Thallus: crustose, mostly endolithic or superficial but indistinct, very thin, ecorticate (except that some corticate granules may occur near the apothecia); surface: pale gray, with an indistinct margin; Apothecia: occurring singly, or clustered in groups, sessile, or constricted at base, concave, flat when mature, or soon convex, 0.3-0.9 mm in diam.; disc: pale brown, dark brown or almost black, smooth, epruinose or rarely very slightly pruinose; margin: prominent, or even with disc, uniform, epruinose or pruinose, even, or slightly flexuose, white, or concolorous with thallus, rarely concolorous with disc, without a parathecial ring; amphithecium: present, with algae filling the medulla or algae sparse, algal layer often discontinuous below hypothecium, (60-)90-200 µm thick, corticate; cortex: indistinctly delimited, +uniform in thickness, or slightly thicker at the base than at the sides, 30-80 µm thick laterally and 35-120 µm thick at base, composed of adglutinated hyphae to apparently cellular, +obscured by granules (pol+, insoluble in K, soluble in N); parathecium: indistinct to well delimited and up to 30 µm wide; epihymenium: shades of yellow or brown, granular (pol+), granules superficial and between paraphyses tips, or also inspersed in the whole hymenium, fine, insoluble in K and insoluble in N; hymenium: hyaline, or pale yellow, 45-70 µm tall; paraphyses: slender, somewhat branched throughout, with few anastomoses, not expanded and usually not pigmented, coherent in K; subhymenium: indistinct; hypothecium; hyaline or almost so, 40-120 µm thick, composed of adglutinated hyphae to apparently cellular, often with some granules; asci: clavate, 8-spored; ascospores: hyaline, simple, ellipsoid, (7.4-)8.9-11.8 x (4.5-)5-5.9 µm; Pycnidia: not seen.; Spot tests: apothecial margin K-, C-, KC-, P- or P+ orange (±75%); disc K-, C-, KC-, P-; apothecia UV negative or ±pale yellow or green; Secondary metabolites: 2,7-dichlorlichexanthone, ±pannarin.; Substrate and ecology: on a wide range of substrates including: calcareous and siliceous rocks, concrete and mortar, dust contaminated bark and many man-made substrates, also on other lichens; World distribution: cosmopolitan species; Sonoran distribution: Arizona, southern California, Chihuahua, Baja California (Guadalupe Island), and Baja California Sur.; Notes: Lecanora dispersa was hitherto considered as a complex of taxa. Thanks to recent progress L. dispersa sensu stricto is currently recognized as having epihymenial granules, that often extend into part or all of the hymenium and that are insoluble in K and N. The presence of pannarin and P+ orange reaction of apothecial margins (detectable especially on inner side of the margins) are also significant in most cases. 

Canada

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

United States

Origin: Unknown/Undetermined

Regularity: Regularly occurring

Currently: Unknown/Undetermined

Confidence: Confident

In Great Britain and/or Ireland:
Lichen / parasite
ascoma of Arthonia clemens parasitises apothecium of Lecanora dispersa
Other: major host/prey

Lichen / pathogen
immersed mycelium of Bispora dematiaceous anamorph of Intralichen christiansenii infects and damages brownish apothecium of Lecanora dispersa

Lichen / parasite
perithecium of Phaeospora parasitica parasitises thallus of Lecanora dispersa

Canada

Rounded National Status Rank: NNR - Unranked

United States

Rounded National Status Rank: NNR - Unranked

Rounded Global Status Rank: G5 - Secure

Reasons: This lichen grows on calcareous rocks, and on mortar and concrete throughout North America. It is especially hardy, as one of the few lichens able to survive in urban areas.