Lichen Colors

Xanthomendoza trachyphillaBrowns Park NWR, Moffat County, CO.

Lichens come in some fabulous colors. They decorate our rocks and trees and in some places they dominate their substrate so heavily that we don’t even see the rock underneath. Only seeing the lichens. The wonderful flatirons of Boulder are a great example. You can see the Pleopsidium flavum from miles away1! Depending on who you ask, lichens cover between 5-8% of the Earth’s land surface2.

The brilliant reds and oranges of the family Teloschistaceae are particularly stunning. The red color comes from a series of different compounds called anthraquinones, in part. The color is so distinctive to the family that is it nearly diagnostic (don’t worry, lichen lovers, exceptions abound).

One fun thing about this group of chemicals is that they turn a deep purple when exposed to potassium hydroxide, called a K test if you want to look cool around other lichen enthusiasts.

Usnea hirta Lyons, CO

Another important lichen color to learn is a rather unique yellow/green (left). This color comes from usnic acid. It is a very common lichen substance. The term lichen substance is a very unimaginative term used for the unique chemical compounds that lichens produce. Lichen substances are very important in taxonomy and often identification.

Lichens in the family Physciaceae are a wonderful blue grey color (below) that is a great test of your photography skills. I, at least, never get the color to show up true.

Physcia sp. – Lyons, CO

Once you are done ogling over some lovely lichen thalli, ponder a simple question. Why are lichens colorful? Lichens live an odd life. They grow extremely slowly and never move, just sitting there soaking in the sun, while their photobiont friends make them sugars.

Peltigera aphthosa – Boulder, CO

The other photosynthetic organisms lichen hunters encounter frequently are a good start for what color a lichen should be. I’m talking about plants (hardcore lichen finders only acknowledge plants as a potential substrate for lichens to grow on; skip this paragraph if it’s upsetting). Plants are green because they want their photosynthetic cells to get as much light as possible and the chlorophyll they use is a bright green. In other words, no other colors are in the way of absorbing precious light. Our good friend Peltigera aphthosa (right) is green (when wet) for a similar reason3. But it is by far the exception; most other lichens need to be cut into to reveal the photobiont. This means the lichen is sacrificing optimal light penetration.

So why are lichens so beautiful? The resources I own spend very little time on the subject. In Brodo’s Lichens of North America we only get two pages. One possibility is that bright colors are protective against ultraviolet radiation. This appears to be very true with our Rusavskia elegans (I promise a lichens in space post soon and, yes, its related). White colors can scatter light, which is protective for species that are in exposed habitat. The lichens can’t afford for their photobiont friends to bake or they won’t live long.

I hope to come back to this question in a new series of posts. Get ready to break out your old biology textbooks, and, far more frighteningly, maybe even a little organic chemistry.

1 Okay, some squinting required, but if you see any lemon yellow up there it’s very likely this species.

2 Asplund, J., & Wardle, D. A. (2016). How lichens impact on terrestrial community and Ecosystem Properties. Biological Reviews, 92(3), 1720–1738. https://doi.org/10.1111/brv.12305

3 While I couldn’t specifically find an answer, the photobiont in Peltigera aphthosa is a green algae in the genus Coccomyxa. Like plants it uses chlorophyll a, but may have different concentrations of other chlorophylls. There are three CO Peltigera that share this character, Peltigera venosa, leucophlebia, and aphthosa. The remaining Peltigera have Nostoc, a blue-green cyanobacteria, as a photobiont. They also are bright green only when wet and brown/green when dry. I’d love to try and figure out why this rather major difference does not put the green algae species in their own genus. Check out this post for some more information about Petigera leucophlebia.

An Introduction

Hello! I am very excited to introduce myself. My name is Nick Moore. I am looking forward to sharing the world of Colorado Lichens and I hope to be a regular contributor to this wonderful site that has been built over the years.

So who am I, you might ask. I am someone who has always loved nature, who only recently decided to learn the ways of lichens, and has leapt headfirst into this new world. Hopefully those that stumble across these posts want to come along for the ride.

Why don’t we start with some of my favorite local species. These are some charismatic species that can be found on just about every hike through the lower foothills of Boulder County.

Rusavskia elegans – Anne U White Trail, Boulder CO. On Granite

By far the most common orange lichen on rock along the front range. Older references may refer to this species a Xanthoria elegans.

Pleopsidium flavum – Mount Sanitas, Boulder CO. On Granite

The answer to what’s that yellow on that rock over there along much of the front range. This lichen has an amazing need to be on vertical rock faces.

In a prelude to what I hope will be a future blogpost this species has been taxonomically unsettled in the state. So I would not be surprised to someday learn that this is the wrong name for this lichen or even that multiple species are involved. That day may come as soon as the right person reads this paragraph!

Dimelaena oreina – Mount Sanitas, Boulder CO. On Granite

Perhaps my favorite front range lichen. Once you learn it you will find it very common on sunny exposed rocks. But, unlike the previous species you will find is accompanied by a whole host of similar colored species. Identifying lichens is hard, observing them in all their beauty is easy.

Parmelia sulcata – Button Rock Preserve, Boulder CO

Start walking up your favorite foothill trail. When you get to a nice cool spot under the shade of a big conifer, look down into the tangle of moss and lichen at the roots of the tree. One of the lichens you find is sure to be this wonderful foliose lichen and you’ll soon find it on other substrates as well. Just be sure to note the raised web of white tissue forming what look like cracks (pseudocyphellae) characteristic of the genus. Keep searching and you will find that sulcata is not the only member of the genus present in Colorado.

I hope you enjoyed the post. Perhaps you noted that each photo here links to my iNaturalist observation for the lichen. I hope to have iNaturalist be a constant part of my posts here, and you can always see more of my photos by searching for @nickmoore91. I post everything from birds, insects, fungi and more. Feel free to reach out!

My CO Lichen Observations – Warning some non-lichenized ascomycete fungi show up in that search!

Welcome, 2022!

Changes are afoot here at Colorado Lichens. After long dormancy, we’ve relocated and cleaned up a bit, and the transition is mostly complete as of March 17. After five years’ absence from Colorado, I don’t know that I have much more to say about the lichens of that lovely state, and will actively seek an interested party to assume this domain and perhaps some of its content.

It looks as though everything is working properly, although you may stumble across missing images. If that happens, please let me know— I’ll have a contact form up soon for reporting issues and general comments.

ID Tips for Lichen Newcomers

How do you start figuring out lichens if you’re a novice, especially if you have no keys? With 85% of my books, including lichen ID materials, still in storage (long story), I’m thrown on the resources of the internet. Here are a few suggestions for exploring lichen basics (off-site links open in a new window):

Guide to British Lichens on Twigs, with picture key! Click to go to site.

Guide to British Lichens on Twigs, with picture key! Click to go to site.

There is an online lichen key from the UK for 60 British lichens on twigs (from the Natural History Museum at South Kensington); they also have a glossary of terms. To get started, choose whether the lichen is fruticose, foliose, or crustose. (See descriptions at our Shapes and Sizes page if you’re not sure.) You eventually get to a color photo of the lichen. If you get one or more results, don’t assume the species is right, but it might at least point you to a genus to check out. (I got a lot of “no results” on my searches, but I was just making up characters.)

You might try checking photos at Ways of Enlichenment, which does a good job of showing many species in each genus.

Steve Sharnoff offers some lichen basics at his website. He also has lots of photos available that may also be helpful, but this site is focused on North America. Some species, however, are widespread, and many genera are.

If you narrow it down to a few species, you can check whether they occur in your area at this database maintained by the Consortium of North American Lichen Herbaria (CNALH). Their records include specimens from all over the world. If you go to their dynamic map and click on your area (and specify a radius to search), they will generate a checklist that you can also use as an interactive key. Very nice!!

Only the lichen portal at CNALH will give you a detailed description of important characters, but at least the others provide visual references.

Note: Also posted this on iNaturalist as a journal entry.