Cyphellostereum galapagoense is a species of basidiolichen in the family Hygrophoraceae. The species is found only in the humid highlands of the Galápagos Islands, where it grows on moss-covered tree branches in misty cloud forests. It was originally classified under a different genus name in 2012 before DNA studies revealed its true evolutionary relationships. The lichen forms blue-green, hair-like strands that create a velvet-textured mat and partners with nitrogen-fixing bacteria to survive in nutrient-poor environments.
Cyphellostereumâ¯galapagoense is a basidiolichen, meaning its fungal partner lies in the basidiomycete family Hygrophoraceae rather than the more familiar ascomycetes. The species was first described in 2012 under the name Dictyonemaâ¯galapagoense by Alba Yánez, Manuela Dalâ¯Forno and Frank Bungartz, based on a single Sanâ¯Cristóbal Island collection. That original placement reflected its thin, bluishâÂÂgreen fibrils and the "jigsaw" fungal sheath typical of Dictyonema species. Subsequent DNA work showed the fungus groups firmly with Cyphellostereum, so Dalâ¯Forno, Bungartz and Robert Lücking transferred it in 2017, resolving the mismatch between morphology and ancestry.
The holotype specimen comes from a PsidiumâÂÂdominated forest on Sanâ¯Cristóbal, where it grew on mosses over a manchineel (Hippomaneâ¯mancinella) branch. It differs from the related C. unoquinoum by having denser, more bluish fibrils and a completely enclosed cyanobacterial sheath. With all confirmed records coming from the archipelago, the taxon is treated as a Galápagos endemic.
The lichen forms a feltâÂÂlike patch of irregularly erect, hairâÂÂfine that give the thallus (the visible body of a lichen) a blueâÂÂgreen sheen. Fibrils are bundles of fungalâÂÂwrapped cyanobacterial "threads", so a casual observer can picture them as tiny strands of braided fishingâÂÂline. No distinct (a margin of fungus tissue) is present, and any (a basal weave of hyphae) appears only as a faint white film. The is Rhizonema, a cyanobacterium whose 7âÂÂ10 ümâÂÂwide cells sit in singleâÂÂrow filaments, each filament being tightly jacketed by 2.5âÂÂ3.5 ümâÂÂthick fungal hyphae with a jigsaw outline. Frequent paleâÂÂyellow âÂÂspecialised nitrogenâÂÂfixing cellsâÂÂpunctuate the filaments and reach the same size range as the ordinary cells.
These heterocysts supply nitrogen to the partnership, a useful service in rainâÂÂwashed treeâÂÂcanopies where other nutrients are scarce. Because the fibrils also grow vertically, the mat takes on a short "pile", recalling the nap of velvet or the fuzz on a peach. No hymenophore (fruiting body) has yet been observed, so reproduction is assumed to be mainly by dispersal of broken fibrils. Field collectors recognise the species by its finer, more erect filaments compared with Dictyonema lookâÂÂalikes, and by the absence of a white prothallus rim.
Confirmed specimens come from the humid highlands of Sanâ¯Cristóbal and Santaâ¯Cruz Islands, Galápagos. The type locality is a semiâÂÂshaded manchineel forest at roughly 392 m elevation where constant mist keeps substrates damp. A second collection from 729 m on Santaâ¯Cruz was made in abandoned farmland behind Elâ¯Puntudo, again within the cool, moistureâÂÂladen "scalesia zone". Both sites share shelter from direct sun and abundant bryophyte cover, conditions that favour waterâÂÂabsorbing filamentous lichens.
The lichen grows as an epiphyte on moss mats that coat tree branches, indicating a reliance on bryophytes for initial anchorage rather than on the woody substrate itself. Such bryophyteâÂÂladen cloud forest fragments are also hotspots for other basidiolichens, which collectively prefer the archipelago's wetter upland microclimates. No mainland records exist, and molecular phylogenies show the Galápagos lineage to be distinct, supporting its status as an island endemic.