EPIPHYTIC LICHENS AS ENVIRONMENTAL

INDICATORS:

PART I: Introduction to structure and biology

LICHENS /Lichenophyta):Symbiotic association of fungi, algae & cyanobacteria

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-,

lugol solution); founder of bioindication by lichens

(Flore lichen de jardin de Luxembourg

11866 De Bary; 1867, Schwenderer: duble nature of lichens; »a

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

• 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

• 1993 Nimis, P.L. The lichens of Italy

• 1992 Purvis et al. : Lichens of Great Britain and Ireland

Lichen symbiosis

• 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”

• 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

• The sama fungus

exibits different

morfology,

depenedent on

photobiont

Morphotypes (phototypes)

Photobionts

• 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 28.650 13.250 46,25

Basidiomycota 16.000 50 0,31

Deuteromycota 17.000 200 1,18

Mastigiomycota 1.170 1 0,09

Myxomycota 625 22 0,32

Zygomycota 765 0 0

Total 64.200 13.500 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

• 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

• 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

• 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

• 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)