SUMMARY
Knowledge on status of peripheral plant populations is important for understanding of species’ adaptation and evolution within their ranges. There is a lack of data on the status of Silaum silaus (Apiaceae) populations at the periphery of its native range. One of the most northern native S. silaus populations is situated in the Republic of Mordovia (Central Russia). This species is considered as Critically Endangered in the region. Population-based studies of S. silaus have been carried out. Reproductive biology, morphometric parameters of individuals, accompanying flora, seed characteristics (mass, germination rate) were investigated. Results showed that at the northern limit of the range S. silaus grows in floodplain meadow community previously disturbed by livestock grazing. The area occupied by the population, however, has increased more than 12 fold over the last 15 years. Increasing fruit production together with decreasing fruit mass was established for the studied population compared to populations in the central part of its native range. In addition, germination rate was very low (2.3–16.7 % depending on edaphic conditions). Additional studies of S. silaus populations are needed in saline steppes of the closely located territories where it occurs as one of the dominant species in the plant community.