Malmidea leucopiperis

Malmidea leucopiperis is a species of corticolous (bark-dwelling), crustose lichen in the family Malmideaceae. It is found in Brazil.

Taxonomy
The lichen was formally described as a new species in 2021 by the German lichenologist Klaus Kalb. The type specimen was collected from Itatiaia National Park (Rio de Janeiro) at an altitude of 850 m. The species epithet alludes to its resemblance to Malmidea piperis, with a key difference in the 's colour—light greyish to beige compared to the dark brown in M. piperis.

Description
Malmidea leucopiperis is a crustose lichen with a continuous thallus measuring 50–80 μm in thickness. Its surface is smooth and dull, appearing grey or greenish grey, and can turn orange-red when abraded. Neither isidia nor soralia (reproductive propagules) are present on this species. The medulla of the thallus is orange-red and has a K+ (purple) chemical spot test reaction.

The of this species is, with cell dimensions of 6–8 μm in diameter. The apothecia of Malmidea leucopiperis are sessile and rounded, ranging from 0.3 to 0.6 mm in diameter and 0.15 to 0.2 mm in height. The apothecial is initially flat, becoming slightly convex, with colours ranging from light beige to brown-grey or brown. Its margin is thin, about 0.1 mm, slightly raised, and varies in colour from whitish grey to dark brownish grey or black.

The is of the piperis-type and mostly hyaline (translucent), though it can appear brownish or blackish at the upper periphery, and lacks hydrophobic granules. The is about 10 μm high and hyaline, while the centrally located  is light greyish to beige, measuring 40–50 μm in height and  is K−. The of Malmidea leucopiperis is either indistinct or slightly, and the hymenium stands 60–70 μm high and is hyaline.

Asci within this species measure 40–50 by 8–10 μm, each containing 6–8. These spores are broadly ellipsoid to, non-septate, and have a uniformly thickened wall with a of approximately 1 μm. Their size ranges from 9–12 by 4–6 μm.

Chemically, this species is characterized by a major presence of norsolorinic acid and the absence of atranorin, as determined through thin-layer chromatography.

Habitat and distribution
Malmidea leucopiperis occurs in the Atlantic rainforest in southern Brazil. It has been recorded from Rio de Janeiro, Pernambuco, and Sergipe.