LIVING AT THE EDGE: A COMPARATIVE STUDY OF THE CENTRAL AND MARGINAL POPULATIONS OF DACTYLORHIZA TRAUNSTEINERI (ORCHIDACEAE) IN EUROPEAN NORTHEAST OF RUSSIA

Abstract

Peripheral populations are considered more vulnerable than central ones, but recent studies have questioned the existence of clear patterns within species ranges. We studied reproductive and demographic characteristics of the rare orchid Dactylorhiza traunsteineri at the northeastern limit of its distribution range (the Subpolar Urals) and compared them with the data of four populations located closer to the center of the range (south of the Komi Republic). In peripheral populations, number of individuals per population, plant sizes, number of owers per individual and seeds per fruit were signi cantly lower than those in populations located closer to the center of the area. Contrary to expectations, the peripheral populations were renewed better than the central ones, which may be due to the high level of moisture availability in the Subpolar Urals. The proportion of juvenile individuals in the peripheral populations was 18.7%, in populations in the south of the Komi Republic - 6.3-6.9%. In addition, we found that in the direction from the center to the periphery of the species range, the proportion of empty space in seeds increased (from 63.9 to 75.6%). This provides the seeds with better volatility and increases the chances of reaching places favorable for germination, which are becoming fewer at the edge of the range.