Assessment Notes

Justification

Hygrocybe noelokelani is native to Hawaii where it was found in three locations on the Big Island, and one on Kauai. It is restricted to Wet Montane Forests which are dominated by Metrosideros polymorpha (ʻŌhiʻa). This tree is under immediate threat by Rapid ʻŌhiʻa Death, a fast spreading disease caused by Ceratocystis fimbriata, so far restricted to the Big Island of Hawaii. Wet Montane Forest habitat is projected to decline at least 20% in the next 20 years, based on the spreading of the Ceratocystis wilt of M. polymorpha, the dominant tree in the habitat. A second threat is the widening of the Saddle Road on the Big Island; this project will destroy several of the kipukas (tree islands amid solidified lava streams) where Hygrocybe noelokelani was found.
Therefore Hygrocybe noelokelani is classified as EN (Endangered) under criterion C1. The total  number of mature individuals is estimated not to exceed 2,500.

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Taxonomic notes

Hygrocybe noelokelani has fruitbodies that are covered in slime, and have a pink cap, a white stem and white gills. It differs from closely related species known to occur in New Zealand in the pink colours of the pileus (Dennis and Hemmes 1997). The name ‘noelokelani’ means ‘the pink rose in the mist or rain forest’.

This species probably belongs in the genus Gliophorus, but there are no molecular data to support that, and a formal transfer to that genus has not been made.

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Geographic range

Hygrocybe noelokelani is endemic to Hawaii (US) and from two islands of the Hawaiian archipelago, Big Island and Kauai.

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Population and Trends

Hygrocybe noelokelani is very rare, only known from a couple of sites on two small islands in Hawaii in threatened habitats (due to tree death and human activities). It has been looked for on the other islands by experienced mycologists who described the species but there are no records from them. It is conspicuous enough and easy to identify as well to be found and identified by amateurs as testified by an award winning essay by a 15-year old person (American Museum of Natural History 2002).

Population Trend: Decreasing

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Habitat and Ecology

Solitary to scattered on bare soil, on soil among mosses, or on moss covered stems of hapu'u (Cibotium spp.) in Montane Mesic Forest (Ohi'a Forest) or Montane Wet Forest (Ohi'a/Hapu'u Forest) (Dennis & Desjardin 1997). Hygrocybe and Gliophorus species are biotrophic (living symbiotically with living plants), but it is not known in which way they interact with the plant and how they obtain sugars (Griffith et al. 2002, Halbwachs et al. 2013, Seitzman et al. 2011).

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Threats

Habitat destruction is the biggest threat to the occurrence of Hygrocybe noelokelani, first of all because of a rapidly spreading deadly disease of the host tree (Metrosideros polymorpha, ʻŌhiʻa), caused by Ceratocystis fimbriata (Keith et al. 2015, Friday et al. 2016.). Ceratocystis fimbriata kills mature trees and since it was first detected in the Kuna and Hilo Districts on the Big Island in Hawaii, it has spread, reached in 2016 the areas where Hygrocybe noelokelani occurs, and is threatening all habitats in which Metrosideros is the dominant tree. The name of the disease, Rapid ʻŌhiʻa Death, is an indication of its sudden appearance and fast work. This will change the whole ecosystem of the islands, as Metrosideros polymorpha is dominant in many different habitats. A second threat is habitat destruction of the kipukas, tree islands in the middle of old lava flows, along the Saddle Road on the Big Island because of widening of the road. The Saddle Road connects Hilo with the observatory on Mauna Kea, and is the shortest route from Hilo to the Kona coast.

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Conservation Actions

Sanitary actions to restrict the spread of Ceratocystis fimbriata are already in place (Friday et al. 2016) and need to be reinforced. Secondly, further widening of the Saddle Road has to be done in such a way that the kipukas (the montane tree islands amid the lava flows, the habitats of the native Hawaiian mushroom species) are spared. The cause of the infection, spread, identity, life cycle and ecology of Ceratocystis fimbriata have to be further researched. Ceratocystis-resistant strains of Metrosideros polymorpha have to be developed.

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Source and Citation

Vellinga, E.C. 2017. Hygrocybe noelokelani. The IUCN Red List of Threatened Species 2017: e.T95384502A95385479. Accessed on 22 November 2025.

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• Country occurrence