Peltigera hydrothyria

Peltigera hydrothyria, commonly known as the waterfan, is a relatively rare aquatic lichen in the family Peltigeraceae, native to North America. It grows in cold, clean mountain streams, where it attaches to rocks and bedrock in shaded, riparian habitats. First described in 1856 as Hydrothyria venosa, it was initially placed in its own genus due to its distinctive gelatinous thallus and aquatic lifestyle. Molecular studies later demonstrated its affinity with the genus Peltigera, leading to its reclassification in 2000. The lichen forms small, blackish rosettes with ruffled margins and prominent veining, features that help it thrive in submerged or semi-aquatic habitats. Three genetically distinct lineages are now recognized within the species, corresponding to eastern North America (var. hydrothyria) and western North America (vars. gowardii and aquatica). The eastern variety, var. hydrothyria, is listed as Endangered on the IUCN Red List due to significant population declines across ......read more on Wikipedia.