Dictyonema discocarpum is a species of lichen-forming fungus in the family Hygrophoraceae. It is a filamentous, blueâÂÂgreen basidiolichen (a lichen whose fungal partner is a basidiomycete) that grows in thin, shelfâÂÂlike mats on tree bark in Bolivian cloud forest. Described inâ¯2013, it is one of three Dictyonema species discovered together in the same Andean reserve and is readily recognized by the tiny, white "pinâÂÂhead" discs that speckle the underside of each shelf.
The species was named by Robert Lücking, Manuela Dal Forno and Karina Wilk from material collected in Madidi National Park, La Paz Department, Bolivia, at about elevation. The specific epithet discocarpum ("bearing discs") refers to its round fruiting patches. DNA sequencing of the internal transcribed spacer (ITS) region places the fungus within Dictyonema in the strict sense (sensu stricto), closely related to the widespread D. sericeum but forming its own clade. Like D. sericeum it forms shelfâÂÂlike lobes, yet only D. discocarpum produces neatly rounded, crispâÂÂedged hymenophores ("discâÂÂshaped" basidiocarps) on the lower surface.
The lichen starts as a felted turquoise crust that soon lifts at the margin to form narrow, horizontal shelves (up to 3 cm long, 1âÂÂ2 mm thick). These overlap shingleâÂÂstyle along the host trunk. Each shelf is composed of countless cyanobacterial threads (fibrils) lying roughly parallel to the substrate. The fungus envelops each thread with jigsawâÂÂshaped cortical cells typical of Dictyonema, creating a tough outer rind only 40âÂÂ60 üm thick. On the underside, the lichen develops minute, snowâÂÂwhite pads 0.2âÂÂ0.6 mm across. These pads are hymenophoresâÂÂthe sporeâÂÂproducing surface of the basidiomycete. In D. discocarpum they are distinctly discâÂÂshaped, explaining the species name and separating it from the irregular, shelfâÂÂedge patches seen in relatives.
At the time of its original publication, D. discocarpum was confirmed to occur only in northâÂÂwestern Bolivia (La Paz Department). The lichen grows epiphytically on rough bark and on trailing lianas in lower montane cloud forest (aboutâ¯1,800âÂÂ2,300 m elevation). The site is persistently humid, with frequent fog and dense bryophyte cover.