the wonderful world of lichen

Speakers: Duncan Wright and Peter Bisset

What Are Lichens?

Composite organisms, not single species

Mixture of fungus + algae/cyanobacteria

Mutually beneficial relationship (symbiotic)

Fungus provides shape/protection, algae photosynthesize for sugars

Once combined, neither can revert to independent state

Named after fungus component (Linnaeus system)

~20,000 species worldwide, ~2,000 in UK

Extremely slow growing: <1mm/year on rocks, faster on trees

Why Study Lichens?

Add environmental interest in urban/rural/coastal settings

Don’t migrate or change seasonally - consistent for observation/photography

Everywhere from North Pole to South Pole (4 species in Antarctica)

Provide food/shelter for invertebrates (mites, molluscs, snails, moths)

Birds use for nesting material

Indicate environmental history/pollution levels

Alien compared to other organisms - very different biology

Lichen Structure & Terminology

Thallus: body of the lichen (what you see)

Three basic types:

Crustose: thin crust, can’t remove with fingernail

Foliose: leaf-like, loosely attached, different upper/lower surfaces

Fruticose: shrub-like, attached by single point (holdfast)

Key features for identification:

Cortex: protective upper surface

Rhizomes: root-like attachments (not true roots)

Cilia: eyelash-like projections (purpose unknown, possibly moisture collection)

Soredia: powdery grains containing fungus + algae

Isidia: coral-like projections that break off

Reproduction Methods

Asexual reproduction via soredia/isidia (contains both partners)

Sexual reproduction through fungal spores only

Multiple genders, very complex

Spores must find algal partner to form new lichen

Nobody has observed lichen formation from scratch

Three fruiting body types:

Lecanorine: “jam tarts” - black center, lighter rim

Lecideine: “wine gums”

Lirellae: “squiggly writing” - various curved shapes

Local Species Examples

Caloplaca flavescens: churchyards on limestone, not sandstone

Diploicia canescens: “pepper pot lichen” - holes in top

Hypogymnia physodes: hollow structure, no lower surface

Flavoparmelia caperata: “40 mile per hour lichen” - fast growing (1cm/year)

Candelaria concolor: near main roads (benefits from car exhaust nutrients)Parmelia sulcata: very common, different upper/lower surfaces

Xanthoria parietina: yellow/orange, common on nutrient-rich sites

Graphis scripta: black “writing” patterns on bark

Identification Resources

Hand lens essential for proper observation

Field guides: Dobson (standard reference), new book by Rebecca Yahr coming December

British Lichen Society website (free resources)

No standard English names - must use scientific Latin names

UV light reveals fluorescent properties in some species

Pioneer species appear first on new surfaces (metal bins, young trees)

Simon Edgington