Biology:Tetramelas gariwerdensis

Short description: Species of lichen

Tetramelas gariwerdensis
Scientific classification
Domain:	Eukaryota
Kingdom:	Fungi
Division:	Ascomycota
Class:	Lecanoromycetes
Order:	Caliciales
Family:	Caliciaceae
Genus:	Tetramelas
Species:	T. gariwerdensis
Binomial name
Tetramelas gariwerdensis Elix (2020)
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Holotype site: Mount William, Victoria

Tetramelas gariwerdensis is a species of saxicolous (rock-dwelling), crustose lichen in the family Physciaceae, described in 2020. It is found in the Grampian Mountains in western Victoria, Australia.

Taxonomy

Tetramelas gariwerdensis is named after its type locality in the Gariwerd (Grampians mountain range) in Victoria, Australia. This region holds cultural significance for the Djab Wurrung and the Jardwadjali, the traditional people of the area. The species is similar to Tetramelas darbishirei, but is distinguished by its [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]], crustose thallus instead of a somewhat erect, [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] thallus.

Description

Tetramelas gariwerdensis is distinguished by its crust-like ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) and tiled ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) thallus, which can spread up to 15 mm in width and 0.3 mm in thickness. The individual tile-like sections ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) vary in shape from round to irregular or angular and range in size from 0.3 to 1 mm wide. These areoles can either be scattered across the thallus or closely packed together (contiguous). The upper surface of the thallus has an off-white to pale yellow colour, characterised by a dull and uneven texture. The thallus does not have a visible border ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]), and the cells of the symbiotic green algae ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] cells) within it measure between 9 and 15 µm in diameter.

The white [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]], or inner layer of the thallus, does not contain calcium oxalate as indicated by its lack of reaction to sulfuric acid, but it does react to iodine, turning pale purple. The lichen's reproductive structures ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) are small, measuring 0.2 to 0.6 mm in width, and [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] in type. These apothecia can be found separately or in small groups, either broadly attached ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) or slightly raised ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) on the thallus. The apothecia's [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] is black, non-powdery ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]), and its shape varies from weakly concave to flat or even convex, becoming wavy ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) as it ages.

The [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] (rim surrounding the disc) is initially prominent and elevated above the disc but becomes level with the disc over time. In a cross-section, it measures 25–35 µm in thickness, with an outer part that is brown-black and an inner part that is paler brown. The tissue supporting the spore-producing [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) is brown to brown-black and 100–120 µm thick. The spore-producing layer ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) itself is 55–70 µm thick, clear, and sometimes contains scattered oil droplets. The layer beneath the hymenium ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) is pale brown and 10–15 µm thick.

The [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] (slender filaments within the hymenium) are 1.5–2 µm wide, with [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] to sparsely branched structures that have dark brown capped tips. The spore-producing sacs ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) are of the Bacidia type and typically contain eight [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]. These spores initially resemble those of the Callispora or Physconia types but mature into the Buellia type. They are brown, ellipsoid to broadly [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] in shape, measuring 15–25 by 7–12 µm. Older spores often become constricted at the division ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) and sometimes curved, occasionally with one or two internal divisions ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]), and have a finely wrinkled ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) outer wall. The [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]], another reproductive structure, are immersed and [[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]] (point-like). The rod-shaped spores ([[Glossary of lichen terms#{{biology:{1}}}|{{Biology:{1}}}]]) produced within these structures measure 4.5–6.5 by 1 µm.

Chemically, the thallus of Tetramelas gariwerdensis predominantly contains atranorin, alongside a minor component of 6-O-methylarthothelin.

Habitat and distribution

Known only from the Grampians in western Victoria, Tetramelas gariwerdensis grows on stone. It is found in association with other lichen species such as Circinaria caesiocinerea, Buellia aethalea, Buellia ocellata, Lecidea lygomma, Ramboldia petraeoides, Rhizocarpon geographicum, and various Xanthoparmelia species.

References

Wikidata ☰ Q108424986 entry