Micarea nigra van den Boom, Guzow-Krzeminska , Brand & Serus .

Guzow-Krzeminska, Beata, Serusiaux, Emmanuel, van den Boom, Pieter P. G., Brand, A. Maarten, Launis, Annina, Lubek, Anna & Kukwa, Martin, 2019, Understanding the evolution of phenotypical characters in the Micarea prasina group (Pilocarpaceae) and descriptions of six new species within the group, MycoKeys 57, pp. 1-30 : 1

Micarea nigra van den Boom, Guzow-Krzeminska, Brand & Serus. sp. nov. Fig. 2E

Diagnosis.

Species characterised by the production of branched isidia, dark greyish to almost black apothecia containing Cinereorufa-green pigment and measuring 0.15-0.5 mm in diam., (0-)1-septate, narrowly ellipsoidal to clavate ascospores measuring 7.5-12 × (2.5 –)3– 4.5 µm and the production of methoxymicareic acid.

Type.

Portugal. Estremadura, W of Lisbon, W of Sintra, Park de la Monserrate, 200 m alt., 38°47.30'N, 9°25.07'W, parkland with mixed (mature) trees and shrubs, on fern tree, 15 Oct. 2015, P. & B. van den Boom 53726 (holotype LG; isotypes UGDA, hb v.d. Boom, mtSSU GenBank accession number: MK562029).

Description.

Thallus inconspicuous, thin, consisting of often branched and vertically proliferating fine isidia; prothallus not seen; areoles up to 0.1 mm in diam.; isidia developing from small areoles, vertically branched and coralloid, in some parts crowded and forming almost a continuous layer, but separated in younger parts of thalli, brownish-green, up to 500 μm tall and 30 μm wide, with a distinct and complete hyphal layer; apothecia abundant, adnate, flat to moderately convex, emarginate, 0.15-0.5 mm in diam., dark greyish to almost black, sometimes with a pale greyish rim; hymenium greenish, with pale brownish streaks, K–, C‒, 30-40 µm tall; epihymenium aeruginose greenish, with Cinereorufa-green pigment, K+ green intensifying; hypothecium hyaline; paraphyses sparse, branched, tips not widened and not pigmented, ca. 1.0‒1.5 µm wide; asci cylindrical to clavate, 24-28 × 9-12 µm, 8-spored; ascospores narrowly ellipsoid to clavate, 7.5-12 × (2.5 –)3– 4.5 µm, (0-)1-septate; micropycnidia inconspicuous, rare, 30-60 µm in diam., with dark brown top ( K–, C‒); microconidia bacilliform, sometimes slightly curved, aseptate, 7-10 × 0.5-0.9 µm; crystalline granules (studied in polarised light) not visible in apothecium, but detected in isidia (sometimes isidia very abundant and sometimes very few), insoluble in K.

Photobiont micareoid, cells thin-walled, 4-8 µm in diam., clustered in compact masses.

Chemistry.

Methoxymicareic acid detected by TLC. Cinereorufa-green in apothecia (epihymenium).

Habitat and distribution.

Abundantly present on a trunk of a fern tree in a parkland where many tropical and exotic fern and tree species have been introduced.

To date, it is only known from the type locality in Portugal (Sintra).

Etymology.

The epithet chosen for this species refers to its very dark appearance, the thallus being dark greenish and the apothecia mostly blackish.

Notes.

This species is resolved in the M. micrococca group ( Fig. 1 ) and is unique because of its dark grey to almost black apothecia and the presence of Cinereorufa-green pigment in epihymenium.

Micarea nigra resembles M. aeruginoprasina , M. isidioprasina and M. pauli . Micarea aeruginoprasina and M. isidioprasina differ in the presence of micareic acid instead of methoxymicareic acid and paler apothecia. In addition, M. aeruginoprasina produces different pigment in the apothecia (Sedifolia-grey). Micarea pauli differs in the production of methoxymicareic acid, Sedifolia-grey pigment in the apothecia and different distribution (see under that species).

Some morphs of M. prasina can also have dark apothecia, but this species contains micareic acid and Sedifolia-grey in the apothecia ( Coppins 1983; Czarnota 2007; Launis et al. 2019a, b). Micarea subviridescens can have blackish apothecia and is sometimes epiphytic, but it produces prasinic acid ( Coppins 1983).

Figures

Figure 1. Maximum likelihood tree based on three-loci dataset. Bootstrap supports ≥ 70 for ML and posterior probabilities ≥ 0.95 (second value) for Bayesian methods are indicated near the branches. The highly supported clades with previously described species represented by numerous sequences are collapsed. Herbarium collection numbers for newly sequenced specimens precede the names of species and type specimens are marked. Newly described species are marked in bold. Micarea micrococca (orange) and M. prasina (blue) clades are indicated with shading. Ancestral states for selected characters reconstructed based on binary or multistate datasets using maximum parsimony (MP) or maximum likelihood methods (ML) are marked for the main clades: M. prasina group, M. micrococca clade and M. prasina clade using red (= present / significant) and white (= absent / insignificant) boxes or? (= uncertain).

Figure 2. Morphology of newly described Micarea species A M. aeruginoprasina (holotype) B M. azorica (holotype) C M. isidioprasina (holotype) D M. microsorediata (holotype) E M. nigra (holotype) F M. pauli (holotype). Scale bars: 200 µm (A−C, E); 300 µm (D, F).