Bet-hedging strategies in <i>Heracleum mantegazzianum</i> Sommier & Levier (Apiaceae) populations in European Northeast Russia

Based on the concept of bet-hedging, this study explores the mechanisms that maintain the Heracleum mantegazzianum Sommier Levier populations size and age structure in the absence of a long-term soil seed bank for this species. The research focuses on the dynamics of mericarpia (“seeds”) in the soil bank of H. mantegazzianum, the number of seedlings, and juvenile individuals in the Middle Taiga subzone of the Komi Republic. The populations of H. mantegazzianum are characterized by the accumulation of a significant number of empty seed coats in the soil, while the median number of viable mericarpia does not exceed 2000 pieces per square meter. A prolonged period of natural stratification, lasting up to six months, guarantees that virtually all the seeds from the previous harvest will mature and sprout promptly in the spring. Consequently, in the European Northeast Russia climate, the plants H. mantegazzianum establish a transient seed bank. The number of juvenile individuals of H. mantegazzianum remains relatively stable at approximately 200 individuals per square meter, attributed to a consistent supply of new seeds, rapid spring development of seedlings, and the retention of individuals in a juvenile stage during their second year of life. The utilization of light resources during spring and autumn, along with the ability to enter a state of dormancy during the summer, contribute to the survival and maintenance of juvenile individuals under conditions of intense intra-specific competition. In H. mantegazzianum, the bet-hedging strategy is implemented through the reproduction of an extremely small fraction (less than 0.01%) of the total population, the presence of a sufficient bank of underground dormant buds, and the ability of juvenile individuals to enter a state of forced dormancy.