Origin and Evolution of the Plague Microbe Yersinia Pestis: Molecular Genetic and Ecological Scenarios

It is known that the direct ancestor of the ‘blood’ plague pathogen – the microbe Yersinia pestis – is the saprozoonotic psychrophilic causative agent of the Far Eastern scarlet-like fever (FESLF) Y. pseudotuberculosis O:1b, and the divergence of these species occurred in the recent historical past, no earlier than 30 thousand years ago in the central regions of Asia without any human involvement. These facts indicate certain changes in the habitat of a certain population (clone) of the FESLF pathogen in the region of Central Asia or adjacent regions, which caused the speciation of Y. pestis. Reconstruction of the plague microbe speciation and evolution (its phylogeny/phylogeography) is based substantially on the molecular-genetic (MG) typing of strains from the extant natural foci and fragments of ancient DNA extracted from the remains of victims of the infection. However, presented phylogenies are not congruent with facts accumulated by such classic sciences as environmental ecology (ECO), biogeography, paleontology, epizootology, etc. These contradictions require the development of an integrated methodology for studying the history of the plague pathogen, combining both the model of neutral evolution, which is the theoretical basis in the MG approach, and adaptive evolution, which is the basis of the ECO approach. Herewith an ECO phylogeny as less controversial should be used as a null hypothesis in the phylogenetics/phylogeography of Y. pestis and a factual basis for the synthesis of ECO and MG approaches to the problem of the origin and global expansion of the plague causative agent.