Hypotarzetta insignis is a striking large spring fruiting fungal species. It is a very rare species with fragmentary distribution in the Mediterranean area. It is ectomycorrhizal with Cedrus, Abies and Pinus spp. In Spain it is known from scattered occurrences in old-growth Pinus forests that are under threat of clearcutting and other human disturbances. In Greece and Turkey it grows with Abies in natural Abies forests, which are also threatened. In Morocco, it is native to the Cedrus atlantica forests of the Atlas. In France it seems to be least endangered, as it grows in planted Cedrus groves, and even with introduced Pseudotsuga menziesii outside the Mediterranean area. In Spain and Greece the species is known well and occurs in threatened habitats; it should be included in a national red list in those countries.  The data from the other countries are incomplete, especially on habitat, and the distribution is very spotty and insufficiently known.  Therefore, it is assessed as Data Deficient.

Hypotarzetta insignis was originally described in the genus Pustularia. It is supposed to be a member of the Pyronemataceae, and takes a unique position in that family, because of the unique growth mechanism concerning the transition from hypogeous to epigeous. It was described from a plantation of Cedrus atlantica in southeastern France.It is also unique in having white fruitbodies; most members of the Pyronemataceae have fruitbodies with orange pigments.

Widespread in the Mediterranean area, but everywhere very localized and rare. Known from the Atlas mountains in Morocco, several locations in central and northern mainland Greece (http://www.mycohellas.gr), one in Turkey (Kaya, A. & Y. Uzun, 2015), several in Spain (Honrubia & Llimona 1981; Honrubia et al., 1983; Mateo, 2011). It is known from a number of disjunct locations in France, where it was introduced with Cedrus atlantica (Berthet & Riousset, 1963; Fouchier & Neville 1998; Doll & Sarraillon 2013).

The species is very localized in five countries around the Mediterranean. Nothing is known about the situation in northern Africa where it grows with Cedrus atlantica. In Spain, Greece and Turkey it seems to be very local in small populations of only a few individuals, and growing with Pinus spp. and Abies borissi-regis. It is not known from Italy and the Balkan, but there are at least six localities in Greece, and one in Turkey. Whether it occurs with Cedrus libani or other hosts in Lebanon and Syria is unknown. It is stable in the Cedrus plantation of the Petit Lubéron in southeastern France where it was introduced, and was reported from a Pseudotsuga plantation in the northeast of France.

Form ectomycorrhiza with various conifer species (notably Pinus spp., Cedrus spp., Abies borissi-regis) in the Mediterranean Area, and also with introduced Pseudotsuga menziesii in northeastern France. Fruiting in spring. Growing in open forests and plantations, at middle elevations with sparse understory of shrubs and bushes. The forests in which the species grows are well established and old-growth. The Cedrus plantation in southeastern France was planted in 1862. Starting out hypogeous, emerging and becoming epigeous. Spore dispersal probably by wind.

The Spanish populations consist of only a few individuals each, and occur in open spaces of old-growth Pinus forests, which are under threat of clearcutting and forest management, and human disturbances. In Turkey and Greece, Hypotarzetta is very rare, populations are small and isolated and the Abies forests in which they occur under constant threat of clearcut and overgrazing. There is no information on the Moroccan population(s).

More research needed to establish the real occurrence of this species, its status in Morocco, and whether the species is native in France.

Berthet, P. & Riousset, L. 1963. Un Pustularia nouveau: P. insignis. Description de l’espèce et remarque sur un caractère cytologique du genre Pustularia. Bull. trimest. Soc. Mycol. France 79: 392–398.
Doll, D. & Sarraillon, F. 2013. Hypotarzetta insignis, une nouvelle espèce pour l’Alsace. Bulletin de la Fédération Mycologique de l’Est 11: 27–29.
Fouchier, F. & Neville, P. 1998. Hypotarzetta insignis, Neournula pouchetii et Geopora sumneriana, Ascomycota printaniers de la cédraie du Petit Lubéron. Bull. FAMM 13: 32–44.
Honrubia, M. & Llimona, X. 1981. Aportación al conocimiento de los hongos del S.E. de España. IV. Tres citas nuevas para la microflora-española: Pustularia insignis, Tuber borchii, Leucogaster cf. floccosus. Anales de la Universidad de Murcia 37: 81–90.
Honrubia, M. & Berthet, P. & Llimona, X. 1983. Contribution à la connaissance des champignons du Sud-Est de l’Espagne. VII. Pezizales (Ascomycètes). Bulletin Mensuel de la Societé Linnéenne de Lyon 51: 46–62.
Kaya, A. & Y. Uzun (2015). Six new genus records for Turkish Pezizales from Gaziantep Provinceg.  Turkish Journal of Botany 39: 506–511.
Mateo, J.F. 2011. Hypotarzetta insignis, una especie muy rara recolectada en Cuenca. Bol. Soc. Micol. Madrid 35: 25-29.

Hypotarzetta insignis (Berthet & Riousset) Donadini.  http://www.mycohellas.gr/mc/viewarticle.asp?a=1145 [accessed Feb 2018]