Acarospora sharnoffii K. Knudsen, Hodková & Kocourk., 2025

Acarospora sharnoffii K. Knudsen, Hodková & Kocourk. sp. nov.

Fig. 4 View Figure 4

Type.

U. S. A. • California, Riverside Co., Joshua Tree National Park, Mojave Desert, Little San Bernardino Mountains , Eureka Peak , below and west of parking area, 34.0197, - 116.3630, 1650 m, on granite, 16 Jan 2012, S. Sharnoff 4107 (holotype-SBBG) GoogleMaps .

Diagnosis.

Similar to Acarospora applanata but differing in being squamulose.

Etymology.

Named after Stephen Sharnoff, lichen photographer, who produced the classic book A Field Guide to California Lichens ( Sharnoff 2014). He collected the first specimen on Eureka Peak in Joshua Tree National Park. A picture of the holotype of Acarospora sharnoffii as A. obnubila is in his book.

Description.

Hypothallus endosubstratal, no algae observed. Thallus of squamules dispersed to contiguous, 0.5–2.0 mm wide, with stipe raised distinctly above substrate, 0.3–0.45 mm thick, with an uneven and irregular topography, replicating by division. Upper surface shiny brown, epruinose or pruinose, with abundant abscission fissures. Lower surface ecorticate, white or brown. Epicortex continuous, 10–40 µm thick. Cortex 20–60 µm thick, upper layer brown 8–12 µm thick, lower layer hyaline, of disarticulated anticlinal hyphae, cells round to irregular, 2–5 µm wide. Algal layer 70–100 µm thick, upper surface even to uneven, continuous below apothecia, algal cells mostly 10–12 µm wide. Medulla 100–200 µm thick, hyphae thin-walled, mostly 4 µm wide, continuous with stipe, becoming periclinal along lower surface. Apothecia rare, usually one per squamule in center, deeply immersed, disc blackish when dry, brownish when wet, 0.3–0.5 mm wide, epruinose, rough, rarely disc expanded to 1 mm wide, reducing the squamule to thalline margin. Parathecium of narrow hyphae 1 µm wide, expanding to ca. 20 µm wide around disc, merging into the cortex. Epihymenium 8–12 µm tall, surface uneven, brown. Hymenium 70–90 (– 110) µm tall, epihymenium 10 µm tall blackish brown, paraphyses 1.0–1.5 µm wide, apices barely expanded in gel caps, hymenial gel IKI + blue to red, hemiamyloid. Asci cylindrical, 50–80 × 10–15 µm wide, ascospores usually small, 2.0–4.0 × 1.0–1.5 µm, often with two oil drops (n = 20). Subhymenium 25–45 µm tall, IKI + blue, euamyloid. Hypothecium 10 µm thick. Pycnidia not observed. Chemistry: not producing secondary metabolites.

Habitat and distribution.

The species is currently only known from the Mojave Desert in Joshua Tree National Park, on Eureka Peak in Little San Bernardino Mountains and on Queen Mountain, on granite from 1627–1670 m. Both these mountain ranges have not been fully explored for lichens. Like Sarcogyne fasciculata it could also be a montane species and could possibly be collected in the San Jacinto or San Bernardino Mountains in Southern California. Since specimens are predominately sterile it may have been collected but never identified.

Additional specimens examined.

U. S. A. • California, Riverside Co., Joshua Tree National Park, Mojave Desert, Little San Bernardino Mountains , Eureka Peak , below summit, on steep north-facing slope, 34.0197, - 116.3630, alt. 1670 m, on granite, contaminated with Endococcus , 28 March 2023, J. Kocourková 11113 & K. Knudsen ( SBBG) GoogleMaps ; • San Bernardino Co., Joshua Tree National Park, Mojave Desert, Queen Mountain , 34.0527, - 116.1026, alt. 1627 m, on granite rock next to drainage, epruinose, contaminated with Lichenothelia convexa , 5 Oct. 2005, K. Knudsen 13749.1 & M. Harding ( SBBG) GoogleMaps .

Notes.

The specimen of Acarospora sharnoffii from Queen Mountain was poor compared to the two collections from Eureka Peak. It was infected with Lichenothelia convexa (syn. Lichenostigma saxicola ), an abundant lichenicolous fungus in Joshua Tree National Park ( Knudsen and Kocourková 2011). The Kocourková collection from Eureka Peak was also contaminated by lichenicolous fungi.

Acarospora applanata and A. fissurata from New Mexico, A. fissa from Czech Republic, and A. scrobiculata from Greenland are also cross hatched with abscission fissures, replicating by division, and rarely producing apothecia ( Magnusson 1935; Knudsen et al. 2021 a, 2023 a; Vondrák et al. 2022). In our current key to Acarosporaceae of southwestern North America, Acarospora sharnoffii is recovered in squamules on non-calcareous rock, Section 8, couplet 11 with A. superfusa from which it differs in being heavily fissured and usually sterile and epruinose ( Knudsen et al. 2023 a). Both species are sympatric at the type locality on Eureka Peak ( Knudsen and Kocourková 2023).