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Alien aquatic plant species have significant ecological and economic impacts on freshwater ecosystems and are mentioned amongst the major threats to aquatic biodiversity. Detection of alien species at the beginning of invasion can help avoid their spread and prevent negative impacts on aquatic ecosystems. This study presents the first records of invasive species Elodea nuttallii in Lithuania. This species was found in three localities of the Nemunas River (southern Lithuania) in 2020 and 2021. The localities were mapped using system grid cells arranged based on geographical coordinates with sides of 6' latitude and 10' longitude. The habitat characteristic and associated species were presented. The identity of Elodea nuttallii was confirmed using a molecular method (sequencing of two regions ITS and psbE-petL). The molecular analysis was effective in supporting the identification of individuals collected in the early stages of growth. We suppose that Elodea nuttallii may be more widespread in the region of north-eastern Poland, north-eastern Belarus and southern Lithuania and will continue to spread north and northeast directions. The expansion of Elodea nuttallii can have a negative impact on valuable natural habitats, particularly on protected throughout Europe water courses with the Ranunculion vegetation. [ABSTRACT FROM AUTHOR]

We demonstrate a wide distribution and abundance of hybrids between the river species Ranunculus aquatilis, R. fluitans and R. kauffmannii with the still water species R. circinatus (Batrachium, Ranunculaceae) in rivers of two postglacial landscapes of East Europe, i.e., Lithuania and Central European Russia. The Batrachium species and hybrid diversity is higher in the rivers of Lithuania (4 species and 3 hybrids vs. 2 and 1) and represented mainly by western R. aquatilis, R. fluitans and their hybrids whereas in Central European Russia, the East European species R. kauffmannii and its hybrid are the only dominant forms. Hybrids make up about 3/4 of the studied individuals found in 3/4 of the studied river localities in Lithuania and 1/3 of the individuals found in 1/3 of the localities in Central European Russia. Such extensive hybridization in river Batrachium may have arisen due to the specificity of rivers as open-type ecosystems. It may have been intensified by the transformation of river ecosystems by human activities and the postglacial character of the studied landscapes combined with ongoing climate change. Almost all hybrids of R. aquatilis, R. fluitans and R. kauffmannii originated from unidirectional crossings in which R. circinatus acted as a pollen donor. Such crossings could be driven by higher frequency and abundance of R. circinatus populations as well as by some biological mechanisms. Two hybrids, R. circinatus × R. fluitans and R. circinatus × R. kauffmannii, were formally described as R. × redundans and R. × absconditus. We found a hybrid which most likely originated from additional crossing between R. aquatilis and R. circinatus × R. fluitans. [ABSTRACT FROM AUTHOR]

Like in many other parts of the world, Phragmites australis distribution and abundance are changing in Lithuania because of the impact of human activities on aquatic habitats. We studied P. australis genetic diversity patterns and the effect of hydrographic modifications, introduced in the mid-late twentieth century with great impact on Lithuanian landscape. The genetic diversity was studied using chloroplast DNA sequences and nuclear microsatellite markers in natural and straightened river stretches for water regulation. We found haplotypes M and L and their variants in the studied populations. The analysis of microsatellites revealed high genetic diversity within populations and significant structure both at the population and river level. We did not find differences in the distribution of genetic diversity between populations growing in natural and in straightened river stretches; however, at the local level, 5 populations in straightened river sites had higher genetic diversity values than populations in nearby natural sites within the same river, confirming seed establishment in disturbed habitats. Our results demonstrate that anthropogenic river modifications have had an impact on the genetic diversity of P. australis populations; however, disturbance is not the only factor that affects genetic diversity recruitment and dynamics in new P. australis stands. [ABSTRACT FROM AUTHOR]

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Alfalfa ( Medicago sativa subsp. sativa) was introduced to Lithuania as a fodder crop and now grows as a weed in natural ecosystems adjacent to its wild relative, sickle medic ( M. sativa subsp. falcata). The hybrid form of these taxa, variegated alfalfa ( M. sativa subsp. varia), is considered an invasive taxon due to its intensive spread. Here, we use inter-simple sequence repeat (ISSR) markers and haplotype analyses of three regions of chloroplast DNA ( psbA- trnH, trnS- trn2GS and trnL- trnF) and the nuclear ribosomal DNA internal transcribed spacer region to study the spontaneous hybridization of alfalfa and sickle medic in natural subpopulations. Plants of the three taxa were collected from 19 subpopulations located at seven sites. ISSR analysis revealed similar values of genetic diversity (expected heterozygosity, band richness, polymorphic band proportion) in subpopulations of the three studied subspecies. Our study revealed a lack of genetic differentiation among these taxa and high differentiation among subpopulations ( Φ = 0.389, P = 0.001). Analysis of the chloroplast DNA regions provides direct evidence for the hybrid origin of variegated alfalfa. Taxon-characteristic haplotypes were identified for subsp. sativa and subsp. falcata in local subpopulations, and two haplotypes specific to the parental taxa were detected in subpopulations of M. sativa subsp. varia. Our study demonstrates the extensive genetic impact of alfalfa on adjacent native subpopulations of sickle medic. [ABSTRACT FROM AUTHOR]

We used RAPDs (random amplified polymorphic DNAs) to analyze genetic diversity in the arctic-alpine yellow marsh Saxifrage (Saxifraga hirculus L.) which is considered to be a glacial relict. Five populations from different regions of Lithuania were studied. A total of 76 individuals were examined in this research. By RAPD analysis 93 loci were detected, of them 71% were polymorphic. All the plants showed different RAPD phenotypes. The percentage of polymorphic bands within populations correlated with population size. UPGMA and PCO analyses showed the genetic specificity of the populations. The genetic distance among individuals in different populations ranged from 0.225 (Juodle population) to 0.29 (Merkine population). Some population-specific minor loci were identified in the Merkinė and Juodlė populations. [ABSTRACT FROM AUTHOR]

We studied genetic diversity within and among populations of warty cabbage (Bunias orientalis L.), which is an alien species in Lithuania and other Baltic countries. In Lithuania, this weed colonises two main types of habitats: railway/roadsides and meadows on riversides. The aim of this study was to assess the genetic structure of invasive populations of B. orientalis in Lithuania and consider the impact of diverse habitats on the partitioning of genetic diversity using inter-simple sequence repeat (ISSR) markers. An analysis of molecular variance (AMOVA) carried out on the basis of ISSR showed that there is high genetic differentiation (46%) among populations of B. orientalis, which is probably caused by the founder effect and limited gene flow. However, we observed no impact of habitat on the genetic difference among populations. Similar levels of ISSR polymorphic loci were observed in riverside (P = 31.67%) and railway/roadsides (P = 30.51%) populations. UPGMA cluster analysis and principal coordinate analysis (PCoA) also did not show grouping of studied populations according to habitat type. High genetic differentiation among populations, as indicated by ISSR markers, confirm multiple independent introductions of this species in Lithuania. [ABSTRACT FROM AUTHOR]

• Lithuanian populations of Nuphar lutea are genetically differentiated. • Reproduction is primarily sexual, and inbreeding appears to be common. • Genetic isolation and inbreeding could increase sensitivity to anthropogenic change. Currently, in Europe, increasing attention is being paid to the genetic diversity of aquatic macrophytes. Insufficient information exists about the river plants of the Baltic states. Our study aimed to evaluate the genetic diversity of Nuphar lutea individuals growing in Lithuanian watercourses. Eighteen populations were studied in the river catchments of Lithuania: Nemunas, Venta and Lielupė. The genetic diversity of the populations was evaluated at microsatellite loci. The population genetic data of N. lutea were analysed by multiple tests, including hierarchical analysis of molecular variance (AMOVA), principal coordinate analysis (PCoA) and the Mantel test. The observed (H O) and expected (H E) heterozygosity values per population were 0.242 - 0.655 and 0.503 - 0.759, respectively. Our study revealed significant differentiation among populations (F ST = 0.162; p < 0.001) and no correlation between genetic and geographical distances; this outcome is in agreement with relatively high inbreeding in populations and implies limited gene flow among subcatchments. [ABSTRACT FROM AUTHOR]