INS 20-6 - What can a red lichen tell us? The belief and the facts about the tropical lichen Herpothallon rubrocinctum (Ehrenb.: Fr.) Aptroot, Lücking & G. Thor

Early in my career there was a lichen that caught my attention: the “Christmas-lichen” (Herpothallon rubrocinctum). What makes it so special? There is a hint in the name (rubro = red; cinctum = surrounded): its thallus is bright red, and it can cover part of the trunks in tropical and subtropical forests. Its appealing color gives even more beauty to these forest’s understories. But not only that, there is a belief in Brazil that the “líquen-vermelho”, as it is commonly called there, is a biological indicator of clean air. But is it? In fact, what science shows might be different.