Merry Christmas! Cryptothecia rubrocincta, the Christmas Lichen

Tom Volk's Fungus of the Month for December 2006

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Cryptothecia rubrocincta from Florida

This month's fungus is a beautiful lichen found on the Gulf Coast of the United States, down thorough Mexico and Central America and into the tropics of South America. It can also be found on the coastal plain of Florida up through North Carolina. Cryptothecia rubrocincta is commonly called the Christmas lichen due to its spectacular red and green color. The red color often encircles the thallus of the lichen, like a wreath. In fact the epithet "rubrocincta" means "red wreath." Sometimes this species is called the Christmas wreath lichen. It's really one of the most spectacular lichens to see.

A lichen is a mutualistic relationship between a fungus (the mycobiont) and an alga or a cyanobacterium (the photobiont). The photobiont provides the fungal partner with sugars from photosynthesis, while the mycobiont provides protection from the environment for the alga or cyanobacterium. This symbiosis allows the lichen to grow in very inhospitable environments, such as on exposed rocks and gravestones. The Christmas lichen is typically found on the sides of trees in open areas that get a lot of sunlight, often in an area where there are lots of palmetto. I'll have more to say about that kind of area later.

another beautiful Christmas lichen

There are perhaps 15,000 species of lichens, almost all of them Ascomycota. Lichenized fungi can be found in 16 orders, 5 of which are entirely composed of lichen-forming fungi. The fungus determines the form of the lichen. Usually reproduction of the fungal partner can be seen with small cups called apothecia, but sexual reproduction is unknown in Cryptothecia.

There are over 24 genera of photobionts; over 70% come from Chlorophyta, the green algae. Eight genera of Cyanobacteria (blue-green algae) are represented. Over 90% of lichens contain a photobiont from either Trebouxia (75% in temperate zones), Pseudotrebouxia, Trentepohlia or Nostoc. Most are not found free living, which means they are dependent on the fungus for their livelihood.

Lichens of all types grow extremely slowly, partially because they are exposed to optimal growing conditions for only a few hours in the morning when still sufficient moisture from fog, dew or recently melted snow to allow photosynthesis to occur at its optimum rate The average annual growth rate usually less than 1 mm-- the known record is 4 mm. You can almost watch them grow. (ha!)

Two lichens have already been fungus of the month: Cladonia cristatella, the British soldier lichen and Cladonia rangifera, one of the reindeer lichens. I've included more details about lichens at both of those pages, so I won't repeat that information here.

Chemistry is very important in the identification of lichens. There are a series of indicator chemicals that are dropped onto the thallus of the lichen-- many lichen change colors when an alkaline chemical such as a 3% solution of potassium hydroxide is dropped onto the thallus. In this case, the naturally occurring red color of Cryptothecia rubrocincta is a result of the chemical chiodectonic acid (Edwards et al., 2004). There are many interesting chemicals found in lichens. Lichenologists suspect that the various chemicals act as protection for the lichen, helping to prevent being eaten by insects or other animals. The Christmas lichen is actually used in Brazil to make dye.

Wakulla Springs area, site of the Florida 2000 NAMA regional foray

I have been lucky enough to collect fungi on the Gulf Coast on several occasions with the Gulf States Mycological Society (mostly with Toby Feibelman and Bill Cibula) and the Texas Mycological Society. People from the South are very nice, and they know their mycology! For a northerner like me, another perk is that I can go to the Gulf coast to collect when it's cold and snowy up here in Wisconsin. You can't beat that. I've also been there during the summer, when it's very hot and muggy-- it is subtropical, you know.

Owing to their location, the fungi on the Gulf coast are an interesting mix of temperate species and tropical species. In the winter months, many species typical of northern areas can be seen, while in the summer the tropical species show up. Many of these tropical species have their spores blown up from the Caribbean islands and South America during hurricanes and other storms.

The area where I have found the Christmas lichen are typically very sandy and very dry, leading to trees and palmettos that are very far apart, as in the picture to the left. This allows a great deal of sunlight to reach the lichens, so these palmetto areas are great places for many other kinds of lichens as well. The lichens can survive where plants cannot because they can survive with very small amounts of water. The particular area in Florida where I took the picture to the left was a mixture of palmetto and longleaf pine, which has perhaps the strangest growth history of any pine.

alligator warningOf course there are dangers of collecting along the Gulf coast that are not found in more northern habitats-- like alligators! You should be careful if you're collecting on the edge of a waterway inhabited by alligators. Leaning over the water to collect a mushroom on a protruding stick may get you more than you expected if there's a 'gator lurking!

Bill Cibula, eminent mycologist at NASA, at a foray for the GSMS in Florida To the left you can see one of the forays of the GSMS in Florida, and at the center is Bill Cibula, who was the guru of mycology in the south for many years. Bill spent most of his career as a mycologist at NASA, pioneering remote sensing of fungi. Always very innovative, he was able to correlate the health of the forest as shown from satellite images with studies of the fungi in the forests themselves. Bill also worked for a time on mushroom cultivation on wastes in zero gravity in anticipation of colonization of the moon or Mars. Bill was also a strong advocate of amateur mycologists and was the mycologist at many GSMS forays and other forays throughout the country. We miss you, Bill.

I hope you enjoyed learning about Cryptothecia rubrocincta, the Christmas lichen. There's always something fun to find if you visit another part of the world. I hope you will have happy holidays.

If you have anything to add, or if you have corrections, comments, or recommendations for future FotM's (or maybe you'd like to be co-author of a FotM?), please write to me at my email address

For a Christmas treat, click here for "Fungi that are necessary for a merry Christmas."

This page and other pages are © Copyright 2006 by Thomas J. Volk, University of Wisconsin-La Crosse.

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Edwards, Howell G. M , Luiz F. C. de Oliveira, and Mark R. D. Seaward. FT-Raman spectroscopy of the Christmas wreath lichen, Cryptothecia rubrocincta (Ehrenb.:Fr.) Thor. The Lichenologist (2005), 37: 181-189