Abstract Detail

Recent Topics Posters

Fernandez, Michael Angelo P. [1], Marutani, Mari [2].

Host Tree Preferences and Mycorrhizal Associations of Guam’s Native Epiphytic Orchids.

As one of the most diverse plant families, Orchidaceae are unified by their obligate dependence on orchid mycorrhizal fungi (OMF) for nutrition. This symbiosis in addition to other biotic interactions have implications in driving the evolution and shaping the distribution of orchids especially in tropical Pacific islands which boast some of the highest number of endemic and rare orchid species. Although the complete life history of many tropical island orchids remains elusive, understanding the factors that influence island speciation is essential for the conservation of especially rare endemics. The Pacific island of Guam is the southernmost island of the Mariana Island chain which hosts 30 unique terrestrial and epiphytic orchid species. We studied the host tree and OMF associations of six native, epiphytic orchid species in Guam: Bulbophyllum guamense, Coelogyne guamensis, Dendrobium guamense, Luisia teretifolia, Taeniophyllum mariannense, and Tuberolabium guamense. B. guamense, D. guamense, and T. guamense are listed as threatened under the US Endangered Species Act of 2015. Eight different sites around the island were surveyed from Oct. 2019 to Feb. 2022 encompassing three of the island’s distinct habitat types: limestone forest (2 sites), volcanic ravine forest (2 sites), and disturbed/urban areas (4 sites). A total of 147 orchid specimens growing on 22 different host tree species were recorded. T. mariannense, a common leafless orchid in Guam, was observed growing on 19 different host trees across all habitats with Calophyllum inophyllum, Hibiscus tiliaceus, and two of Guam’s most invasive trees, Leucaena leucocephala, and Vitex parviflora, being the most common. B. guamense, D. guamense, and C. guamensis were commonly observed growing on Cocos nucifera and Pandanus tectorius, common tree species of undisturbed limestone forest and volcanic ravine forest. T. guamense was found growing exclusively on the invasive V. parviflora in volcanic ravine forest and the few specimens of L. teretifolia were found growing on V. parviflora and C. inophyllum in volcanic ravine forest and disturbed/urban areas respectively. OMF colonization of orchid roots was examined by sampling pelotons, or hyphal coils, within root cortical cells situated near the point of attachment to the host tree. OMF species were cultured and isolated DNAs were identified via Sanger DNA sequencing. We found that Tuberolabium guamense was associated with the OMF family Ceratobasidiaceae in the order Cantharellales and Bulbophyllum guamense with the OMF order Atractiallales. Taeniophyllum mariannense was associated with the OMF family Sebacinaceae in addition to several non-OMF endophytes whose roles in orchids remain unknown. Mycorrhizal samples of C. guamensis, D. guamense, and L. teretifolia are currently being identified.

1 - University of Guam, College of Natural and Applied Sciences, 303 University Dr., UOG Station, Mangilao, GU, 96923, USA
2 - University of Guam, Agriculture and Life Science CNAS, 303 University Dr., UOG Station, Mangilao, GU, 96923, USA

Host Tree
Island Ecology

Presentation Type: Recent Topics Poster
Number: PRT001
Abstract ID:1309
Candidate for Awards:None

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