Population biology of the endemic species Pimpinella tragium Vill

For the first time for the European part of Russia, a study of the population biology of the endemic species of chalk and limestone Pimpinella tragium Vill. in natural habitats of the Voronezh region was carried out. The species is an obligate calcephyte, prefers open chalk substrates. Biomorphological analysis made it possible to classify Pimpinella tragium as a herbaceous polycarpic taproot plant. Due to the presence of a powerful taproot, the species promotes the fixation of weak chalky substrates. In the future, open groups of calciphilic vegetation with the participation of Pimpinella may appear on the Cretaceous substrate.  Six-year monitoring of the main stages of development of Pimpinella tragium made it possible to identify 4 ontogenetic periods and 9 age states: latent (seeds), pregenerative (seedlings, juvenile, immature and virginal individuals), generative (young, middle-aged, old generative individuals), postgenerative (senile individuals). The paper presents the morphometric characteristics of individuals of different age groups. The ontogenetic structure of Pimpinella tragium cenopopulations was studied, the type of the basic spectrum was revealed. Most cenopopulations have a left-sided spectrum; the absolute maximum is more often represented by young individuals, the local maximum – by middle-aged individuals. For some populations, a centered ontogenetic spectrum was noted with maxima on middle-aged generative individuals. The formation of the ontogenetic structure of Pimpinella tragium cenopopulations is significantly influenced by the physical characteristics of the Cretaceous substrate, and hence the physiological characteristics of this species. The ability of the species to reproduce only by seed is of great importance, since in different years the germination and survival rate of seedlings can differ sharply.