A noticeable and rather bright-looking lichen Platismatia lacunosa (Ach.) WL Culb. et CF Culb.] was found on the Commander Islands.  This is the first reliable record of the species in Russia. Previously, it was erroneously indicated for various regions of Northern Eurasia, confused with the much more common species Asahinea chrysantha (Tuck.) WL Culb. et CF Culb.].

Platismatia lacunosa (Ach.) WL Culb. et CF Culb.] Photo by Irina Stepanchikova

Platismatia lacunosa is a rather large leafy lichen, the rosettes of which can reach 16 cm in diameter, and the blades up to one and a half cm wide.The bright grayish-white color of the upper surface of the blades with a light brown tint at the edges immediately attracts attention, and a well-pronounced relief mesh pattern complements the unusual appearance of the lichen.

Platismatia lacunosa on the Commander Islands was found only on  Medny Island, where it grows in the mountains on large stones and rocky outcrops. The lichen is rare on the island and is registered in individual localities. It is curious that this species, known from the nearest island of the Aleutian ridge - Attu Island,  has never been see on Bering Island. It is neither known on Kamchatka - the nearest to the Commanders territory - nor on the Kuriles. Apparently, the biogeographic border between Medny Island and  Bering Isand, is the border of distribution of this "American" lichen, which is much more common on the Pacific coast of North America and the Aleuts.

Lichen community on coastal rocks. Photo by Irina Stepanchikova

The discovery was made by Dmitry Gimelbrant and Irina Stepanchikova, lichenologists from the V.L. Komarov RAS and St. Petersburg State University. Experts began their work on studying the lichen flora of the Commander Islands back in 2019, after spending a field season on Medny Island. In 2020, scientists studied lichens on Bering Island, where the last studies of this kind had been carried out in 1879. 

Lichens are a symbiosis between fungi and algae These complex organisms do not belong to plants, although they also play the role of producers in the ecosystem: they convert the energy of the sun into organic matter through photosynthesis and become food for animals.

Studies of lichen flora on Bering Island. Photo by Irina Stepanchikova

They dominate the tundra that prevails on the Commander Islands These diverse organisms of bizarre shapes, colors and shades, as well as the communities they form, are home to many small invertebrates and a source of food for a wide variety of organisms. In addition, they are among the first to reclaim an environment of little use for other lifeforms, creating soil on bare rock, and thus allowing other less hardy neighbors - plants and animals - to settle there.