Psammina tropica
Psammina tropica is a species of corticolous crustose lichen of uncertain classification in the Ascomycota. This lichen was discovered in 2016 growing on tree bark in disturbed forests of the Brazilian Amazon, with specimens found in both Amapá and Rondônia states. It is distinguished by its unique star-shaped reproductive structures that have 3–6 arms, each made up of several cells, which help identify it from related species.
Taxonomy
Psammina tropica was described as new to science in 2016 by André Aptroot and Marcela da Silva Cáceres from material collected in the Amapá National Forest. The holotype was gathered on tree bark in disturbed forest near the field station at about 30 m elevation; paratypes came from Rondônia. The specific epithet refers to its occurrence in the tropics. Species of Psammina can be lichenicolous or lichen-forming; P. tropica differs from the other lichenized species, P. palmata, by having septate, palmate conidia and a comparatively large, corticate thallus with a sterile zone around its edges.
Description
The thallus forms patches up to about 4 cm across; it is corticate, smooth, dull, continuous, thin, and olive gray, and is bordered by a whitish hyphal up to about 1 mm wide. The photobiont is. Ascomata were not observed. Sporodochia are abundant over the thallus center but absent from a 1–2 mm marginal zone; they are whitish gray, irregular to rounded, 0.1–0.3 mm in diameter, and only about 15 μm high. Conidia are hyaline and palmate, with 3–6 arms that are each 4–7-celled; conidia are about 20–25 μm in diameter. P. tropica is unreactive with standard spot tests; thin-layer chromatography detected no lichen substances.
Habitat and distribution
Psammina tropica grows on tree bark in disturbed forest. It is known only from Brazil, with collections from Amapá and Rondônia, at roughly 30–100 m elevation. No additional Brazilian locations have been reported as of 2025.