Acarospora minuta K. Knudsen, J. W. McCarthy & Kondrysová, 2025

Acarospora minuta K. Knudsen, J. W. McCarthy & Kondrysová sp. nov.

Fig. 5 View Figure 5

Type.

Canada • Newfoundland and Labrador, Newfoundland, Western Newfoundland, Port-au-Port East, Route 462, Pine Tree Road to the top of Table Mountain (south of Point-au-Mal), alpine coastal limestone barren , 48.5953, -58.6611, alt. 345 m, on siliceous rock among limestone scree, 3 Aug. 2017, J. W. McCarthy 3347 & C. McCarthy (CANL-holotype) GoogleMaps .

Diagnosis.

Similar to Polysporina limborinella in having small ascospores but differs in having an epilithic brown thallus and occurring in Canada and not in Switzerland ( Nimis et al. 2018).

Etymology.

Named for the small size of its ascospores.

Description.

Hypothallus endosubstratal, no algae observed. Thallus of dispersed thick brown areoles, beginning at base of apothecia and expanding to 1 mm wide and 300–400 μm thick. Upper surface shiny brown, epruinose. Epicortex up to 15 μm thick and continuous. Cortex 20–50 μm thick, narrow upper layer brown, less than 10 μm thick, lower layer hyaline, cells irregular in shape, 2–4 μm wide. Algal layer 80–100 μm thick, uninterrupted, algal cells 10–15 μm wide, continuous or not beneath apothecia. Medulla obscure, sometimes with a few scattered algal cells, hyphae 2–4 μm wide. Apothecia usually one per areole, occasionally two to six, 0.2–0.4 mm wide, 100–200 μm tall. Margin elevated up to 50 μm above the disc, dividing into four or five segments, thin, hyphae 1–2 μm wide, outer layer black 10 μm wide, inner layer hyaline. Disc black, with or without one umbo. Hymenium 90–140 μm tall, paraphyses 1 μm wide, apices unexpanded, some branching, often filled with oil drops, hymenial gel IKI + red or blue turning red in squash, hemiamyloid. Asci 45–60 × 15–20 µm, ascospores mostly 2–3 × 0.5–1.0 μm (n = 40), thin ellipsoid, sometimes oil drops, several hundred per ascus. Subhymenium 20–50 μm tall, IKI + blue. Hypothecium continuous with margin and thallus, sometimes distinct directly below apothecia, hyaline and narrow, sometimes golden yellow. No pycnidia observed. Not producing secondary metabolites.

Habitat and distribution.

Known only from two localities, growing on siliceous rocks among limestone on Table Mountain in western Newfoundland, Canada, and on mafic gabbro rock in Annieopsquotch Mountains in the southwestern interior of Newfoundland, Canada.

Additional specimens examined.

Canada • Newfoundland and Labrador, Newfoundland, Port-au-Port East, Route 462, Pine Tree Road to the top of Table Mountain (south of Point-au-Mal), limestone scree slopes along forested gully stream, alpine coastal limestone barren , 48.601, -58.6542, alt. 250 m, on siliceous rock among limestone scree, 3 Aug. 2017, J. W. McCarthy 3346 & C. McCarthy ( NBM) GoogleMaps ; • Port-au-Port East, Route 462, Pine Tree Road to the top of Table Mountain (south of Point-au-Mal), alpine, coastal limestone barren , 48.5953, -58.6611, alt. 345 m, on siliceous rock among limestone scree, 3 Aug. 2017, J. W. McCarthy 3348 & C. McCarthy ( NFLD) GoogleMaps ; • Port-au-Port East, Route 462, Pine Tree Road to the top of Table Mountain (south of Point-au-Mal), alpine, coastal limestone barren , 48.5953, -58.6611, alt. 345 m, on siliceous rock among limestone scree, 3 Aug. 2017, J. W. McCarthy 3349 & C. McCarthy ( SBBG) GoogleMaps ; • southwest Newfoundland, Burgeo Highway (Route 480), Annieopsquotch Mountains , 48.2804, -57.7051, alt. 535 m, on mafic rock, 9 Oct. 2018, J. W. McCarthy 3751 & C. McCarthy ( CANL) GoogleMaps .

Note.

Sequences were only recovered from one of several specimens we studied.

Two other species with carbonized epihymenial accretions have epilithic thalli, Sarcogyne albothallina in our key and Acarospora tasmaniensis , occurring in soil crusts in Tasmania. Other taxa may rarely have a chasmolithic or epilithic thallus, usually formed by exposure of endolithic thallus by erosion of substrate.