The increasing impact of anthropogenic factors and climate change affect the growth of a number of taxa of hybrid nature. These taxa are widespread among various taxonomic groups of aquatic and semi-aquatic plants. The genus Sparganium L. В is not an exception. In that regard, the aim of this study is to conduct biomorphological investigation of Sparganium × longifolium Turcz. ex Ledeb., evaluate qualitative and quantitative criteria for the hybrid similarities and differences with its parental species, as well as to analyze data on its habitat characteristics. Samples were collected in 2014-2016 from waterbodies in European Russia (Tver and Yaroslavl oblasts). In the study on biomorphology of S. × longifolium we used live and fixed materials, as well as herbarium funds of IBIW, MXA and MW. To establish and specify taxonomic features of the hybrid under study, indicating to its similarity with a certain ancestral species, our data on the morphology and ecology of S. emersum Rehm. and S. gramineum Georgi. are used. During field studies, the type of a water object where the hybrid was detected, ecological characteristics of its habitat (type of soil, depth, water temperature and pH) are determined; the list of taxa which enter into the cenosis composition is compiled. The biomorphological investigation of S. × longifolium shows that by life form this hybrid, as well as its parental species, is a vegetative-mobile evidently-polycentric annual or biennial plant of vegetative origin with a racemose root system. The following should be attributed to the characteristic features justifying the hybrid origin of S. × longifolium: 1) a wider, slightly carinated lamina (as in S. emersum); 2) a branched inflorescence (as in S. gramineum); 3) the lower covering leaf of inflorescence, often exceeding the total length of the latter; 4) fruits with a straight (as in S. emersum) as well as bent (as in S. gramineum) style. Interestingly, some populations of S. × longifolium are rich in terate forms that can be explained by back crossing with one of the parental species or pleiotropic mutation(s). It is established that S. × longifolium is not widespread in European Russia, is a typically freshwater species, occurring in the littoral zone of mesotrophic and dystrophic waterbodies (usually in lakes of glacier origin). At present, its appearance in lake ecosystems is due to accelerated eutrophication caused by increasing human activities. Perhaps earlier this hybrid formation occurred in peripheral zones of the range of S. gramineum under cyclic climate changes. Observations suggest that S. × longifolium exceeds S. gramineum in ecological potentials. At the same time, habitat features of the latter have an effect on the hybrid distribution potential (limitation of habitat spectrum) which is hardly exceed S. emersum by its ecological and coenotic characteristics.

No abstract

Sparganium longifolium was reported as a hybrid between S. emersum and S. gramineum based on its intermediate type or the common characteristics of its parent species. Its hybrid origin needs to be confirmed using molecular technology. We investigated the origin of S. longifolium based on 10 populations of S. emersum, S. gramineum and S. longifolium from five lakes in European Russia, using sequences of six nuclear loci and one chloroplast DNA fragment. Haplotype network, principal coordinate analysis and genetic clustering based on data of nuclear loci confirmed that S. longifolium is the hybrid between S. emersum and S. gramineum. We found that the natural hybridization between S. emersum and S. gramineum is bidirectional but asymmetrical, and the latter mainly acts as maternal species. We also found that all samples of S. longifolium were F1 generations, and thus hypothesized that S. emersum and S. gramineum could likely maintain their species boundary through the post-zygote reproductive isolation mechanism of F1 generation sterility.

No abstract

No abstract

Lobelia dortmanna L. is one of the few rare, slowly growing relic plants occupying areas of the littoral zone of water bodies with low nutrient content and subject to wave action. Even in such difficult conditions, this plant successfully passes its entire life cycle, actively blossoms and fruits. That is why the peculiar features of the individual development of this plant in various geographical conditions is a matter of great interest. For the first time, this study considers in detail the ontogeny of the genet of L. dortmanna in oligotrophic lakes of Tver oblast. Detailed characteristics of the following age stages of individuals are given: resting seeds, seedlings, juvenile, young and adult vegetative, latent generative, middle-aged and old generative and quasisenile plants. It is shown that the transition to the juvenile age stage occurs at the end of the first year of life, the virginile age stage lasts two years, and the generative stage of development occurs in the fourth year of life. The change in the growth pattern of the rosette main shoot of Lobelia, from orthotropic to anisotropic, occurs in the second year of life. The establishment and further development of the generative organs of the plant and associated change in the growth of the main shoot from monopodial to simpodial occurs in the fourth year of life. At the same time, the branching of the main shoot begins by formation in the axils of the uppermost assimilating leaves (the last in front of the apical inflorescence) – 1–2 lateral rosette shoots. These are future ramets (vegetative diasporas), which ensure, in the future, the vegetative reproduction of the individual and spread to new territories. Taking into account that in lakes of Tver oblast, Lobelia groupings form dense aggregated clusters on the bottom, the transition of individuals to a quasisenile age state (in the fifth year of life) enables them to rejuvenate and survive after the death of the maternal shoot. The formation and further development of rosette lateral shoots allows the plant to re-occupy the territory via vegetative or seed propagation. Complete morphological disintegration (vegetative reproduction) occurs in the fifth year of life. The genets’ ontogeny is completed by the formation of a compact clone from the detached lateral rosette shoots.

No abstract

Nuphar lutea (L.) Sm. (Nymphaeaceae Salisb.) belongs to the category of highly active cenose-forming plants in water bodies and water flows. The material for study of morphological peculiarities and seed productivity of the fruits of this species was collected mainly in the lake ecosystems of the Central Part of European Russia and Republic of Belarus. In the study we used biomorphological and ontogenetic approaches. Seed productivity was surveyed by direct count of number of seeds in the fruit. By abundance (in descending order), the significant reliable inter-lake differences in a number of morphological parameters of the fruit fall into the following sequence: number of rays of stigma of fruit (in six pairs of lakes) > length of fruit (in four pairs of lakes) > diameter of the stigma of fruit (in three pairs of lakes) > diameter of fruit (in two pairs of lakes) > length of the neck of the fruit (in one pair of lakes). Intra-regional differences in certain morphological parameters of fruits (by number of rays of stigmas) were most notably manifested only in the Belarus lakes which are similar by trophic status. All the differences in the fruits’ morphology could be due to differences in the habitat by the amount of nutrients in water and soil. The amount of seed productivity of the fruits from N. lutea varies broadly. Analysis of this parameter depending on the character of soils in which the plants grew indicated reliable results only in the case of muddy (296 ± 81) and sandy soils (179 ± 13). We determined that distribution of generative diasporas of N. lutea across large distances is related not only to presence of floating ability in the seeds, but also the “multi-step” process of their release: first – mericarps from fruits, and then seeds from mericarps. In the experimental conditions, most seeds directly sunk to the bed (70%) and the rest continued to float on the surface of the water during a month. Low germination of the seeds of the water-lily in the laboratory conditions (4–6%) with use of different means and terms of dry stratification was due to the fact that they have an organic morphophysiological intermediate type of rest. Having such a mechanism causes portioned and prolonged germination, allowing the species to survive in non-favourable conditions and accumulate generative diaspores in the soil. Despite the fact that the initial stages of ontogenesis in the laboratory and natural conditions have no significant differences, we found polyvariance in their tempo of development. First of all, this is related to different dates of transition of the plant from one age state to another. In the case of N. lutea, one should also note the morphological polyvariance of ontogenesis related to change in morphologic characteristics of plants depending on the water level. The obtained results give a more complete picture of the peculiarities of generative reproduction of N. lutea, necessary for understanding the ecosystem role of this plant and its impact on biological processes in water bodies.