Punctelia bolliana

Family: Parmeliaceae

Eastern Speckled Shield (Punctelia bolliana) is a medium-sized foliose lichen recognized by its distinct white maculae (speckles) scattered across a gray-green to olive thallus. It is a frequent and often overlooked inhabitant of hardwood bark in eastern North America, including much of Minnesota. When fresh and hydrated, colonies can appear vividly green, especially in cool, humid conditions.

This page documents field observations used for identification. Visual presentation and artistic interpretation are handled separately in the Gallery section, Eastern Speckled Shield.

Description

The thallus is foliose, tightly adnate to the substrate, forming rounded to irregular rosettes that may coalesce into larger patches.

Upper surface: pale gray-green to olive; smooth to weakly wrinkled
Maculae: abundant, irregular white flecking across the thallus; a defining feature of the genus
Lobes: rounded, overlapping, typically 4–10 mm wide
Lower surface: black centrally with paler margins
Rhizines: simple to sparsely branched

Colonies often appear healthiest and most colorful during damp weather, when green tones intensify.

Apothecia and Reproduction

Apothecia are frequent and often numerous in mature colonies.

Discs: olive-green to brownish-olive when fresh; darkening with age or drying
Margins: thalline, persistent, often slightly paler than the disc

The olive coloration of fresh apothecia can be confusing when compared to guide descriptions that emphasize brown tones based on dried or herbarium material.

Vegetative reproduction occurs through soredia, though these may be sparse or inconspicuous compared to some related species.

Identification

Key features for field diagnosis:

Color: gray-green to olive, often greener when hydrated
Surface: conspicuous white maculae
Form: foliose, tightly attached rosettes
Apothecia: common; olive-toned when fresh
Substrate: hardwood bark

This combination of maculate surface, olive-green tones, and frequent apothecia is the most reliable way to recognize Punctelia bolliana in the field.

Similar Species

Rough Speckled Shield (Punctelia rudecta)

Typically grayer overall
Apothecia often less abundant
Maculae may appear weaker or less sharply defined

Fresh field material of P. bolliana is best separated by its green-olive coloration, abundant maculae, and frequent apothecia on hardwood bark.

Habitat and Ecology

Substrate: hardwood bark
Habitat: woodlands, forest edges, urban trees
Distribution: eastern North America; widespread in Minnesota

The species tolerates a range of light conditions and is commonly found at eye level on mature trees.

Ecology and Notes

Fresh, hydrated specimens may appear greener and more vibrant than expected from printed guides or herbarium images. Close inspection of maculae and apothecia color in the field provides more reliable identification cues than color descriptions alone.

References

Minnesota Lichen Guide
Consortium of North American Lichen Herbaria
Brodo, I. M., Sharnoff, S. D., & Sharnoff, S. Lichens of North America