1. Substrate of xerotolerant fungi


A. Situation of favourable substrate in the field (with special emphasis on Orbiliomycetes)


Xeric substrate comprises dead woody substrate (bark and wood, fruits), but also dead herbaceous substrate like stems, culms or leaves. Xeric substrate is exposed to drying winds and often also direct sunshine. Lignicolous xerotolerant Orbiliomycetes and other asco- and basidiomycetes fruit on the dead branches of trees and shrubs from near the base up to the highest parts of the canopy. Xerotolerant species are not restricted to areas of low annual precipitation. They occur in nearly every plant community all over the world. Yet, particularly Orbiliomycetes show a much higher species diversity in semiarid (semidesert) areas compared to regions with a higher annual precipitation (temperate-atlantic, arctic-boreal, tropical).



Germany, Tübingen, very old, partly still corticated, broken branch of Quercus robur ca. 3 m above ground, colonized by Orbilia myrioeuonymi sp. nov., O. aprilis, O. coccinella, O. vinosa, Mollisia ligni, Durella connivens, D. atrocyanea, Chaetosphaeria myriocarpa


Luxembourg, trunks of young living Fagus, wound with detached bark 0.2-0.8 m above ground, leg./phot. G. Marson, with Orbilia aristata, O. aradi, Hyalorbilia aff. oreadum, Pyrenopeziza sp.


France, Haute-Loire, Picea abies forest, still-attached living branches at roadsides frequently show resinous wounds (cankers, see right photo), probably due to forestry activity. Phot. G. Marson

dto., resinous wounds of Picea abies ca. 2 m above ground, inhabited by Lilapila oculispora gen. & sp. nov. Leg./phot. G. Marson



USA, Nevada, Mojave desert, Yucca schidigera with Orbilia denticulata sp. nov. in 0.5-1.5 m above ground, on the dead leaves hanging down. Leg./phot. G. Marson


USA, Arizona, dead shrub of Purshia mexicana var. stansburiana, with Orbilia purshiana sp. nov. on the decorticated branches in 1-2 m above ground. Leg./phot. G. Marson

USA, Arizona, Southern Sonora desert, Stenocereus thurberi (Organ Pipe Cactus) with Orbilia calyptrata sp. nov. and O. aff. trapeziformis sp. nov. growing on those dead parts where remnants of decayed "flesh" is still attached to the central axis, 0-1 m above ground. Leg./phot. G. Marson



B. Collected substrate of xerotolerant fungi (Orbiliomycetes) showing various types of surface decay


Unexperienced persons have often difficulties in the field to recognize suitable substrate and to detect apothecia of xerotolerant Orbiliomycetes on them. Even experienced persons quite often fail to find apothecia and cannot explain the reasons. Some substrates are full of them, often in mixed populations of several species, while others are nearly empty.

Xeric substrate is most often greyed by the presence of light to dark brown hyphae of hyphomycetes (“black yeasts”), frequently showing an olive component due to the mixed growth with green air algae. Both organisms form a biofilm over the decayed surface of wood and bark, especially on the weather-exposed face. Here or more towards the weather-sheltered side Orbiliomycetes use to grow. While the “black yeasts” occur from arctic-boreal to semidesert climates, algae become more and more sparse with increasing aridity, and are often almost completely absent on substrate from semideserts. Usually, favourable xeric substrate is in a rather progressed stage of decay. Nevertheless, often only an outer layer of 0.1-1 mm is decayed while the inner parts of wood are very undecayed. The surface is often fibrillous by separating wood fibrils, and eventually becomes strongly uneven and eroded. Very often deep longitudinal cracks into the decorticated wood occur at the upper, exposed face, and along this cleft apothecia are preferably found. Quite often old beetle galleries decorate the naked wood surface. These galleries form one of the favourable niches for Orbiliomycetes.



USA, Arizona, decorticated branch (ca. 23 mm thick) of Pinus ponderosa 1.5-2.5 m above ground, with old beetle galleries in which O. microsoma sp. nov. grows. Leg. G. Marson

USA, Arizona, decorticated branches of Purshia stansburiana with Orbilia purshiana sp. nov. Leg. G. Marson

Germany, Tübingen, corticated dead stems of Clematis vitalba hanging in 2 m above ground, with O. pleioeuonymi sp. nov. & O. subtrapeziformis sp. nov..

USA, Nevada, dead petioles of Yucca schidigera, 0.5-1.5 m above ground, with Orbilia denticulata sp. nov. Leg. G. Marson



C. Populations of Orbiliomycetes on natural substrate, intermixed growth with lichens and other fungi


Xerotolerant ascomycetes inhabit most kinds of exposed organic matter which rapidly dries down after rainy weather. In this instance they share their ecological niche with lichens and often fruit in quite close association with them. However, lichenized ascomycetes are able to colonize branches and trunks already at a very early stage of decay, and a large ecological group of lichens even grow on rocks. Ascomycetes without an algal partner, like Orbiliomycetes, need organic substrate and fruit on predominantly very decayed plant tissue.


USA, Arizona, dry wood of Purshia stansburiana, with Orbilia purshiana sp. nov. (black) and ?Lecanora. Leg. G. Marson

France, Alpes-de-Hautes-Provence, corticated branch (18 mm diam.) of Cedrus atlantica 4-5 m above ground, with Orbilia flagellispora & Caloplaca holocarpa agg. Leg. G. Marson


Australia (NSW), decorticated twig (ca. 5 mm diam.) of Pittosporum phillyreoides 0.2-1.5 m above ground, with Orbilia pleioaustraliensis sp. nov. Leg. G. Marson

Germany, Saarland, 9 mm thick dead branch of Amelanchier ?lamarckii in a park, 1.5 m above ground, in cross cracks of bark Orbilia aristata. Leg. H. Aeberhard


Germany, Tübingen, corticated branch (12 mm thick) of Salix alba 2.2 m above ground, with Orbilia pseudoaristata sp. nov. & Xanthoria parietina.

USA, Nevada, petioles of Yucca schidigera 0.5-1.5 m above ground, with Orbilia denticulata sp. nov., leg./phot. G. Marson


Germany, Rheinland-Pfalz, fallen needle of Pinus sylvestris, with Liladisca acicola gen. nov. (Li) & Lophodermium pinastri (Lo). Leg. L. Fuckel