R-L categories correct, but text here does not match final assessment. Developed and updated version published at IUCN´s Red List update, July 18th 2019.
Gloiocephala cerkezii is sarotrophic fungus growing on plant remains known only from two small localities in Croatia; a small grassland and a disused orchard. It was described in 2008 (Tkalčec & Mešić 2008). Its agaricoid sporocarps are rather small (5–20 mm broad and 10–25 mm high), but macroscopically very distinctive (dark, slender, central stipe and very reduced, vein-like lamellae), so it is obviously an exceptionally rare species. It is assessed as Vulnerable using the criteria D1.
Exceptionally rare, but macroscopically distinctive species, known only from Croatia.
Known only from two small localities (sites) in NW Croatia, 40 km apart. Adequate habitat on one of these two localities is now devastated and lost.
Gloiocephala cerkezii is known only from two small localities in Croatia. It was found for the first time in 2002, published as new in 2008, and has never been reported from anywhere else. Today, the habitat on the northern locality (neglected orchard with Prunus domestica as substrate of G. cerkezii) is completely devastated and changed. The habitat on the southern locality (small grassland with Carex hirta sedge as substrate of G. cerkezii, ca 20 x 10 m) is still there, but abundance of Carex hirta is lower then 15 years ago. Therefore, the known population of the species is declining. However, since G. cerkezii can lives on two different plant substrates which are not rare, it can be assumed that other localities exist, at least in Croatia. The real number of localities is estimated at 50 with less than1000 mature individuals in total.
Population Trend: Decreasing
Gloiocephala cerkezii lives as a saprotroph on plant remnants. It was found in two different habitats: (1) in a small grassland with a few Alnus glutinosa trees, on dead parts of Carex hirta sedge, and (2) in a neglected orchard with Prunus domestica trees, on dead plum twigs on the ground. Sporocarps found between July and October.
Considering that only known locality with adequate habitat remained (on very small area, near the forest road and hunting lodge), and that a number of assumed localities is rather small, the species is under a threat of stochastic events which can lead to the habitat degradation and loss.
To prevent a degradation or loss of habitat on the single known site with adequate habitat remained (near the forest road and hunting lodge), it is important to enclose a small grassland to prevent access for vehicles and disposal of material. This small area should get a some sort of formal protection status.
Further field research on adequate habitats (grasslands with Carex hirta and extensive or neglected plum orchards) is needed, in order to get a more accurate knowledge of its population size and distribution.
Tkalčec, Z., Mešić, A. (2008). Gloiocephala cerkezii, a new species from Croatia. Mycologia 100(2): 306–310.