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posted: 10/6/2012 10:50 AM

Why you should like lichens

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  • A closer look at lichen at Tekakwitha Woods in St. Charles. The gray-colored lichen is called Physcia millegrana, the orangish-greenish is Candelaria concolor. They are known only by their scientific names.

       A closer look at lichen at Tekakwitha Woods in St. Charles. The gray-colored lichen is called Physcia millegrana, the orangish-greenish is Candelaria concolor. They are known only by their scientific names.
    Laura Stoecker | Staff Photographer

  • Lichen and jelly fungus share a tree branch at Tekakwitha Woods in St. Charles. The gray-colored lichen is called Physcia millegrana, the orangish-greenish is Candelaria concolor. Jelly fungus is the wavy brown gelatinous growth on far right, which is called Tremella foliacea.

       Lichen and jelly fungus share a tree branch at Tekakwitha Woods in St. Charles. The gray-colored lichen is called Physcia millegrana, the orangish-greenish is Candelaria concolor. Jelly fungus is the wavy brown gelatinous growth on far right, which is called Tremella foliacea.
    Laura Stoecker | Staff Photographer

  • Lichens, a partnership between algae and fungi, come in different colors, can live on tree trunks for many years, and do no harm.

      Lichens, a partnership between algae and fungi, come in different colors, can live on tree trunks for many years, and do no harm.
    Courtesy of Jan Riggenbach

  • Lichens live on tree branches all over. Shown are two kinds of lichens at Tekakwitha Woods in St. Charles.

       Lichens live on tree branches all over. Shown are two kinds of lichens at Tekakwitha Woods in St. Charles.
    Laura Stoecker | Staff Photographer

 
By Valerie Blaine
Forest Preserve District of Kane County

They're friends with benefits. They lead unassuming lives, and their living arrangement goes largely unnoticed. They get along famously, and they're committed to each other for life.

This odd couple is called lichen, a partnership of algae and fungi.

Lichens are among the most fascinating yet overlooked and underappreciated organisms in Illinois. Their unique lifestyles and niches are well worth exploring.

Lichen partners are classically codependent, but it's a win-win situation. The fungal partner cannot make its own food. The alga can. The alga needs someone to lean on. The fungus is there for it. Scientifically speaking, this is called symbiosis. The algal partner provides food by photosynthesis, and the fungus provides form, structure and stability. It's a lovely liaison.

The success of the relationship is evidenced by the fact that lichens are found all over the world. They occupy many different niches in all kinds of habitats, from frozen tundra to rocky deserts, hardwood forests to ancient ruins, and swamps to cemeteries. Over 400 species live here in the Prairie State. They're pretty hardy and don't ask for much, just a substrate (something to grow on), a little sunlight, and some moisture once in a while.

So, you may be asking, how will I know a lichen when I see one? If you spot something from afar that looks like yellow paint on a branch, a bluish-gray coating on a rock, lime green spots on a fence post, or a black blob on a boulder -- chances are, you've got lichen. Look very closely and you'll see the lichen's shape and form. It may be flattened and leaflike, hugging a twig or a branch. Or, it may be crust-like, plastered to a rock or a piece of bark. Lichen may also be branched like miniature shrubs. Some appear to be attached to the substrate by small suction cups.

What do lichens do, anyway? Like all organisms, they grow. And, like all organisms, they reproduce. But, it's complicated. Sometimes lichens reproduce vegetatively, without the hassle of finding a partner. They do this by making special packets of algae and fungus that are carried by wind or water or critters to generate new lichen.

Sometimes, just to mix things up, lichens reproduce sexually. Sexual fusion of fungal cell nuclei takes place in fruiting bodies called apothecia, resulting in spores. The spores are disseminated hither and yon, and if lucky, one will land in just the right spot to germinate. The trick is that the newly germinated fungus needs to snare an alga or it will perish. A fortuitous union may occur, or the fungus may "steal" an alga from another lichen. All's fair in lichen love.

Once a new lichen is formed, it begins to grow. Very, very slowly. Lichens grow so slowly that you'd have to wait for centuries to see them gain a few inches. And they can, indeed, live for centuries. Lichens are among the oldest organisms on earth, with records of arctic lichen reaching the ripe old age of 4,000, give or take a few years.

Lichens are relatively consistent in growth rate. Based on lichens' steady growth and longevity, scientists can use them to determine the age of rocks. This dating method is called lichenometry. It's akin to counting the growth rings on the cross section of a tree to determine how old the tree was when cut down. In lichenometry, a lichen's growth rate is extrapolated to the number of striations, or lines, to estimate years.

Lichens are also used in air quality monitoring. These organisms readily absorb water and air from their environment, and all the chemicals that come along. Some species are highly intolerant of air pollution. Their populations diminish as air quality declines. Lichens are thus the canaries-in-the-coal mine, a telling sign of air pollution.

Lichens have lots of other uses. Some species are edible for both people and wildlife. In their magnificent tome "Lichens of North America," Irwin Brodo and Sylvia and Stephen Sharnoff wrote that horsehair lichen is a traditional food source for Indians of the Pacific Northwest. And, according to "Native American Ethnobotany," published by the University of Michigan, Potawatomi Indians made a vegetable soup with the lichen Parmelia physodes.

In the Old World, Swedes used lichen in distilling brandy -- until they exhausted the lichen supply in the late 1800s. In Siberia, lichen was used as a flavoring for beer.

Lichens have an up side and a down side for wildlife. Reindeer and caribou are lichen connoisseurs. Lichens make up 90 percent of the winter diets of these boreal ungulates. However, wolves have been on the wrong end of lichen use. Scandinavians once used the lichen Letharia vulpina to poison wolves. The fatal concoction was made by mixing Letharia with reindeer blood, meat and ground glass.

Medicinally, lichens hold tremendous potential. The lichen known as rock tripe has been studied as a growth inhibitor of HIV, the virus leading to AIDS. Usnic acid from the lichen Usnea is extracted for its antibiotic properties. Some lichens have cathartic effects, both as laxatives and expectorants. Some are some are used as tonics and poultices. Medical research has barely scratched the surface of the biochemical benefits of lichens.

And, of course, there's beauty -- natural and otherwise. Those oh-so-attractive wigs worn by the bourgeoisie in 16th century Europe were dusted with lichen. Colors extracted from lichens are also used in art and ceremonial body painting, for hair cleansing and fragrance. Lichens produce beautiful colors as natural dyes in weaving.

Lichens are beautiful, useful, and just plain cool.

• Valerie Blaine is a naturalist with the Forest Preserve District of Kane County. She welcomes readers' questions, comments and suggestions. Email her at blainevalerie@kaneforest.com.

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