Peltula

Peltula is a genus of small dark brown to olive or dark grey squamulose lichens. These lichens typically grow on rocks in arid and semi-arid environments worldwide. They consist of a fungus living in symbiosis with a photosynthetic partner, specifically a cyanobacterium of the genus Chroococcidiopsis. Peltula is the only genus in the family Peltulaceae, which belongs to the Lichinomycetes, a class of fungi that form lichens. The genus includes about 50 recognised species, which have a variety of growth forms ranging from flat and crust-like to more complex, leaf-like structures. Peltula lichens play important ecological roles in harsh environments, contributing to soil stability and nutrient cycling.

To cope with their challenging habitats, Peltula species have evolved various adaptations. These include specialised protective layers and the ability to withstand both drought and flooding. The thalli of Peltula lichens are typically small, with a stratified structure consisting of an upper , a , a medulla, and usually a lower . Peltulaceae generally lack secondary metabolites, which distinguishes them from many other lichen families. The genus has a cosmopolitan distribution, with members found across various continents, occupying diverse including rocks, soil, and occasionally tree bark. Molecular phylogenetics studies have significantly altered the classification of these lichens. Formerly separate genera are now incorporated into Peltula, rendering Peltulaceae a monogeneric family.