Lichens

Why study lichens?• Important part of Ireland’s biodiversity

with ~1,165 species• West of Ireland very important

Photo: Maria Long

• Pollution indicators• Disappearance of

lichens led to black (melanistic) form of peppered moth

• Hawksworth & Rose scale (1970)• 0-10 for acid and

basic bark

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/E/Evolution.html

• Used for dyeing e.g. crottle

• Used in medicine

• Used in perfumes & pot pourri

• Lichens provide food and/or shelter for animals http://www.irishlichens.ie/pages-lichen/l-18.html

• Under-recorded• Year-round activity

What are lichens?• A lichen is ‘an ecologically obligate, stable

mutualism between an exhabitant fungal partner and an inhabitant population of extracellularly located unicellular or filamentous algal and/or cyanobacterial cells’ (Hawksworth et al., 1995)

• A lichen is ‘a stable self-supporting association of a fungus (mycobiont) and an alga and/or cyanobacterium (photobiont)’ (Hawksworth et al., 1995)

• 1860s – Simon Schwendener – true nature of lichens

• ‘..the unnatural union between captive algal damsel & tyrant fungal master’ Crombie, 1874

• Symbiotic relationship i.e. mutual benefit to both

• Fungus– provides the alga with structure and shelter from

extremes of temperature, light and moisture.- forms the majority of the lichen

• Autotrophic alga provides heterotrophic fungus with carbohydrates

• Cyanobacterial partner (if present) fixes nitrogen also

• Allows both to survive in niches and habitats that they would be unable to survive in alone

• Very different to bryophytes! – Some may look like

some thallose liverworts but lichens are:• usually tougher &

opaque• a different colour

on the underside

Fungal partner• Name given to the lichen

applies to fungal partner (mycobiont)

• Different fungus in each lichen

• 98% of lichens in phylum Ascomycota

• Remaining 2% in the Basidiomycota and Fungi Imperfecti

• ~13,500 lichens globally (some estimates up to 18,000)

Photobiont partner• ~40 genera of photobiont:

~2/3 algae and ~1/3 cyanobacteria• Same photobiont can occur in many lichensMost common:

algae cyanobacterium

Trebouxia genus

Trentepohlia genus

Nostoc genus

Growth forms• Foliose - Thallus (lichen

body) is leaf-like- May have rhizines

http://1.bp.blogspot.com/-AcO6nxzHY1U/TXfbl1TopxI

Growth forms• Fruticose- Shrubby/ branched

Growth forms• Leprose- ‘Powdery’ - No fruiting bodies

Growth forms• Crustose – Thallus lies flat

on substratum– Most common

form

Sexual Reproduction• Fungal partner – long-lived fruiting bodies release

spores• After germination the spore must meet a suitable

algal partner before it can develop further

AscomycotaAscocarps - Most common– spores in ascus - usually 8 spores – produced in perithecia & apothecia

BasidiomycotaBasidiocarps- Spores on a basidium ->

Ascocarp fruiting bodies

Various forms of apotheciaHymenium

Apothecia fruiting bodies Disc-

shaped Lecanorine – the margin is the same colour as the thallus (contains algal cells)

Lecideine – No thalline margin

http://www.fungalpunknature.co.uk/Others/MossLichGall/LecanoraChlarotera.jpg

Lirellate (elongate)

Athonioid – apothecia are poorly defined

‘Squash preparations’Multiseptate spores

Muriform spores

Graphis scriptaGraphina anguina

Lichen reproduction - Asexual• Thallus fragmentation or • More specialised structures: 1) Isidia - minute outgrowths from the thallus that

contain both fungal and algal cells and are easily broken off by passing animals and invertebrates and dispersed

http://gis.nacse.org/lichenair/

Lichen reproduction - Asexual

2) Soredia - fine powdery granules also containing both fungal and algal cells and can be spread by water, animals and wind.

http://www.kollathdesign.com/images/gallery/soredia.jpg

Lichen acids

• Secondary metabolites– antibiotic properties to defend

themselves from bacteria and fungi– allelopathic effects - assist in competing

for space with higher plants and bryophytes

– prevent against being eaten

• ~400 known • 1-3 in any given lichen• Help with identification

Chemical tests

• Potassium chloride (K)• Sodium hypochlorite (C) & • Para-phenylenediamine (Pd)• Cause characteristic colour changes• Drops usually placed on the cortex

for example…..

Lichen Ecology• Climate – wetting/drying cycles• Light availability –shade-tolerant spp.• Quality of environment – air pollution,

disturbance,etc

Substratum type – important in identification alsoLichens can be:- corticolous (growing on bark)- saxicolous (growing on rock)- lignicolous (growing on wood)- terricolous (growing on soil)- muscicolous (growing on moss)- lichenicolous (growing on

other lichens)

The condition of the particular substratum is

also a factor, for example, acid rocks/bark may

support a different range of species than basic

rocks/ bark.

Collecting - Equipment

• Hand lens (x 10 & x20)• Spray bottle• Knife• Secateurs (for cutting twigs)• Hammer & chisel (for collecting lichens on rocks)• Paper packets

Some books on lichens:

• Lichens – An Illustrated Guide to the British and Irish Species by Frank S. Dobson (5th edition, 2005). The Richmond Publishing Company Ltd.

• Lichens by Oliver Gilbert. (2000) by Harper Collins.

• Lichens on Trees (British Plant Life No 3) by Alan Orange (2000) National Museum of Wales.

• The Lichen Flora of Britain and Ireland by O.W. Purvis, B.J Coppins, D.L. Hawksworth, P.W. James & D.M. Moore (1992) The British Lichen Society

Some lichen websites:

• Lichens of Ireland Project: http://www.lichens.ie/

• LichenIreland Project: http://www.habitas.org.uk/lichenireland/

• Photographs of Irish lichens: http://www.irishlichens.ie/

• The British Lichen Society: http://www.thebls.org.uk/