Dactylorhiza incarnata (L.) Soó (Orchidaceae, Liliopsida) on the northern border of its distribution area: Population structure and seed productivity

Abstract

The results of the study of the population biology of the rare orchid Dactylorhiza incarnata (L.) Soó on the territory of the Komi Republic (north-east of European Russia), where the species is located on the northern border of its range, are presented. Data on the population structure, morphometric features of plants, and reproductive characteristics of the species are given. It was found that the size of plants and the number of flowers in the inflorescence of this species in the region is lower than in the more southern parts of its range. The populations size ranges from 30 to 350 individuals with their average density of 0.7–3.7 per 1 m2 , and it is common for this species in other parts of its distribution area. Reproductive success is associated with the weather of the second decade of June because the flowering time of the species in the region happens in this time. It was found that the seed size of D. incarnata (0.55×0.20 mm) on its northern border is smaller than in other parts of the range. The seed productivity is rather high: one fruit contains an average of 6.2 thousands of seeds and one individual could produce about 49.4 thousands of seeds. Temperature during flowering time and precipitation during seed ripening may affect seed quality. The presence of juvenile individuals (%) in all the studied populations shows seed recruitment in populations of this species at the northern limit of the range, despite a lower seed set in comparison with southern populations.