Sarea difformis: A fungus that lives on conifer resin

**Black spruce resin with *Sarea difformis*.**

Conifer resin oozing from a tree is an inhospitable place. The terpenoid chemicals in resin are toxic to many forms of life, but not all. Even though conifer resins are full of anti-fungal and anti-bacterial compounds, some organisms have found a way around that. One of these is a fungus called Sarea, a genus of fungi that grows on the resins of pines, spruces, firs, and cedars. Organisms that live on resins are called resinicolous (resin plus “colous” meaning “inhabitant”).

From lichen to fungus

At one time, Sarea was thought to be a lichen, but because it lacks a photobiont (symbiotic photosynthetic organism), it has been “demoted” to a fungus. The tiny (barely 1 mm across) fungus bodies pictured above and below growing on the resin of a black spruce are, to the best of my knowledge, the apothecia (reproductive structures) of Sarea difformis. Cross-sections of the fruiting body examined under a microscope would make identification more certain, but that’s a bit out of my reach right now.

**A few small fruiting disks (marked by red arrows) of the fungus *Sarea difformis* are growing on the darker portions (are those part of the fungal body?) of the resin. Can you find more?**

I have looked for research papers on how Sarea can live on conifer resin, but the results have not yielded much information. Does it actually break down the resin components into simple carbohydrates? If so, then does it do this on its own, or is there a symbiotic relationship with bacteria or another fungus? Are the fungal hyphae growing in the resin or merely on top? How does it disperse? A lot of questions, and I’m sure there are answers somewhere.

Taxonomy

Sarea is a genus in the phylum Ascomycota (cup fungi, sac fungi), which includes familiar mushrooms like morels and the blue mold in Roquefort cheese. The taxonomy of the genus Sarea is not entirely settled, so some species may be moved to other genera, and species from other genera may be moved to Sarea. Also, new species are being discovered.

A similar resinicolous species that might be encountered in northern coniferous forests is Sarea (Zythia) resinae. It can be distinguished morphologically by the color of its apothecia. Sarea difformis has black apothecia, and Sarea resinae has orange apothecia.

Rare?

Sarea is not a rare fungus, but because of its small size and peculiar habitat, it is just rarely seen. It occurs throughout the cooler regions of the northern hemisphere.

Sources and additional reading

Pins and needles

**This may be a *Calicium* species. It has an immersed thallus. It is growing on weathered white cedar wood at the edge of a forest, and shaded most of the day.**

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.

**Whisker lichen apothecia. This species has an immersed thallus. Growing on a weathered balsam fir stump near the edge of a small wetland in a forest.**

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.

**A species of whisker lichen on an old white pine stump. Possibly a *Calicium* species.**

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

**Tiny whisker lichens are growing on or from this green crustose lichen on an alder branch.**

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.

Summer is over

A jade plant I started from a cutting two years ago. In the winter, it lives under grow lights, but in the summer, it enjoys the fresh air and the rays of the sun. Tomorrow, it will have to come back indoors along with the *Echevarria*, *Sansevieria*, *Tradescantia*, and the epiphytic *Zygocactus*, *Hatiora*, and *Rhipsalidopsis* cactus.

We’ve had exceptionally warm weather for the last week, and even before that, the temperatures were just plain nice. But Sunday is the last day of temperatures in the 70s and 80’s. Yesterday it was 90 degrees in the shade. Tomorrow it will cool down to the 60s, and there is a chance of frost for three nights in a row.

After Monday, I will probably have to cut them down and store the tubers for the winter. The same is true for the tuberous begonias and the gladiolus. And all the houseplants I set out for their summer vacation will need to be brought back in.

A stalled high-pressure system is bringing the warm weather. Winds are from the south and gusting to 30 mph. The warm weather, while enjoyable and welcome so late in the year, is bringing problems to the already dry forests and fields. Even the wetlands are dry. Very dry.

A View from LeVeaux Mountain

LeVeaux Mountain is a part of the Sawtooth Mountains in northeastern Minnesota and located in Cook County. It rises about 1,586 feet above sea level and 986 feet above Lake Superior. On its south side it overlooks Lake Superior. On LeVeaux Mountain’s north are spectacular views of a forest including a stand of ancient sugar maple. To the east is the Onion River named after all the wild leeks that grow in the sugar maple forests. To the west are miles of thick forest and swamps.

**Part of the Superior Hiking Trail spur loop on LeVeaux Mountain.**

A section of the Superior Hiking Trail goes by LeVeaux Mountain with a small spur loop on the west side that makes accessing the mountain possible. Most of the land that includes the mountain is part of the Superior National Forest and so anyone can walk off the trail without violating private property laws. However, the terrain is rugged and steep cliffs and talus slopes ring much of the mountain making casual hiking dangerous. I don’t recommend it for people unfamiliar with hiking in roadless or trail-less places. You could get seriously hurt.

**Loose rocks, trees, and soil slowly slide down the north face of LeVeaux Mountain.**

I’ve hiked off trail on and around LeVeaux Mountain several times but I’ve gone prepared (including studying maps and aerial photos well beforehand) and dressed in suitable clothing not the shorts, t-shirts, and sneakers I often see on some day hikers using the trail. Such treks have been rewarding and physically challenging but that’s what I was seeking.