| There are dozen thousands of lakes on the globe; most of them are rather small, their period of life barely exceeds 100 - 1000 years (TILTZER & SERRAYA, 1990; HERDENDORF, 1990). Mainly because of this short life period, the lakes are inhabited by average, widely distributed forms of animals and plants. However, about 10 of the lakes are well known to all biologists working in the field of taxonomy and speciation of freshwater life; they call such lakes "ancient" ones. First of all, it refers to their ancient origin and long period of life. The most famous among existing ancient lakes are: Baikal (Asia: Siberia), Tanganyika (Africa) and other lakes of the Great African Rift Zone, Biwa (Asia: Japan), Ohrid (Europe), Caspian Sea (Eurasia), Khubsugul (Asia: Mongolia), Titicaca (South America). The second main characteristics of the lakes, except for their age, is great and unusual diversity of their fauna and flora that includes up to 60-80% of endemic species.
Many new fascinating discoveries have been made by scientists within last 4-5 years: comprehensive knowledge on biodiversity, ecology, phylogeny and molecular evolution of ancient lakes, up-to-date information on their geological development and paleolimnology have been recently published. Unfortunately, some of the unique lacustrine ecosystems recently underwent serious changes in the ecosystem structure and experienced a real invasion by introduced exotic species (lakes Biwa, Victoria). Variations in the structure of natural biodiversity and ecosystem cause changes in the quality of lake water - the main source of pure freshwater for vast territories (lakes Biwa, Baikal and others). Sedimentary strata concentrated on the bottom of ancient lakes within millions of years are considered as perfect records, often - the only and main evidence of the paleoenvironmental reconstructions and global climatic changes. Thus, ancient lakes considered as unique models and natural laboratories for understandingboth natural processes of speciation, evolution of flora and fauna, evolution of lacustrine ecosystems, and also global changes in the environment on our planet. Therefore, attempts to understand and adequately reconstruct natural history of ancient lakes, predict their ecosystem function and development in the future, finally, protect their natural environments and water quality should be considered as one of the highest priorities of the world scientific community in XXI century.
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