Diorygma microsporum

Diorygma microsporum has a crustose thallus that can reach up to 5 cm (2 in) in diameter and has a thickness of 50–120 μm. Its surface is smooth to uneven and has a light greyish-green colour. The lichen features dense clusters of stellately (star-like) branched lirellae, measuring 1–5 mm long, 0.15–0.25 mm wide, and 0.1 mm high. The disc is partly exposed, with a flesh-coloured to light red-brown hue and covered in white pruina. Its excipulum is orange-brown and 15–25 μm thick. The ascospores are ellipsoid, measure 12–15 by 6–7 μm in size, and strongly iodine-reactive. It contains norstictic acid as its sole lichen product.

Similar species. Diorygma microsporum shares some similarities with D. poitaei in appearance; however, it is distinguished by its smaller ascospores and the presence of norstictic acid in its thallus. Another one of the few species with small spores, Diorygma cameroonense, is distinguished from D. microsporum by its chemistry, as it contains stictic acid and constictic acid as major lichen products.

Diorygma microsporum has a relatively broad neotropical distribution, as evidenced by collections from northeastern Brazil, Colombia, and Florida. It has also been recorded in Tamil Nadu, India. This lichen species is typically found on tree trunks in the shady understory of undisturbed lowland and lower montane rainforests, making it a bioindicator of forest health.

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