276 ACTA BOT. CROAT. 84 (2), 2025 Acta Bot. Croat. 84 (2), 276–279, 2025 CODEN: ABCRA 25 DOI: 10.37427/botcro-2025-018 ISSN 0365-0588 eISSN 1847-8476 Short communication Stellaria ruderalis (Caryophyllaceae) in the Caucasus, new records and species habitat preferences Pavel Novák1†*, Vojtěch Taraška2†, Veronika Kalníková1,3, Petr Hubatka1, Jaroslav Rohel1, George Fayvush4 1 Masaryk University, Faculty of Science, Department of Botany and Zoology, Kotlářská 2, CZE-611 37 Brno, Czech Republic 2 Moravian Museum, Department of Botany, Hviezdoslavova 29a, CZE-627 00 Brno, Czech Republic 3 Beskydy Protected Landscape Area Administration, Nádražní 36, CZE-756 61, Rožnov pod Radhoštěm, Czech Republic 4 Institute of Botany after the name of A. Takhtajyan NAS RA, Department of Geobotany and Ecological Physiology, Acharyan str. ARM-0063, Yerevan, Armenia Abstract – Stellaria ruderalis (Caryophyllaceae) is an annual herb of the S. media group, recently described in Central Europe and later discovered in other regions of the continent and beyond. Here, we provide novel data on its occurrence in the Caucasus Biodiversity Hotspot, where the species has not been collected since its description as new to science. Stellaria ruderalis was discovered at 14 sites in eastern and central Georgia (2022–2023) and northern Armenia (2023). It inhabited various ruderal habitats as well as deciduous and mixed forests. It is presumably a common component of the regional flora, although overlooked to date. Thus, its tentative IUCN classification is proposed here as Data Deficient (DD). Keywords: biogeography, Caucasus, flora, habitat, Stellaria media agg. Introduction The Caucasus is a mountainous region forming a boundary between Europe and Asia. For its extraordinarily diverse biota, it is considered one of the 36 global biodiver- sity hotspots. Its rich vascular plant flora (~6400 species) has an endemism rate of ~25%, and the related vegetation and habitat diversity is also considerably high. Armenia and Georgia are countries in the South Caucasus, whose floras harbour a significant portion of the taxonomic richness of the hotspot (Mittermeier et al. 2004). Despite intensive re- search of the regional flora, which has a two-century-long tradition, many neophytes have been discovered only re- cently (e.g. Kikodze et al. 2010). Examples of regionally nov- el species are those recently described as new to science (e.g. Piwowarczyk et al. 2023), belonging to which is Stellaria ruderalis M. Lepší, P. Lepší, Z. Kaplan et P. Koutecký. This allotetraploid taxon of the Stellaria media group ( Caryophyllaceae, Alsinoideae) is an annual or winter annual herb, mainly flowering from March to May. Individuals then finish their life cycle, persisting in the dry summer and autumn periods exclusively in a seed bank. Members of the group are native to Eurasia and North Africa. However, re- gional differences in their inner taxonomic division do not allow adoption of individual species’ distribution without careful investigation of herbarium material or living plants. The current concepts of European members of the group recognize S. media (L.) Vill. (s. str.; 2n = 4x = 40), S. pallida (Dumort.) Crép. (2n = 2x = 22), S. neglecta Weihe (2n = 2x = 22), S. cupaniana (Jord. & Fourr.) Béguinot (2n = 2x = 22; sometimes merged with the previous species), and the most recently described species S. ruderalis (2n = 4x = 44) (Lepší et al. 2019, El Mokni et al. 2023). Plants of the Stellaria media group are a frequent component of various habitats in the Caucasus, including various natural (forests) as well as artificial habitats (trampled sites, road margins, railways, fields), shaded or open (Novák et al. 2023). Our knowledge of the global distribution of S. ruderalis is still far from com- plete. The species was described from the Czech Republic, and was known to occur in Central Europe (Lepší et al. 2019, Novikov et al. 2020, Dudáš et al. 2022), but it has also * Corresponding author e-mail: pavenow@seznam.cz † These authors contributed equally to this work STELLARIA RUDERALIS NEW FOR THE CAUCASUS ACTA BOT. CROAT. 84 (2), 2025 277 been recorded in the European Mediterranean Basin, in- cluding Sardinia, the Balkans (Lepší et al. 2019) and the Iberian Peninsula (Sáez 2020), as well as Tunisia (El Mokni et al. 2023), Algeria and Morocco (GBIF 2024) in North Africa. There have been no published reports on S. ruderalis for the Caucasus to date, nor there are any entries for this species in databases Euro+Med (2006–2023) and POWO (2024). On the other hand, four vouchers collected in Trans- caucasia (Armenia, Georgia) and stored under the name S. media in the herbarium of the Natural History Museum in Vienna (W) have recently been revised as S. ruderalis by J. Walter (GBIF 2024). Moreover, plants with similar seed morphology and chromosome number of 2n = 44 from Tbilisi were mentioned by Peterson (1936). This evidence suggests the long-standing occurrence of this species in the area. Still, field observations of the species in the Caucasus are missing since it was described as new to science, and there are no data on its distribution, abundance, and habitat preferences in that area. The main goal of our contribution is to report new sites of Stellaria ruderalis discovered in Armenia and Georgia since 2022, provide their ecological circumstances and dis- cuss the species’ position in the context of regional biodi- versity. Material and methods We collected Stellaria ruderalis in Armenia and Geor- gia during botanical field expeditions in 2022 and 2023. We documented each site of the species with a herbarium spec- imen and acquired its precise geographical position (WGS 84) and elevation by a GPS receiver. Phytosociological rele- vés were recorded in several sites and stored in the Trans- caucasian Vegetation Database (Novák et al. 2023). Soil pH is provided for these sites, which were analysed from dried samples of topsoil (upper 15 cm) in a suspension with de- ionized water (2:5) by a portable Greisinger instrument. The herbarium specimens were studied morphologically in detail and afterwards stored in the herbaria of Masaryk University, Brno (BRNU), Moravian Museum, Brno (BRNM), and the National Herbarium of Georgia, Botani- cal Institute of Ilia State University, Tbilisi (TBI). Revisions of all reported herbarium specimens were carried out by Z. Kaplan (Institute of Botany, Czech Academy of Science), one of the authors of the S. ruderalis description (Lepší et al. 2019). The nomenclature follows Euro+Med PlantBase (Euro+Med 2006–2023) for plants and EuroVegChecklist (Mucina et al. 2016) for vegetation syntaxa. To provide ba- sic climatic characteristics, we extracted climatic data for the sites from Worldclim 2.1 Bioclim (spatial resolution of 30 seconds). They included BIO1 Annual Mean Tempera- ture and BIO12 Annual Precipitation (Fick and Hijmans 2017). Results and discussion Stellaria ruderalis has been discovered at 14 sites (Fig. 1) within the Caucasus Biodiversity Hotspot in Armenia and Georgia since 2022. Based on the aforementioned sources, it should be considered a new member of the regional flora. Below, we provide an overview of our findings of the species in both countries (Fig. 1, On-line Suppl. Tab. 1). Sites and their environmental conditions In Armenia, Stellaria ruderalis was discovered in the forested northeastern part of the country (860–1060 m a.s.l.). The measured topsoil pH at its sites was 5.29–6.82, i.e. moderately to slightly acidic reaction. The site annual mean temperature was 9.1–9.6 °C (median 9.6 °C), while an- nual precipitation was amounted to 507–537 mm (median 518 mm). In Georgia, we report S. ruderalis from ten sites across the central and eastern parts of the country in steppes as well as within deciduous and coniferous forest zones (410–1600 m a.s.l.). Its populations thrive in contrasting climatic conditions, including sub-Mediterranean and mountain continental types. The sites’ annual mean tem- perature was 5.6–12.3 °C (median 8.6 °C), while the amount of annual precipitation was 516–926 mm (median 727 mm). Our observations indicate that the species may grow along the whole elevation gradient of natural forests. Habitats Armenian sites consisted of deciduous mesophilous (phytosociological class Carpino-Fagetea) and xeromesoph- ilous forests (Quercetea pubescentis). The species was col- lected in forests dominated by Carpinus betulus and C.  orientalis where it preferred spots with a topsoil disturbed by freely-grazing cows, like other annuals (e.g. Galium aparine, Geranium lucidum, Viola arvensis). Analogically, it was revealed in Georgian deciduous and mixed mesophilous forests (Carpino-Fagetea) with Acer velutinum, Carpinus Fig. 1. Distribution of the reported Stellaria ruderalis sites (red triangles) in Georgia and Armenia. A boxplot provides median (bold line), interquartile range (box) and range of values (whis- kers) of elevation of the sites. NOVÁK P., TARAŠKA V., KALNÍKOVÁ V., HUBATKA P., ROHEL J., FAYVUSH G. 278 ACTA BOT. CROAT. 84 (2), 2025 betulus, C. orientalis and Picea orientalis. They included both ruderalized types with understory dominated by shade-tolerant nitrophytes in Tbilisi (Fig. 2) and well-pre- served forest types in the Lagodekhi (Greater Caucasus) and Rkoni (Lesser Caucasus) surroundings. However, most of the Georgian sites consisted of various frequently disturbed and slightly shaded artificial habitats like road embankments, from the colline to the upper mountain belt, with the highest site of the whole dataset at the elevation of 1600 m (Lesser Caucasus). Sparse thermo- philous trampled vegetation in a city pavement (Digitario sanguinalis-Eragrostietea minoris) harboured S. ruderalis in Mtskheta near Tbilisi. Our observations are aligned with the reported species' ecology (Lepší et al. 2019). Conservation status and prospective for further research Stellaria ruderalis used to be mentioned as S. media (Lepší et al. 2019). The latter species was also found during our surveys in Georgia (e.g. Levitana village, Shida Kartli Region; BRNM 845570). The distribution and ecological differentiation of both species remain unclear in the Cau- casus due to this confusion. S. ruderalis appears widespread in the investigated regions, having a broad habitat and cli- matic niche, although overlooked to date. Further investi- gations in the field and public herbaria are needed to sup- port this assumption. Therefore, we propose a tentative classification of S. ruderalis as Data Deficient (DD) accord- ing to the IUCN Red List guidelines (IUCN 2024) for Ar- menia and Georgia. Acknowledgement This paper was published on the occasion of the 100th anniversary of Acta Botanica Croatica. We thank Zdeněk Kaplan for his kind revisions of the reported herbarium specimens and Manana Khutsishvili from the National Herbarium of Georgia for storing the specimens in the herbarium. Otar Abdaladze, Ketevan Bat- satsashvili and Jana Ekhvaia kindly provided regional lit- erature. Two anonymous reviewers are acknowledged for their valuable remarks on the early manuscript. The study was supported by the Czech Science Foundation (project 19-28491X). The contribution by V. Taraška appears through the institutional support of long-term conceptual development of research institutions provided by the Min- istry of Culture of the Czech Republic (ref. MK000094862). Author contribution statement P.N. and V.T. share the first authorship, they wrote the initial draft of the manuscript, the former additionally com- piled the figures and managed data from GIS layers while the latter solved the taxonomic and biogeographic issues. 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