This paper presents information about ten new alien plant species recorded in Lithuania in the period from 1995 to 2014. These species belong to eight families: Cucurbitaceae (Lagenaria siceraria), Juncaceae (Luzula sylvestris), Lamiaceae (Physostegia virginiana, Sideritis montana), Poaceae (Melica altissima, Miscanthus sacchariflorus), Portulacaceae (Claytonia perfoliata), Scrophulariaceae (Digitalis purpurea), Solanaceae (Datura inoxia) and Zygophyllaceae (Tribulus terestris). Three species (Claytonia perfoliata, Sideritis montana and Tribulus terestris) were introduced accidentally, whereas other seven species were introduced deliberately and later escaped from cultivation. One species, Luzula sylvatica, is ascribed to the group of established aliens, whereas other recorded species are treated as casual. Local establishment of Claytonia perfoliata, Digitalis purpurea and Melica altissima is expected, whereas Miscanthus sacchariflorus can become established and even invasive in the future.
Addition of nine alien plant species and correction of the taxonomic position of one alien species was provided in this publication. Occurrence of three species, Gossypium hirsutum, Leymus racemosus and Senna obtusifolia, has not been reported in Lithuania, yet. Gossypium hirsutum and Senna obtusifolia are casual grain immigrants and their naturalization in the country is unlikely. Leymus racemosus probably has spread to Lithuania from Kaliningrad region of Russia, where it has been introduced intentionally. Currently, this species is treated as naturalized in the Curonian Spit (Western Lithuania). The status of Bellis perennis, which previously had variously been treated as native or alien species in Lithuania, was discussed. Although Malus domestica, Medicago ×varia, Oenothera casimiri and Salix ×fragilis have been reported occurring in Lithuania long ago, their status in the country has not been clearly defined. Considering non-native origin of one or both parental species of these four species, they also should be treated as alien in the country. Based on the results of taxonomic treatments, the occurrence of Salix euxina in Lithuania was confirmed. Cultivated and escaped plants, formerly known under the name Aronia melanocarpa, in fact are intergeneric hybrids and should be treated as ×Sorbaronia mitschurinii. Distribution, habitats, naturalization and impact of ten alien species were discussed. Notes on the taxonomy of several alien species were presented. Comments on improper documentation of several published molecular studies were presented and problems of the result interpretation were discussed.
Gudžinskas Z., Petrulaitis L., Arlikevičiūtė L., 2014: Vaccinium macrocarpon - a new alien plant species in Lithuania [Stambiauogė spanguolė (Vaccinium macrocarpon) - nauja svetimžemė rūšis Lietuvoje]. - Bot. Lith., 20(1): 41-45.
Extensive colonies of V. macrocarpon Aiton were found in 2013 during the investigations of the flora of Rėkyva wetland complex (Šiauliai district) in a cutover and abandoned Piktmiškis peatbog situated in the environs of Rėkyva village. This species was widely distributed on about 31 ha area and solitary individuals or small patches were recorded in various distance from the dense population in bog woodlands. It is supposed that seeds of this species were dispersed by birds. V. macrocarpon should be treated as a naturalized species in Lithuania. Recommendation to use V. macrocarpon for re-cultivation of cutover peatbogs should be considered with caution in order to avoid its probable invasions in natural, disturbed and degraded bog habitats. Notes on cranberry nomenclature and taxonomy are also provided
Helianthus grosseserratus M. Martens was first recorded in Lithuania in 2014. Rather large population of this species was found in Siauliai district (northern Lithuania), in the vicinity of Bridai village, on the territory of recultivated former municipal dump. This species can be easily distinguished from other perennial Helianthus species by glabrous stem, long, serrate, alternate leaves on the upper part of the stem and spindle-shaped roots. Supposedly, H. grosseserratus was brought to the area with garden waste or soil used for dump recultivation about 30 years ago and recently it has established in the locality. In the investigated capitula, no developed seeds were found. H. grosseserratus reproduces vegetatively by rhizomes and under favourable conditions can survive for a long time.
Woody plant species in recent decades have increasingly often been recorded escaped from cultivation and naturalized. In 2013, a new alien woody species Amorpha fruticosa L. (Fabaceae) was first found in Lithuania. In several Central European countries, A. fruticosa is recognized as invasive species that pose serious threat to natural habitats and ecosystems. To date, A. fruticosa has been registered in three localities in Lithuania: two populations in Ukmergė district and one population in Prienai district. Considering the present state of revealed A. fruticosa populations, it is concluded that this species in Lithuania is already naturalized and potentially invasive. Estimated total area occupied by A. fruticosa in three known localities is about 0.2 ha. In certain areas this species can become abundant and invade significant areas of meadow, forest-edge and other open habitats. Therefore, its immediate control and subsequent eradication can reduce risk of future invasion. Cultivation of A. fruticosa should be forbidden outside the ornamental plantations.
Alien plants are one of the most dynamic and rapidly changing components of flora. Many intentionally introduced plants, which formerly were in cultivation only, now are increasingly found escaped and occur in anthropogenic or seminatural habitats. During field investigations in the southern districts of Latvia in 2014-2016, six new alien plant species were recorded: Allium nutans, Hylotelephium spectabile, Solidago ×niederederi, Symphyotrichum dumosum, S. lanceolatum and S. novae-angliae. To date, four species, Allium nutans, Hylotelephium spectabile, Symphyotrichum dumosum and S. novae-angliae, occur as casual aliens in Latvia. Solidago ×niederederi should be ascribed to the group of established species, whereas Symphyotrichum lanceolatum has naturalized and is potentially invasive. Notes on morphology and identification of species as well as characteristics of the recorded populations are discussed. A note on 20 other alien plant species recorded in wastelands, abandoned meadows and unused arable fields in the south-western part of Daugavpils city is also provided.
Two species of the genus Thesium (T. ebracteatum and T. linophyllon) are constantly recognized as members of the flora of Lithuania. However, the study on plants currently occurring in Lithuania and usually identified as T. linophyllon revealed that in fact they belong to T. ramosum. The analysis of all available data on the occurrence of T. linophyllon in Lithuania indicated that this species has never been recorded. The report on the occurrence of T. linophyllon, published at the end of the 18th century, was based on misidentified T. ebracteatum. Thus, T. linophyllon should be excluded from the list of vascular plants of Lithuania. Occurrence of T. ramosum was reported for the first time in the country. Currently, one population of this species with two subpopulations are known in the environs of Varnikai village (Trakai distr., Trakai Historical National Park). Morphological description of T. ramosum and diagnostic features of this species were provided. The structure and habitat conditions of two subpopulations were investigated in 2017. The present population of this species was revealed to consist of 52 individuals. Occurrence of young individuals in one subpopulation indicates generative reproduction of T. ramosum. Negative relationship between the number of T. ramosum individuals and the coverage of Poaceae species, and positive relationship between the coverage of Fabaceae species were revealed. Localities of T. ramosum in Lithuania are far from the area of its native distribution, and this species is ascribed to the group of established alien species. Further spread and invasion of the species is not expected.
Many woody plant species that originate from various regions of the world have been introduced in other regions or continents and are used in ornamental gardening, silviculture, erosion control, for fruit sources or other purposes. Woody plants selected for introduction usually originate from regions with similar climate conditions; therefore, after certain time lag they start to spread outside places of cultivation, become naturalized or even invasive. In addition to 77 woody alien plant species reported in Lithuania, ten new species were recorded and analysed in this paper. Information on the native and anthropogenic ranges, first record in Lithuania, size of populations, habitats, reproduction and naturalization of Aralia elata, Berberis thunbergii, Caragana frutex, Celastrus orbiculatus, Cornus alba, Cytisus austriacus, Hydrangea arborescens, Pinus strobus, Rhus typhina and Thuja occidentalis is presented. All these species have been introduced intentionally and are used mainly in ornamental gardening. Three of the reported species, Berberis thunbergii, Hydrangea arborescens and Thuja occidentalis, currently are casual species. Remaining seven species were recognized as naturalized in Lithuania, and five of these, i.e. Aralia elata, Celastrus orbiculatus, Cornus alba, Pinus strobus and Rhus typhina as well as Berberis thunbergii, which currently is treated as a casual, have very high or high probability of getting invasive. Constant survey of potential habitats, detection of new escaped alien plants, particularly of trees and shrubs, is the best way to reveal potentially dangerous species and make timely decisions for their control or eradication, if necessary.
The list of invasive alien species of European Union concern currently includes 23 plant species. The aim of this study was to assess the potential and importance of introduction pathways for invasive alien plant species in Lithuania, to estimate probability of their establishment and further spread in the country. Analysis of all available information revealed that three species (Asclepias syriaca, Heracleum sosnowskyi and Impatiens glandulifera) currently occur in Lithuania and the latter two are widespread invasive species in the country. The remaining 20 plant species have not been registered in the wild in Lithuania so far. Four of these, Gunnera tinctoria, Lysichiton americanus, Myriophyllum aquaticum and Pennisetum setaceum, are occasionally cultivated in gardens or other outdoor areas, and six species, e.g. Cabomba caroliniana, Eichhornia crassipes, Lagarosiphon major, are cultivated in aquaria or other indoor spaces. Naturalization of seven species is unlikely in the country, whereas naturalization of 13 species (Lysichiton americanus, Myriophyllum aquaticum, Pennisetum setaceum, etc.) is plausible. Five of the analysed and still not recorded species are recognized as potentially invasive in Lithuania; the invasion of five species is plausible and that of 10 species is unlikely. The most important pathway of introduction of the analysed species is ornamental gardening. Three species that have not been recorded in Lithuania, but occur in the neighbouring regions of Europe (Elodea nuttallii, Heracleum mantegazzianum, Heracleum persicum) can enter the country by natural means. Importance of permanent studies and surveys on alien plants aiming to ensure early detection and eradication of invasive species is discussed.
Alien invasive woody plant species, particularly those associated with nitrogen-fixing bacteria, are of special concern, because they may cause drastic changes in entire ecosystems. Although most of invasive species of Lithuania originate from other continents, one of these, Cytisus scoparius, is native to Europe. Fast spread of this species in Lithuania and its invasion to forest, coastal and continental sand, occasionally grassland habitats, stimulated us to study demographic structure of its populations. The aim of this research was to evaluate density, life stage and age structure of the populations, and to analyse relationships of the age of individuals with their life stages, height and stem diameter. Five populations were studied in the western, southern and eastern parts of Lithuania in July–August 2017. For the study, we selected stands of this species occupying at least 0.1 ha in a uniform habitat. We applied sampling plot method, and studied at least 100 individuals in each population, excluding seedlings. The age, life stage, height and stem diameter of 583 individuals were studied. The average density of individuals ranged between 5.15 individuals/m2 and 15.40 individuals/m2. Juvenile individuals reach the stage of vegetative adults on the second or third growth season, occasionally on the third year they reach even the stage of generative adults. The average age of juveniles was 1.10 years, of vegetative adults it was 2.99 years and 6.26 years of generative adults. The oldest generative individual was 28 years old. Linear regression analysis of the relationship between the plant age and the stem diameter revealed that the age predetermined the stem diameter variance by 81.0% in the studied populations. This study revealed that densities of C. scoparius individuals of all life stages in disturbed and undisturbed habitats were sufficient to sustain longevity and further expansion of populations. Therefore, appropriate measures for control and eradication of this species should be applied, particularly in the habitats of high conservation value.