Slide 1
A lichen combines a fungus with food-making partners
A lichen contains a fungus living with partners that make food using light, such as algae or cyanobacteria, a group of bacteria. Together they form a recognizable composite body.
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The fungus supplies much of that body's structure. The photosynthetic partner produces carbon compounds, so the visible crust or tuft is not simply a small leafless plant.
Slide 2
The partnership can form crusts, lobes or branches
Lichens can form crusts, leaflike lobes or branching growths. These forms help describe them before a species is identified.
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Colour alone rarely settles identification. Specialists may inspect microscopic structures or chemical reactions, because unrelated-looking growth conditions can alter appearance and similar species can share obvious features.
Slide 3
Some fragments carry both partners to a new site
Some lichens spread fragments containing both main partners. A fragment can establish without first locating a new photosynthetic companion.
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Fungal spores take a different route: a successful spore must encounter a suitable partner. Packaging partners together and dispersing only the fungus solve reproduction in different ways.
Slide 4
A tree can be a surface rather than a food source
Lichens grow on rock, bark and other exposed surfaces. Their presence on a tree does not automatically mean they are feeding on the tree.
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Bark texture, chemistry, light and moisture help select the community. Two nearby trees can therefore host different lichens without either tree being diseased or harmed by the occupants.
Slide 5
Changes in lichens can reveal changes in the air
Different lichens respond differently to pollution and nutrients in the air. Researchers can use changes in communities as environmental evidence.
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Interpretation needs local context and species knowledge. A bare trunk by itself cannot diagnose air quality, because shade, bark properties and disturbance also influence whether lichens establish.
Sources
- Lichen Biology
British Lichen Society
- Lichens and air quality
US Forest Service