Relationship of generic and species diversity of dytiscids in the water sub-basins of Mongolia according to their biogeographic regions. Abbreviations: AO – species of Arctic origin; BO – Boreal species; HO – Holarctic species; TU – Turanian species; ME – Mediterranean elements; OR – Oriental; PLA – Palearchearctic; PL – species distributed throughout the whole Palearctic; SZ – species of the Steppe zone.