Plant families that are characterized by their symbioses are useful models to test hypotheses related to temporal and spatial variation in symbiotic associations. This study assessed mycorrhizal diversity from multiple sites to compare mycorrhizal communities within the roots of a rare orchid across its natural distribution within the North American tallgrass prairie. Fungal diversity was assessed by utilizing nuclear ribosomal internal transcribed spacer (nrITS) barcoding in two consecutive years by sampling plant roots at 11 sites in 2013 and 2014. Prairie management treatments that are generally applied to the study sites were taken into account, in addition to edaphic characteristics, to explain the variation in mycorrhizal communities of Platanthera praeclara Sheviak and Bowles over space and time.
Results/Conclusions
Across two years, 306 sequences yielded 39 Operational Taxonomic Units (OTUs) from two fungal families, Ceratobasidiaceae and Tulasnellaceae, in roots of P. praeclara. Ceratobasidiaceae was the dominant fungal family at majority of the sampled sites and was represented by 77% of the nrITS sequences. Short pairwise sequence distances (π = 0.039 ± 0.03, n=238) among the sequences of Ceratobasidiaceae and phylogenetic clustering of the OTUs suggested that P. praeclara forms specific associations toward fungi from Ceratobasidiaceae. Fungi from the fungal family Tulasnellaceae (π = 0.135 ± 0.06, n=69) represented a broader phylogenetic breadth, with the orchid being less specific in its associations with the OTUs from this family. Despite the overall specificity, fungal communities in roots tended to vary (p<0.05) among majority of the sites. Further, mycorrhizal fungal community composition changed from one year to the next. Clustering of sites with similar land management treatments was not observed, and nonmetric multidimensional scaling did not segregate sites by land management. However, fungal communities were more similar across the northern sites when compared to fungal communities associated with the species across the southern sites (p=0.03). Correlations between the observed fungal communities and edaphic characteristics were not evident.