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).
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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 |
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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 |
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USA, |
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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.
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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, |
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USA, Nevada, dead petioles of Yucca schidigera, 0.5-1.5 m above
ground, with Orbilia denticulata sp. nov. Leg. G. Marson |
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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.
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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 |
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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 |
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Germany, Rheinland-Pfalz, fallen needle of Pinus sylvestris,
with Liladisca acicola gen. nov. (Li) & Lophodermium pinastri
(Lo). Leg. L. Fuckel |
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