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Target lichen species for 6-zone air quality monitoring system in
northwestern Washington and southwestern British Columbia

Fred M. Rhoades, Biology Department, Western Washington University, Bellingham WA <fredr@cc.wwu.edu>
This resource is designed for use with a sampling protocol designed by Irene Hinkle of Western Washington University. The protocol is temporarily unavailable.

     Different lichen species are differently sensitive to a variety of air pollutants. This 6 zone system is based on the sensitivity of selected species to sulfur dioxide (SO₂). The zones and their SO₂ sensitivity cutoffs are: 1 >75   2 55-75   3 45-55   4 35-45   5 10-35   6 <10 (µg SO₂/ m³). That is, zone 1 lichens are most tolerant and zone 6 lichens are most sensitive.
     These zone ratings were estimated by reference to known sensitivities to SO₂ in other areas of the world and general knowledge of their distribution in the pacific northwestern United States and adjacent Canada. Monitoring of SO₂ levels critical for these species has not been done here. The actual presence of a species will depend not only on its sensitivity to sulfur dioxide, but its sensitivity to other pollutants, to the nature of other environmental variables such as moisture, salt spray, etc., and to whether reproductive structures of that lichen species have made it to the site.

     Particularly useful in determining these ratings are the data gathered by Linda Geiser and colleagues in the U.S. Forest Service Region 6 Lichen and Air Quality web site (http://www.fs.fed.us/r6/aq/lichen/). In addition, the knowledge of the local abundance and distribution of these species was used to choose this particular set of species for the target area. Included in this table are other species that you might confuse with the targets.

     The common names used here are those suggested by Trevor Goward in "Lichens of British Columbia. Illustrated Keys. Part 1 - Foliose and Squamulose species, and Part 2 - Fruticose Species." Ministry of Forests Research Program. Crown Publications. Victoria, B.C. Canada. These keys are available on line:   Foliose and Squamulose   Fruticose

Introductory background information on lichens. Includes link to information on identification, including sources and recipes for lichen spot test reagents.
Non illustrated table of the 16 target species, arranged by zone.

Dichotomous key to the 16 target species plus look-alike species in the table below.

Quick-access table of thumbnail illustrations of target species and look-alikes. From the thumbnail table you can move directly to the cells in the table below.

Concordance table of species on Claire Dalby's Lichens and Air PollutionWallchart with our local species. (Chart no longer available, but other related resources are available from British Lichen Society, here)

Table of target species and look-alikes

The following table is arranged by growth form, starting with crustose species (below), then foliose species, then fruticose species and finally some of the non-target look alike species that might be confused with the targets. In the photographs, the yellow scale line is 1 centimeter, any inset illustrations are approximately 5 times the scale of the main illustration, and diagnostic features are indicated with red pointers. For an enlarged view of each species, right click on an image and choose "View Image".


Target species	Zone	Photograph	Notes (particularly diagnostic characters are in red) Green: Comments about other species that might be confused and represent the same zone Blue: Comments about other species that might be confused and represent different zones *Underlined species* are links to other species
		Crustose target species
*"Unlichenized Algae"*	1		Not a lichen but a free-living alga not associated with lichen-forming fungi. In England this is known as Protococcus viridis. The exact identity of our species is unknown. Characterized by dark, grass-green coloration, usually in areas that get wet (below branches, shady sides of trunks, etc.)
*Graphis scripta* "Hieroglypics Lichen"	4		Gray crust with black, elongate-branched bodies. There really are no other common species like this in our area. *Graphis elegans* is similar but much rarer: the fruiting bodies of this spieces are double "rimmed" when viewed under a hand lens. Likely *G. elegans* has a similar sensitivitity to *G. scripta*
		Foliose target species
*Hypogymnia physodes* "Hooded tube"	2		Mineral gray, hollow, foliose thallus that is sorediate below lip-shaped lobe tips. No pores. No rhizines. *Physcia adscendens* and *P. tenella* are much narrower, smaller and aren't hollow; see *Parmelia sulcata* which is not hollow and has rhizines below *Hypogymnia tubulosa* is more sensitive and is sorediate at trumpet-shaped lobe tips. All other *Hypogymnias* are non sorediate
*Lobaria pulmonaria* "Lungwort"	6		large, olive green, foliose thallus with sorediate-isidiate ridges above and brown, felty tomentum and splotchy cream below *Lobaria oregana* is usually in conifer forests, is more yellow green, and lacks soredia (may have flattened "lobules" on lobe margins and ridges); *Peltigera collina* and other Peltigeras are of similar sensitivity and may be confused because of similar colors and size -- they are veined underneath and are usually more characteristic of lower trunk habitats
*Melanelia fuliginosa* "Shiny brown lichen"	3		*Melanelia* spp. are olive brown, medium sized foliose lichens with closely adhering thalli. They sometimes are very difficult to see against darker bark backgrounds. *Melanelia subaurifera* (next species) has patches of soredia among short isidia on the lobe surfaces. Tuckermannopsis chlorophylla is more tufted, browner and has sorediate lobe edges.
*Melanelia subaurifera* "Powdery Brown Lichen"	3		*Melanelia* spp. are olive brown, medium sized foliose lichens with closely adhering thalli. They sometimes are very difficult to see against darker bark backgrounds. *Melanelia fuliginosa* (previous species) is isidiate only, with short, unbranched isidia on the lobe surfaces. Tuckermannopsis chlorophylla is more tufted, browner and has sorediate lobe edges.
*Menegazzia terebrata* "Magic treeflute"	5		Mineral gray, hollow, foliose thallus with pores in upper surface and scattered clusters of soredia *Hypogymnia* species do not have pores in the upper surface and are less "tidy" in their appearance
*Parmelia hygrophila* "Salted shield"	3		Medium lobed, mineral gray foliose; lobes rounder and slightly wider compared to *P. sulcata; simple rhizines (or branched just at the tip), isidia (or isidiate soredia) scattered on lobe surface see Parmelia sulcata* which is more tolerant
*Parmelia sulcata* "Powdered shield"	1		Medium lobed, mineral gray foliose; lobes narrower and slightly scalloped compared to *P. hygrophila; squarrosely branched rhizines, powdery soredia along raised ridges See Hypogymnia physodes* -- its lobes are hollow and lack rhizines See *Parmelia hygrophila* which is more sensitive. *Hypotrachina sinuosa* is much more sensitive, has a yellowish cast and dichotomously-branched rhizines, with soredia restricted to the margins of lobe tips. *Parmeliopsis* species are very narrow lobed and closely adhere to bark; Parmeliopsis hyperopta is mineral gray; **Parmeliopsis ambigua** is yellow-green. Both are more sensitive
*Parmotrema arnoldii* "Powdered scatter-rug"	5		A large, mineral gray, foliose lichen with ciliate margins and soredia in crescent-shaped bunches along lobe margins *Cetrelia cetrariodies* is similar in appearance and sensitivity but lacks the ciliate margins; it is characteristic of wetter habitats *Platismatia glauca* is more tolerant and is extremely variable in appearance; soredia/isidia or none on the lobe surfaces, but lacks marginal cilia
*Physcia adscendens* "Hooded rosette"	2		Small, mineral gray, foliose thallus with marginal cilia and hood-shaped clusters of soredia (soralia) at the ends of lobes. *Physcia tenella* is similar in appearance and sensitivity but the soralia are flat and not hood-shaped. *Physcia aipolia* is more sensitive, lacks soredia but has apothecia.
*Physcia aipolia* "Gray-eyed rosette"	3		Small, mineral gray, foliose thallus without marginal cilia; with apothecia Other *Physcias (see Physcia adscendens*) are sorediate and more tolerant
*Tuckermannopsis chlorophylla* "Shadow ruffle"	3		**Tuckermannopsis (AKA Cetraria)chlorophylla** is a tufted, olive brown (brown on the bottom), somewhat tufted, foliose thallus with soredia on the margins. Melanelia spp. are usually a bit greener . In any case they are more closely appressed to the substrate. *Tuckermannopsis orbata* is less sensitive and lacks soredia and usually has smaller lobes or black dots along the margins.
*Xanthoria polycarpa* "Pincushion orange lichen"	2		Tiny (lobes less than 1 mm wide), orange, foliose thallus with apothecia Two other species are found commonly and share sensitivity with *X. polycarpa. X. hasseana* is also apotheciate but has long white rhizines instead of short white holdfasts. *X. candelaria* differs in being sorediate (may or may not have apothecia) X. parietina is rarer, more sensitive and has wider lobes (greater than 2 mm wide). *Candelaria concolor* is also more sensitive -- it is greener/yellower, lacks apothecia, and is sorediate.
		Fruticose target species
*Evernia prunastri* "Stag's horn"	2		Flattened, yellow-green thallus is staghorn (Y) branched, and lighter on one side. Any soredia present are on the surface of the lobes. The thallus illustrated here is quite small. *Ramalina farinacea* is easily confused but is less dichotomously branched, more wiry and has soredia only on the edges of lobes. *Ramalina dilacerata* (apotheciate) and R. roesleri (sorediate) are lacerated with openings through the thallus lobes. Both species are more sensitive.
*Usnea rigida* "Eyed beard"	5		Yellow-green, tufted, fruticose thallus with round branches containing a resistant central cord; apothecia present *Usnea longissima* is very long with short lateral branches, lacks apothecia and is characteristic of trees in wet environments. *Usnea filipendula* is more tolerant; it is pendulous and irregularly branched.Alectoria sarmentosa is long and draping and lacks a central cord.
*Usnea* tufted "Nit beard and others"	3		Yellow-green, tufted, fruticose thallus with round branches containing a resistant central cord; no apothecia *Usnea subfloridana* (the species illustrated here with isidate soralia) and many similar tufted species are difficult to distinguish from each other. *Alectoria sarmentosa* is long and draping and lacks a central cord. See *Usnea rigida* which is much more sensitive; *Sphaerophorus globosus* is more sensitive, it is tan, without a central cord and sometimes with swollen black bodies on lobe ends
		Look alike species
*Hypotrachina sinuosa* "Green loop"	5?		*Hypotrachina* species are yellowish, not the mineral gray of *Parmelia* species (*Parmelia sulcata* at the upper right) and have dichotomously-branched rhizines, with soredia restricted to the margins of lobe tips.
*Peltigera membranacea* "Dog pelt"	4?		*Peltigeras have raised veins and rhizines on their lower surfaces, while Lobarias have only areas of brown fuzz. Colors of Peltigera* species are usually slate bluish gray as in the species shown here (there is a group of green *Peltigera* species but they grow on the ground, as do most Peltigeras). *Lobarias are green. The apothecia (cups) of Peltigeras are on the margins of lobes while those of Lobarias are on the upper lobe surface. The one species of Peltigera* that usually grows on trunks (*P. collina*) has sorediate lobe margins.
*Platismatia glauca* "Rag bag"	2?		*Platismatia glauca* is an extremely common, tolerant species. It is probably our most variable lichen. It invariably lacks ciliate margins and pure soredia. Often, but not always, it bears numerous isidia or sorediate isidia on the surfaces and edges of lobes (not in abundance in the individual illustrated here and there is a small piece of *Hypogymnia enteromorpha* emerging from the lower center of the thallus).
*Alectoria sarmentosa* "Common witch's hair"	4		Yellow-green, pendulous, fruticose without central cord *Bryoria* species are brown to black
*Ramalina farinacea* "The dotted line"	2		*Ramalina farinacea* can sometimes resemble *Evernia* *prunastri, but Evernia* is usually broader, more evenly branched, lighter colored on one side and "flabbier". In addition, the soredia on *Evernia* are more widely scattered across the lobes, whereas those of *R. farinacea* always occur in clusters (soralia) on the margins of the lobes.
*Tuckermannopsis orbata* "Variable ruffle"	2		**Tuckermannopsis (AKA Cetraria) orbata is more tolerant than Tuckermannopsis chlorophylla**. It lacks sorediate lobe margins, may or may not have apothecia, but usually has lobe margins that are covered with black dots (pycnidia).
*Usnea longissima* Methuselah's beard"	5?		*Usnea longissima* is long and trailing with many short, lateral fibrils and few other branches (compared to all other species of *Usnea). U. longissima* is always found near open water, either the margins of rivers and streams or of lakes or standing water in swamps.
*Sphaerophorus globosus* "Clustered coral"	4?		*Sphaerophorus* globosus is brown to brownish green, darker than the yellow-green color of *Usnea* species. In addition, *Sphaerophorus* often, but not always, bears dark, round fruiting bodies on the ends of its lobes.