Investigating Specificity and Diversity of Orchid Mycorrhizal Fungi  of Vanilla Planifolia and Dendrophylax lindenii

Johnson, Lynnaun

doi:https://doi.org/10.21985/n2-sczr-sm14

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Investigating Specificity and Diversity of Orchid Mycorrhizal Fungi of Vanilla Planifolia and Dendrophylax lindenii

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Conservation efforts start with understanding the life cycle and interactions of species. For example, orchid conservation requires understanding pollinators as well as mycorrhizal fungi because these are mutualisms orchids require. For instance, all orchids require assistance from orchid mycorrhizal fungi (OMF) to germinate and some orchid species continue to be dependent on OMF as adults acquiring nutrients from their fungal associations. The primary goal of my dissertation was to investigate the diversity of OMF in epiphytic orchids (the most common ecology) and the orchid’s dependency on this association. This association has been studied less frequently and rigorously in epiphytic orchids compared to terrestrial orchids. Amplicon sequencing was used in Chapter 1 to study the fungal community of epiphytic and terrestrial roots of the hemiepiphytic orchid, Vanilla planifolia. The analyses revealed diverse fungal symbionts colonizing both epiphytic and terrestrial roots of V. planifolia including OMF and ectomycorrhizal (ECM) fungi. In Chapter 2, I used amplicon sequencing to investigate mycorrhizal helper bacteria associated with the OMF of V. planifolia. Mycorrhizal helper bacteria were ubiquitous in epiphytic and terrestrial roots but co-occurred less frequently with OMF compared to ECM fungi. Amplicon sequencing was again used in Chapter 3 to examine the diversity and specificity of OMF as well as the potential role of OMF as drivers of host tree preference in a leafless epiphytic orchid, Dendrophylax lindenii. Dendrophylax lindenii was found to associate with a single OMF (Ceratobasidium sp.) but the data were inconclusive regarding the role fungi play as drivers in influencing host preference. The dependence of D. lindenii on fungal symbionts was studied in Chapter 4 using stable isotope data. Stable isotopes 2H and 13C were shown to be enriched for D. lindenii compared to its surrounding vegetation which suggests that D. lindenii is dependent on fungal derived carbon in its natural habitat.

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