Variability of morphological structures in Cypripedium calceolus (Orchidaceae) and their relationship with the habitat conditions in the southern taiga ecosystems, Russia

Abstract

Cypripedium calceolus is one of the most studied orchids both in the world, and in Russia as well. Currently, C. calceolus is considered as a threatened species in most countries within its range. In many countries, this taxon is extremely rare being included in the national Red Data Books and on Red Lists. To date, there is a lack of research aimed to identify the life strategies of this threatened plant and to determine the ecological and coenotic preferences. The present study is aimed to identify and evaluate the individual and population parameters of C. calceolus in various ecological-coenotical conditions of the southern taiga subzone within the Kirov region (European Russia) in order to develop methods and approaches for monitoring the C. calceolus populations. In the study area, the edaphic preferences of C. calceolus correspond to regimes from dry-forest-meadow to wet-forest-meadow according to the soil moisture scale. According to Tsyganov's ecological scales, this orchid prefers nitrogen-poor, poorly acidic and nitrogen-poor soils. Cypripedium calceolus confines to a relatively stable to weakly variable moisture. We found a statistically significant influence of habitat conditions to the leaf characteristics, namely leaf width (27.78%) and number of veins (7.17%). The range of the vegetation condition effects on the morphological parameters of the C. calceolus individuals is wider. The leaf length, the number of leaf veins were recognised as stable biological indicator traits. The number of leaves, the lip length, and the length of the lip blade were considered as taxonomic indicator traits, while only the number of flowers was recognised as an ecological indicator trait. Other morphological traits (shoot height, leaf width, lip width) were changing the variability level depending on the year and population by falling into different groups of indicator traits. The vitality analysis of the C. calceolus populations showed that most populations have been estimated as thriving ones. During the study period, we found a positive trend towards the C. calceolus individuals' vitality improvement in spruce (Picea abies) forests. This also affected the conservation status of this threatened orchid.

Keywords

• climate factor
• conservation value
• ecological scale
• monitoring
• orchids
• rare species
• vitality