Punctelia

Punctelia is a genus of foliose lichens belonging to the large family Parmeliaceae. The genus, which contains about 50 species, was segregated from genus Parmelia in 1982. Characteristics that define Punctelia include the presence of hook-like to thread-like conidia (asexual spores), simple rhizines (root-like structures that attach the lichen thallus to its substrate), and point-like pseudocyphellae (tiny pores on the thallus surface that facilitate gas exchange). It is this last feature that is alluded to in the vernacular names speckled shield lichens or speckleback lichens. Punctelia lichens grow on bark, wood, and rocks. The genus has a worldwide distribution, occurring on all continents but Antarctica. Species are found in temperate to subtropical locations. Punctelia has centres of distribution in the Neotropics and Africa; about half of the known species occur in South America. The photobiont partners of Punctelia are green algae in the genus Trebouxia. Some pollution-sensitive......read more on Wikipedia.