A Walk Through Time

The Lichen Consolidation

435 Million Years Ago

Lichen land pioneers spread. Hardy and long-lived (some reach 9000 years of age), these low-lying photosynthesizers are an arresting example of symbiosis.

Just as bacteria and protoctist mergers led to algae, lichens represent a merger of fungi with photosynthesizers (algae and/or cyanobacteria). An entirely new life form, lichens enjoy the algae's ability to use solar power to make food and the fungi's ability to store water and protect themselves from the elements.

Through rock weathering, lichens play a significant role in the geological cycle. Crustose lichens produce acids which chemically decompose rocky substrates; lichens manufacture a variety of acids depending upon the nature of the rock. Lichens also produce a glory of pigments. We still do not understand how or why.

Top and middle: Over 25,000 fungal species consort with photosynthetic companions, producing eminent varieties of lichens. (Photograph by Roger Leo, top-left, courtesy New England Science Center, Stephen and Silvya Sharnoff, top-right, Lois Brynes, mid-right and left)

Bottom: On the left is a healthy fungus; on the right, a healthy alga. Their merger produced the British Soldier Lichen (center, also in photograph at top-right). Taking everything we know about algae and fungi, we still never would have predicted the outcome of their synergy. (Illustration by Christie Lyons)

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