Knightiellastrum

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Knightiellastrum is a one‑species fungal group in the family Icmadophilaceae. Its only species is Knightiellastrum eucalypti, a bark-dwelling lichen found in Tasmania, Australia. It was first described in 2011 by Gintaras Kantvilas as Icmadophila eucalypti, from old Eucalyptus obliqua trees near Hartz Mountain. DNA studies led to a reclassification: in 2018 it was renamed Knightiella eucalypti, and in 2020 it was placed in the new genus Knightiellastrum, showing it is more distant from Icmadophila than previously thought.

What it looks like: Knightiellastrum eucalypti has a squamulose (scaly) thallus that forms large, irregular colonies up to about 50 cm across. Each scale (squamule) is 1–5 mm wide, and colors range from white to pale grey, sometimes with pale beige or blue tones. The top surface is dull and smooth; the underside is white. Edges start finely toothed and later develop small lobes. The thallus is rich in crystals visible under polarized light and dissolves in potassium hydroxide (KOH). It reproduces mainly by soredia, small powdery propagules at the margins.

Biology: The photobiont (the partner alga) is a single-celled green alga about 5–11 μm in diameter. The lichen lacks obvious fruiting bodies and relies on soredia for dispersal. Chemically, it contains thamnolic acid. In tests, it shows K+ yellow, P+ orange, and no reaction with C or UV light.

Habitat: This lichen lives on the trunks of very old trees in Tasmania, especially wet eucalypt forests with Eucalyptus obliqua and cool temperate rainforests. It prefers shaded, lower trunk surfaces and is often found growing alongside other bark-dwelling lichens. It can also appear on Athrotaxis selaginoides. Because it favors very old trees, it can serve as an indicator of ancient forest in ecological studies.