Acarospora tejonensis K. Knudsen & Kocourk. sp. nov. Fig. 5 Type. 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). Diagnosis. 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. Etymology. Named after the type locality in Tejon Ranch in Tehachapi Mountains. Description. 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. Habitat and distribution. 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. Selected specimens examined. 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). Notes. In our key to southwestern North America Acarosporaceae (Knudsen et al. 2023 a) 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.

Published as part of Knudsen, Kerry, Cho-Ah-Ying, Jessica, Kocourková, Jana, Hodková, Eva, Malíček, Jiří & Wang, Yan, 2025, The diversity of Acarosporaceae (Acarosporales, Lecanoromycetes) in California, pp. 183-210 in MycoKeys 112 on pages 183-210, DOI: 10.3897/mycokeys.112.138580