Abundance and distribution of Corallorhiza odontorhiza reflect variations in climate and ectomycorrhizae

Abstract

The abundance and reproductive activity of orchids have been linked to variations in weather conditions, but few investigators have examined the relationships between orchid flowering dynamics and the distribution and abundance of mycorrhizal fungi. We quantified the abundance of flowering individuals of Corallorhiza odontorhiza, a mycoheterotrophic orchid, over a 14-year period and mapped the distribution of individuals in six of the 14 years. For two seasons, we conducted intensive and extensive studies of the mycorrhizal fungi that were associated with C. odontorhiza. The annual abundance of flowering plants was statistically related to growing-season precipitation and winter temperature, and the distribution of individuals within the study plot was related to the abundance and distribution of appropriate host fungi. We used DNA sequencing to identify ectomycorrhizal root tips that hosted Tomentella fungi that could potentially support C. odontorhiza. We found that Tomentella spp. were distributed throughout the study plot and on all ectomycorrhizal tree species, including in areas that have historically supported few or no orchids. However, there were fewer ectomycorrhizal trees, total ectomycorrhizal root tips, and root tips hosting Tomentella spp. in areas with few or no orchids compared to areas with abundant orchids. Furthermore, one Tomentella taxon dominated in C. odontorhiza rhizomes but was never found except immediately adjacent to C. odontorhiza plants. This suggests that abundance of flowering C. odontorhiza reflects both the presence of ''preferred'' taxa and abundance of appropriate host fungi associated with ectomycorrhizal roots. Results of this research provide the first indication that the relationship between plants and mycorrhizal fungi may be influenced by both the relative abundance of fungi that are sufficient to support orchid growth and by the presence of particular fungal types that are especially good at supporting orchid growth.

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

“…These fungi have previously been shown to associate with orchids that typically occur in forests. For example, the major fungi associating with the mycoheterotrophic Corallorhiza odonthorhiza were Tomentella fungi34. In the forest orchids Cephalanthera damasonium and C. longifolia several members of the Thelephoraceae, including Tomentella and Pseudotomentella , were found in germinating seeds35 (Bidartondo & Read 2008).…”

The Effects of Above- and Belowground Mutualisms on Orchid Speciation and Coexistence

“…The fungi within each clade were grouped further into operational taxonomic units (OTUs) defined by 95% sequence similarity, as determined by the furthest-neighbor algorithm in DOTUR (Schloss and Handelsman 2005). It is possible that the use of ITS sequence similarity cutoffs to define OTUs representing putative species may underestimate fungal diversity; however, this methodology is widely used in mycorrhizal research (Nilsson et al 2008;McCormick et al 2009;Lievens et al 2010), because of the difficulties associated with obtaining multigene phylogenetic data from environmental samples. Note that for a subset of orchid taxa, we confirmed that identified fungi were mycorrhizal and not other associated fungi by field seed-germination experiments described below.…”

From the past to the future – glacial refugia, current distribution patterns and future potential range changes of Diodonopsis (Orchidaceae) representatives

“…Numerous research aimed to recognize variables affecting the distribution and abundance of various orchids (e.g. Bergman et al 2006, O'Malley 2009, McCormick et al 2009, Bunch et al 2013, García-González et al 2016 indicating the importance of geography, soil chemistry, phorophyte specificity, presence of mycorrhizal fungi and pollinators, landscape heterogeneity, as well as landuse history. However, climate is the most important component of fundamental niche which is formed as a result of evolution.…”