Malmidea allopapillosa

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

Taxonomy

The lichen was formally described as a new species in 2021 by the German lichenologist Klaus Kalb. The type specimen was collected by the author in 1980 from a cloud forest in the surroundings of Tovar, Páramo de Mariño, (Mérida) at an altitude of . The species epithet refers to its resemblance to Malmidea papillosa.

Description

Malmidea allopapillosa is a crustose lichen with a thallus that is either continuous or cracked and measures 50–100 ÃŽÂ¼m in thickness. The surface of the thallus is smooth and dull, with warts that are 0.2–0.3 mm in diameter and with a whitish-grey colour. This species lacks both isidia and soralia. The of the thallus reacts to a solution of potassium hydroxide (i.e., the K spot test) with a yellow colouration, while the medulla of the thallus is white is K−. The medulla of the warts is peach-coloured to pink, with an orange-red reaction with K+, which soon changes to lemon-yellow. The of this species is , with cells measuring 6–8 ÃŽÂ¼m in diameter.

The apothecia of Malmidea allopapillosa are sessile and rounded, measuring 0.3–0.8 mm in diameter and 0.4–0.5 mm in height. The apothecial are flat and range in colour from light to dark brown. The margin of the apothecia is thin, approximately 0.05 mm thick, and varies in colour from whitish-grey to dark brownish-grey. As the lichen ages, the margin is excluded, forming a piperis-type excipulum that is more or less hyaline (translucent) or brown at the periphery, with the inner part being hyaline and lacking hydrophobic granules. The is about 15 ÃŽÂ¼m high and varies from hyaline to light brown, while the centrally located is 70–90 ÃŽÂ¼m high, narrowing towards the margin, and has a reddish to dark brown colour unreactive to K. The is brown, and the hymenium is hyaline, measuring 130–150 ÃŽÂ¼m in height. The base of the apothecia is partially filled with opaque granules that react K+ (greenish-yellow).

The asci of Malmidea allopapillosa measure 90–120 by 20–25 ÃŽÂ¼m. Each ascus contains 6–8 broadly ellipsoid, ascospores that lack septa. These ascospores have walls that are equally thickened and , measuring 14–17 by 8–10 ÃŽÂ¼m with a of 1 ÃŽÂ¼m.

Chemically, this species is characterised by the presence of atranorin as a major component, along with approximately 10 unidentified xantholepinone substances, detectable using thin-layer chromatography. Its lookalike Malmidea papillosa lacks atranorin and has a different set of xantholepinones.

References