Asclepias speciosa (Apocynaceae, Asclepiadoideae): a rare or unrecognized alien species in Europe?

Studies on populations of Asclepias syriaca L. in Lithuania revealed the occurrence of a new alien plant species, the North American native Asclepias speciosa Torr. (Apocynaceae, Asclepiadoideae), in southern parts of Lithuania – the first report of the latter species in Europe. Interestingly, a thorough analysis of herbarium specimens revealed that A. speciosa had first been collected in Lithuania in 1962, but the specimen was misidentified at the time as A. syriaca. The newly discovered population of A. speciosa occupies mesic grasslands, tall-herb fringe communities and arable field habitats. Sexual reproduction of this species was not recorded; it spreads locally by means of vegetative reproduction. We present here an exhaustive analysis of morphological characteristics and differences between A. speciosa and A. syriaca and other species of the genus, as well as a key for identification of alien Asclepias species in Europe. We predict that the effect of A. speciosa on native habitats and communities, and its economic impact, are comparable to those of the highly invasive A. syriaca. Although A. speciosa currently occurs very rarely as an alien species in Europe, its existence in other regions of Europe is highly probable

Lotus maritimus L. (Fabaceae), alien species new to Lithuania

Information about the first record of alien species Lotus maritimus L. (Fabaceae) in Lithuania is provided. This species was found in disturbed grassland along the railway line in Panevėžys district (northern part of Central Lithuania), Berčiūnai village in June 2021. It is supposed that seeds of this species have been accidentally in-troduced with rock material used to maintain railway embankment. Species composition of the habitat in Lotus maritimus locality is presented. The recorded population consists of a large number of generative individuals. This species could also grow in other parts of Lithuania, as the plants produce viable seeds and might spread to new areas. Currently, Lotus maritimus is considered as a casual species in Lithuania; however, it may naturalise locally in the future

The first records of two alien woody species, Cornus alternifolia and Cornus amomum, in Lithuania

Two native species from North America, Cornus alternifolia and Cornus amomum (Cornaceae) have escaped from cultivation in Lithuania and are recorded as new alien species. Cornus alternifolia was found in an alluvial forest habitat in Vilnius, occupying an area of ca. 0.49 ha. The population consists of about 900 individuals of which ca. 100 were growing to 1-3.5 m high, though fruiting individuals were not found. Cornus amomum is recorded from the Siauliai district, on the banks of a water reservoir in a shrub-dominated habitat. The population consists of four mature individuals with fruits and several young individuals grown from seeds. Cornus alternifolia has already been reported to have escaped in Slovakia; Cornus amomum is reported for Lithuania as an escaped plant for the first time in Europe. Both species occupy habitats analogous to their native range and are dispersed mainly by birds. Their naturalization, spread and invasion to natural habitats of temperate regions of Europe is probable. Therefore, the spread of these species should be monitored, and rapid response measures, if deemed necessary, should be taken

Drivers and effects of cryptic invasion of Cornus sanguinea subsp. australis in Lithuania

Most alien plant species are usually discovered in new areas either immediately or within a relatively short period of time after their introduction. However, the introduction, spread, and invasion of some species go unnoticed for a long time. In Lithuania, such an alien plant is Cornus sanguinea subsp. australis, whose cryptic invasion has gone unnoticed due to its similarity to the native subsp. sanguinea. Cornus sanguinea subsp. australis is native to southeastern Europe and western Asia and is considered alien in other parts of Europe. This study, which was carried out between 2018 and 2022 in the territory of Lithuania, aimed to identify the distribution of the subsp. australis, as well as assess certain reproductive traits and its impact on the species diversity of the invaded communities. The results showed that the cryptic invasion of subsp. australis in Lithuania has been going on for several decades and is now well advanced. We found that the alien subspecies grows faster and that individuals in analogous habitats mature earlier than the native subsp. sanguinea. Furthermore, subsp. australis, compared to subsp. sanguinea, produces more flowers per inflorescence (84.0 +/- 25.0 and 49.7 +/- 20.9, respectively) and sets and ripens more fruits (25.6 +/- 9.7 and 18.2 +/- 7.6, respectively), which are among the most important factors for its further fast spread and invasion. The results of the vegetation analysis showed that the increase in abundance of both subspecies has a negative effect on species diversity in the community. However, the effect of the native subspecies on plant species diversity was negligible, while the effect of the alien subspecies was moderately negative and significant (r = -0.47; p < 0.05). Based on the results of the study, we can conclude that the alien subsp. australis performs better than the native subsp. sanguinea. Considering the current distribution and the drivers of dispersal, we suppose that subsp. australis will continue to spread rapidly in Lithuania and may pose a threat to the native subsp. sanguinea populations

Pietiniuose Latvijos rajonuose aptiktos naujos svetimžemės augalų rūšys

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

Ką mes saugome? Miškinės mėtos (Mentha longifolia) ir artimų rūšių atvejo analizė Lietuvoje

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

Nauji svetimžemiai Cornus (Cornaceae) genties taksonai Lietuvoje ir Latvijoje

Plants of the genus Cornus are valued for their ornamental qualities, are often grown in gardens, parks, or other public plantings, and form various shelterbelts. This increases the likelihood that these bird-dispersed plants will escape from their sites. This paper provides information on the first record of C. mas in Lithuania in 2021 at two sites. This species is currently considered a casual alien species, but may become locally naturalised in the future. This study confirmed that C. sericea is widespread in Lithuania, and the oldest herbarium specimen of the species was collected in 1997. Cornus sericea, like C. alba, is naturalised and potentially invasive in Lithuania. The alien subspecies of C. sanguinea (C. sanguinea subsp. australis) was found for the first time in Lithuania and Latvia in 2018. Available data show that this subspecies is naturalised in both countries, and its abundance in some areas in Lithuania indicates that it may become an invasive plant. The paper discusses dispersal vectors, occupied habitats, and the potential for spreading three alien Cornus taxa

Drivers and Effects of Cryptic Invasion of <i>Cornus sanguinea</i> subsp. <i>australis</i> in Lithuania

Most alien plant species are usually discovered in new areas either immediately or within a relatively short period of time after their introduction. However, the introduction, spread, and invasion of some species go unnoticed for a long time. In Lithuania, such an alien plant is Cornus sanguinea subsp. australis, whose cryptic invasion has gone unnoticed due to its similarity to the native subsp. sanguinea. Cornus sanguinea subsp. australis is native to southeastern Europe and western Asia and is considered alien in other parts of Europe. This study, which was carried out between 2018 and 2022 in the territory of Lithuania, aimed to identify the distribution of the subsp. australis, as well as assess certain reproductive traits and its impact on the species diversity of the invaded communities. The results showed that the cryptic invasion of subsp. australis in Lithuania has been going on for several decades and is now well advanced. We found that the alien subspecies grows faster and that individuals in analogous habitats mature earlier than the native subsp. sanguinea. Furthermore, subsp. australis, compared to subsp. sanguinea, produces more flowers per inflorescence (84.0 ± 25.0 and 49.7 ± 20.9, respectively) and sets and ripens more fruits (25.6 ± 9.7 and 18.2 ± 7.6, respectively), which are among the most important factors for its further fast spread and invasion. The results of the vegetation analysis showed that the increase in abundance of both subspecies has a negative effect on species diversity in the community. However, the effect of the native subspecies on plant species diversity was negligible, while the effect of the alien subspecies was moderately negative and significant (r = −0.47; p australis performs better than the native subsp. sanguinea. Considering the current distribution and the drivers of dispersal, we suppose that subsp. australis will continue to spread rapidly in Lithuania and may pose a threat to the native subsp. sanguinea populations

Lietuvoje aptiktos naujos svetimžemės sumedėjusių augalų rūšys

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

Asclepias syriaca L. (Apocynaceae) and its invasiveness in the southern part of the Boreal region of Europe - evidence from Lithuania

Common milkweed, Asclepias syriaca L. (Apocynaceae), has become a problematic invasive species in southern regions of Europe and has been added to the list of invasive alien species of concern of the European Union. For a long time, this alien species had not been considered a potential invader in the northern regions of the continent. This study is an attempt to evaluate the potential invasiveness of A. syriaca in the southern part of the Boreal biogeographic region of Europe as by observations made in Lithuania. To this point, the plant has been recorded from 38 sites and the total area occupied by its stands is about 1.29 ha in the country. The size of A. syriaca stands at the different sites varies significantly, from a few individuals to stands covering an area of 0.74 ha. Most frequently, A. syriaca occupies anthropogenic herb stands, unmanaged xeric and mesic grasslands, and was recorded from arable field habitats. In eight of the 17 studied sites A. syriaca sets fruit and produces viable seeds. We suppose that stands setting fruit and producing viable seeds are represented by individuals of several genotypes, whereas some quite large stands are represented by vegetative descendants of one single individual and, therefore, fruit set is absent. Although most of the currently known stands are relics of former cultivation or escaped from areas of recent cultivation, at one site it is considered to be of seed origin. As by the quite large number of A. syriaca localities in Lithuania, its intense vegetative spread, and production of fruits and viable seeds, we predict further future spread and invasion in Lithuania. Thus, A. syriaca should also be treated as a potentially invasive species in other locations of the southern part of the Boreal biogeographical region of Europe