Lichens – Hiding in Plain Sight
Lichens are organisms growing on trees, rocks and soil that we come across on a daily basis. You may not know what they are... but you have definitely seen them before
BRIT Collections
Botanical Research Institute of Texas | Fort Worth Botanic Garden
Plant specimen (2019-12-28) by M. Dal FornoBRIT Collections
What are lichens?
Lichens are complex symbiotic systems formed by a main fungal partner (the mycobiont), a green algal and/or a cyanobacterial partner (the photobiont), along with a diverse community of microorganisms formed, primarily, of bacteria and fungi (the microbiome).
Lichenization: a fungal lifestyle
Based on nutritional strategy, fungi can be decomposers, yeasts, parasites and establish different types of symbiotic relationships, such as lichens, mycorrhiza and endophytes. Lichenization has evolved multiple times throughout the fungal tree of life.
Types of lichens
There are approximately 20,000 species of lichens recognized so far and many more yet to be discovered!
Lichens have different colors, textures, habits, preferences, rich chemistry, and many more unique characters we utilize for identifying them.
The three main lichens
1. crustose
2. fruticose
3. foliose
Aside from these major ones, others include gelatinous, filamentous, squamulose and dimorphic. The body of a lichen is called a "thallus", which is the resulting structure of these symbioses.
Plant specimen (Fruticose lichen)BRIT Collections
Fruticose lichen
Fruticose lichen is shrubby, stringy, or hairy-looking and named for its beard-like strands. Sensitive to air pollution, it's a natural air quality indicator.
Plant specimen by Manuela Dal FornoBRIT Collections
Fruticose lichen
An unidentified species of Usnea, a genus whose members are commonly called beard lichen.
Plant specimenBRIT Collections
Crustose lichen
Crustose lichens are crust-like; some even look like paint spots. This is an example from the Trypetheliaceae family.
Plant specimenBRIT Collections
Crustose lichen
Herpothallon rubrocinctum, is commonly called the Christmas lichen for its festive red-green hues, resembling holiday decorations. It thrives in tropical regions with high humidity.
Plant specimenBRIT Collections
Foliose lichen
Foliose lichens are generally leafy, forming lobes. This species, from the genus Cora, is particularly diverse in the tropics.
Plant specimenBRIT Collections
Foliose lichen
This species from the genus Sticta, commonly referred to as the spotted felt lichens.
Plant specimen (2019-12-29) by M. Dal FornoBRIT Collections
Where can you find lichens?
Literally anywhere! Some examples of habitats include woodlands, northern coniferous forests, rainforests, tropical forests, grasslands, and mangroves.
Plant specimen desertBRIT Collections
Lichens also live in extreme environments
In deserts, lichens develop protective layers to reduce water loss and go dormant in droughts.
lichens: ground litterBRIT Collections
...and some rather unusual places.
Plant specimenBRIT Collections
Love lichens?
Start today by looking on trees, rocks, soil, pavement, and walls in your neighborhood!
Story created by Manuela Dal Forno, Botanical Research Institute of Texas and Fort Worth Botanic Garden.
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