Myriotrema thailandicum is a species of crustose lichen in the family Graphidaceae. It was formally described as a new species in 2002 by lichenologists Natsurang Homchantara and Brian J. Coppins.
Taxonomy and Description
The species was first published in the journal The Lichenologist (volume 34, issue 2, pages 113–140) in a paper titled "New species of the lichen family Thelotremataceae in SE Asia." The type specimen was collected from Namtok Phlio National Park in Chanthaburi Province, Thailand, at an elevation of approximately 100 m (330 ft), where it was found growing on both rocks and tree trunks in lowland rainforest.
The lichen has a thin, uneven to coarsely verrucose thallus that is smooth and shiny, greenish-grey in color, with a dense cortex and a white medulla. It contains the depsidone fumarprotocetraric acid, and sometimes has trace amounts of protocetraric acid. The ascomata are thelotremoid (immersed to erumpent, with round to irregular pores and carbonized margins). The ascospores are muriform (with both transverse and longitudinal septa), ellipsoid to fusiform in shape, measuring 15–35(–40) × 7–13 μm.
Taxonomic Status
The taxonomic status of Myriotrema thailandicum has been subject to revision. A 2010 re-evaluation by Papong, Boonpragob, Mangold, Divakar, and Lumbsch proposed reducing M. thailandicum to a synonym of Ocellularia thelotremoides (Leight.) Zahlbr., arguing that the two taxa exhibit substantial morphological overlap in thallus texture, ascoma development, ascospore morphology, and chemistry. Under this treatment, the species is considered a morphological variant of the earlier-described Ocellularia thelotremoides.
However, subsequent analyses, including a 2016 worldwide key, have upheld M. thailandicum as a distinct, accepted species by some authorities. The Catalogue of Fungi of Colombia and Index Fungorum continue to list it as an accepted species. The 2017 inventory of Thai lichenized fungi by Aptroot et al. retains the taxon under Graphidaceae with reference to its synonymy under O. thelotremoides.
Distribution and Habitat
The species was originally described from Thailand, with the type locality in Namtok Phlio National Park, Chanthaburi Province. It is a corticolous (bark-dwelling) lichen inhabiting tropical lowland rainforests, growing on the smooth bark of deciduous trees. It favors shaded, humid microhabitats in the forest understory. If treated as synonymous with Ocellularia thelotremoides, its distribution would be pantropical, with records from Southeast Asia, Africa, and South America.
References
- Homchantara, N.; Coppins, B.J. (2002). "New species of the lichen family Thelotremataceae in SE Asia." The Lichenologist. 34 (2): 113–140. doi:10.1006/lich.2002.0382.
- Papong, K.; Boonpragob, K.; Mangold, A.; Divakar, P.K.; Lumbsch, H.T. (2010). Taxonomic revision of thelotremoid lichens in Thailand. The Lichenologist.
