Assessment Notes

Justification

Known from only a very small number of records, Craterellus costaricensis is currently only known from a small area of Costa Rica. The potential host species (Quercus copeyensis = Q. bumelioides) has a wider range, and so the mushroom could too. However, the species' scarcity means that it is highly unlikely to be Least Concern, and so this prevents an assessment as Data Deficient (i.e. it cannot be anything from Least Concern to Critically Endangered). Taking into account the species' scarcity, the population size is here estimated to be 1,000-2,000 mature individuals, split into multiple, tiny subpopulations. The species is thought to have disappeared from one intensively surveyed site, and agricultural activities beyond are likely to be impacting the species further. Therefore, C. costaricensis is precautionarily assessed as Endangered under criterion C2a(i), although further research is urged.

---

Geographic range

This species is known to occur within Costa Rica. Three specimens appear to be known, with it having been found at Villa Mills and also at Estrella, Cartago province (Wu and Mueller 1995, GBIF 2022). The potential host species (Quercus copeyensis = Q. bumelioides) is widespread in Central America and so the mushroom could have a wider distribution than currently known.

---

Population and Trends

This species has been rarely observed, although it is fairly inconspicuous. It has only been found once in 30+ years of intensive surveying at one site (G. Mueller pers. obs.). As such, the population size is expected to be small. Estimating 5-10 mature individuals per site (see Dahlberg and Mueller 2011), and using an appropriate scaling factor that takes into account the amount of available habitat as well as the apparent scarcity of the species (x 200), gives a total population size of 1,000-2,000 mature individuals. With the species' scarcity it is probable that individual sites could represent separate subpopulations, especially as it has disappeared from one intensively surveyed site (G. Mueller pers. obs.) and there has been no re-colonisation. This disappearance from this site, as well as the potential impacts of anthropogenic threats elsewhere in its putative range (e.g. agriculture) mean that the population is considered to be in decline.

Population Trend: Decreasing

---

Habitat and Ecology

Collections have been made from soil in Quercus copeyensis (= Q. bumelioides) forest (Wu and Mueller 1995).

---

Threats

The intensively surveyed site from which it has disappeared is undergoing constant active change due to cutting as it is a research plot, which could be a potential reason for its apparent disappearance there. Elsewhere, small scale agricultural activities may be impacting the habitat, and thus the species.

---

Conservation Actions

This species has been collected from the La Amistad protected area (see UNEP-WCMC and IUCN 2022). No conservation actions can be recommended at this time without further research. Further research into this species' habitat preferences and distribution is required.

---

Source and Citation

Mueller, G.M. & Westrip, J.R.S. 2025. Craterellus costaricensis. The IUCN Red List of Threatened Species 2025: e.T269706326A269706328. Accessed on 26 November 2025.

---

• Country occurrence