Assessment of the conservation status of a species, first, should be based on its clearly defined taxonomic identity. Insufficient knowledge of certain taxonomic groups may lead to misidentifications, misinterpretations and become an obstacle for conservation. Mentha longifolia, listed as a protected plant species of Lithuania since 1981, belongs to a taxonomically complex group of species. The aim of this research was to examine available herbarium specimens of M. longifolia and verify their identification, specify distribution of this species in Lithuania and evaluate its conservation status in the country. The study was based on the analysis of herbarium specimens and information provided in references and databases. We studied a total of 93 specimens initially identified as M. longifolia. Morphological features of 30 leaves (leaf length, leaf width, petiole length, distance from leaf base to the widest place, length of leaf tooth) of both M. longifolia and M. ×villosa were measured on herbarium specimens. After the revision of herbarium specimens, we revealed that 37.6% of specimens initially identified as M. longifolia belong to other species (mostly to M. ×villosa) and 29.0% of specimens cannot be identified precisely because of the early stage of development. Only 33.4% of M. longifolia specimens were identified precisely. Thus, M. longifolia, previously supposed as quite widespread in Lithuania, after the revision appeared to be restricted mainly to the southern and south-eastern parts of the country. Applying the IUCN criteria, M. longifolia was evaluated as data deficient (DD) species. Analysis of leaf morphological traits revealed that M. longifolia and M. ×villosa can be differentiated by the length and the width of leaf blade, the distance from leaf base to the widest part of leaf and by the ratio between the length and the width of middle cauline leaves. This study revealed that taxonomic revision of the genus Mentha in Lithuania is required. Distribution of species, ecology and state of populations, impact of alien species on native congeners should be estimated in the future.
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.
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.
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.