Free DNA in nature as a tool of ecological monitoring of the environment

Abstract

Free DNA in nature or the environmental DNA (eDNA) contains unique information about the diversity not only of unicellular but also of multicellular organisms – fungi, plants, invertebrates and vertebrates in the past and contemporary nature. eDNA of a soil surface and of an aquatic environment may indicate a presence of contemporary living organisms and deposits, sediments and glaciers – wildlife diversity in the geological past. Fungi are reducers, symbions and parasites and play an important ecological role in nature, and so it is important to know their taxonomic and functional characteristics. Analysis eDNA in samples of forest soil showed that ascomycetes and basidiomycetes are represented most of all. They were identified as mycorrhizal types, plant pathogens and saprotrophes. In soils of different climatic zones DNA of numerous taxons of plant (herbs, shrubs, trees), unicellular and multicellular animals (protozoans, earthworms, birds, mammals) was discovered. In spite of this unknown species of fungi and earthworms were discovered. It was ascertained that eDNA of soil surface layer do not move practically and it is able to display a complete taxonomic filling of vertebrates and relative biomass of individual species. Researches of eDNA of freshwater ecosystems is focused to identify and control spreading of invasive species of crustaceans, mollusks, fishes, amphibians and reptiles with the goal of conservation of biological diversity and ecological balance. It is shown that eDNA may be a better tool to identify these species in comparison with traditional methods of audio and visual observation. At the same time a population size and an ontogenetic stage are not important. Another research direction of eDNA in a fresh water aims to identify species of aquatic animals (crustaceans, insects, fish, amphibians and mammals) at risk of extinction. A short time of eDNA existence in freshwater ecosystems is very useful for a nature protecting, because it can indicate a presence, status and disappearance of species. Thus eDNA of previous population, which is rapidly destroyed, will not interfere with the analysis. However, it is necessary to remember that in river ecosystems eDNA moves with the stream at a great distance. Further researches of eDNA in seawater samples are necessary, because in this aquatic environment the ability to move and storage time of free genetic material is insignificant. In land deposits, water sediments and glaciers free DNA do not move and may be preserved for long periods – till hundreds of thousands of years, that gives a possibility to obtain valuable information about the wildlife of paleoenvironments. In samples of permafrost deposits was found eDNA of numerous taxons of fungi, plants, three species of beetles, two species of fossil bird moa, mammoth, bison, horse. Water sediments is rich in eDNA also. In sea sediments extracellular DNA is much more than in sea water. Moreover, the anoxic conditions slow down destructive processes that ensures its long-term preservation. Sea sediments, especially estuary sediments are used to determine influence of human activities on the biological communities of ecosystems. Sediments of freshwater lake also contain eDNA, which represent degrading consequences of human interaction with the environment. Results of eDNA study of lake sediments as well as a study of soil deposits complement results of a study of pollen and fossil plant residues. It confirms a feasibility to combine traditional and molecular genetic methods in ecological researches to obtain most authentic data about past plant diversity. eDNA of many organisms is contained in glaciers. The analysis of this DNA permitted to identify 57 taxons of fungi, 8 orders of higher plants, taxons of protozoans and insects.