Mammals of 98 species are the food sources of 124 species of fleas in the Caucasus. The formation of the modern fauna and flora of the Caucasus occurred in the Neogene and Quaternary periods, due to both mesophilic and xerophilic floristic and faunistic complexes. The main migration flows were carried out within the Ancient Mediterranean. In the Pliocene, the Caucasus may have been inhabited by flea species that were parasites of mammals a forest landscapes of Europe, as well as of Western and Central Asia. In the Pleistocene and Holocene, the majority of the xerophilic biocenoses were formed, and the flea fauna was replenished with several semi-desert species. According to the distribution of hosts and vectors, natural foci of plague in the Caucasus may have existed as early as the Pliocene, while those in the Ciscaucasia were formed during the xerothermal epochs of the Quaternary.
Kotti et al. (Wed,) studied this question.