Morphology and ecological characteristics of Sparganium × longifolium (Typhaceae) in the Central part of European Russia

Abstract

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.

Molecular confirmation of the hybrid origin of Sparganium longifolium (Typhaceae)

“…The haplotype networks, PCoA analysis and STRUCTURE analysis based on the six nuclear loci confirm that S. longifolium is a hybrid between S. emersum and S. gramineum , providing molecular support for previous morphological analyses 5 . Furthermore, all individuals with intermediate admixture coefficient (Fig.…”

“…This hypothesis is possible based on the observations from hybrids in European Russia. The pollen viability was checked in S. longifolium samples from Vysokovskoe Lake and Sabro Lake, and the vast majority of checked pollens were sterile 5 . In addition, flowering plants of S. longifolium often do not form seeds, or the seeds are puny and significantly inferior to normal seeds in size 5 .…”

“…The pollen viability was checked in S. longifolium samples from Vysokovskoe Lake and Sabro Lake, and the vast majority of checked pollens were sterile 5 . In addition, flowering plants of S. longifolium often do not form seeds, or the seeds are puny and significantly inferior to normal seeds in size 5 . However, the hypothesis is only based on our limited sampling, which is contrary to the conclusion inferred from morphological characteristics that it is fertile and may backcross with parental species 1 .…”

“…This hybrid occurs commonly in regions where both parents grow together and often occupies habitats where S. gramineum is absent due to its high adaptability under eutrophic conditions 1 . The hybrid origin of S. longifolium was emphasized by 5 based on their detailed biomorphological investigation. The hybrid was considered fertile 1 and backcrossing with its parent species was used to explain the phenomenon that some populations of S. longifolium were rich in terate forms 5 .…”

“…The hybrid origin of S. longifolium was emphasized by 5 based on their detailed biomorphological investigation. The hybrid was considered fertile 1 and backcrossing with its parent species was used to explain the phenomenon that some populations of S. longifolium were rich in terate forms 5 . So far, only one case study at the molecular level has been conducted for S. longifolium .…”