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 Thallus: areolate or verruculate, overall up to 3 cm wide; round to irregular, convex, occasionally ±lobed, 0.3-1.5 mm in diam., 0.3-0.7(-1.1) mm thick; dispersed or in small contiguous indeterminate groups; rim: usually black; areoles: (or verrucae); upper surface: richly red-brown or dark brown, usually glossy, but occasionally dull at lower elevations, convex, smooth to rugulose, epruinose; lateral cortices: paraplectenchymatous, indistinct to distinct in water or K, 40-130 µm thick; cells: various in size and shape; syncortex: sometimes with periclinal hyphae visible, 5-20 µm thick; eucortex: upper layer dark pigmented and 10-50 µm thick, lower layer smoky or hyaline, 25-50 µm thick; algal layer: ±even; medulla: white, opaque, paraplectenchymatous; lower surface: lacking or narrow, white to dark; attachment: broadly to more narrowly attached and elevated, but without developing a stipe; Apothecia: usually 1(-4) per areole; disc: black to dark red, very rough, epruinose, plane to concave; parathecium: ±yellow, expanding to ±90 µm, often forming a dark parathecial crown around the apothecium, especially in higher elevation populations; epihymenium: smoky to yellowish brown but fading downward, with an uneven surface, c. 20 µm thick; hymenium: hyaline to pale yellow, 62-150 µm tall; paraphyses: (1-)1.5-2 µm wide at base, usually slender, apices up to 3-5 µm wide, usually with dark hoods or pigment marks in a thick gel, septation ±various, with long or short cells, with frequent oil drops; subhymeniun: hyaline, c. 20 µm thick; hypothecium: 15-25 µm thick; asci: clavate, often breaking open easily, 70-80(-110) x 10-27 µm, 100+-spored; ascospores: hyaline, simple, mostly broadly ellipsoid, 4-5(-7) x 1.3-3 µm; Pycnidia: immersed, hyaline, spherical to conical, 60-100 µm wide, up to 200 µm tall, usually abundant in small, infertile verrucae; conidia: bacilliform, 1-2(-4) x 0.7-1.5 µm; Spot tests: UV-, all spot tests negative; Secondary metabolites: none detected.; Substrate and ecology: in full sun on hard granite, volcanic, and carbonate rocks at elevations from 500-3350 m, sometimes beginning on thalli of Aspicilia or other hard rock pioneers; World distribution: western North America; Sonoran distribution: Arizona (one historic report), southern California and Baja California.; Notes: Magnusson named A. nitida from a single specimen collected from Greenland in 1935. The name was applied to Colorado specimens by Anderson and Weber, apparently without reference to the type. But the western North American species was originally named by Magnusson as A. elevata from a Hasse collection from Big Rock in the San Gabriel Mountains of southern California (holotype, FH!). If identical with type of A. nitida, the Greenland specimen would become synonymous with A. elevata. Acarospora. elevata is characterized by being C- & K- and having dark glossy areoles or verrucae with large rough black apothecia. Otherwise, it is quite variable in cortical thickness and anatomy, hymenial height, and spore size. However, the general appearance of its areoles is uniform. When dark brown with a reduced syncortex, the areoles are not glossy, and this occurs especially at lower elevations below the snowline where specimens are often reduced in size; these forms were called Thelocarpon albomarginatum and A. washingtonensis. It is common in California but apparently restricted to high elevations in the Rockies. Acarospoa elevata usually occurs above 1400 m, but some populations occur lower in coastal California. Red mites often ravage it at mid-elevations. 


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© Lichen Unlimited: Arizona State University, Tempe.

Source: Lichen Flora of the Greater Sonoran Desert Region

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