Aggregatorygma isidiatum Aptroot, L.A. Santos & M. Cáceres, sp. nov.
Index Fungorum number: IF 902390; Mycobank number: MB 902390; Facesoffungi number: FoF 16049; Fig. 1
Etymology – Named after the isidia.
Corticolous Aggregatorygma differing from all known species in the genus by the presence of isidia and the absence of ascomata.
Holotype – ISE 27452
Thallus crustose, discontinuous, following the surface of the substratum, not corticate, dull, pale creamish white, up to 5 cm diam., under 0.1 mm thick, not surrounded by a prothallus. Isidia of thallus colour, not corticate, irregularly globose with constricted base, 0.1–0.2 mm wide and high. Photobiont trentepohlioid. Ascomata and pycnidia not observed.
Chemistry – Thallus UV–, K–, P–. TLC: confluentic acid. Ecology and distribution: On tree bark in primary rain forest; only known from Brazil.
Material examined – Brazil. Amapá: Floresta Nacional do Amapá, upstream of the station, alt. 30 m, 0° 58ʹ N, 51° 36ʹ W, on tree bark in primary forest, 20 Aug. 2015, M.E.S. Cáceres & A. Aptroot (ISE 27452, holotype; isotype in ABL herbarium).
GenBank numbers – OR759506 (holotype) and OR759506 (paratype).
Note – This species is well characterized by its isidia, which could be called pseudisidia if one sticks to the strict definition of isidia as corticated structures. So far, only three species have been described in the genus (Cáceres et al. 2014; Aptroot & Feuerstein 2020; Aptroot et al. 2022), all from Brazil and all in the last decade. They are all fertile and miss the isidia.
Figure 1 – Aggregatorygma isidiatum (ISE 27452, holotype). Width of picture=2 mm