Arctoparmelia (aka “Ring Lichens”)

Location Summary

Substrate: on siliceous rocks usually in the open.

Range: Boreal & arctic regions.  Mainly arctic & alpine.

Identification Characteristics

Description: Yellowish Green; Similar to Xanthoparmelia except lower surface is instead velvety, ivory white to gray, black, or purplish; often narrower lobes.  Narrow-lobed (0.3 – 0.5 mm across), dull greenish yellow foliose lichens, commonly forming concentric rings of radiating lobes, with the thallus dying in the center of the rosette; lower surface with a dull, white or pale tan to very dark gray cortex; rhizines unbranched & scattered.  Photobiont green (Trebouxia?).

Apothecia: Lecanorine, with brown disks & thallus-colored margins.

Spores: Colourless, 1-celled, ellipsoid, 8 per ascus.

Chemistry: Cortex PD-, K+ yellow, KC + gold, C- (usnic acid with atranorin).

Lookalikes: Xanthoparmelia but differing in chemistry & a lower surface is different. Xanthoparmelia grows in many places Arctoparmelia does not.  Xanthoparmelia super-ficially resembles Arctoparmelia but usually has a shiny upper surface, a brown to black, shiny lower surface with branched rhizines, & an entirely different medullary chemistry.

Bibliography: Macrolichens of the Pacific Northwest, by Bruce McCune & Linda Geiser, Lichens of North America, by Brodo, Sharnoff, & Sharnoff

 

Database Entry:  Distance Everheart 12-26-13