Haematomma alborussulum (Nyl.) S. Ekman & J. Gerasimova, 2017

Gerasimova, Julia V. & Ekman, Stefan, 2017, Taxonomy and nomenclature of seven names in Bacidia (Ramalinaceae, Lecanorales) described from Russia, Phytotaxa 316 (3), pp. 292-296 : 293

Haematomma alborussulum (Nyl.) S. Ekman & J. Gerasimova , comb. nov.

MycoBank no.: MB820116

Lecidea alborussula Nyl. (1884: 213) . Bacidia alborussula (Nyl.) Zahlbr. (1926b: 173) . Type:— RUSSIA. Chukotka Peninsula : “sinus Konyam ad fretum Bering, 64° 50 lat. bor., 173° long. occid. (Greenw.)”, 28–30 July 1879, E. Almquist s. n. (lectotype, designated here: S L32108!); [in Nylander’s handwriting:] “Fret. Behringii, Konyambay”, undated, E. Almquist s. n. (isolectotype: H-NYL 17561!).

Lecidea alborussula var. callosynopsis Nyl. (1887: 228) . Bacidia alborussula var. callosynopsis (Nyl.) Zahlbr. (1926b: 173) . Type:— RUSSIA. Chukotka Peninsula: “sinus Konyam ad fretum Bering, 64° 50 lat. bor., 173° long. occid. (Greenw.)”, 28–30 July 1879, E. Almquist s. n. (syntype: S L32114!).

Bacidia alborussula , including its var. callosynopsis , was described from the Chukotka Peninsula at the Bering Strait, where it was collected on siliceous rock. The thallus is yellowish white and areolate, with a white cobwebby prothallus along the edge and between discontiguous areoles. The areoles have a soft, powdery, almost sorediate surface. Apothecia are up to 1 mm diam., dark red and become strongly convex with a suppressed proper exciple (no obvious thalline margin), sometimes aggregated and tuberculate. Paraphyses are strongly branched and set with orange-brown crystals, mostly in the upper part. These crystals dissolve into a K+ violet solution, not forming any needles. Ascospores are filiform to bluntly acicular, straight to ± curved or helical, 25–40 × 2.5 μm (26–48 × 3.0 μm according to Nylander 1884), with 3 thin septa. Asci are Haematomma - type sensu Staiger & Kalb (1995), including a narrow axial body.

Bacidia alborussula clearly belongs in the genus Haematomma and does not seem to correspond to any of the currently recognized taxa ( Staiger & Kalb 1995, Brodo et al. 2008). The apothecial pigment crystals seem to correspond to haematommone, as characterized by Staiger & Kalb (1995). The combination of the saxicolous substrate, the characteristics of the pigment crystals, long and narrow ascospores, and convex apothecia without visible thalline margin seems to be unique within the genus. The var. callosynopsis described by Nylander (1887), judging from the type material in S, is a morph with young and aggregated apothecia that otherwise corresponds well with the nominal variety. It should be pointed out that the close relationship with Haematomma ochroleucum (as ‘ Lecanora haematomma ’) was pointed out already in the original description.