EPIPHYTIC LICHENS AS ENVIRONMENTAL
INDICATORS:
PART I: Introduction to structure and biology
HHistoric overview
- Very few notes about lichens from antique and middle ages; in culture of Knosos_
dies for house painting
- Micheli, 1727 (Nova Plantarum Genera); 300 lichen species, first drawing of ascus;
soralia treated as seeds
- Carl Lineus (1753, Species Plantarum, only 80 lichen species
- Scopoli (Flora carniolica, 1772, Vol. II; 54 taxa, 52 possible to indentify by todays
nomenclature)
- Acharius (Ach.) ; 1803; » A father of lichenology«; Methodes Lichenum; 1810 –
Lichenographia universalis;
- 1814 – Synopsis Methodica Lichenum; a concept of lichen species is founded;
progress in lichen thallus anatomy: asci, ; a huge herbarium in Helsinki
- Fries, E. (FR.) - 1821 – Systema mycologicum; » a father of mycology«; 1831 –
Lichenographia europaea reformata; a concept of lichenized fungi - lichens as part of
fungi!
- 1850 _De Notarius; Massalongo (Italy); Koerber (Germany), Fries, Th.M.
(Upsalla) – new contributions
- 1822—Nylander; cca 1.000 taxa !; first reflexion on duble nature of lichens;
excursions to tropics; 1866
first chemical kew for lichens; »spot test« (K+, Cl-,
11866 De Bary; 1867, Schwenderer: duble nature of lichens; »a
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symbiotic structure
- 1877 Stahl - first success in cultivations of lichens, development from spores; even
today difficult task
- 1890 Vainio, E. : » Lichens are fungi«; lichens are classified in the fungi system, but
he was aware of their symbiotic nature.
- 1921 1940 Zahlbruckner; Catalogus lichenus universalis – stil today one of the
most important
lichenological publications
- 1907 Zopf; » Die Flechtenstoffe«; introduces the importance of lichens substances;
for biology of lichens and taxonomy; he described more than 100 substances, today
over 600!
- 1954 Asahina & Shibata; Chemistry of the lichen substances; further development
in the field of lichen
substances
More recent and contemporary lichen literature and
lichenologists
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1969 Poelt, J. : Bestimungsschluessel europaischer
Flechten
1973 Ahmadjian, V. & M.E. Hale : The lichens
1974 Henssen, A., & H-M. Jahns: Lichens. Eine
Einfuehrung in die Flechtenkunde
1983 Hale, M.E. : The biology of Lichens
1984 Hawksworth, D.L. & Hill, D.L. : The lichen
forming fungy.
1988 Galun et al. : Handbook of Lichenology
1984 Honegger, R : lichen cytology,
physiology
1995 Wirth, V (1980, 1987): Flechtenflora
1993 Santesson, R. : The lichen of Sweden and
Norway
Lichen symbiosis
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semantic problems with definition ( De Bary 1866, Schwenderer 1867, …. ,
Ahmadjian 1982. Hawkworth et al. 1988, Hawksworth & Honeggger 1994,…
fungus : exobiont (= exhabitant); mykobiont; heterotrophic partner
alga (cyanobacterium): endobiont (inhabitant); photobiont ; autotrophic
partner
stabile, selfsustaining association of fungus and alga (cyanobacterium);
ecologicaly: obligatory mutualism; different types of symbiosis:
mycobiont as inhabitant – mycophycobiosis; »endophytes« of brown alga;
mycobiont as exhabitant: the most common type of symbiosis in lichens;
two biont symbiosis : the most common type; three- biont symbiosis:
formation of cephalodia (N2 fixation);
Special types of “symbiosis”
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morphotypes (phototypes) (in Slovenia Lobaria amplissima- green
alga; Dendriscocaulon sp. – cyanobacterium; similar in Scotland:
Sticta canariensis – Sticta dufourii; in New Zealand: Sticta filix –
Dendriscocaulon sp.
2 mycobiont – 1 photobiont symbiosis: obligatory parasits of
lichenised fungi, four stages of relations;
4 partner symbiosis: lichenicolous fungi ( 3 photobionts- 1
mycobiont; 3 photobionts –1 mycobiont, 3 mycobionts – 1
photobiont
Morphotypes (phototypes)
• The sama fungus
exibits different
morfology,
depenedent on
photobiont
Photobionts
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cca 100 species of algae, some
cyanobacteria, green algae:
Chlorococcales: cocal green
algae
Trebouxia ; in 70-80% of all
lichens
Coccomyxa, Myrmecia
Chlorella; …
Trentepohliales
Trentepohlia, Phycopeltis
cyanobionts:
Chroococcales: Gleocapsa
Stigonematales: Stigonema
Nostocales: Nostoc
MYCOBIONTS
Ascomycets are the most spread mycobionts
• Lichenisation
occurreed several
times in the evolution
of ascomycets
• Several groups of free
living ascomycets are
descendants of
“delichenised” taxa
Taxon total number of species
lichenised
%
Ascomycota
Basidiomycota
Deuteromycota
Mastigiomycota
Myxomycota
Zygomycota
Total
28.650
16.000
17.000
1.170
625
765
64.200
13.250
50
200
1
22
0
13.500
46,25
0,31
1,18
0,09
0,32
0
21
Thallus structure
• There are three basic
thallus types:crustose,
foliose and fruticose
• Fungus makes major
part of biomas, except
at certain cyanolichens
• Thallus morfology
depends on fungus
structures
Vegetative thallus structures
• Fastening structures
are well developed on
foliose thalli –
• Rhizine- projections of
fungal lower cortex
• Fibrile –fungal
projections of thalli
edges
Main types of thallus structure
• Heteromerous:photobi
onts in gonidial layer
(green algae);
dorsiventral or radial
• Homeomerous:
cianobionts evenly
distributed btween the
two cortex layer
Vegetative propagules:soredia
• Soralia, in which
soredia are formed are
widespread structures
• Position, shape, colour
and size are important
for taxonomy
Vegetative propagules: isidia
• Isidia are miniature
thallus like structures
• Shape, size, colour
and site of appearance
are important for
taxonomy
Sexual reproduction: only
fungus:ascomata, basidiomata
• Apothecium, the most
spred type of ascomata
• Dick shaped, sunk in
warts, elongated
(lirella) or petiolated
• Lecanorine, lecideine,
coniocarpous
Sexual reproduction: ascomata,
basidiomata
• Perithecium, in the
thallus sunk ascomata
of diverse structure
• Basidiomata are
mostly perennial,
basidiomata are
ephemeral
Ascospors and vegetative parts of
ascomata
• Ascospors are
developed in asks
• Number, size, colour
and cell wall structure
Are important for
taxonomy
• Vegetative part of
ascomata are also
relevant
BIOLOGY: as a system lichens
are autotrophic
• Fungus creates “microenvironment” for
photobionts (water, nutrient uptake; light
intensity control, defence against herbivores
and pathogens)
• Photobiont makes “food” for fungus
(carbohydrates, amino acids)
• Fungus synthetises secondary metabolites
Comunication with environment: H2O, CO2, nutrient
uptake
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Poikilohydrous and
poikilothermic organisms
There is structural
regulation of water and
nutrient uptake by
specialised hyphae
Pseudocyphelae or cyphelae
act as stomata
Cephalodia with cianobionts
bind atmospheric N2
Internal structure of thallus
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In heteromeric thallus fungal
hyphae are differentiated in two
cortex layers and medulla, of
very different cell wall
structures
Photobionts are in gonial layer
below upper cortex
Medular hyphae are highly
hydrophobic, what enables
gass transport
Communcations between
partners
• Several types of
haustoria have been
developed for nutrient
exchange between
partners, depending on
type of simbionts
• Cell wall structure of
both partners is again
crucial
Which currency is used by photobionts?
• Green algae export
mostly sugar alcohols
• Cianobionts export
sugars
Mutual contact causes production of secondary
metabolites- lichen substances
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Lichen substances have several
important tasks:
regulate conductivity of cell
walls and thallus
defence thallus against patogens
and herbivors,
modify thallus light properties
ECOLOGY
• Lichens are probably first atempt to settle harsh
terrestrial environment by autotrophs; symbiosis
was necessary
• Mycologist treat them sometimes just as one of
the possible life style of fungi
• All their structural and physiological adaptation
enable them to settle axtrem biotopes; in more
favurable enviroments they are outcompeted by
mosses and higher plants
Where lichens prevail?
Extreme, harsh environments:
1-very cold and dry: polar and mountain tundras
2- very hot and dry: deserts, semideserts
Favurable environments:
microsites where they are not outcompeted by
other “plants” (rocks, barren soil, man made
substrates)
Epiphytic life-style
Major ecological groups
• Epiphytic: corticolous:on bark;
lignicolous:on wood; folicolous: on leaves)
• Terricolous: on ground (soil); muscicolous:
on moss; saxicolous: on rocks
Ecosystem function
• Primari producers (taiga, tundra, deserts,
clifs, rocks, steppes)
• Soil formation (rocks, clifs)
• Water and nutrient retention (epiphytes in
forests)
• Formation of microhabitats (avertebrates)
and row material (material for nests)
Importance for mankind
• Food (rare old-fashion practices; Lecanora
esculenta (Bible); Cetraria islandica –periods of
hunger in past in polaric regions
• Fodder: raindeer breeders
• Dyes for textil walls (Antique, Middle ages)
• Row material for perfums and
phytopharmaceutical products
• Bioindication of environment (air pollution, forest
continuity)
Biodiversity
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Lichen diversity – number of species:
Total
cca 16.500
Austria
2.300
F.R Germany
1674
Italy
2145
Norway&Sweden
2271
Slovenia
cca 900 ( →1200-1400)