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The European Habitats Directive was adopted to halt the rapid loss of biodiversity and has become an important instrument for protecting biodiversity in the European Union. Three aquatic plant species protected under the European Habitats Directive have so far been found in Lithuania: Aldrovanda vesiculosa, Caldesia parnassifolia, and Najas flexilis. Our aim in this study was to evaluate the former and current distribution and the status of conservation of the target species. Screening for the above-mentioned protected aquatic plant species was performed in 73 natural lakes throughout Lithuania in 2019–2021. We confirmed extant populations of Aldrovanda vesiculosa in four lakes, Caldesia parnassifolia in two lakes, and Najas flexilis in four lakes in the northeastern part of the country. We studied Aldrovanda vesiculosa populations three times (2015, 2019, and 2022) in Lake Rūžas and once each in Lake Apvardai and Lake Dysnai (2020). The population density of Aldrovanda vesiculosa ranged from 193.4 ± 159.7 to 224.0 ± 211.0 individuals/m2, the mean length of plants ranged from 12.5 ± 2.1 to 14.3 ± 2.7 cm, and the mean number of apices ranged from 2.0 ± 0.7 to 2.2 ± 0.9 per individual. The habitat of Aldrovanda vesiculosa in Lake Rūžas covered an area of about 3 ha. The number of generative individuals of Caldesia parnassifolia widely varied between years in Lake Rūžas. All populations of Najas flexilis were small, although the potential habitats in the studied lakes cover relatively large areas. We propose designating all lakes with populations of Aldrovanda vesiculosa, Caldesia parnassifolia, and Najas flexilis as special areas of conservation, as well as developing and implementing action plans for the conservation of these species and their habitats.

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.

Distribution and ecological requirements of Chara filiformis A. Braun in Hertzsch in Lithuanian water bodies were studied. This species has quite limited distribution in central and northern Europe...

Aquatic Ranunculus (sect. Batrachium) include homophyllous and heterophyllous plants. The development of floating leaves may be induced by genetic mechanisms or/and environmental conditions and this fact complicates the morphologically based identification of species. DNA-based studies provide the opportunity to expand the knowledge of this complicated group. We studied heterophyllous Ranunculus with well-developed capillary and intermediate leaves and visually homophyllous plants with capillary leaves from a single river basin, with the aim to evaluate their genetic polymorphism and taxonomic status&mdash, whether the plants with well-developed and weakly expressed intermediate leaves belong to different forms (taxa) or if they just express morphological variation of one or two taxa in a specific, very variable river environment. The studied heterophyllous and homophyllous plants from different rivers showed high genetic differentiation and a low level of genetic diversity within these groups. The molecular analysis did not reveal any inter simple sequence repeat (ISSR) polymorphism associated with the development of intermediate leaves. An analysis of nuclear ribosomal internal transcribed spacers ITS1&ndash, 2 sequences revealed several ribotypes, which indicated the genetic heterogeneity of studied plants and indirectly confirmed the hybrid origin of some of them. Sterile plants originated from crossing of R. circinatus and R. penicillatus were discovered in the Skroblus River, however, identification of the parental species was impeded by the polymorphism detected. For this reason, cytological studies were performed and allowed confirmation of the hybrid origin of these plants.

Aims: To create a comprehensive, consistent and unequivocal phytosociological classification of European marsh vegetation of the class Phragmito-Magnocaricetea. Location: Europe. Methods: We applied the Cocktail method to a European data set of 249, 800 vegetation plots. We identified the main purposes and attributes on which to base the classification, defined assignment rules for vegetation plots, and prepared formal definitions for all the associations, alliances and orders of the class Phragmito-Magnocaricetea using formal logic. Each formula consists of the combination of “functional species groups”, cover values of individual species, and in the case of high-rank syntaxa also of “discriminating species groups” created using the Group Improvement (GRIMP) method. Results: The European Phragmito-Magnocaricetea vegetation was classified into 92 associations grouped in 11 alliances and six orders. New syntaxa (previously invalidly published according to the International Code of Phytosociological Nomenclature) were introduced: Bolboschoeno maritimi-Schoenoplection tabernaemontani, Glycerio maximae-Sietum latifolii, Glycerio notatae-Veronicetum beccabungae, Schoenoplectetum corymbosi and Thelypterido palustris-Caricetum elongatae. Based on a critical revision, some other syntaxa were rejected or excluded from the class Phragmito-Magnocaricetea. Conclusions: This work provides the first consistent classification of the class Phragmito-Magnocaricetea at the European scale, which is an important tool for nature conservation. Our classification largely respects previously existing concepts of syntaxa, but it also proposes modifications to the recently published EuroVegChecklist. This work also provides a protocol that can be used for extending the current classification to new syntaxa and geographical regions.

Genetic diversity as a basic indicator of biological diversity is extremely important for the characterization of species, for the development of conservation strategies and as an independent measure of environmental conditions. Despite the importance of Batrachium species as an indicator of the sustainability of riverine ecosystems, studies on the genetic variation of Batrachium populations are rather scarce. Therefore, it is crucial to study Batrachium species diversity and population structures to understand the status of Batrachium species and populations and provide measures for evaluating the future risk of diversity loss. Sixteen Batrachium populations were analyzed using morphological characters and molecular markers (inter simple sequence repeats [ISSRs] and trnH-psbA sequences). The study revealed agreement between these types of data in distinguishing separate groups of species found in Lithuanian rivers. Our study revealed a clonal structure and a low level of genetic diversity in most of the studied Batrachium populations. The low degree of genetic diversity, high level of genetic differentiation and low level of gene flow between populations of riverine Batrachium species in Lithuania indicated that a conservation strategy should be adopted. Long-term observations should be carried out, and the condition of Batrachium species and the impact of anthropogenic activities should be evaluated. Finally, we recommend that certain anthropogenic activities should be regulated by legislation in particular river stretches.

The results of the recent (2014-2015) inventory and three historical datasets (1949-1959, 1960-1980 and 1997-2007) were analyzed in order to track the long-term changes of charophytes in the largest estuarine lagoon of the Baltic Sea. The present species composition of charophytes in the estuarine part of the Curonian Lagoon consisted of 7 species, including tolerant to salinity (Chara aspera, C. contraria, C. globularis and Nitellopsis obtusa) and typical brackish-water species (Chara baltica, C. canescens and Tolypella nidifica). The highest congruence of species was between the 1997-2007 and 2014-2015 datasets, which covered respectively eutrophication and post-eutrophication periods. The 1949-1959 dataset (closest to the reference conditions) differed by the absence of typical brackish-water species. The 1960-1980 dataset (the major period of eutrophication) was relatively poor in study sites and species. During the last 6 decades, only tolerant to salinity freshwater species were constant and abundant; only Nitella mucronata can be considered as extinct. Recently, C. contraria became dominant and widespread. The changes in the charophyte species composition, abundance and distribution can be explained by different intensity of surveys and/or density of study sites, but also by the increased exposure to brackish waters since 1980s and/or recently reduced effect of eutrophication.

In this study, we focused on relatively inexpensive and commonly used fishermen class sonar in order to test its ability to detect stands of charophytes and other groups of submerged angiosperms in the shallow and turbid waters of the Curonian Lagoon. Based on the length of macrophytes, height thresholds (20 and 30 cm) were established in order to distinguish charophytes from submerged angiosperms in obtained echograms. The echograms were visually analysed by two experts. We successfully discriminated 3 echofeatures (bare bottom, stands of charophytes and submerged angiosperms), whereas angiosperms from different morphology groups could not be distinguished. Below 1 m depth, the stands of charophytes and submerged angiosperms were clearly distinguished, thus their maximum colonization depth could be delineated. The accuracy of the discrimination could be reduced by free-drifting mats of filamentous algae, resulting in the overestimation of charophytes. Our approach can be useful for the mapping of monospecific stands of submerged vegetation and could be an important additional tool for macrophyte monitoring and water quality assessment in shallow and turbid waterbodies.

Butkuvienė J., Sinkevičienė Z., Žvingila D., 2014: Batrachium (Ranunculaceae) in the rivers of Lithuania [Batrachium (Ranunculaceae) Lietuvos upėse]. - Bot. Lith., 20(1): 46-56. Batrachium (DC.) S.F.Gray is one of the most complicated taxonomic groups of aquatic plants. Identification to species level often is very difficult because of simplified morphology and variable taxonomic interpretation of the group. This paper reports the results of the revision of herbarium specimens of Batrachium from flowing waters. The occurrence and distribution of Batrachium fluitans and Batrachium pseudofluitans in the rivers of Lithuania are presented as well as morphological characters important for the separation of these taxa are discussed

Caldesia parnassifolia (L.) Parl. is a "near threatened" species in Europe and it has been treated as extinct in Lithuania, the latest gathering dating back to 1957. Occurring there at the northern border of its range, this species was recorded only once at the beginning of the 19th century and twice in separate localities in the middle of the 20th century. In summer 2015, after an interval of almost 60 years, C. parnassifolia was found in a new locality, more than 100 km north of those previously known. A very abundant population composed of vegetative and flowering (turion forming) individuals was spread over about 3.5 ha area in Lake Rūžas, known as a unique Lithuanian habitat of Aldrovanda vesiculosa. C. parnassifolia formed almost monodominant stands along swampy shores and less abundantly occurred in communities of floating leaved species (mainly Nuphar luteum and Potamogeton natans) at a depth of 0.5-1 m. It is likely that implemented measures to improve the habitat condition for A. vesiculosa were favourable for the appearance of C. parnassifolia., Caldesia parnassifolia (L.) Parl. Europoje yra atsidūrusi prie išnykimo ribos, Lietuvoje paskutinį kartą pastebėta tik 1957 m. ir todėl laikyta išnykusia. Ši rūšis Lietuvoje yra šiauriniame savo paplitimo arealo pakraštyje ir buvo rasta tik vieną kartą XIX a. pradžioje (Vilniaus apylinkėse) ir du kartus XX a. viduryje (Alytaus ir Lazdijų rajonų Daugų ir Ilgio ežeruose). 2015 m. vasarą, beveik po 60 m. pertraukos, C. parnassifolia rasta Rūžo ežere – radvietėje, daugiau kaip 100 km nutolusioje nuo anksčiau žinomų. Ši vieta geriau žinoma kaip kitos Europinės svarbos rūšies – Aldrovanda vesiculosa buveinė, kurioje C. parnassifolia anksčiau nebuvo pastebėta. Labai gausią C. parnassifolia populiaciją sudarė vegetuojantys ir žydintys (turionus formuojantys) individai, paplitę apie 3,5 ha plote, 0,5–1 m gylyje. Prie užpelkėjusių pakrančių apie 0,5 m gylyje C. parnassifolia sudarė beveik grynus sąžalynus, giliau ne taip gausiai augo visoje įlankoje vyraujančių plūdurlapių augalų (daugiausia Nuphar luteum ir Potamogeton natans) bendrijose. Panašioje buveinėje ji buvo rasta 1954 m. Daugų ežero Banduragio įlankoje. Šiuo metu nėra žinoma kaip širdžialapė kaldezija atsirado Rūžo ežere. Viena iš palankių aplinkybių galėjo būti perteklinės augalijos šalinimas, atliktas 2014 m., siekiant pagerinti pūslėtosios aldrūnės augimo sąlygas.

Sinkevičienė Z., 2013: Confirmation of Utricularia australis occurrence in Lithuania [Utricularia australis auga ir Lietuvoje]. - Bot. Lith., 19(2): 161-164. Occurrence of Utricularia australis R. Br. on the territory of Lithuania was confirmed by finding it in Lake Kampinis, Varėna district municipality. Morphological differences between similar species U. australis and Utricularia vulgaris as well as species composition of the association Utricularietum australis and accompanying communities are presented and discussed.

Sinkevicienė Z., 2013: Succisella inflexa – a neglected species in meadows of Lithuania [Succisella inflexa – pražiūrėta Lietuvos pievų rūsis]. – Bot. Lith. 19(1): 67–71. Succisella inflexa (Kluk) Beck. is one of the rarest red-listed species in Lithuania, occurring at the northern border of its range. Based on herbarium specimens, only five localities were known in SE Lithuania (Trakai, Varėna and Salcininkai districts) in the period of 1956–1983. In 2007 and 2009, new localities in the Salcia River valley near Žygmantiskės village (Salcininkai distr.) and in the Merkys River valley near Moliai village (Varėna distr.) were recorded. The populations survived in wet meadows of Calthion, Caricion communities, in the intensively grazed floodplain. They were composed of flowering and vegetative plants and seemed to be in good condition. The limited occurrence of S. inflexa in Lithuania is related to the species distribution on the edge of its range. The late blooming time in August–September was the main reason why this species was neglected during the former investigations on these meadows usually studied before mowing in June or July. After the discovery of new populations, S. inflexa is expected to be more distributed in the natural valleys of the Merkys River catchment area.