During the 1950s-1960s, the Merkys river basin, the largest protected area of Lithuania, underwent severe anthropogenic regulations. Within the Baltic States, the genetic diversity of Phalaris arundinacea populations is unknown and how they might be affected by anthropogenic activities such as river regulation. The objectives of this study were to compare molecular parameters (SSRs or microsatellite loci) within and among populations from natural river fragments with populations from regulated river parts. Study populations have greater genetic diversity within, rather than among, populations. The upstream portion of the Merkys basin populations had lower genetic diversity compared with further downstream. The mean number of polymorphic SSR loci was lower for populations from regulated parts of the river basin compared with natural ones. Main principle coordinate analysis revealed populations of regulated rivers at marginal positions. Bayesian clustering showed that current populations are admixtures of 3 distinct genetic groups, based on STRUCTURE analysis (K = 3 groupings) in geographic subdivisions of (a) downstream populations (Varėnė, Verseka, Upper Grūda, Lower Grūda, Upper Merkys, Lower Merkys), (b) upstream populations (Upper Šalčia, Beržė, Lower Šalčia, Visinčia, Lower Šaltykščia, Nedilė), and (c) the 2 regulated sites in the distinct geographic area of Taurupis and Upper Šaltykščia.P. arundinacea in the Merkys river basin does not all belong to a single, random-mating population encompassing its tributaries or among populations across its geographic scales. In several instances, river regulation might impair the genetic diversity of P. arundinacea populations.

The present study evaluated genetic diversity of Lithuanian populations of Lythrum salicaria in relation to parameters of riparian environment. Growing along Nemunas, Seaside and Lielupė river basins, 15 populations were examined using amplified fragment length polymorphism markers. Molecular data were related to the river basins, type of land use and cover, natural vice versa regulated fragments of the rivers. Population mean genetic diversity parameters were as follows: percentage of polymorphic loci (57.2), expected heterozygosity (0.183), polymorphismc information content (0.218). Mantel test revealed correlation (R2 = 0.0986, p = 0.01) between genetic and geographic distance of populations. Greater genetic diversity within, rather than among populations (ΦPT = 0.213) was observed. According to the Bayesian clustering, studied populations are admixtures of two gene pools. Analysis of molecular variance revealed significant differentiation between populations belonging to distinct river basins, between populations from natural vs. regulated fragments of the rivers.

Currently, there is an increasing focus on understanding the interactions between genetic features of the invader and environmental factors that ensure the success of invasion. The objective of our study was to evaluate the genetic diversity of Lithuanian populations of highly invasive small balsam (Impatiens parviflora) by amplified fragment length polymorphism (AFLP) markers and to relate molecular data to biotope features defined by employing neighboring species of herbaceous plants. Low polymorphism of I. parviflora populations was observed at AFLP loci. Hierarchical analysis of molecular variance did not reveal differentiation of populations depending on biotope, geography, or road types. Bayesian analyses of AFLP data demonstrated many genetic clusters. Our results suggest multiple introductions of I. parviflora into Lithuania. The polymorphism of AFLP loci of populations significantly correlated with the total coverage by herbaceous plants in the sites. Defined by principal component analysis, the variability of study sites was most related to the coverage of herbaceous plants and least related to the molecular features of I. parviflora populations. The sites with I. parviflora were classified into agricultural scrubland, riparian forest, and urban forest biotopes. Of them, urban forest was distinguished by the highest coverage of I. parviflora and the lowest Ellenberg indicatory values for light, soil acidity, and richness in nutrients.

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Data on alien species show that plant invasions are caused by a complex combination of characteristics of invasive species (invasiveness) and characteristics of invaded environment (invasibility). Impatiens parviflora is one of Europe’s top invasive species. The present study aimed to evaluate molecular diversity of populations of highly invasive in Lithuania I. parviflora by applying several DNA markers and relating genetic parameters to abiotic and biotic environment. For sampling, urban forests, riparian forests, and agrarian shrublands were selected. Three different DNA-based techniques, Simple Sequence Repeats (SSR), Inter Simple Sequence Repeat (ISSR) markers, and Random Amplified Polymorphic DNA (RAPD), were used for detecting genetic variation between 21 populations. All population individuals were monomorphic and homozygotic for four loci and heterozygotic for one locus by SSR analysis. Hierarchical analyses of molecular variance at ISSR and RAPD loci revealed significant differentiation of populations depending on geographic zones of the country. Bayesian Structure analyses of molecular data demonstrated existence of many genetic clusters and this finding is in support to multiple introduction of the species. The polymorphism extent at ISSR loci was positively correlated with the total coverage of herbaceous plant species. The coverage by I. parviflora was negatively correlated with the total number of herbaceous species and light in the sites. Our results indicate that Lithuanian sites with I. parviflora might be distinguished by high soil nutrient levels. According to the principal component analysis, the coverage by I. parviflora was a more important variable of populations compared to molecular data or parameters of abiotic environment. In conclusion, complexity of invasibility and invasiveness factors determine the variability of I. parviflora sites, including genetic traits, coverage of invasive species and conditions of environment that were significant and interrelated.