Hydropunctaria maura, still often called by the older name Verrucaria maura and commonly known as tar lichen, is a species of saxicolous (rock-dwelling), crustose lichen belonging to the family Verrucariaceae. A perennial species that does not experience seasonal variations, it is the type species of the genus Hydropunctaria. The medulla is a black basal layer that forms columns (Latin: punctae) to the upper surface and isolates the algae into pockets near the upper surface. The black band formed by H. maura can often be seen at a distance as a marker of the high water point.
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In this Dossier
Saxicolous lichen in the context of Corticolous lichen
A corticolous lichen is a lichen that grows on bark. This is contrasted with lignicolous lichen, which grows on wood that has had the bark stripped from it, and saxicolous lichen, which grows on rock.
Examples of corticolous lichens include the crustose lichen Graphis plumierae, foliose lichen Melanohalea subolivacea and the fruticose Bryoria fuscescens.
Saxicolous lichen in the context of Flavoparmelia caperata
Flavoparmelia caperata, the common greenshield lichen, is a foliose lichen that grows on the bark of trees, and occasionally on rock.
Saxicolous lichen in the context of Cladoniaceae
The Cladoniaceae are a family of lichen-forming fungi in the order Lecanorales, comprising about 560 species distributed amongst 18 genera. This family is one of the largest among lichen-forming fungi and is globally distributed, from Arctic tundra to tropical rainforests, favouring humid environments while being intolerant of arid conditions. Molecular phylogenetics has significantly advanced the understanding of their complex taxonomic history, revealing intricate evolutionary relationships and leading to a refined classification. Notable members include reindeer moss and cup lichens of the genus Cladonia, which consist of about 500 species and forms a significant part of the diet for large mammals in taiga and tundra ecosystems.
A distinctive feature of many Cladoniaceae species is their dimorphic thallus: a scaly or crust-like primary form and a fruticose (shrub-like) secondary form known as a podetium or pseudopodetium. These lichens typically grow on soil, decaying wood, or tree trunks, with a few species found on rocks. They form symbiotic associations with green algae, usually from the genus Asterochloris. The family is known for its diverse secondary metabolites—over 70 have been identified—which play roles in species identification and ecological functions such as protection against UV radiation and herbivore deterrence. Genomic studies have uncovered significant variation in mitochondrial DNA among Cladoniaceae species, contributing to the understanding of their evolution and diversity.