In August and September 2021, a research group from the Botanical Garden and Institute of the Far Eastern Branch of the Russian Academy of Sciences,  based in Vladivostok. The focus of scientists' research was bryophyte plants.

Gymnomitrion concinnatum (Lightf.) Corda is one of the most drought-tolerant liverworts in the flora of the Commander Islands. Photo by K.G. Klimova.

Bryophyte plants are a large and diverse group of small plant organisms that usually receive little attention. Except that in the swamps and tundra it is impossible to neglect the dense carpet formed by these plants. These are the most interesting organisms, the oldest of the higher plants, preserved to this day. They occurred at the dawn of terrestrial life, in the Ordovician period of the Paleozoic Era, or about 450 million years ago. They were crucial in the formation of modern living conditions on Earth  Spreading rapidly overland, in the absence of meaningful competition, occupying all suitable habitats, they played a huge role in the formation of the ozone screen, protecting all living things from deadly ultraviolet radiation. By the way, if the ozone screen disappears, modern plants except the bryophytes will not tolerate this event. Bryophyte plants will have to recreate it again, as once before at the dawn of terrestrial evolution. In addition, bryophyte plants released organic acids into the substrate on which they grew (stones, rocks), causing its rapid destruction. As a result, a huge amount of phosphorus compounds was washed into the oceans, which caused the global "flowering" of the world's oceans and the death of many organisms. However, due to this the event that sea water acquired chemical characteristics close to modern ones.

Marchantia polymorpha L. with female reproductive organs and brood bud baskets in the cover of the marshy community. Photo by K.G. Klimova.

For humans the value of bryophyte plants in the utilitarian aspect  is small. The main importance to this day is peat, which is used as a combustible material and for loosening soils. However, in nature, the importance of bryophytes can hardly be overestimated. It is thanks to the dense moss cushion, which has a colossal hygroscopicity, that moisture accumulates in the litter of plant communities - especially in the northern countries - forming a favorable water regime for both plants growing in these communities and to avoid catastrophic floods. A notorious consequence of deforestation is the disappearance of the moss cushion and, as a result, mudflows that destroy natural communities and human infrastructure.

Riccardia chamedryfolia (With.) Grolle among bryophytes in a depression in a moss-sedge swamp. Photo by K.G. Klimova.

In tropical forests, where the ground cover of bryophytes is practically absent, they grow on trees, covering the trunks with a dense carpet. This carpet is a habitat for many insects and other invertebrates, which in turn are an element of the food chain of the rainforest, as well as a substrate for the majority of well known species of orchids. Speaking about the importance of bryophytes in nature, it is worth mentioning the huge reserves of peat in Russia. You may wonder what is peat, if not just a combustible material? In fact, peat is actually preserved carbon. Therefore, the processes of global warming in the Arctic are so dangerous - the temperature rises and peat deposits begin to decompose rapidly, forming carbon dioxide. Its release leads to the formation of a greenhouse effect, which in turn further accelerates the process of decomposition of peat. As a result, a vicious circle is launched. To begin the cycle it's enough to have a small increase in temperature, for example, caused by human activity.

Mesoptychia rutheana (Limpr.) L.Soderstr. et Vana is a new species for the Commander Islands. Photo by K.G. Klimova.

When we say "bryophyte plants", we should understand that we are dealing with a prefabricated group that unites completely unrelated elements within itself. These are real mosses, liverworts and Anthocerotophyta or hornworts. The ancestors of modern liverworts appeared first in the evolutionary process. They were the focus of the expedition's close attention. This group has the name due to some of their representatives resembling liver in shape, which determined the appearance of such a peculiar name and the use in the Middle Ages for treatment of liver diseases (latin: Similia similibus curantur), but without much effect, it must be admitted. Liverworts - the oldest group of plants - has a number of specific features in their appearance, structural organization and physiology. Let's name two of the most important of them:

1. These higher plants in their composition have both deciduous and thallus forms, which was mistakenly interpreted at the end of the Renaissance as evidence of their belonging to algae. In fact, this is living evidence that nature in those distant times has not yet decided what is better for a plant - leaves or simple whip-like structures, like algae have.
2. Liverwort cells, unlike all other higher land plants, have no vacuoles (as you know, when we enjoy the taste of a fruit, we actually enjoy the contents of special cellular organelles called vacuoles). Instead of vacuoles liverworts have special formations - oil bodies. These are also organelles, but they are filled with liquid fats, with alkaloids and other substances dissolved in them. This feature, on the one hand, allows the plant to get rid of unnecessary metabolic products, and on the other hand, makes liverworts poisonous to almost all living beings. For humans, this is actually an inexhaustible source of natural antibiotics, which is especially important in the modern era of rapid adaptation of bacteria to existing antibiotic drugs.

Nardia scalaris Gray growing on top of a sphagnum pillow. Photo by K.G. Klimova.

Liverworts specialists in Russia can be counted on the fingers of one hand. Why did they choose Bering Island as a research area? It is clear that the various historical vicissitudes associated with the discovery of the islands and the history of their development could not leave an imprint on the decision-making. The main reason is the position of the Commander Islands at the western end of the Aleutian Island chain - a migration route for moisture-dependent flora between Asia and North America. The existence of the so-called Beringian land bridge during the glacial periods, located much further north is well known today. However, it was, conventionally speaking, dry and cold. The Aleutian island chain has never been a bridge (although some groups of islands united during periods of marine regressions), but it was an intermittent route for the migration of more warm and moisture-loving species between the two continents. This path is called Hultenia in biogeography, after Eric Hulten, the Swedish explorer who first described the phenomenon. The devision of the islands by water barriers complicated the migration process, but on the other hand, led to the formation of the so-called "island effect", which is interesting for us in terms of the preservation of a number of species on the islands (which are a kind of refuge for them), and disappearence of others in the North Pacific, Asia or America (and sometimes everywhere). This factor determines not only the high taxonomic richness of the flora of the Commander Islands, but, to a large extent, its highest uniqueness, in comparison with the flora of the nearby Kamchatka Peninsula.

Calypogeia orientalis k-99-24-21_1_ Oil bodies inside the cells of Calypogeia orientalis Buczk. & Bakalin. Photo by V.A. Bakalin

It is still too early to talk about specific results. Liverworts, like bryophytes in general, are small plants. For their accurate determination you need a microscope and painstaking work in the laboratory, often using molecular genetic methods. However, it is already clear that the expedition was successful. The number of species known on the island has increased significantly, there are very interesting finds, possibly even new species for science. But we will tell you about this as soon as new information appears.

The data was provided by the head of the group, Doctor of Biological Sciences, Head of the Cryptogamic Biota Laboratory of the Botanical Garden-Institute Vadim Andreevich Bakalin and a member of the expedition, Researcher of the same laboratory Ksenia Gennadyevna Klimova.