Three new lichens told apart by a bloom

Pruina is a finely crystalline, white or greyish bloom covering the surface of the thallus or the apothecial discs of some lichens. It tends to be treated as a detail, whereas it is in fact a diagnostic character, dependent on chemical composition and on how the crystals are deposited.

Fengxia Liang's team reviewed the Chinese Acarosporaceae from exactly that angle. The result: three new pruinose species — Sarcogyne bayingolinensis, S. parasitica and S. yiliensis — and one species new to China, Acarospora iqbalii. The conclusions rest on a combination of morphological, chemical and phylogenetic analysis.

The distinguishing characters are so fine that they are worth listing to convey what this work involves. All three new species have an IKI+ blue hymenial gel. S. bayingolinensis is marked by a lobate thallus margin and no pruina surrounding the apothecial disc. S. parasitica has areoles with deep fissures around the disc and lives parasitically. S. yiliensis has a thin hymenium, 50–60 micrometres, and a tall subhymenium of 50–80 micrometres.

The authors also filled in the picture for known species: they showed that A. tianshanica occurs in two chemical types, with or without gyrophoric acid, and supplemented the molecular data for A. glaucocarpa from China. The paper closes with a key to the pruinose Acarosporaceae.

It is worth remembering why lichens appear in a section on new fungal species. A lichen's name is the name of a fungus — the photosynthesising partner has its own, separate name. A lichen is a way of living, not a taxon.

Rock-dwelling lichens of this group have a value for monitoring that macrofungi do not. They grow slowly, measured in millimetres per decade, and stay in place for decades or longer. A site can therefore be revisited years later and compared, instead of waiting for a fruiting season.

That is exactly why lichens are a classic indicator of air quality and habitat continuity. The price is difficulty of identification: settling it requires chemical reagents, a microscope and — as this paper shows — increasingly a sequence as well.

What the paper establishes

Sarcogyne bayingolinensis, S. parasitica and S. yiliensis were delimited in Xinjiang by combining morphology, chemistry and ITS, mtSSU and nuLSU phylogeny. All have an IKI-positive blue hymenial gel, but differ in pruina distribution, fissuring and hymenium height. S. parasitica was collected on Acarospora bohlinii and is known only from its holotype. That supports describing a parasitic habit, but the study did not quantify harm or test the mechanism. It also reports A. iqbalii from China for the first time and two chemical types of A. tianshanica. Both Acarospora and Sarcogyne were non-monophyletic in the analysis, so broader sampling may alter genus boundaries. One locality does not establish endemism, rarity or threat status.