Eastern Speckled Shield Lichen

Description

Eastern Speckled Shield Lichen occurs across North America but is especially common in central United States. It is very common in Minnesota. It is found in open woodlands, fields, and roadsides. It grows on the bark of deciduous trees.

The vegetative body (thallus) is leaf-like (foliose), bluish-gray, and divided into branches (lobes). The lobes are small to medium-sized, mostly 1 ⁄16″ to ¼″ (2 to 6 mm) but up to ⅜″ (10 mm) in diameter. On older parts of the thallus, the lobes become wrinkled and folded and develop many small lobe-like growths (lobules) both on the edges and across the surface. The upper surface does not have powdery dull granules (soredia), shiny granules (isidia), or a chalky or “frosted” surface (pruina). However, it does have abundant, tiny, globular chambers (pycnidia) embedded in the thallus with an opening through which fungal spores are released. The pycnidia look like pale brown to black pinpricks on the thallus surface. This is the feature that gives the lichen its common name. The lower thallus surface is pale tan and is covered with pale unbranched anchoring structures (rhizines) up to the lobe edges.

Brown, slightly raised, disk-like, spore-producing structures (apothecia) are always present, usually abundant. The disks are broad, ⅛″ to ⅝″ (3 to 15 mm) in diameter, and are shaped like a plate with a ring around them. They are brown inside and the ring is made of tissue similar to the thallus. Larger disks often have a convoluted shape.

Similar Species

Ecology

Substrate

Trees

Growth Form

Foliose

Habitat

Open woodlands, fields, and roadsides

Hosts

Deciduous trees