Gyalolechia allochroa
Gyalolechia allochroa is a species of saxicolous crustose lichen in the family Teloschistaceae. It forms a thin, smooth crust on siliceous rocks in subtropical mountain regions and shows marked colour variation, occurring in both bright yellow and grey-white forms depending on light exposure. The lichen is characterised by abundant disc-like fruiting bodies with egg-yolk yellow rims and contains the pigments parietin and fragilin, which account for its distinctive colouration. It is known to occur only on three mountains in South Korea, where it was first discovered and described in 2011.
Taxonomy
The lichen was formally described as a new species in 2011 by Yogesh Joshi, Jan Vondrák, and Jae-Seoun Hur, as a member of the genus Caloplaca. The type specimen was collected from Mt Jobong at an elevation of 980 m, where it was found growing on siliceous rock. The species epithet allochroa, derived from allochrous, means. The species was reclassified in the genus Gyalolechia in 2013, as part of a major molecular phylogenetics-informed reorganisation of the family Teloschistaceae.Description
Gyalolechia allochroa forms a thin, smooth, crustose thallus on rock that is usually 6–8 cm across but only about 70–90 micrometres thick. The thallus can be continuous, finely cracked, or broken into small, and a dark grey, filamentous is often visible along cracks and edges. Two colour morphs occur: a yellow form and a grey-white form. In shaded or less exposed sites the yellow morph shows orange-brown, whereas on strongly sun-exposed faces the thallus turns distinctly grey and the discs become brownish-black. Apothecia are abundant, 0.3–1.0 mm across, and, meaning the rim is formed only by fungal tissue rather than by the thallus; this rim is smooth, persistent, and egg-yolk yellow to yellow-orange, usually paler than the disc, which may carry a faint greenish-yellow frost.Internally, the upper hymenial layer gives a K+ reaction and contains yellow-brown granules; the hymenium beneath is clear and rich in oil droplets, over a hyaline. The is well developed and the thallus lacks a. The ascospores are hyaline and two-celled with a narrow central bridge, mostly 12.5–21.5 × 6–11.5 μm with a 2.5–7.5 μm. Small rod-shaped conidia about 2.1–2.5 × 0.7–0.9 μm are produced only rarely. Standard spot tests on the thallus are largely negative: K−, C−, KC−, P− and UV−. The apothecia contain mainly the anthraquinone pigments parietin and fragilin ; fragilin predominates in yellow thalli, whereas grey-white thalli show only traces of these compounds, accounting for the species' colour variation.