''Astrothelium bivelum'' is a species of corticolous (bark-dwelling), crustose lichen in the family

Trypetheliaceae The Trypetheliaceae are a family of mainly lichen-forming fungi in the order Trypetheliales. Genera *'' Alloarthopyrenia'' – 1 sp. *''Aptrootia'' – 3 spp. *'' Architrypethelium'' – 8 spp. *''Astrothelium'' – ca. 275 spp. *'' Bathel ...

. Found in Brazil, it was formally described as a new species in 2016 by lichenologists

André Aptroot André Aptroot (Heemskerk, 1961) is a Dutch mycologist and lichenologist. In 1993 he did his PhD at the University of Utrecht under the supervision of Robbert Gradstein (nl). His dissertation was titled "Systematic studies on pyrenocarpous li ...

and Marcela Cáceres. The type specimen was collected by the authors in the Parque Natural Municipal de Porto Velho ( Porto Velho,

Rondônia Rondônia () is one of the 26 states of Brazil, located in the northern subdivision of the country (central-western part). To the west is a short border with the state of Acre, to the north is the state of Amazonas, in the east is Mato Grosso, ...

), in a primary

rainforest Rainforests are characterized by a closed and continuous tree canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforest can be classified as tropical rainforest or temperate rainfores ...

. The lichen has a smooth and somewhat shiny, ochraceous-green thallus with a 0.4 cm-wide rough and irregular prothallus; the thallus covers areas of up to in diameter. The presence of the lichen does not induce the formation of

gall Galls (from the Latin , 'oak-apple') or ''cecidia'' (from the Greek , anything gushing out) are a kind of swelling growth on the external tissues of plants, fungi, or animals. Plant galls are abnormal outgrowths of plant tissues, similar to be ...

s in the

host A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places * Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman * Michel Host ...

. The ascomata are pear-shaped (''pyriform''), measure 0.5–0.7 mm in diameter, typically aggregate in groups of two to six, and are usually immersed in the bark tissue. The characteristics that distinguish it from other members of '' Astrothelium'' include the diffusely , ascomata that are covered by thallus and have an external pink pigment, with each containing a single group of fused ascomata; and the 5- septate ascospores. ''A. bivelum'' is one of the few ''Astrothelium''-like species with 5-septate ascospores that does not contain lichexanthone.

References

bivelum Lichen species Lichens described in 2016 Taxa named by André Aptroot Taxa named by Marcela Cáceres Lichens of North Brazil {{Dothideomycetes-stub