U.S.A. • California: Riverside Co., Joshua Tree National Park, Mojave Desert, Sheep’s Pass, at base of Ryan Mountain, on gentle west-facing slope covered with small rocks and pebbles of granite and gneiss, 34.001, -116.1268, alt. 1369 m, on granite, 20 Dec 2010, K. Knudsen 13222 (holotype-SBBG).

Figure 2. 

Acarospora alba, Knudsen 13181 Isotype A chasmolithic thallus and young apotecia B apothecia one per areole with thin white margin (Holotype). Scale bars: 500 μm (A, B).

Similar in having a non-stratified thallus like the possibly extinct central European species Acarospora variegata but differing in not producing gyrophoric acid, not developing a distinct cortical layer which is poorly developed in A. variegata, and having an opaque white upper surface, not translucent in water.

Named for the white non-translucent upper surface of the unstratified thallus.

Thallus growing in the upper layer of substrate, endolithic to epilithic, covering 1–3 cm in width, an unstratified matrix of gelatinized intricate to anticlinal hyphae, 1–4 µm wide, intermixed with substrate crystal, with thin cracks splitting the upper layer into areoles irregular in shape, 0.3–1.0 mm wide, 200–400 µm thick. Upper surface ecorticate, white, epruinose, sometimes with small pale patches of reddish-brown pigment observed in thin sections at 1000×, not translucent when wet. Algae scattered or in thin clusters, algal cells 7–16 µm wide, not forming a continuous algal layer. Apothecia 0.1–0.5 mm wide, usually one per areole, oval to irregular in shape, disc black when dry, dull reddish brown when wet or not changing color, epruinose to lightly pruinose, rugulose or smooth, immersed and even with thallus surface or emergent and elevated above the thallus surface, with a thin white thalline margin 20–50 µm wide. Parathecium 10–40 µm wide, hyphae 2 µm wide, sometimes visible as parathecial ring around apothecial disc same color as epihymenium. Hymenium (100–)120–150 µm tall, cupular, usually tallest in center, epihymenium ca. 10 µm tall, reddish-brown, paraphyses mostly 1 µm wide, not branching, apices unexpanded, hymenial gel IKI+ blue to red, hemiamyloid. Asci 80–90 × 22–26 µm, clavate, ascospores mostly 3–4 × 2 µm, ellipsoid, several hundred per ascus (n = 20). Subhymenium 20–25 µm tall, IKI+ blue, euamyloid. Hypothecium Y-shaped, the central axis of hyphae extending down in a bundle, the arms 15–30 µm thick embracing the V-shaped subhymenium and continuous with parathecium. Pycnidia not observed. Chemistry: not producing secondary metabolites.

Known only from two locations on granite in full sun in the Mojave Desert in Joshua Tree National Park at approximately the same elevation of 1347–1369 m. The two specimens were collected about ten miles from each other. The sequences of the paratype were contaminated by a common parasitic lichenicolous fungus in Joshua Tree National Park, Acarospora destructans, though the parasite had not produced apothecia, and the thallus of A. alba showed no signs of contamination (Knudsen et al. 2022a). Sequences were only obtained from the holotype. Based on extensive collecting in Joshua Tree National Park since 2005 by Knudsen and Kocourková, the species is considered rare (Knudsen et al. 2013; Knudsen and Kocourková 2023).

U.S.A. • California, Riverside Co., Joshua Tree National Park, Mojave Desert, off trail between Skull Rock and Jumbo Rocks, 33.9958, -116.0653, alt. 1347 m, on granite, 19 Dec 2010, K. Knudsen 13181 (SBBG).

The white pigmentation of the thallus, like the white layer of pruina on Acarospora peltastica, increases surface albedo to protect the algal layer in the intense sunlight of the desert. Acarospora alba has a non-translucent white surface when wet while the white layer of A. peltastica is translucent when wet, the brown from a pigmented lower layer visible through the transparent pruina and epicortex. In our current key of Acarosporaceae of southwestern North America A. alba is recovered in section 8, couplet 8, with A. arenacea and A. bolleana, both with non-translucent white surfaces. Acarospora arenacea has euamyloid hymenial gel and thalli with deeply cross-hatched surfaces and ultimately produces elevated lecideine apothecia that are reddish-brown or black with carbonized epihymenial accretions (Magnusson 1952; Knudsen et al. 2023a). Acarospora bolleana has hemiamyloid hymenial gel like A. alba but differs in having a thallus of scattered white areoles becoming solitary lecideine apothecia. while A. alba has a continuous unstratified white thallus with immersed or emergent black apothecia.

U.S.A. • California, Riverside Co., Joshua Tree National Park, Mojave Desert, common on lower north slope of Malapai Hill, 33.9431, -116.0875, alt. 1190 m, on basalt, 5 Dec 2012, K. Knudsen 12772 (holotype, isotype-SBBG).

Figure 3. 

Acarospora indistincta Knudsen 12772 Isotype A habit of the thallus of convex dispersed squamules with immersed apothecia B detail of squamules (infected with Lichenostigma sp.) Scale bars: 500 μm (A, B).

Similar to Acarospora veronensis but differing with a thicker cortex (50–)90–100 vs. 10–20(–30) µm and in being squamulose.

Named for its lack of an appealing and distinctive phenotype. Many brown Acarospora look similar, especially ones like A. indistincta in the morphological veronensis group having one immersed apothecium per brown areole or squamule.

Hypothallus endosubstratal, no algae observed. Thallus of convex dispersed squamules, 0.3–1 mm wide, 0.4–0.7 mm thick, with rounded edges, sometimes irregular in shape, usually not replicating by division, covering areas of several centimeters. Upper surface brown, shiny or dull, rarely pruinose. Lower surface white. Epicortex 10–40 µm thick. Cortex (60–)90–100 µm thick, of mostly round cells 2–5 µm wide, upper layer red brown, 10 µm thick, lower layer hyaline. Algal layer 90–150 µm thick, even, dense, continuous below apothecia, not interrupted by hyphal bundles, algal cells 10–15 µm wide. Medulla 180–250 µm thick, of anticlinal hyphae thin-walled and 2 µm thick, continuous with the stipe. The majority of squamules are sterile. Usually one apothecium per areole, immersed, below thallus level, punctiform, expanding up to 0.4 mm wide, disc dark brown, epruinose, sometimes becoming slightly elevated in thalline margin. Parathecium indistinct or 10 µm wide of narrow hyphae 1 µm wide. Hymenium mostly 90–100 µm tall, epihymenium 10–20 µm tall, red-brown, surface uneven, paraphyses 1.0–1.5 µm wide, hymenial gel IKI+ blue turning red, hemiamyloid. Asci clavate 50–60 × 15–21 µm, ascospores several hundred, thin ellipsoid, 3–4 × 1–1.5 µm (n = 20). Subhymenium 40–50 µm tall, IKI+ blue, euamyloid. Hypothecium 20–30 µm tall, IKI-. Pycnidia not observed. Chemistry: not producing secondary metabolites.

Acarospora indistincta is currently only known from Joshua Tree National Park in the Mojave Desert and Sonoran Desert on granite and basalt in full sun.

U.S.A. • California, Riverside Co., Joshua Tree National Park, Mojave Desert, Little San Bernardino Mountains, Eureka Peak, north of summit in canyon, 34.0344, -116.3477, alt. 1591 m, on granite, 22 Feb 2006, K. Knudsen et al. 5249 (SBBG); • Eureka Peak, below summit, 34.0317, -116.3487, alt. 1670 m, on granite on steep north-facing slope, 28 March 2023, J. Kocourková 11125 & K. Knudsen (SBBG); • Malapai Hill, 33.9375, -116.0843, alt. 1165 m, on basalt rubble at base of hill, 5 Dec 2010, K. Knudsen 12637.2 (SBBG); • Sonoran Desert, north slope of Cottonwood Mountains, Pinkham Canyon 33.7787, -115.9317, alt. 970 m, on granite, 8 Dec 2010, K. Knudsen 12897.1 (SBBG); • San Bernardino Co., Joshua Tree National Park, Mojave Desert, Queen Mountain, 34.0523, -116.1031, alt. 1636 m, rare on granite, 5 Oct 2012., K. Knudsen 13721 & M. Harding (SBBG); • just outside Joshua Tree National Park, off Covington Flats Rd., along road to radio tower, 34.0766, -116.3497, alt. 1219 m, on granite, 9 Apr 2006, K. Knudsen 5782 (PH, SBBG).

In our current key of Acarosporaceae of southwestern North America, Acarospora indistincta is recovered in section 8, couplet 11, with squamules epruinose, differing from Trimmatothelopsis oreophila in having a shorter hymenium 90–100 vs. (130–)170–220(–250) μm high (Knudsen et al. 2023a).

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).

Figure 4. 

Acarospora sharnoffii Kocourková 11113 Paratype A habit of the sterile thallus (infected with Endococcus sp.) B squamules with abscission fissures. Scale bars: 1 mm (A, B).

Similar to Acarospora applanata but differing in being squamulose.

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.

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.

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.

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); • 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) .

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. 2021a, 2023a; 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. 2023a). Both species are sympatric at the type locality on Eureka Peak (Knudsen and Kocourková 2023).

U.S.A. • Kern Co., Tehachapi Mountains, Tejon Ranch, Martinez Ridge, fir and oak forest, 34.9352, -118.6477, alt. 1738 m, on granite, 19 April 2016, K. Knudsen 18838 (SBBG-holotype, isotypes).

Figure 5. 

Acarospora tejonensis Knudsen 18838 Holotype (A–C, F, H), Knudsen 18838 Isotype (D, E, G) A habit of the thallus with prolongated marginal areoles B vertical section through apothecium and margin of areole C variability of the thallus, black areoles with immersed apothecia sometimes reduced to a prominent margin D vertical section through apothecium showing parathecium with narrow hyphae E thallus of areoles lining crevices F young asci showing tholus G paraphyses slightly widened at tips, terminal cells orange-brown H ascospores. Scale bars: 1 mm (A, C, E); 100 µm (B); 20 µm (D, G); 50 µm (F); 5 µm (H).

Similar to A. veronensis but with a thicker cortex, 30–50(–70) vs.15–30 µm and a usually higher hymenium (100–)120(–150) vs. 80–90(–100) µm.

Named after the type locality in Tejon Ranch in Tehachapi Mountains.

Hypothallus endosubstratal, no algae observed. Thallus areolate, areoles 0.2–1.1 mm wide, 150–270 µm thick, angular, contiguous to dispersed, marginal areoles can be prolongated and lobate, becoming elevated by a mycelial base, replicating by division, covering areas up to 4 cm or more. Upper surface light to dark brown, sometimes partly black, epruinose, rugulose to smooth. Lower surface white. Epicortex lacking. Cortex 30–50(–70) µm thick, upper layer dark brown, 10–30 µm thick, lower layer hyaline, hyphae usually disarticulated, cells round to irregular, mostly small, 1–3 µm wide, rarely up to 5 µm wide. Algal layer up to 100 µm thick, uninterrupted, algal cells 8–12 µm wide, continuous below apothecia. Medulla white, 0.2–0.7 mm thick, hyphae obscure in water, intricate and gelatinized, mostly 1 µm wide. Apothecia immersed, usually one per areole, sometimes 2–5, sometimes with areole reduced to a prominent margin, the disc dark, epruinose, same color as thallus, 0.1–0.3 mm wide, rarely to 0.5 mm wide. Parathecium indistinct to 20 µm wide of narrow hyphae 1 µm wide, merging with the cortex. Hymenium cupular, (100–)120(–150) µm tall, epihymenium dark reddish brown, 10 µm tall, paraphyses 1–2 µm wide, apices unexpanded or slightly widened in terminal reddish brown gel cap, hymenial gel IKI+ reddish orange, hemiamyloid. Asci 90–120 × 10–20 µm, cylindrical to clavate, ascospore several hundred per asci, small, thin ellipsoid, 3–4 × 1 µm (n = 20). Subhymenium 20–40 µm tall, IKI+ blue. Hypothecium indistinct to 10 µm thick. Pycnidia not observed.Chemistry: not producing secondary metabolites.

U.S.A., California. on Santa Rosa Island (Channel Island National Park), in Carrizo Plain National Monument, and in the Tehachapi Mountains, from 198–1738 m, on sandstone and siliceous rock in full sun.

U.S.A. • California, Santa Barbara Co., Santa Rosa Island, South Point, 33.8950, -120.1159, alt. 183 m, on sandstone growing with A. socialis, 14 June 2009, K. Knudsen 11422 (SBBG); • San Luis Obispo Co., Carrizo Plain National Monument, canyon south of Hurricane Road, but near road, Elkhorn Hill, north-facing slope, 35.2074, -119.7026, 838 m, on siliceous rock, 28 March 2016, R. Rosentreter 19464 (SBBG).

In our key to southwestern North America Acarosporaceae (Knudsen et al. 2023a) Acarospora tejonensis is recovered in Section 8 couplet 12, areoles with an average hymenium height of 120 μm in couplet 13 with Myriospora hassei and Acarospora worthingtoniana. Acarospora tejonensis differs from M. hassei in not having an interrupted algal layer or a hymenium up to 200 μm high. It differs from A. worthingtoniana in having a thicker cortex [30–50(–70) vs. ca. 20 μm], a narrower parathecium indistinct to 20 μm vs. 40–100 μm wide, and in not having abundant apothecia in each areole.

Because Acarospora tejonensis usually has one apothecium per small areole without producing secondary metabolites, it belongs to the morphological A. veronensis group. It may be in California collections misidentified as A. veronensis if the hymenium and cortex is not measured or as A. americana if the parathecium is not measured. Acarospora tejonensis differs from A. veronensis especially in the having a higher hymenium (100–150 vs. 60–100 µm) and thicker cortex [30–50(–70) vs. 15–30 μm]. Acarospora tejonensis differs from A. americana in having a narrower parathecium (Knudsen 2021). The two species are sympatric in California. Acarospora tenebrica has similar anatomical measurement as A. tejonensis except apices of the parathecial hypae widen up to 3 μm. Acarospora tenebrica occurs in southwestern Texas and New Mexico while A. tejonensis is known only from central California. Magnusson (1956) reported the North African species Acarospora obscura as occurring in California. “Whether the identity between the American and the African specimens is complete is not easy to state owing to the smallness of areoles” (Magnusson 1929). We examined an isotype of A. obscura from H. Acarospora obscura has flat smooth brownish-black areoles less than 0.5 mm wide, cortex less than 30 µm thick, broadly attached with a black underside, punctiform immersed apothecia 0.1–0.3 mm wide, parathecium indistinct to 15 µm wide, with a low hymenium less than 100 µm. We have seen no specimens of A. obscura from California. Acarospora tejonensis can have small dark brownish-black areoles like A. obscura but differs in the thicker cortex 30–50(–70) µm, a thickening mycelial base, a higher hymenium usually 120 µm tall. The specimen of A. tejonensis from Santa Rosa Island has areoles both small and all black. It is probable Magnusson identified a small blackish specimen of A. tejonensis as A. obscura.

U.S.A. • New Mexico, Lincoln Co., Chihuahuan Desert, Tularosa basin, Oscura, near Road 54, 33.4863, -106.0925, alt. 1475 m, SW-NE oriented crest above the valley, southernmost hill, on northwest facing slope, on acid sandstone outcrop, 17 March 2022, J. Kocourková 10863 (PRM, holotype).

Figure 6. 

Sarcogyne fasciculata Kocourková 10863 Holotype (A, B, D–F), Kocourková 10971 Paratype (C) A habit of the thallus B detail of stipitate squamules with immersed apothecia C apothecia with reduced thallus squamules to thalline margin D vertical section of apothecium with developed parathecium E young ascus with ascospores F IKI+ amyloid reaction of hymenium and subhymenium. Scale bars: 1 mm (A, C); 500 μm (B); 100 µm (D, F), 50 µm (E).

Similar to Sarcogyne nogalensis but becoming squamulose.

Based on the species forming distinctive fascicles of squamules with interconnected stipes while in the process of splitting apart when replicating by division.

Hypothallus endosubstratal, no algae observed. Thallus of squamules or subsquamulose areoles, 0.2–0.5(–1.0–2.0) mm wide, 250–500 μm thick, with stipe 50–200 μm high, forming dispersed to contiguous colonies up to 3×2 cm, sometimes imbricate, with an uneven `topography, replicating by division. Upper surface light or dark brown, rarely shiny, epruinose, the lobes curling downward around the stipe, smooth or with abscission fissures when beginning to replicate by division, forming fasciculate structures of interconnected stipes of squamules during replication. Lower surface pale white sometimes with an undertone of pale brown, corticate with periclinal hyphae, hyaline, up to 20 μm thick. Epicortex, uneven, ca 10 μm thick. Cortex 20–40(–60) μm thick, upper layer ca. 10 μm thick of dark brown round cells, lower layer hyaline of round cells or ellipsoid cells 2–3 × 1.5–2.0 μm. Algal layer 70–120 μm thick, dense, uninterrupted, continuous below apothecia. Medulla obscure, white to pinkish-brown, 100–200 μm thick, hyphae continuous with stipe, 2–4 μm wide, thin-walled, sometimes disarticulated cells expanded or irregular, 4–8 μm wide. Apothecia immersed, darker brown than thallus, in San Bernardino Mountains specimens black, often concave, 0.1–0.6 mm wide, epruinose, occasionally looking pseudolecanorine with squamule reduced to thalline margin, sometimes apothecia in raised parathecial margin. Parathecium up to 60 μm wide, hyphae 2–3 μm wide with apices in brown pigment caps to 5 μm wide, merging with cortex. Hymenium 60–80(–120) μm tall, highest in center, epihymenium 10–15 μm tall, light brown, paraphyses 1.5–2.5 μm wide, apices unexpanded in brown gel caps 2–4 μm wide with upper black pigment line, hymenial gel IKI+ dark blue bleeding into parathecium and hypothecium. Asci (40–)50–75 × 10–20 μm, narrowly cylindrical to inflated clavate, ascospores, 2–4 × 1.5–2.5 µm (n = 20). Subhymenium 20–40 µm tall, IKI+ blue. Hypothecium 10–30 µm tall, hyphae 2 µm wide. No pycnidia observed. Chemistry: not producing secondary metabolites.

Sarcogyne fasciculata occurs in the Chihuahuan Desert in New Mexico on HCl- sandstone from 1475–1616 m and in southern California on granite in the Little San Bernardino Mountains and the San Bernardino Mountains at elevations 1650–2167 m.

U.S.A. • California, Riverside Co., Joshua Tree National Park, Mojave Desert, Little San Bernardino Mountains, Eureka Peak, E and West of the summit, 34.0132, -116.3502, alt. 1675 m, abundant on granite, 22 Feb 2006, K. Knudsen 5212 (SBBG); • San Bernardino Co., San Bernardino Mountains, conifer forest, above dirt road to Fish Creek, 34.1483, -116.7720, alt. 2167 m, common on granite boulder, 23 Nov 2014, K. Knudsen 17163 (BRY-C, SBBG). • New Mexico, Lincoln Co., Chihuahuan Desert, Carrizozo, Valley of Fires Recreational Area, Malpais Lava Flow, 33.8300, -105.9264, alt. 1616 m, on northwest-facing slope above lava flow, on sandstone pebble, 18 March 2022, J. Kocourková 10848 (hb. K&K), • 33.3503, -105.9227 alt. 1615 m, on northwest-facing slope above lava flow, on sandstone outcrop in full sun, 22 March 2020, J. Kocourková 10974, 10971, 10930 (hb. K&K, SBBG).

Sarcogyne fasciculata was first reported from the San Bernardino Mountains as immature S. squamulosa (Knudsen and McCune 2013; Knudsen et al. 2017). It was assumed in this population the typical apothecia of S. squamulosa had not formed yet. Sarcogyne fasciculata differs from S. squamulosa in not forming elevated brown lecideine apothecia with a parathecium expanded up to 80 µm to form a margin. The apothecia of S. fasciculata remain immersed in the squamule or areole and rarely expand reducing the areole or squamule to a thalline margin.

In our current key of Acarosporaceae of southwestern North America Sarcogyne fasciculata is recovered in Section 8, and couplet 9 brown species with euamyloid hymenial gel with S. nogalensis (Knudsen et al. 2023a). Young specimens of S. fasciculata that are subsquamulose may be confused with S. nogalensis. But Sarcogyne nogalensis remains areolate and does not become stipitate as well as genetically not being closely related (Fig. 1; Knudsen et al. 2023a).