Taxonomic comment: The registration identifier cited in the protologue, 'Mycobank MB 516797', was not issued for the name published; see Art. F.5.6 (San Juan); instead MB#807401 is the correct number under which the name was registered.
Tpe: U.S.A. CALIFORNIA: San Bernardino Co., Joshua Tree National Park, Little San Bernardino Mountains, east of Long Canyon on hillside, 34u049310 N, 116u269310 W, 1316 m, on gravelly soil of decomposed granite, Oct. 4, 2011, Knudsen 13688 w/ M. Harding (holotype: UCR; isotypes: UCR).
Description. Hypothallus of abundant endosubstratal rhizohyphae, binding the soil and rock particles in a continuous biological soil crust to several cm in diam. Thallus epilithic, crustose, poorly differentiated, becoming areolate at edges, or of distinct areoles, dispersed or contiguous, 0.2–0.3 (20.6) mm in diam., 0.2–0.3 mm thick, round to irregular, light to dark brown on upper surface, epruinose, smooth or fissured, broadly to narrowly attached, with usually pale lower surface. Upper, lateral, and lower cortices 10–20 (–40) mm thick, paraplectenchymatous, cells globose to irregular, mostly 2–4 mm diam., hyaline, with a thin brown pigmented upper layer mostly one or two cells thick, with or without a thin epicortex of gelatinized hyphae. Algal layer mostly 200 mm thick, upper and lower strata uneven, uninterrupted by hyphal bundles, continuous below apothecia, algal cells mostly 10 mm in diam. Medulla 40–60 mm thick, of gelatinized hyphae mixed with substrate particles, or distinct hyphae continuous with abundant rhizohyphae, hyaline, thin walled, branching, 2.5–5 mm wide, IKI–. One apothecium per areole, erumpent, the areoles sometimes becoming reduced, forming the base of the apothecium, until only the apothecia are visible and the thallus appears endolithic. Apothecia scattered or sometimes in dense clusters, mostly round, small, 0.2–0.5 mm in diam., margin thin, brown, raised above the disc, smooth or rough, sometimes undulate. Disc reddish brown to dull brown, reddish orange when wetted, epruinose, smooth or scabrid. Exciple to 120 mm wide, hyaline within, outer layer dark pigmented, c. 10–20 mm thick. Hymenium usually 80–100 mm tall, IKI+ unstable, blue, yellow-green, or red, K/IKI+ blue, epihymenium c. 10 mm high, with reddish-brown diffuse pigment, hymenium inspersed with oil drops, paraphyses not branching, conglutinate, 2–3 mm wide, cells 5–10 mm, often with oil drops, apices unexpanded or expanded to 4 mm with dark pigmented cap. Asci clavate, Acarospora-type stain in K/IKI, mostly 50–65 315–20 mm, 100+ ascospores per ascus. Ascospores simple, hyaline, ellipsoid, mostly 4–5 3 2 mm. Subhymenium to 20 mm thick, IKI+ blue. Hypothecium prosoplentenchymatous, 10–15 mm wide, expanding into excipular margin. Pycnidia absent to frequent, conidia simple, hyaline, 2–2.5 3 1.5–2 mm, mostly broadly ellipsoid to subglobose. Spot tests negative.
Other specimens examined. U.S.A. IDAHO: Ada County, Snake River Plain, south of Kuna, B. McCune 31907 (OSC). WASHINGTON: Benton County, Horse Heaven Hills, Plot 304, May 21, 1999, J. Ponzetti (OSC).
Etymology. The species is named in honor of the NPS botanist Mitzi Harding, who discovered the lichen forming extensive soil crusts in the Mojave Desert in Joshua Tree National Park in California.
Distribution. Western North America (California, Idaho, Washington) from 497–1316 m. We found no more populations of S. mitziae in Joshua Tree National Park (California) in over 70 days of fieldwork, suggesting that it is part of the Pleistocene relictual element of the lichen biota in the northwest region of the park (Knudsen et al. 2013). The Idaho and Washington populations also suggest it is not a desert species. It has not been discovered in coastal southern California or in the Sierra Nevada Mountains by the authors.
Ecology. Sarcogyne mitziae is an obligate terricolous lichen based on the extensive rhizohyphae of the hypothallus and the biological soil crusts it forms. In the type collection from the Mojave Desert, S. mitziae was not associated with other lichens. Biotic soil crusts with one or two lichen species are common in the southwestern Mojave Desert in Joshua Tree National Park, probably due to climatic restraints (Knudsen et al. 2013; Pietrasiak et al. 2011). In Idaho, S. mitziae grew with the yellow Acarospora schleicheri (Ach.) A. Massal, within extensive, nearly continuous, species-rich lichen-bryophyte soil crusts in relatively old Artemisia shrub steppe on the Snake River Plain. In southern Washington the species was found in a species-rich plot with Arthonia glebosa Tuck., crustose Aspicilia taxa, Buellia punctata A. Massal., Cladonia pocillum (Ach.) Grognot, Diploschistes muscorum (Scop.) R. Sant., Lecanora zosterae (Ach.) Nyl., Leptogium sp., Massalongia carnosa (Dicks.) Körb., Trapeliopsis bisorediata McCune & Camacho, the large moss Syntrichia ruralis (Hedwig) F. Weber & D. Mohr, and extensive short mosses. Sarcogyne mitziae was growing with Pseudoroegneria spicata (Pursh.) Á. Löve without Artemisia, which in this area implies that it had burned in recent decades (Ponzetti et al. 2007). The type collection has some bleached areoles infected by Lichenothelia convexa Henssen, a common saxicolous and lichenicolous micro-fungus in the Mojave Desert that attacks a wide range of lichens (Kocourková & Knudsen 2011; Muggia et al. 2012), while no lichenicolous fungi occurred on the specimens from Idaho and Washington.
Differentiation. Because of the apothecia with brown margins and discs that turn orange when wetted, Sarcogyne mitziae resembles the more robust Sarcogyne novomexicana H. Magn., but has smaller apothecia (0.2.–0.5 mm vs. 0.8–2.0 mm), an inspersed hymenium, and a terricolous habit with a corticate thallus. The latter species is saxicolous, endolithic, and prefers limestone or calcareous drainages on granite. Both species occur in Joshua Tree National Park in California. Only two species of Sarcogyne are known to have corticate epilithic thalli and both are terricolous but differ significantly from S. mitziae. Sarcogyne crustacea K. Knudsen & Kocourk. from the lower coastal elevations of the mountains of southern California differs from S. mitziae in usually forming a non-areolate thallus, having reddish-black apothecia with a black margin, non-inspersed hymenium, and longer narrow conidia (Knudsen & Kocourková 2010). Sarcogyne brunnea K. Knudsen & Flakus from the Andes in South America (Bolivia, Ecuador) differs from S. mitziae in having pruinose brown areoles, black discs not changing color when wetted, a higher non-inspersed hymenium, and an algal layer interrupted by hyphal bundles (Knudsen et al. 2012). The only other terricolous species in the genus is S. terrena H. Magn. from Brazil, which is currently only known from a historic collection (Knudsen et al. 2012). Like S. mitziae, S. terrena has an extensive hypothallus of rhizohyphae, but differs in lacking an episubstratic thallus and possessing consistently smaller apothecia with a punctiform disc and a higher non-inspersed hymenium with branching paraphyses. Though inspersion is an informative character, all the material of S. mitziae we have seen was relatively recent. Inspersion in the hymenium had decreased in the oldest collection from 1999. Sarcogyne crustacea and S. mitziae are the only terricolous species from the genus reported from North America. Sarcogyne arenosa (Herre) K. Knudsen & Standl. and S. similis H. Magn. are saxicolous species which have occasionally been found in biological soil crusts in southern California (Hernandez & Knudsen 2012; Knudsen et al. 2013). It is common, especially on consolidated granite alluvium, for saxicolous lichens to occasionally occur in biological soil crusts with obligate terricolous species. Sarcogyne arenosa differs from S. mitziae in usually having a very thin ecorticate white or dun-colored thallus or a white rim subtending the margin and a non-inspersed hymenium while S. similis has larger black apothecia with a black margin, a non inspersed hymenium, and an endolithic thallus.