Malmidea leucopiperis is a species of corticolous (bark-dwelling), crustose lichen in the family Malmideaceae. It is found in Brazil.
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 . The species epithet alludes to its resemblance to Malmidea piperis, with a key difference in the 's colourâÂÂlight greyish to beige compared to the dark brown in M. piperis.
Malmidea leucopiperis is a crustose lichen with a continuous thallus measuring 50âÂÂ80 üm 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 6âÂÂ8 üm 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 üm high and hyaline, while the centrally located is light greyish to beige, measuring 40âÂÂ50 üm in height and is KâÂÂ. The of Malmidea leucopiperis is either indistinct or slightly , and the hymenium stands 60âÂÂ70 üm high and is hyaline.
Asci within this species measure 40âÂÂ50 by 8âÂÂ10 üm, each containing 6âÂÂ8 . These spores are broadly ellipsoid to , non-septate, and have a uniformly thickened wall with a of approximately 1 üm. Their size ranges from 9âÂÂ12 by 4âÂÂ6 üm.
Chemically, this species is characterized by a major presence of norsolorinic acid and the absence of atranorin, as determined through thin-layer chromatography.
Malmidea leucopiperis occurs in the Atlantic rainforest in southern Brazil. It has been recorded from Rio de Janeiro, Pernambuco, and Sergipe.