Ruffle lichens are rather large, broad-lobed foliose lichens that are loosely attached to the substrate. The rounded edges of the lobes usually lift up and look ruffled. Hairlike cilia arise from the lobe edges. They usually grow on tree bark.
Missouri has about 12 species of ruffle lichens (Parmotrema spp.). They can be challenging to identify to species, and specialists use chemical tests to separate them. As a group, however, they are rather easy to identify, with their broad, ruffled, uplifted lobes with eyelash-like cilia along the edges. The undersurface of these lichens often shows a band of a different color (a so-called naked zone) along the margins of the lobes. In many cases, the underside is blackish, with the outer edge brown, tan, or whitish.
Soredia and isidia are common in ruffle lichens: these are two kinds of small, granular-looking vegetative reproductive structures that form on portions of the lichen body (thallus). Soredia, as they erupt out of the thallus, typically look fluffy, while isidia (when you look closely) usually are like shiny bumps, because they are covered by the protective outer cortex of the lichen. A lichen species usually doesn’t create both soredia and isidia — only one or the other — so noting which kind of structures are formed, and where they occur on the lichen’s thallus, can help identify the species.
Rounded, cup-shaped apothecia (spore-bearing structures) may also be present in ruffle lichens.
Like other foliose lichens, ruffle lichens grow outward from a central point and have a branching, lobed structure. They have a definite lower surface.
A lichen is an organism that results when a fungus species and an algae species join together. Although the relationship between the fungi and algae is quite intimate and integrated, the lichen that is formed does not much resemble either of the components. Learn more about lichens on their group page.
Similar species: Of Missouri’s approximately 436 species of lichenized fungi, about 150 are ones with a more or less foliose growth form.
Lichens begin as tiny spots but may grow to cover several square inches. Groups of ruffle lichens may grow and coalesce to cover rather large areas, several inches in length or diameter.
Statewide.
Habitat and Conservation
Ruffle lichens may occur on tree bark, stone, or other substrates; some may be more common in sunny or open areas, while others are usually found in cool, shady places. Different species have different habitat preferences.
Status
Three of Missouri’s 12 species of ruffle lichens are listed as Missouri species of conservation concern, meaning that they are rare or restricted to very limited areas, and to some degree are vulnerable to extirpation from our state:
- The southern powdered ruffle lichen (P. hypoleucinum) is listed as critically imperiled;
- P. madagascariaceum (also called P. xanthinum) is unranked (meaning that its Missouri status is unknown and needs further study); and
- P. tinctorum is listed as imperiled in our state.
Missouri’s lichen populations deserve broader and deeper study.
Even though lichens may cover large areas of trees, they are not parasites and do not damage trees.
Life Cycle
Lichens can reproduce sexually (via spores) or vegetatively (asexually).
Sexual reproduction in lichens occurs in much the same manner as other fungi. Special structures called apothecia give off spores, which are created as the result of a fusion of gametes (sperm and ova) that occurs in the apothecial tissues. Apothecia in ruffle lichens are usually cup-shaped, with the rim and bulbous outside of the cup the same color as the rest of the lichen. When lichens reproduce via spores, only the fungal component is reproduced. The germinating fungal spore must quickly attach to a suitable algal partner, or it perishes.
Soredia are tiny ball-like packets of fungus and algae that form under the surface (cortex), then erupt from breaks in the upper cortex, rather like tiny pimples. The tiny pimple-like breaks in the cortex are called soralia. Patches where clusters of soredia are forming make the surface of a lichen look rough, crumbly, and dry: fluffy, grainy, or mealy.
Isidia are another way lichens package portions of themselves to be broken off and distributed elsewhere. Isidia are little raised buds or tubes that form on the upper surface of a lichen, consisting of the upper, skinlike cortex and the medulla layers, so like soredia, isidia include samples of the algae. Instead of a pimple whose contents start a new lichen, think of a wart where the entire thing pops off to start a new lichen. Because isidia are covered with cortex tissue, they look rather shiny (use a hand lens), while soredia look dry and dusty.
Human Connections
Lichens are common yet mysterious. Use a hand lens to examine these combo-organisms. You may see insects living among them. The seemingly primitive nature of lichens, mushrooms, and mosses and other nonvascular plants makes them wondrous. They can thrive where other life-forms cannot, and they support other types of life, becoming a micro-habitat on their own.
Because lichens, with their soft, absorbent tissues, are extremely sensitive to air pollution, they are good indicators of air quality. Scientists use them sentinels of forest health.
Ecosystem Connections
Several types of birds, including ruby-throated hummingbirds, eastern wood-pewees, and many types of warblers and vireos, harvest lichens to build their nests. Often, they decorate the outside of the nest with lichens, which provides excellent camouflage. The nest, perched on a tree limb and covered with lichen, looks just like an old lumpy knot on the limb.
Because many lichens provide cover for several types of insects, insect-eating animals often focus their hunting on lichen-covered places on trim limbs and trunks. Birds that forage for insects among lichens include nuthatches, the brown creeper, chickadees, titmice, woodpeckers, and numerous vireos and warblers. Other animals that look for insect prey among lichens include several types of spiders and the larvae of green lacewings.
Many animals have markings and coloration that helps them blend in with the mottled background of lichen-covered bark or rock. Examples include the backs of birds such as yellow-bellied sapsuckers and brown creepers, gray treefrogs, and the prairie lizard. Eastern collared lizards, with their mottled gray-tan backs and minty green legs, blend in with the lichen-covered rocks of their glade habitat.
Lichen moth caterpillars feed on lichens, and so do lichen grasshoppers, which live in Missouri’s glades. Both the caterpillars and lichen grasshoppers are camouflaged to blend in perfectly with lichen-covered rocks. Many other animals eat lichens, including deer.
Tree trunks and branches are habitats unto themselves, and many insects that typically rest on tree trunks and limbs are lichen-camouflaged. Eyed click-beetles and eastern Hercules beetles are just a few of the many insects that blend in. Also, countless species of noctuid, underwing, sphinx, geometrid, and other night-flying moths rest unbothered during the day on tree trunks. They are hidden by their drab but exquisitely ornate wing patterns; a green cast in many species helps them mimic lichens and mosses. The minty-green and black-patterned green marvel (Agriopodes fallax) is a beautiful example. Often, caterpillars have similar camouflage.
Mosses, liverworts, hornworts, and lichens seem rather similar, but these organisms are in very different groups. Mosses, liverworts, and hornworts are small, low plants usually found in damp habitats. Unlike more familiar plants, they lack veinlike structures and do not produce flowers or seeds — instead, they produce spores. Meanwhile, lichens are not plants at all: they are a collection of different fungi that have photosynthetic algae living within their tissues.