Tassiloa digitaurea
Tassiloa digitaurea is a species of lichen in the family Teloschistaceae. It was described from collections made in Chilean Patagonia in 2011 and is characterized by forming tiny, cushion-like tufts with bright orange, finger-like projections that earned it the vernacular name Goldfinger fire-dot lichen. The species was later moved to a new genus called Tassiloa based on molecular analysis that showed it was distinct from other similar lichens. It appears to be endemic to western Patagonia, where it grows on volcanic rock in windy shrublands and coastal grasslands.
Taxonomy
Caloplaca digitaurea was described in 2011 by Majbrit Søgaard, Ulrik Søchting, and Sancho from material collected at the Cueva del Milodón Natural Monument, near Puerto Natales in Chilean Patagonia. Molecular data placed it close to the Sonoran Desert species C. wetmorei, but the two share only 93% sequence similarity and differ markedly in ecology and morphology: C. wetmorei is a parasite with tiny apothecia, whereas C. digitaurea is free-living and produces apothecial discs twice as large. The species epithet combines the Latin digitatus with aureus and alludes to the vivid orange, finger-like —hence the suggested English vernacular name "Goldfinger fire-dot lichen".In a three-gene molecular analysis Sergey Kondratyuk and colleagues recovered C. digitaurea and C. wetmorei as a well-supported clade that sits in the Catenarina clade of subfamily Teloschistoideae. Because the pair share a distinctive microfruticose, isidiate thallus and parietin-based chemistry, the authors raised the group to genus level under the name Tassiloa, honouring the German lichenologist Tassilo Feuerer. They made two new combinations, Tassiloa digitaurea and T. wetmorei, and diagnosed the genus by its orange, isidia-like lobules, zeorine to lecanorine apothecia with a exciple, and anthraquinone profile.
Description
The thallus forms minute, cushion-like tufts up to 2 mm tall, composed of mostly vertical, cylindrical 60–100 micrometres thick and up to 1.5 mm long. These lobules resemble swollen isidia and give the lichen a micro-shrubby appearance. Their surface is uneven and, coloured a brilliant orange-yellow that deepens in older parts. The internal partner is a Trebouxia-type green alga.Apothecia are scarce and nestle among the lobules. Young show a thin internal rim the same colour as the disc and thallus, but with age this develops into a slightly raised, paler border that is often masked by overgrowing isidia. Mature apothecia measure 0.8–1.5 mm across; the disc is flat, deep orange and dusted with a medium-coarse . Internally the is fan-shaped, narrowing from roughly 80 μm laterally to 20 μm at the base; the hymenium is 60–100 μm tall and threaded by branched paraphyses with slightly swollen tips. Eight ellipsoid spores develop per ascus; each is divided by a single narrow septum, measuring 13–16 × 6–7 μm. No pycnidia have been observed. Chemical analysis shows parietin as the dominant secondary metabolite, with traces of teloschistin, fallacinal, parietinic acid and emodin—an assemblage of compounds corresponding to A of Søchting.