Essential lichens

Walking among the sandstone boulders of Red Rock State Park or the igneous formations of Malibu Creek State Park, you may have noticed splotches of black, green or orange. Wandering among the chaparral, maybe you've seen colorful scablike growths on the tree trunks and shrubs. Have you ever sat down next to a rock and started picking at a crustaceous growth that may or may not be part of the rock itself?

If any of those experiences ring true, you have found yourself in the presence of one of the planet's most interesting life-forms.

Although a seemingly benign force in nature, lichens are essential in maintaining healthy ecosystems. While classified as a single species, lichens are unlike any other species on the planet in that they are an alliance of two or three separate organisms. They incorporate species from three separate kingdoms: fungi, plant and/or monera.

Fungi cells are always present in lichens, most often in combination with algae. Occasionally fungi cells join solely with cyanobacteria or in combination with the algae and cyanobacteria. In most cases, the threadlike hyphae of the fungus wrap around algal cells, forming one cooperative organism.

SYNERGY- Lichens are an alliance of separate organisms. While organisms within lichen may live individually, many species of lichen fungus cannot exist without the aid of the algae. The fungus is known as the mycobiont while the algae or cyanobacteria is referred to as the phycobiont, which is responsible for photosynthesis. By photosynthesizing, phycobionts produce carbohydrates necessary for the survival of the fungus. Often algae cells are destroyed by the fungus harvesting the energy. But because algae cells reproduce more quickly than they are consumed, lichens are able to maintain this relationship.

While it is clear how the fungus benefits from this association, what are the advantages for the algae? Through fungi's ability to store water and minerals, algae attains the nutrients necessary to photosynthesize. The fungi are also thought to provide the physical structure for the lichen. But if algae is able to exist independently of the fungus, why be lichen? I believe the answer exists in distribution.

Nature's pioneers

Lichens are amazing at colonizing the most remote and inhospitable places conceivable. They are prolific in the arctic tundra, wellestablished in barren deserts and have even survived 15 days in the vacuum of space under harsh radiation differentials. So while algae can live without its fungal counterpart, its distribution would be limited without the ability of the fungus to harvest water.

In addition to distribution, lichen's symbiotic relationship plays an essential role in ecology. Because they can occupy inhospitable environs, lichens are pioneers of seemingly lifeless places, especially bare rock and desert sands. As lichens colonize rocks, they collect moisture. In some cases the water will freeze, expand and pry off tiny bits of rock.

In other cases, acids released from lichens will cause the decomposition of the rock. Both this chemical and physical erosion begin the extremely important process of building topsoil. As these fragmented bits of rock accumulate, they provide fertile ground for more complex plant life to inhabit. From there a diverse ecosystem originates.

Beyond soil formation, lichens are an important resource. Birds and squirrels use lichen to build their nests. Deer will resort to eating lichen in times of hardship, as will wild turkey. Many larval species in the Lepidoptera order (moths, butterflies, and skippers) feed entirely on lichen. For arctic caribou, lichens are 90 percent of their winter diet.

Unclassifiable

Of equal importance, lichens have become indicators for pollutants. Because of their sensitivity to manufactured toxins, they cannot tolerate air pollutants and therefore do not grow. They tell the tale of clean or polluted air in a particular area.

Lichens are also highly valued for the colorful dyes made from boiling or soaking them in ammonia. Additionally, they are used in antibiotic salves, deodorants and herbal tinctures. While some are edible when faced with a survival situation, I would not say they are palatable.

Lichens are thought to be one of the oldest living organisms in the world. Slow-growing- less than a millimeter per year- they create tremendous change over centuries, creating fertile growing places from once desolate land.

Ancient and extremely stable, this life-form seems hard for our culture to wrap its mind around. The symbiotic relationship has been described as parasitism, commensalism (benefiting one organism without harming the other) or mutualism (both organisms benefiting).

Is it because this life-form lives so outside the realm of our understanding that we don't know how to classify it? Perhaps we need to look more closely at lichens and broaden and enhance our understanding of relationships with others.

Reach Meghan Walla-Murphy at mwallamurphy@yahoo.com.