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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.

The current inventory was mainly based on revising herbarium specimens collected since the 19th century and confirmed twenty-one Characeae species in Lithuania. They are representatives of five genera: Chara (12 species), Nitella (5), Tolypella (2), Lychnothamnus and Nitellopsis (by one species each). Thirteen species mentioned in references or labels of herbarium specimens were not confirmed. The occurrence of the Characeae species was recorded in 251 map grid cells (42% of the total number 593). Herbarium specimens were collected from 693 water bodies, mainly lakes. Chara globularis was the most common species, recorded in 150 map grid cells and more than 250 water bodies. Ten species (C. aspera, C. contraria, C. filiformis, C. subspinosa, C. tomentosa, C. virgata, C. vulgaris, Nitella mucronata, N. flexilis, Nitellopsis obtusa) were recorded in the interval from 100 to 50 grid cells and also belong to the group of common species. Chara papillosa and C. strigosa were recorded less than in 50 grid cells and should be considered quite common. Eight species (C. baltica, C. canescens, Lychnothamnus barbatus, Nitella confervacea, N. gracilis, N. syncarpa, Tolypella nidifica, T. prolifera) were recorded in ten or fewer grid cells and belong to the group of rare or very rare species. The occurrence of species that have not been confirmed by the herbarium specimens was discussed., Atlikus herbariumo pavyzdžių, surinktų nuo XIX a. pradžios, reviziją, patvirtinta, kad Lietuvoje aptinkama 21 maurabraginių (Characeae) šeimos dumblių rūšis. Jos priklauso penkioms gentims: Chara (12 rūšių), Nitella (5 rūšys), Tolypella (2 rūšys), Lychnothamnus ir Nitellopsis (po 1 rūšį). Trylika rūšių, paminėtų herbariumo pavyzdžių etiketėse ir kituose šaltiniuose, nebuvo patvirtintos. Characeae rūšių paplitimas buvo užfiksuotas 251 geografinio tinklo kvadrate (42 proc. kvadratų iš visų 593 kvadratų). Analizuoti herbariumo pavyzdžiai surinkti 693 vandens telkiniuose, daugiausia ežeruose. Chara globularis yra Lietuvoje labiausiai paplitusi rūšis, užregistruota 150-yje tinklo kvadratų ir daugiau kaip 250-yje vandens telkinių. Dešimt rūšių (Chara aspera, C. contraria, C. filiformis, C. subspinosa, C. tomentosa, C. virgata, C. vulgaris, Nitella mucronata, N. flexilis, Nitellopsis obtusa) yra užregistruotos nuo 100 iki 50 kvadratų ir taip pat priskirtinos prie dažnų rūšių. Chara papillosa ir C. strigosa buvo užregistruotos kiek mažiau negu 50-yje kvadratų ir gali būti priskiriamos prie gana dažnų rūšių. Aštuonios rūšys (Chara baltica, C. canescens, Lychnothamnus barbatus, Nitella confervacea, N. gracilis, N. syncarpa, Tolypella nidifica, T. prolifera) užregistruotos dešimtyje ar mažiau kvadratų ir priskiriamos prie retų arba labai retų rūšių grupės. Straipsnyje taip pat aptariamos rūšys, kurių vardai minimi literatūros šaltiniuose arba įrašyti herbariumo pavyzdžių etiketėse, tačiau jų buvimas Lietuvoje nepasitvirtinovvvvv

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...

Background: Wet, intermittently flooded freshwater coastal and shallow water habitats are notable for their high biodiversity. Many of the usually semiaquatic annuals or small perennials common in such habitats are in decline due to the high sensitivity of such habitats to changes caused by anthropogenic and natural factors. The Euro-Siberian semiaquatic Elatine hydropiper rarely occurs in Lithuania and is protected there and in other Baltic and Central European countries. In 2020, we found a large population of Elatine hydropiper in southern Lithuania (Varėna district) in Lake Pabezninkai and its exposed shores. The water level of the lake has receded by about 1.5–1.6 m since 2018, exposing wide, wet, and sandy or silty shores. The aim of this study was to determine the status of the Elatine hydropiper population and to assess its potential for long-term survival. The objectives of the study were to (a) determine the size and quantitative characteristics of the population, (b) assess the seed bank in the shallows and exposed shores of the lake, (c) assess the species diversity in the communities with Elatine hydropiper, (d) evaluate the conservation value of the studied species and the lake habitat. Methods: The studies were carried out between 2020 and 2021. The number and coverage of plant patches as well as seed bank studies were carried out at three sites with different shoreline substrate. At each site, the number of patches and coverage was assessed in 50 sample plots of 100 cm2. The seed bank was examined in the top 5 cm of the substrate. A total of 90 substrate samples were analyzed. Results: We found that Elatine hydropiper grows on ca. 0.38 ha in the lake and on ca. 0.95 ha on the shores. On the exposed shores, the mean number of Elatine hydropiper patches per 1 m2 was 2155 ± 1241.5 and their mean cover was 23.17% of the surface. Seed bank analyses revealed that the seeds and seed shells were significantly more abundant in the bottom sediments than in the shore sand or silt. The mean number of seeds per liter of soil was 85.8 ± 210.2, and the mean number of seed shells was 217.0 ± 265.8. Conclusions: The assessment of the status of the species in Lithuania according to the IUCN (International Union for Conservation of Nature) criteria has led us to conclude that it should now be classified as vulnerable [A3; B1ab(iii); C2a(ii); D2]. The key to protecting Elatine hydropiper and other co-occurring rare species with similar ecological and biological characteristics, as well as the plant communities of shallows and exposed wet banks, is to protect their habitats. The survival of the species and their habitats could be assured by recurring significant water level fluctuations in the lake, resulting in periodic emergence of patches of wet sand or silt free from perennial vegetation.

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.

River riparian ecosystems deteriorate because of anthropogenic factors that are related to industry, intensive agriculture and tourism. Two native species, Bidens tripartita and B. cernua, are weeds widespread in Lithuania on river banks and other habitats. An alien species, B. frondosa, is also widespread in the same habitats. We investigated the genetic diversity of B. frondosa, compared its population structure to that of related species and assessed the possibility of genetic interaction between B. frondosa and native congeners. Genetic analysis of populations was based on inter-simple sequence repeats (ISSR) polymorphism. Our results revealed high genetic differentiation in the B. frondosa populations (48.2%) and high genotypic diversity (i = 0.99). Bayesian cluster analysis using the program Structure revealed signs of gene flow between B. frondosa and the native species; however, principal coordinate analysis did not support this result. Our results do not indicate the role of interspecific hybridization in the invasiveness of B. frondosa. Įvairūs antropogeniniai veiksniai (intensyvi ūkinė veikla, turizmas, klimato kaita ir kt.) pažeidžia upių ekosistemas, sudarydami sąlygas plisti invaziniams augalams. Lietuvoje upių, ypač Nemuno, ir kitų vandens telkinių pakrantėse sparčiai plinta invazinis ilgakotis lakišius (Bidens frondosa L.). Ši rūšis sąveikauja su vietinėmis rūšimis ir dažniausiai jas išstumia. Upių pakrantėse ir kitose natūraliose bei antropogenizuotose augavietėse paplitusios dvi vietinės lakišiaus rūšys – triskiautis (B. tripartita) ir pelkinis (B cernua). Triskiautis lakišius yra žinomas ir kaip laukų bei daržų piktžolė. B. frondosa kai kuriose Europos šalyse irgi yra laikoma dirbamų laukų piktžole. Siekiant nustatyti, kokie genetiniai veiksniai gali būti palankūs plisti ilgakočiui lakišiui, tirta ir palyginta šių trijų rūšių populiacijų genetinė sandara bei įvairovė. DNR polimorfizmas buvo nustatytas paprastųjų pasikartojančių sekų intarpų (angl. inter-simple sequence repeats – ISSR) metodu. Tyrimo rezultatai parodė didelę B. frondosa populiacijų genetinę diferenciaciją ir genotipų įvairovę. Nors Bayeso klasterių analizė, atlikta programa Structure, rodė tam tikrus genų srauto tarp rūšių požymius, tačiau pagrindinių koordinačių analizė šio rezultato nepatvirtino. Tyrimo rezultatai parodė, kad tarprūšinė hibridizacija nėra B. frondosa invazyvumo priežastis. Šiai svetimkraštei rūšiai plisti palankus veiksnys gali būti didelė populiacijų genetinė ir genotipinė įvairovė., Įvairūs antropogeniniai veiksniai (intensyvi ūkinė veikla, turizmas, klimato kaita ir kt.) pažeidžia upių ekosistemas, sudarydami sąlygas plisti invaziniams augalams. Lietuvoje upių, ypač Nemuno, ir kitų vandens telkinių pakrantėse sparčiai plinta invazinis ilgakotis lakišius (Bidens frondosa L.). Ši rūšis sąveikauja su vietinėmis rūšimis ir dažniausiai jas išstumia. Upių pakrantėse ir kitose natūraliose bei antropogenizuotose augavietėse paplitusios dvi vietinės lakišiaus rūšys – triskiautis (B. tripartita) ir pelkinis (B cernua). Triskiautis lakišius yra žinomas ir kaip laukų bei daržų piktžolė. B. frondosa kai kuriose Europos šalyse irgi yra laikoma dirbamų laukų piktžole. Siekiant nustatyti, kokie genetiniai veiksniai gali būti palankūs plisti ilgakočiui lakišiui, tirta ir palyginta šių trijų rūšių populiacijų genetinė sandara bei įvairovė. DNR polimorfizmas buvo nustatytas paprastųjų pasikartojančių sekų intarpų (angl. inter-simple sequence repeats – ISSR) metodu. Tyrimo rezultatai parodė didelę B. frondosa populiacijų genetinę diferenciaciją ir genotipų įvairovę. Nors Bayeso klasterių analizė, atlikta programa Structure, rodė tam tikrus genų srauto tarp rūšių požymius, tačiau pagrindinių koordinačių analizė šio rezultato nepatvirtino. Tyrimo rezultatai parodė, kad tarprūšinė hibridizacija nėra B. frondosa invazyvumo priežastis. Šiai svetimkraštei rūšiai plisti palankus veiksnys gali būti didelė populiacijų genetinė ir genotipinė įvairovė.

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.

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.