Seed Productivity of Epipactis atrorubens (Hoffm.) Besser (Orchidaceae, Liliopsida) on the Northern Border of its Distribution Area

Abstract

The Orchids due to their biological features, high decorative properties and poor resistance against anthropogenic factors are one of the most vulnerable components in vegetation of the world. Their conservation cannot be efficient without the knowledge on their reproductive biology. These data are especially important for species on the borders of their distribution area with additional reproduction limiting factors. Our study object is a rare orchid species Epipactis atrorubens (Hoffm.) Besser. During field works on the territory of the Komi Republic (northeast Russia), we studied 50 populations of E. atrorubens. Reproductive characteristics (fruit set, seed productivity and seed morphometry) were studied in 19 of them. We established that the main limiting factor in the North is a short vegetation period. Frosts damage generative shoots and do not allow seeds to ripe. The capsule of E. atrorubens on the northern distribution border contains fewer seeds than in the central part of areal. Also less is the indicator of real seed productivity. Within the Komi Republic on sample of two sites (the Timan Range and the Ural Mountains), we also see the decrease in all reproductive characteristics from south to north: the number and size of flowers, the number and quality of seeds decrease, their shape changes. However deterioration in seed productivity is compensated by an increase in seed volume. The populations of less than 50 shoots, in which juvenile plants are not marked, are in critical condition.