The black stubble in the top photo are the fruiting bodies of a lichen. I found them growing on a piece of weathered cedar of an old birdhouse. I had set up that birdhouse about twenty-five years ago at the edge of a field and forest. Over the years, as the forest grew around the birdhouse, these tiny lichens began growing on the wood.

Lichens are a varied lot. Depending on the species, they can look like dust, little shrubs, gossamer, leaves, or overlapping shingles. Some lichens, like the one in the top photo, resemble whisker stubble or tiny straight pins. They are, fittingly, called whisker lichens and pin lichens.

Whisker lichens are minute, measuring just 1 to 2 millimeters in size. Most only grow on old wood or the bark of old trees. Many species are considered indicators of stable forest environments with long-term ecological continuity.

Taxonomy

The fungal partner (mycobiont) in whisker lichens are members of the Ascomycota, a group of fungi known as cup fungi or sac fungi. Familiar Ascomycota include morels, penicillium molds, and yeasts that are used to ferment bread and beer.

The algal partner (photobiont) is a green alga, usually a species of Trebouxia, a genus of unicellular algae that exists in almost all habitats. They can be free-living, but many species form symbiotic relationships with fungi to form lichens.

Description and terminology

The thallus (body) of whisker lichens may be minutely rough-surfaced (verruculose-granular) or immersed. If immersed, the fungal hyphae and the algae photobiont grow just below the surface of the substrate.

Whatever the thallus form, the apothecia (fruiting bodies) are borne on a long or short stalk, or rarely, sessile. They may be gray, blackish-brown, or greenish-black. At the top of the apothecia is a globose to lenticular capitulum (“little head”), a cup-shaped structure that produces spores.

Determining species

Species determination in whisker lichens is complicated. Morphological characters can only go so far. At best, you might get to genus. For positive identification, microscopic examination of the capitulum and spores is necessary.

Finding whisker lichens

I have found whisker lichens growing on weathered jack pine twigs while photographing other lichens. Most of the ones I have seen seem to prefer old, weathered wood, but I did find one on green crustose lichen that was growing on an alder branch. It may have been a lichen parasite. These are interesting fungi that you can find with a hand lens, or in my case, a macro lens, scanning up and down the trunks and branches of trees, weathered wood, and other lichens.

Further reading

• Consortium of Lichen Herbaria: Calicium
• Ways of Enlichenment: The Stickpins
• Using calicioid lichens and fungi to assess ecological continuity in the Acadian Forest Ecoregion of the Canadian Maritimes
• Encyclopedia Britannica: Ascomycota