| Abstract [eng] |
The Thymus genus is characterised by gynodioecy, when population of the same species is comprised of hermaphrodites and females individuals. The proportion of hermaphrodite and female individuals can differ both in different species and in different populations within the same species. The aim of this work was to evaluate the occurrance of gynodioecy, that determines sex polymorphism within Thymus genus (Thymus pulegioides L., Thymus serpyllum L. and their interspecific hybrid Thymus × oblongifolius Opiz), in natural populations of Lithuania biota, wich differ in ecological conditions and age; and also to establish differences between hermaphrodite and female individuals blossoms using particular morphological features. There was totally 51 T. × oblongifolius, 48 T. pulegioides and 39 T. serpyllum populations explored. The communities with Thymus descriptions were made according to squares shuttle descriptive approach, using J. Braun-Blanquet school of vegetation survey and classification principles. In each population all the Thymus sp. hermaphrodites and females individuals, and their proportions in the population were counted. In order to calculate the density of T. pulegioides, T. serpyllum and T. × oblongifolius individuals, populations size was measured and Thymus sp. individuals were counted. And finally the illumination, relief, exposition, coverage of the herbs, shrubs, trees, mosses and lichens was valued. In this work from each species totally 300 hermaphrodites and 300 females blossoms widths, and also 150 hermaphrodites and 150 females pistil lengths were measured. It was established, that the blossoms of T. pulegioides, T. serpyllum and T. × oblongifolius hermaphrodites are wider than females individuals blossoms. The pistils of T. pulegioides, T. serpyllum and T. × oblongifolius hermaphrodites are longer than pistils of female individuals. The gynodioecy is most frequent in T. pulegioides, less frequent in T. × oblongifolius and rare in T. serpyllum species. 25% of all examined T. pulegioides and almost 4% of T. × oblongifolius populations were composed of females individuals only. In T. serpyllum populations absolutely female populations were not found. T. × oblongifolius and T. pulegioides gynodioecy is more frequent in low density (till 6 individuals/10 m2) populations. T. serpyllum gynodioecy is more frequent in middle density (43-57 individuals/10 m2) populations. Working time was assessed T. × oblongifolius, T. pulegioides and T. serpyllum populations homogeneous volume of the female plant's dependence on some of the environmental factors. It is established, that in populations, where is flank or flat relief, strong light and high or low herbs coverage, gynodioecy of T. × oblongifolius and T. serpyllum was expressed slightly. But in these populations gynodioecy of T. pulegioides species was expressed strongly. Was established the reliable negative correlation among the coverage of herbs and amount of females in the populations of T. pulegioides (r=-0,30, p<0,05), and the reliable positive correlation among the coverage of herbs and amount of females in the populations of T. × oblongifolius (r=0,31, p<0,05). T. pulegioides gynodioecy is most frequent in Molinio-Arrhenatheretea elatioris communities. T. × oblongifolius gynodioecy less frequent of antropogenic and not formed communities. T. serpyllum gynodioecy weakly in all communities, less antropogenic and not formed communities. |
