[Acarospora interspersa H. Magn.]
ASU Lichen Herbarium
Thallus: areolate, overall up to 5 cm wide areoles: usually round, (0.2-)0.7-1(-1.3) mm in diam., 0.2-0.6 mm thick, solitary, dispersed or emerging along an axis or from other lichens, becoming contiguous through division of the thallus along fissures in upper surface down through attaching hypha; rim: ±down-turned, sometimes white upper surface: dark to yellow brown or an orange-brown, glossy, convex, rugulose, fissures evident in even smallest thallus, epruinose lateral cortices: paraplectenchymatous but originating from anticlinal prosoplectenchyma, 30-40 µm thick; cells: regular, obscured in water, clear in K; syncortex: 6-35 µm thick, with thin periclinal to intricate hyphae usually visible; eucortex: upper layer various shades of golden or reddish brown fading into indistinct lower hyaline zone 15-20 µm thick algal layer: uneven, algal cells not dense, interrupted by hyphal bands (but in very flat specimens appearing solid with a plane upper surface) medulla: white, obscure, intricately prosoplectenchymatous lower surface: white, ecorticate attachment: broad and eventually elevating areoles (gomphate) without forming a stipe Apothecia: 1-4 per disc, forming in the center of areole, immersed, with visible beginning of a thalline margin, rarely becoming sessile and fully lecanorine disc: brown or black, plane, smooth or rough, sometimes convex; occasionally with interascal plectenchyma forming gyrose formations parathecium: expanding around disc up to c. 35 µm wide epihymenium: reddish brown, thickly conglutinated, 15-20 µm thick hymenium: pale yellow to hyaline, 80-110 µm tall; paraphyses: 1.7-2 µm wide at base; apices expanded, 3-4 µm wide subhymenium: pale yellow, c. 10 µm thick; hypothecium: distinct, c. 10 µm thick asci: narrowly clavate, 70 x 10-15 µm, 100+-spored ascospores: hyaline, simple, narrowly ellipsoid (3-)4.5-6 x 1.6-2 µm Pycnidia: c. 100 µm in diam. (Magnusson 1933) conidia: bacilliform, 2.5-3 x 0.8-1 µm (Magnusson 1933) Spot tests: UV-, cortex C+ red Secondary metabolites: gyrophoric acid (major), lecanoric acid (minor), 3-hydroxygyrophoric acid (trace), methyl lecanorate (trace) (HPLC, J.A. Elix, pers comm.) Substrate and ecology: on granite and volcanic rock; juvenile parasite in one specimen (Nash 16, 215 ASU) growing on and out of Aspicilia species, but no evidence it is obligate or host-specific parasite World distribution: southwestern North America and Mexico Sonoran distribution: Arizona, southern California (Santa Cruz Island), Baja California (Guadalupe Island), Baja California Sur and Sonora. Notes: This description differs slightly from details of Magnusson's description of the holotype (UPS!), because the type is not a typical specimen. The center of distribution appears to be in Mexico. Specimens differ and a more accurate description and distribution should emerge from further collections and study. Some specimens of A. nevadensis can look similar to A. interspersa, but the areoles of the former species are not as consistently round and its spores are broadly ellipsoid and have a mucilaginous layer around the thick walls. Tentatively a collection by Wet-more with no chemistry from Santa Cruz Island is included in this taxon; its spot tests reactions are negative, and it needs further comparisons with collections from the Channel Islands and central California.
Thallus: areolate, emerging from areoles of Dimeleana oreina or independent but scattered or forming small patches up to 2 cm across among areoles of D. oreina areoles: mostly 0.5-0.8 mm wide, less than 0.4 mm thick, mostly angular, becoming convex upper surface: brown, very dark with black undertone to mahogany, dull to glossy, epruinose, smooth to deeply fissured or warty lower cortices: paraplectenchymatous, 30-50 µm thick; syncortex: 10-12 µm thick; eucortex, dark pigmented narrow upper layer, hyaline lower layer algal layer: even and not interrupted medulla: white, prosoplectenchymatous lower surface: dark attachment: broad, continuous with attaching hyphae, not truly stipe-forming, but attaching hyphae can be long and attenuated, from competition for probably light with areoles of D. oreina Apothecia: one or two per areole, often lacking disc: black, rough and uneven to almost gyrose with ridges, epruinose parathecium: thin or poorly developed, but apparently expanding rarely to form blackened parathecial crown epihymenium: dark brown, 10-15 µm thick hymenium: hyaline, (60-)80-120 µm tall; paraphyses: 1.8-2 µm wide at mid-level, apically mostly expanded, 3-4 µm wide subhymenium: 20-30 µm thick; hypothecium: indistinct asci: cylindrical, 50-70 x 10-15 µm, 50-60-spored ascospores: mostly globular, 3-6 µm wide, with distinct perispores Pycnidia: not seen Spot tests: UV-, all spot tests negative Secondary metabolites: none detected. Ecology and substrate: independent or emergent in thalli of Dimeleana oreina World Distribution: North America (Nevada, New Mexico and Wyoming) Sonoran distribution: not yet known, but expected to occur as it is documented from NW and E of Arizona. Notes: Four specimens collected from Nevada and Wyoming by T. H. Nash were studied and a neotype selected from among them. The holotype was deposited in the Bouly de Lesdain in Dunkirk and was apparently lost during WW II. This description above differs from protologue in one important fact: specimens were not C+ red in cortex. The author thinks C+ spot test reaction in holotype was from chemistry derived from the host which was definitely C+ red according to Magnusson (1930). Acarospora succedens has not yet been found independent of D. oreina. While several other species have been observed growing out of thalli of other lichens (A. dispersa, A. interspersa, A. obnubila), they do not appear to be obligatory or host-specific juvenile parasites. Further specimens of A. succedens need examination to establish the º of host-specificity. Its round spores with a perispore, low number per ascus, C- reaction, and well-developed syncortex are a distinct suite of characters for this western North America species. Several other species of Acarospora are common among thalli of D. oreina so caution is required in making a determination.