Malmidea coralliformis

Malmidea coralliformis is a corticolous (bark-dwelling), crustose lichen in the family Malmideaceae.^[1] It was described in 2011 from northern Thailand. The species has a densely warted thallus with coral-like branching warts and ascospores that lack septa and are halonate. It resembles M. aurigera but lacks atranorin and tends to have larger spores.

The species was introduced as Malmidea coralliformis by Klaus Kalb in 2011 as part of a study establishing Malmidea and its family Malmideaceae. The holotype was collected in Thailand, Chiang Mai province, Doi Suthep–Pui National Park at about 700 m elevation, in a humid Dipterocarpus forest. The epithet coralliformis refers to the conspicuous, partly ramified, coral-like warts on the thallus.^[2]

The thallus forms a thin, crust-like growth (about 50–70 μm thick) on bark and is densely warted (verrucose), with individual warts about 0.2–0.3 mm high and 0.1–0.3 mm wide that often coalesce and branch; soredia and isidia are absent. The medulla is whitish and reacts K+ (orange). Apothecia (the spore-producing discs) are sessile, rounded and 0.7–1.1 mm in diameter; the disc is brown to dark grey-brown with a thin, biatorine margin of the granifera type. The rim tissue (proper exciple) is hyaline peripherally and internally shows a medullary layer of loosely arranged, periclinally arranged hyphae bearing hydrophobic granules that partly dissolve in potassium hydroxide solution with a greenish-yellow reaction. The subhymenium is brown, the hypothecium (tissue beneath the hymenium) is blackish-brown and K–, and the hymenium is 75–100 μm high. Asci are 60–70 × 13–15 μm. Ascospores number 6–8 per ascus, are colourless, ellipsoid, non-septate and halonate, measuring 10–17 × 6–10 μm. The authors report several unknown xantholepinones as the detectable chemistry and note the absence of atranorin.^[2]

The species is known from northern Thailand (Chiang Mai province), where it grows on tree bark in humid evergreen Dipterocarpus forest around 700 m elevation. The original material was collected along the trail to Monthanthan waterfall in Doi Suthep–Pui National Park.^[2]