34 Nebraskaland • April 2020
Lichens
How Fungi Became Farmers
Story and photos by Gerry Steinauer
ost people have seen lichens, those green, gray or
yellow growths on the bark of trees, the shaded side
of old sheds or on rocks down by the creek, but few
take notice of them. If they do, many assume they are
a plant, moss, fungus or who knows what.
Lichens are none of the above, and are instead a strange
living partnership between a fungus and one or more alga
species that look (and act) like a single species. Viewed in
another light, they are fungi that have taken up farming
using algae.
Lichens fi rst appeared in the fossil record nearly 400
million years ago, and the union of fungi and algae has
occurred several times over evolutionary history. Today, more
than 19,000 known species live in habitats ranging from the
frozen poles to steamy tropical rainforests, from bone-dry
deserts to rocky mountaintops. They come in an amazing
array of colors, sizes and forms.
The Organism
Most people are familiar with the mushroom-forming
fungi, but the majority of lichen-forming fungi belong to the
M
Lichens grow on a variety of substrates, mainly rock, soil, bark and wood. Above, several species of foliose lichens grow on a
partially-shaded, old barn door in southeastern South Dakota.
