Variability of Morphological Characteristics of Hedysarum grandiflorum (Fabaceae, Dicotyledones) in Various Ecological Conditions of the Southern Volga Upland

Abstract

In recent decades the interest to the study of Hedysarum has increased. Researchers touched upon the classical issues of morphology and variability of external features of Hedysarum grandiflorum and other species of Hedysarum (to clarify morphology, to more accurately separate existing species, to describe the morphology of new species, including rare ones) providing almost no detailed descriptions. The paper provides information about the morphology of external features of H. grandiflorum in the Southern Volga Upland. The study was conducted in 2007–2018. We have studied 23 H. grandiflorum cenopopulations in habitats with various environmental conditions, where more than 600 counting sites were laid, and concluded that the morphological features of H. grandiflorum are rather variable and the values of morphometric parameters are higher in the northeastern part of the study area. The well-being of the population is achieved due to some heterogeneity in the size of individual plants and by means of suppressing the growth and size of separate cenopopulations. The decrease in the parameters of signs is often associated with a higher anthropogenic load. Dimensional indicators of individuals from the cenopopulations of the species studied depend on the thickness of soil, which decreases from fescue-feather grass to petrophyte steppes. Cluster analysis has allowed us to divide the cenopopulations into southern, northern and northeastern ones, and those with anthropogenic impact. The least variable and most informative morphological features of H. grandiflorum (in the descending order of importance) are: the length of the standard, the diameter of the caudex, the plant height, the number of foliole pairs, the number of inflorescences, the number of leaves, the length of the unpaired foliole, the number of flowers on the inflorescence, the length of leaves and the width of the unpaired foliole. In the overwhelming majority of the plants encountered, all the petals of the corolla were of uniform light yellow color, turning into a white tint to the edges of the petals. In some cenopopulations, the corolla can be colored differently and unevenly, especially at the keel. Approximately 0.3% of individuals of the corolla petals and/or the lower part of the keel and/or veins are light blue or light pink, less than 0.07% has a light magenta or even light purple tint of the veins of the carina, edges of the petals or the whole corolla. Similar individuals are found in other regions. Many scientists noted this peculiarity a long time ago and had already described this phenomenon as a color variation (for example, H. grandiflorum var. violaceum) or less often, as a subspecies (for example, H. grandiflorum ssp. argenteum). Individuals with recessive coloring of the corolla from the area of study are called intraspecific color variations.