Donatas Naugžemys

Lobelia dortmanna L. is an endangered isoetid species and a key bioindicator of oligotrophic soft-water lakes. This study investigates the morphological variability, population structure, and genetic diversity of L. dortmanna in two Lithuanian lakes: Lake Ešerinis (sandy, oligotrophic) and Lake Salinis (sludgedy, mesotrophic). Results demonstrate significant morphological plasticity; individuals in the nutrient-rich, sludged sediments of Lake Salinis exhibited higher dry biomass, longer leaves, and more extensive root systems. However, despite this "gigantism," the Lake Salinis population showed a critical lack of recruitment, with almost no seedlings observed. Genetic analysis revealed a completely monomorphic state across all individuals. This combination of high phenotypic plasticity and genetic uniformity suggests that while Lobelia dortmanna can morphologically adjust to moderate environmental shifts, its lack of genetic variation poses a severe long-term threat, necessitating active restoration and potential reintroduction.

Sago pondweed (Stuckenia pectinata (L.) Börner) is a genetically and ecologically diverse submerged macrophyte, notable for its versatile reproductive characteristics, with a broad global distribution, excluding only the Arctic and Antarctic regions. This cosmopolitan species remains underexplored genetically in Lithuania compared to some other European regions. The aim of this study was to investigate the state and distribution of genetic diversity across Lithuanian river populations. We analyzed genetic variation in ten riverine populations using both simple sequence repeats (SSRs) and intersimple sequence repeats (ISSR). Genetic distances between genotypes and populations, as revealed by SSR markers, correlated with those determined using ISSR markers, confirming consistency across the two marker systems. STRUCTURE analysis revealed the presence of two distinct genotype pools. Our study demonstrated that the majority of genetic variation resides within populations, with an F_ST value of 0.212 (SSR) and a Φ_PT value of 0.352 (ISSR). These findings suggest high genetic differentiation among populations. The absence of a relationship between genetic diversity and hydrochemical or hydromorphological parameters at plant collection sites suggests that the population structure of this species is shaped primarily by evolutionary and/or demographic mechanisms, rather than by local environmental hydrochemical conditions. Overall, this study revealed high within-population genetic diversity and underlying genetic structure in S. pectinata populations across Lithuanian rivers.

This study describes the first complete chloroplast genome of Ranunculus cf. penicillatus and provides new insights into the genetic composition and evolutionary relationships of the Ranunculus genus. The genome was assembled and characterized using high-throughput sequencing technologies, revealing a circular structure encompassing 158,313 base pairs. Comparative analysis with the chloroplast genomes of related species within the Ranunculus genus highlights notable variations in structural organization, which can elucidate potential adaptive evolutionary mechanisms. Phylogenetic analyses conducted using the maximum likelihood approach resulted in the placement of Ranunculus cf. penicillatus within a well-defined clade, revealing its relationship with other taxa. This study not only enriches the existing plastid genomic data of the genus Ranunculus but also serves as an additional resource for future studies on the phylogenetics, systematics, and conservation biology of this diverse group of aquatic plants. The findings highlight the importance of complete chloroplast genomes in the Ranunculus section Batrachium, an evolutionarily young group of aquatic plants, for understanding plant diversity and evolution. The genome can be accessed on GenBank with the accession number PV690257.

Common reed is often used as a model plant to study the anthropogenic impacts on ecosystems at local and global scales. As a community-forming species, it is directly exposed to the impacts of human activities on the ecosystem. The aim of our study was to evaluate the patterns of genetic diversity in common reed stands located in habitats that are differently affected by anthropogenic factors. We studied whether riverbed modifications, land cover in the neighborhood of the stand and the chemical and physical parameters of the river water affect the genetic diversity of P. australis at the studied sites. Using DNA fingerprinting, we genotyped 747 plants from 42 sites located in 16 small Lithuanian rivers. Bayesian clustering and principal coordinate analysis revealed two main gene pools at the population (river) level. At the site level (i.e., considering all sites independently of their rivers), polymorphism was high even between sites in the same river. Our study revealed a negative relationship between the concentration of nitrogen compounds and the genotypic richness of P. australis populations. We did not find any correlations between the other chemical parameters of the water and the parameters of the genetic diversity. Additionally, there were no genetic differences between sites in modified and unmodified river sections or between sites that differed in land cover type in the neighborhood of the stand.