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Cladina stellaris and Stereocaulon tomentosum

Cladina stellaris and Stereocaulon tomentosum

Bryant is the author of today's entry:

I would like to thank Richard Droker (aka wanderflechten@Flickr) for this image of a lichen community near White Pass, Yukon. The highly branched/shrub-like species of lichen towards the upper half of the image is Cladina stellaris (formerly Cladonia stellaris) and the more coral-like species occupying much of the lower third of the image is Stereocaulon tomentosum. The vascular plant is crowberry, or Empetrum nigrum. If you think that this image looks like a miniature forest, you are not the only one. A major economic use of Cladina stellaris is for miniature trees on small scale models by hobbyists and architects alike.

Lichen communities like this one can dominate a local environment. Often forming dense mats, lichen communities can out-compete plant species for real estate by preventing seedlings from establishing themselves. Seedlings that do manage to take root may be pulled out or damaged by the repeated swelling and contracting of the lichen with changes in moisture. Lichen communities can also affect the underlying soil systems by regulating soil nutrients, retaining soil moisture, and maintaining microbiological communities.

Cladina stellaris (commonly known as star-tipped reindeer lichen) often forms large and rather dense mats in its widely distributed range. As its common name suggests, it is a major source of food for both reindeer and caribou, especially in the winter. Cladina stellaris contains the liver-toxic substance usnic acid, used in products like perfumes and antibiotics. Usnic acid has a bitter taste, which has deterred indigenous peoples from eating raw lichens. However, reindeer and caribou can tolerate the acid with the aid of rumen microorganisms. It has even been proposed that usnic acid aids in digestion by reindeer because it can be successfully metabolised by the rumen microbes. Indigenous peoples discovered that the partially digested lichen found in the first stomachs of reindeer and caribou can indeed be eaten, as the usnic acid has been broken down.

Stereocaulon tomentosum is a woolly lichen with rounded gall-like growths that contain blue-green algae. Richard has also taken a close-up image of the woolly hyphae and gall structures.

8 Comments

This is very cool!

How large/small are the lichen on this wonderful photo?

How beautiful! A reminder of the wonder beneath our feet! Thank you.

Thanks to Bryant for a wonderfully informative description. One correction, to quote McCune, Bruce, and Geiser, Linda (2009) Macrolichens of the Pacific Northwest, "Species in Cladonia subgenus Cladina, also known as reindeer lichens, were formerly placed in the familiar genus Cladina. Molecular evidence shows reindeer lichens to be part of Cladonia in its current sense (Stenroos et al. 2002). Reindeer lichens are richly branched, lack a persistent primary thallus, and have a cobwebby surface texture because they lack a cortex."

I would say that when you click on the image the larger version appears close to life size.

thank you a most interesting posting

Um, isn't 'Caribou' just alternative (North American) common name for 'Reindeer', Rangifer tarandus?

Re: the Cladina / Cladonia issue. That's my fault. I changed Bryant's entry from Cladonia to Cladina based on what I first found on the Ways of Enlichenment site -- and I didn't delve deeper into their site to find out that they had taxonomic notes explaining why they are using Cladina instead of Cladonia (for ecological / field work reasons, as opposed to being strictly molecular). Fred Rhoades was the first to point out the change to me, so I sent a note to the folks at Ways of Enlichenment and they directed me to use the same resource as Fred for the latest in lichen taxonomy: the North American Lichen Checklist. So, now I know. And I have to apologize to Bryant.

As to the reindeer / caribou issue: I'm not certain what to comment on that. Some sites say, "No difference, other than one is domesticated and one is wild." Others say, "Classified as two different subspecies" or “many different subspecies”. And, the “science is unsettled” and still in need of additional molecular study.

Glad that is all cleared up. To be honest, I didn't realize there might have been a discrepancy there. Thank you again Richard for regularly submitting such high quality images, which have sparked a serious interest in lichenology for me.

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