The Ontogenesis and Structure of Population of Rindera tetraspis Pall. (Boraginaceae) in Orenburg Oblast

Assessment of the modern status of populations of rare plant species by population-ontogenetic methods is used for solving problems of conservation and restoration of natural communities. The object of the study is a rare species of the European Russia, Rindera tetraspis Pall., a poorly studied threatened steppe endemic. The purpose of the research was to assess the modern status and ontogenetic structure of cenopopulations of R. tetraspis in the Urals within Orenburg oblast. Three administrative districts of Orenburg oblast in the Urals were surveyed in 2016–2019, and as a result, six cenopopulations were identified and studied. Their phytocenotic allocation was assessed by conventional geobotanical methods. It has been revealed that wheat grass (Agropyron desertorum), wormwood (Artemisia lercheana)–Psathyrostachys calciphyte, and bluegrass (Poa bulbosa ssp. vivipara)–feather-grass (Stipa capillata) steppe communities predominate. The main population characteristics, the density of plants, and the ontogenetic composition, have been determined. The total density in the surveyed cenopopulations varies from 4.7 to 10.7 plants/m², and the effective density is from 3.2 to 5.9 plants/m². The ontogenesis has been described and eight ontogenetic stages have been revealed. Senile plants were not found. All the studied cenopopulations of R. tetraspis are normal incomplete and are dominated by middle-aged generative plants. According to the delta–omega classification, there are three are young, two transitional, and one mature cenopopulations. Their status is relatively satisfactory, but only one of the six is protected: it is located in the specially protected natural area Troitskie Melovye Mountains. Regular monitoring of the status of the populations is necessary for stronger protection of the species.