''Graphis tetralocularis'' is a species of

crustose lichen Crustose lichens are lichens that form a crust which strongly adheres to the Substrate (biology), substrate (soil, rock, tree bark, etc.), making separation from the substrate impossible without destruction. The basic structure of crustose lichen ...

in the family

Graphidaceae The Graphidaceae are a family of lichens in the order Ostropales. Distribution and ecology The vast majority of Graphidaceae species are restricted to the tropics. Most Graphidaceae species are epiphytic (i.e. they grow only on plants). Gener ...

. Found in Rwanda, it was formally described as a new species in 2005 by Christina Bock and Markus Hauck. The

type specimen In biology, a type is a particular wiktionary:en:specimen, specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to a ...

was collected by the first author from Akagera National Park at an altitude of ; here it was found growing on a twig of a ''

Nuxia floribunda ''Nuxia floribunda'', the forest elder, forest nuxia or wild elder, is a species of tree in the Stilbaceae family, that is native to moist regions of southern Africa, East Africa and central tropical Africa. Habit It usually grows to between 3 ...

'' tree. It is only known to occur at the type locality, which is a dry forest dominated by the trees ''Nuxia floribunda'', ''

Haplocoelum gallense ''Haplocoelum'' is a genus of plants in the family Sapindaceae The Sapindaceae are a family of flowering plants in the order Sapindales known as the soapberry family. It contains 138 genera and 1858 accepted species. Examples include horse che ...

'', and ''

Strychnos usambarensis ''Strychnos usambarensis'' is a shrub or small tree up to 15m tall or a 70m long liane of Sub-Saharan Africa, occurring in forest and woodland, mountain ravines and coastal bush, often on rocky slopes and named for the Usambara Mountains of Tanza ...

''. The lichen has a thin, smooth, whitish grey to grey-green crustose

thallus Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms wer ...

. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''tetralocularis'' refers to the unusual morphology of its four-chambered

ascospore An ascus (; ) is the sexual spore-bearing cell produced in ascomycete fungi. Each ascus usually contains eight ascospores (or octad), produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera or s ...

s. ''Graphis tetralocularis'' contains trace amounts of atranorin, a secondary chemical that can be detected using the technique of thin-layer chromatography.

References

tetralocularis Lichen species Lichens described in 2005 Lichens of Rwanda {{Ostropales-stub