The dissertation is devoted to the establishment of the classification of leeches of the family Erpobdellidae, primarily its Palearctic members, and to the determination of patterns of morphological evolution and geographical distribution. Over the past twenty years, the accumulation of new data has led to revealing many inconsistencies between phylogenetic positions and morphological features of individual taxa and diagnoses of genera, which in turn necessitates a taxonomic revision with maximum coverage of taxa, using modern phylogenetic methods and taking into account the principle of stability, which became our goal. To achieve this goal, we studied the phylogenetic structure of the family Erpobdellidae, the morphological features of representatives of different evolutionary linages of erpobdellid leeches and described the patterns of their geographical distribution. The scientific novelty of this work is that we determined the phylogenetic structure of the family Erpobdellidae. It was shown that the Palearctic members of the genera Erpobdella and Dina do not actually belong to the same evolutionary lines as the Nearctic members of these genera, and the composition of the genera Erpobdella, Dina, Mooreobdella and Nephelopsis needs to be revised. It should be noted that the representatives of different evolutionary lineages are limited in their distribution by the Palearctic or the Nearctic, which contradicts previous views. Also, the results of phylogenetic analysis indicate that the species of the genus Trocheta belong to two evolutionary lineages, one of which corresponds to the genus Trocheta, and the other, Blanchardia, was synonymized more than eighty years ago. Species delimitation demonstrated significant species diversity of erpobdellids in the Western Palearctic, especially among Caucasian members of the genera Trocheta and Dina. Different types of annulation was found to occur in different evolutionary lineages of
erpobdellids independently. The theoretical significance of the work is determined by the fact that on the basis of molecular-phylogenetic, as well as morphological and biogeographical data, the taxonomy of the family Erpobdellidae at the level of genera was revised. Based on these data, it was proposed to review the composition of the genera Erpobdella, Dina, Trocheta, Mooreobdella and Nephelopsis. The paper revealed the patterns of
distribution of erpobdellids and demonstrated the cryptic diversity of erpobdellid leeches in the Caucasus. The systematic significance of features of external and internal morphology was investigated. In add ition, the standard for describing erpobdellid leeches was revised and the dissection technique was improved. During this research, genetic markers were selected that best reflect the evolutionary history of erpobdellid leeches at different scales.
