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

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

Fig. 3 View Figure 3

Type.

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) GoogleMaps .

Diagnosis.

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

Etymology.

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.

Description.

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.

Habitat and distribution.

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.

Additional specimens examined.

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) GoogleMaps ; • 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) GoogleMaps ; • Malapai Hill , 33.9375, - 116.0843, alt. 1165 m, on basalt rubble at base of hill, 5 Dec 2010, K. Knudsen 12637.2 ( SBBG) GoogleMaps ; • 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) GoogleMaps ; • 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) GoogleMaps ; • 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) GoogleMaps .

Notes.

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. 2023 a).