OTUs belonging to different orchid families/genera. (b) Pie chart displaying the frequency distribution of sequences belonging to the different families/genera.
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f1: Diversity of putative orchid mycorrhizal fungi detected in the roots of fourteen Dactylorhiza species sampled in 35 populations across Europe.(a) The number of OTUs belonging to different orchid families/genera. (b) Pie chart displaying the frequency distribution of sequences belonging to the different families/genera.

Mentions: After exclusion of global singletons and doubletons, a total of 522 OTUs (94511 sequences) were retrieved, of which 115 (65754 sequences – 68.3% of all sequences) were considered as putative species of orchid mycorrhizal fungi (Table S1). Most orchid mycorrhizal fungi were related to members of the Tulasnellaceae (30 OTUs – 38402 sequences), Ceratobasidiaceae (33 OTUs – 18408 sequences) and Sebacinales (32 OTUs – 7835 sequences) (Fig. 1a,b). Besides a large number of ectomycorrhizal fungi related to Thelephora/Tomentella (19 OTUs) was also found, but the number of sequences (1106 sequences – 1.16% of the total number of sequences) was much lower (Fig. 2a,b). Additionally, some members of the fungal genera Armillaria (1 OTU), Atractiella (1 OTU), Clavulina (6 OTUs), Coprinus (2 OTUs), Cortinarius (2 OTUs) Inocybe (7 OTUs), Marasmius (1 OTU), Mycena (6 OTUs), and Psathyrella (2 OTUs) were sporadically observed (Fig. 1a), but in all cases the number of sequences was low (Fig. 1b). Because the mycorrhizal status of these fungi is doubtful, they were not considered in all subsequent analyses.


Habitat-driven variation in mycorrhizal communities in the terrestrial orchid genus Dactylorhiza
Diversity of putative orchid mycorrhizal fungi detected in the roots of fourteen Dactylorhiza species sampled in 35 populations across Europe.(a) The number of OTUs belonging to different orchid families/genera. (b) Pie chart displaying the frequency distribution of sequences belonging to the different families/genera.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5121631&req=5

f1: Diversity of putative orchid mycorrhizal fungi detected in the roots of fourteen Dactylorhiza species sampled in 35 populations across Europe.(a) The number of OTUs belonging to different orchid families/genera. (b) Pie chart displaying the frequency distribution of sequences belonging to the different families/genera.
Mentions: After exclusion of global singletons and doubletons, a total of 522 OTUs (94511 sequences) were retrieved, of which 115 (65754 sequences – 68.3% of all sequences) were considered as putative species of orchid mycorrhizal fungi (Table S1). Most orchid mycorrhizal fungi were related to members of the Tulasnellaceae (30 OTUs – 38402 sequences), Ceratobasidiaceae (33 OTUs – 18408 sequences) and Sebacinales (32 OTUs – 7835 sequences) (Fig. 1a,b). Besides a large number of ectomycorrhizal fungi related to Thelephora/Tomentella (19 OTUs) was also found, but the number of sequences (1106 sequences – 1.16% of the total number of sequences) was much lower (Fig. 2a,b). Additionally, some members of the fungal genera Armillaria (1 OTU), Atractiella (1 OTU), Clavulina (6 OTUs), Coprinus (2 OTUs), Cortinarius (2 OTUs) Inocybe (7 OTUs), Marasmius (1 OTU), Mycena (6 OTUs), and Psathyrella (2 OTUs) were sporadically observed (Fig. 1a), but in all cases the number of sequences was low (Fig. 1b). Because the mycorrhizal status of these fungi is doubtful, they were not considered in all subsequent analyses.

View Article: PubMed Central - PubMed

ABSTRACT

Orchid species are critically dependent on mycorrhizal fungi for completion of their life cycle, particularly during the early stages of their development when nutritional resources are scarce. As such, orchid mycorrhizal fungi play an important role in the population dynamics, abundance, and spatial distribution of orchid species. However, less is known about the ecology and distribution of orchid mycorrhizal fungi. In this study, we used 454 amplicon pyrosequencing to investigate ecological and geographic variation in mycorrhizal associations in fourteen species of the orchid genus Dactylorhiza. More specifically, we tested the hypothesis that variation in orchid mycorrhizal communities resulted primarily from differences in habitat conditions where the species were growing. The results showed that all investigated Dactylorhiza species associated with a large number of fungal OTUs, the majority belonging to the Tulasnellaceae, Ceratobasidiaceae and Sebacinales. Mycorrhizal specificity was low, but significant variation in mycorrhizal community composition was observed between species inhabiting different ecological habitats. Although several fungi had a broad geographic distribution, Species Indicator Analysis revealed some fungi that were characteristic for specific habitats. Overall, these results indicate that orchid mycorrhizal fungi may have a broad geographic distribution, but that their occurrence is bounded by specific habitat conditions.

No MeSH data available.