Abstract
To study and conserve biological diversity is one of the most important tasks of protecting natural ecosystems. According to long-term data, the biodiversity of invertebrates of Mordovia State Nature Reserve accounts for 6823 species out of 10 types of invertebrates: Rhizopoda (58 species), Porifera (1), Platyhelminthes (156), Nematoda (67), Annelida (4), Acanthocephala (1), Mollusca (62), Bryozoa (1), Rotifera (80), and Arthropoda (6393). Thus, the Mordovia State Nature Reserve belongs to one of the hotspots of biodiversity in the forests of the temperate zone in European Russia. It is home to a large number of rare species and three endemic species. The protected area is connected by ecological corridors with other territories and can be a source of genetic and species diversity for nearby ecosystems.