Impact of Weather Conditions and Inflorescence Size on the Reproductive Success of Dactylorhiza traunsteineri (Orchidaceae)

The results of an 11-year study of the rare orchid Dactylorhiza traunsteineri (Saut. ex Rchb.) Soó population on the northeastern border of its range (the Komi Republic, northeastern European Russia) are presented. Our research shows that weather factors (air temperature and precipitation) influence various traits that determine the reproductive success of this species. Significant positive correlations are found between the temperature of August of the previous growing season and parameters such as the size of the inflorescence and the number of generative plants in the population. The fruit set is positively affected by precipitation during the flowering of the species (the third ten days of June) and the overall moisture content of the territory in the current growing season. A negative correlation is found between fruit set and the size of the inflorescences of individual plants, while the height of the plants does not affect the effectiveness of pollination. The sizes of seeds and embryos of D. traunsteineri significantly differ in different years of research, but no reliable links between these traits and weather conditions are revealed. A negative correlation is found between seed volume and fruit set in individual plants. In the fruit of D. traunsteineri, 3211 to 5172 seeds are formed in different years; the real seed productivity of an individual is 10 696–44 262. Tall plants produce more seeds per fruit. A positive relationship between real seed productivity and precipitation of the current growing season is revealed. The final indicator of reproductive success at the population level is the number of young (juvenile) plants. They are present in the studied population throughout all the years of the study; their proportion varies from 3.5 to 13.9%. Positive reliable correlations between the number of juvenile individuals and the temperature of August, as well as the sum of the active temperatures of the entire previous growing season, are revealed.