MOSCOW, 17 Aug. SPbPU scientists as part of an international research team have developed a method that allows deciphering the demographic history of a species by analyzing its DNA. According to the authors, unlike existing methods, their solution can reconstruct multiple gene exchanges (through crossings) between several different populations, which will help scientists shed light on obscure points in human demographic history. The results are published in the scientific journal Molecular Biology and Evolution.
Scientists can reconstruct the demographic history of a species not only with the help of archeology, but also with genomics, since such a history is «imprinted» in the genome of the species and can be reconstructed based on the frequencies of nucleotides in genes in populations, that is, in groups of individuals occupying a certain territory.
Over the past 50 years, scientists have made significant progress in this direction, but existing methods have limitations, said researchers at Peter the Great St. not two, but several populations took part in the transfer act. nauka-1879522294.html» data->
The experts said that the process of evolution and the demographic history of any species can be depicted in the form of a graph — a geometric figure, in the nodes of which there are historical populations, and the edges correspond to the relationships between them, as well as modern populations. On such a graph, events of separation of populations or their mixing (admixture) are visible, which lead to the emergence of new populations. According to scientists, the structure of the graph can sometimes be established on the basis of archaeological data, but most often the graph is restored by mathematical methods.
Researchers from St. Petersburg Polytechnic University, All-Russian Institute of Plant Genetic Resources. N.I. Vavilov, the University of Southern California (USA) and the University of Vermont (USA) have developed a method that can cope with complex admixtures in order to more accurately describe the demographic history of the species.
According to the developers, the program has a wide application potential. Admixture structures, based on origin, the nature of genetic variation within and between populations. Without this information, errors can occur in inferring the demographic history of species, in identifying genetic targets for human disease therapy, and in predicting complex traits in plant and animal breeding programs.
The authors of the program tested it during reconstruction cultivation of chickpeas, which ranks third in the world in production among food legumes.
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“According to archaeological evidence, chickpeas were first cultivated in the Fertile Crescent about 10,000 years ago. However, its subsequent distribution, accompanied by adaptation to cultivation conditions, to the Middle East, South Asia, Ethiopia and the Western Mediterranean remains unclear and cannot be reconstructed only on the basis of archaeological and historical data,” said the head of the Research Laboratory of Mathematical Biology and Bioinformatics Maria Samsonova of the Institute of Physics and Mechanics of SPbPU.
To decipher the history of chickpeas, scientists studied samples of historical chickpea varieties from the collection of the All-Russian Institute of Plant Genetic Resources, collected at the beginning of the last century under the guidance of Russian geneticist N.I. Vavilov, and tested complex historical hypotheses about the migration and admixture of historical chickpea populations within and between the main regions of cultivation.
Chickpeas have two market types, «desi» (small dark seeds) and «kabuli» (large yellow seeds), whose geographic origin is a matter of dispute. Ethiopian chickpeas can be genetically traced back to ancestral populations from Turkey, Lebanon, or India, and in every region «kabuli» may have mixed with local «desi».
Based on linguistic data, scientists suggest that kabuli chickpeas originated in Central Asia and are named after the Afghan city of Kabul. On the other hand, there is a version that «kabuli» appeared in modern Turkey (after «desi»), since «kabuli» chickpea is common in the regions neighboring Turkey and for a long time was considered a plant brought from India and Ethiopia already in modern times.
«Using the developed models and methods, we have shown that Ethiopian chickpea populations have historical chickpea populations from India and the Middle East as ancestral. This suggests the existence of a sea route from South Asia to Ethiopia. As for the origin of chickpea «kabuli», significant evidence has been obtained of its origin from Turkey, and not from Central Asia,” Samsonova explained. This work was supported by the Russian Science Foundation grant No. 22-46-02004.
July 10, 09:00