Names: Amandinea punctata, Buellia punctata, Tiny Button Lichen
Description: Thallus thin & barely perceptible to moderately thick, cracked or areolate. Exciple uniformly pigmented dark brown.
Colour: Gray to brownish. Green when wet.
Apothecia: 0.2 – 0.5 mm in diameter, with a thin black margin that often disappears in maturity
Spores: (7-) 11 – 16 x (4-) 5 – 8 um, not constricted, 8 per ascus.
Substrate: On various types of bark & wood, & occasionally on siliceous rock.
Lookalikes: Amandinea polyspora, an East Temperate species, is very much like A. punctata but has 12 – 32 spores per ascus, somewhat smaller spores (7.5 – 11.5 x 3.5 – 5.5 um), & an exciple that is pale within. It grows only on bark. Two species of Amandinea with incipient to well-developed lecanorine margins are A. milliaria (aka R. milliaria). The latter has apothecia that erupt from the pale gray thallus, sometimes leaving a very thin thalline border outside the lecideine margin. It is almost entire coastal, from Main to Texas, with a few records from the shores of the Great Lakes. Amandinea dakotensis has a dark gray-green thallus, & the apothecia, although also initially erupting, finally have well-developed lecanorine margins as in species of Rinodina. It is found throughout the midwest, rarely occurring on the east coast.
Bibliography: Lichens of North America, by Brodo, Sharnoff, & Sharnoff
Database Entry: Distance Everheart 12-26-13