Aloha nui! My name is Taylor Jenkins and I’ve been working with BIISC through the Pacific Internship Programs for Exploring Science (PIPES) program to investigate the distribution, establishment, and fungal interactions of a non-native epiphytic orchid (Epidendrum nocturnum) across Puna.
E. nocturnum occurs naturally in Florida, Central America, and Northern South America, and has been observed by BIISC staff to be naturalizing across Puna. This species and other genera of non-native epiphytic orchids have yet to be studied formally or assessed for weed risk on Hawaiʻi Island. This project aimed to identify and assess environmental variables which are associated with orchid presence, as well as explore the connection between Rapid ʻŌhiʻa Death (ROD)-impacted forests and orchid establishment.
The study investigated the impact of bark surface texture characteristics, canopy openness, elevation, rainfall, host tree DBH (diameter at breast height), and ROD-presence on both orchid abundance and recruitment across sites. These two dependent variables tell a slightly different story, where recruitment (the number of seedlings around a mature plant) may better explain seed capture and establishment compared to abundance (the total number of mature and seedling individuals), which is a cumulative measure of orchid presence over a longer timeline.
Introduction:
Current literature suggests that bark surface texture characteristics and light availability are among the primary limiting factors to orchid establishment, though precise germination site requirements are not well known. Several studies support that rugose and non-peeling bark may facilitate epiphyte establishment (Adhikari and Fischer, 2012; Rasmussen et al., 2015; Fernandez et al., 2026), and that certain epiphytic species may thrive under moderate to high light intensity associated with canopy openness (Adhikari and Fischer, 2012; Fernandez et al., 2026).
The ubiquity and distribution of orchid mycorrhizal fungi (OMF) is another important factor influencing germination and host tree specificity of epiphytic orchids, and may have an interactive effect with other environmental variables (Rasmussen et al., 2015; Alghamdi, 2019; Swift et al., 2019).
The project was split into two studies, one focusing on orchid recruitment, and the second focusing on orchid abundance. Both studies center around the same environmental predictor variables:
- Bark Rugosity (smooth, medium, rough)
- Bark Peeling Quality (stable, partial, high shedding)
- % Bark Sloughing (<20%, 20–40%, 40–60%, 60–80%, >80%)
- Canopy Openness (<20%, 20–40%, 40–60%, 60–80%, >80%)
- Elevation (ft)
- Rainfall (2024-2025 average) (in)
For the recruitment-focused portion of this project, we asked the following questions:
- Does recruitment of E. nocturnum occur more frequently in ROD-impacted ʻōhiʻa forests vs. non ROD-impacted ʻōhiʻa forests?
- Do host trees in ROD-affected forests provide optimal conditions for the germination and establishment of E. nocturnum through changes in bark surface texture and canopy openness?
For the abundance-focused portion of this project, we asked:
- Does bark surface texture and canopy openness influence the abundance of E. nocturnum across sites?
- What host trees does E. nocturnum associate with?
- What orchid mycorrhizal fungi (OMF) taxa that associate with E. nocturnum through root peloton culture and DNA sequencing.
Methods:
The first study of this project compared orchid recruitment between a heavily ROD-impacted ʻōhiʻa forest, and an ʻōhiʻa forest with limited ROD detection, under similar environmental conditions (rainfall, elevation, forest stand age). Fifteen GPS points were randomly selected across each study site, and the first ʻōhiʻa host tree with a mature orchid (bearing flowers or fruit) observed at each point were selected for recruitment assessment. The number of seedlings and other mature individuals on the host tree were noted, along with tree DBH, bark surface texture characteristics, and canopy openness. Bark surface texture data was determined subjectively through visual analysis. Canopy openness was measured using hemispherical photography (180˚ fish eye lens) on a smartphone and analyzed using a gap light analysis software to produce a percentage of canopy openness.
The second study of this project investigated whether bark surface texture characteristics and canopy openness influence the abundance of E. nocturnum across sites, and includes a variety of host tree species. Similarly to the first study, we collected tree DBH, bark surface texture characteristics, canopy openness, and additionally, host tree species identity. Five sites were selected for sampling across Puna based on previous observations of E. nocturnum presence. Orchid root samples were collected at four of the five sites using a protocol adapted from Fernandez et al. (2026). Fungal pelotons were isolated from root samples and grown on potato-dextrose agar plates for subsequent PCR and DNA sequencing to determine OMF identity.
Results:
This project found that elevation and rainfall were significant negative predictors of E. nocturnum presence (both abundance and recruitment), suggesting that high elevation and rainfall may hinder optimal conditions for germination and establishment of the species. Additionally, bark rugosity (rough > medium) and degree of bark peeling (high > partial) were significant predictors of orchid recruitment, suggesting that these characteristics may promote the germination and establishment of the species.
These findings carry ecological, economic, and community significance for Hawaiʻi Island. Identifying bark condition and climate as significant predictors of E. nocturnum presence provides quantitative evidence relevant to the species’ formal risk classification, as well as a foundation for future study.
DNA sequencing of peloton cultures identified two fungal taxa that are known orchid mychorrizal fungi. This results suggests a generalist strategy of fungal association, meaning E. nocturnum may have a greater propensity to spread into varied habitats as facilitated by diverse fungal partners.
For more information on this project, check out my ArcGIS Story Map here: https://arcg.is/1OLKGf1
Citations:
Ackerman, J. (2012, February). Orchids Gone Wild. Orchids. American Orchid Society. http://www.aos.org
Clifford, P., & Kobayashi, K. (2012). Naturalizing Orchids and the Hawaii Pacific Weed Risk Assessment System (OF-51). Honolulu, HI: University of Hawai‘i at Mānoa, College of Tropical Agriculture and Human Resources.
Rasmussen, H. N., Dixon, K. W., Jersáková, J., & Těšitelová, T. (2015). Germination and seedling establishment in orchids: A complex of requirements. Annals of Botany, 116(3), 391–402. https://doi.org/10.1093/aob/mcv087
Adhikari, Y. P., & Fischer, A. (2012). Distribution pattern of the epiphytic orchid Rhynchostylis retusa under strong human influence in Kathmandu valley, Nepal. Botanica Orientalis: Journal of Plant Science, 8, 90–99. https://doi.org/10.3126/botor.v8i0.5956
Fernandez, M. A. P., Ogura-Tsujita, Y., & Marutani, M. (2026). Mycorrhizal specialization for Tulasnellaceae fungi in Taeniophyllum marianense, a leafless epiphytic orchid native to Guam. Journal of Plant Research, 139(3), 409–424. https://doi.org/10.1007/s10265-026-01699-z
Petrolli, R., Zinger, L., Perez‐Lamarque, B., Collobert, G., Griveau, C., Pailler, T., Selosse, M. A., & Martos, F. (2022). Spatial turnover of fungi and partner choice shape mycorrhizal networks in epiphytic orchids. Journal of Ecology, 110(11), 2568–2584. https://doi.org/10.1111/1365-2745.13986
What is the HPWRA? | Plant Pono. (2020). In Plant Pono. https://plantpono.org/plant-assessments/
Contact for inquiry: tqjenkin@hawaii.edu
