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 paintingMicheli, 1727 (Nova Plantarum Genera); 300 lichen species, first drawing of ascus; soralia treated as seedsCarl Lineus (1753, Species Plantarum, only 80 lichen speciesScopoli (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 HelsinkiFries, 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 contributions1822—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

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 task1890 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 importantlichenological publications1907 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

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 – 1photobiont

• 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 46,25Basidiomycota 16.000 50 0,31Deuteromycota 17.000 200 1,18Mastigiomycota 1.170 1 0,09Myxomycota 625 22 0,32Zygomycota 765 0 0Total 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:photobionts 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 tundras2- very hot and dry: deserts, semidesertsFavurable 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)