Assessment Notes

Justification

Haloaleurodiscus mangrovei is a saprotrophic fungus found growing on decaying wood in the mangroves of the South Kuroshio regional ecosystem in Japan. Fruiting bodies have only been documented on two occasions, in 2001 and 2003, at one site on Iriomote Island. Although the number of localities is probably larger, there is a limited amount of suitable habitat in the region and the species has not been found in Okinawa Island despite sampling efforts for Basidiomycota. Together with the lack of occurrences since its description in 2005, this suggests that H. mangrovei is a rare species. The population size is estimated to be at most 600 individuals, with no evidence of population decline at this time, although there are potential threats that could rapidly impact the species. The species is assessed as Vulnerable (VU) D1+2.

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Taxonomic notes

Haloaleurodiscus mangrovei is the type species of the monotypic genus Haloaleurodiscus. It was described in 2005 based on its morphological characteristics and phylogenetic analysis (Maekawa et al. 2005).

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Geographic range

The species has only been documented from one site in the Iriomote Island in Japan (Maekawa et al. 2005).

Environmental DNA sequencing records from sediments in Brazil, Germany, Canada, Vietnam and China (GBIF 2023) suggest that it may have a wider distribution. However, in the absence of evidence for the presence of mature individuals, these potential occurrences are not considered in this assessment.

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Population and Trends

Fruit bodies have only been documented on two occasions, in 2001 and 2003, in one site on the island of Iriomote. It is possible that the species occurs in more localities within the mangroves of the South Kuroshio regional ecosystem and its inconspicuousness and need for microscopy for identification have limited the number of observations. This makes the number of localities potentially larger but not possible to determine. Nevertheless, the area of mangroves in the South Kuroshio ecosystem was estimated at 7.3 km² in 2020 (Inoue et al. 2024, preprint), limiting the amount of suitable habitat in the region. Moreover, the same authors have also studied the biodiversity of basidiomycetes on the island of Okinawa, in the same region (Maekawa et al. 2003) and did not report this species for the island. This, together with the lack of occurrences since its description in 2005, suggests this is not a common species. Therefore, a multiplier of 100 for unknown locations is applied in this assessment for the calculation of population size. Following guidelines by Dahlberg and Mueller (2011) it is assumed six mature individuals exist per site (three logs per site, each with two mature individuals) for a total of 600 individuals.

There is no evidence of a current population decline. It was estimated that the area of mangroves in the region increased in the period between 1970 and 2020 (Inoue et al. 2024, preprint). A future decrease in population might occur through habitat decline, with a projected 8.2% of the area submerged in 50 years in a future scenario of extreme sea-level rise. Still, this is below the thresholds for population size reduction used in criterion A.

Population Trend: Unknown

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Habitat and Ecology

Haloaleurodiscus mangrovei is an annual resupinate fungus that causes white pocket rot. It was found growing on decaying branches and trunks of Sonneratia alba in a mangrove forest, both above and below the high tide mark in the mangroves of the South Kuroshio regional ecosystem (Maekawa et al. 2005).

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Threats

The mangroves of the South Kuroshio are threatened by climate change and its effect on sea level rise, change in frequency and intensity of extreme events, as well as the increase in temperature. A decrease in habitat quality is also a threat to this species, as it is estimated that this mangrove ecosystem is currently undergoing some degradation. The area is affected by pollution, such as drifted trash washed ashore, and by tourism focused on mangroves in the region. However, preventative measures have been put in place to reduce direct human impact caused by tourism (Inoue et al. 2024, preprint).

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Conservation Actions

Mangroves in the South Kuroshio province are under conservation measures. The known site is part of the Iriomote-Ishigaki National Park as well as a Natural World Heritage site (Inoue et al. 2024, preprint). Targeted search efforts in areas of appropriate habitat in the region are needed to better estimate the population size and trends, as well as its distribution. Localities where eDNA for this species has been recorded should be targeted for field surveys to identify whether mature individuals occur outside the known range for this species.

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Source and Citation

Cunha, S.P. & Gonçalves, S.C. 2025. Haloaleurodiscus mangrovei. The IUCN Red List of Threatened Species 2025: e.T271051712A271051716. Accessed on 20 November 2025.

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• Country occurrence