Distributions of vascular plants in the Czech Republic. Part 10

The 10th part of the series on the distributions of vascular plants in the Czech Republic includes grid maps of 44 taxa in the genera Carex, Colchicum, Cytisus, Draba, Dracocephalum, Jurinea, Klasea, Lactuca, Onopordum, Petrorhagia, Serratula, Silybum and Xanthium. These maps were produced by taxonomic experts based on examined herbarium specimens, literature and field records. Both native and alien species are represented. Particular attention was paid to critically threatened species. Carex macroura has been documented in the Czech Republic from only two populations in northern Bohemia. The nearest populations in its core range in Russia are separated by a gap of about 2,500 km. Dracocephalum austriacum has been recorded at about 14 sites, with the majority of populations confined to the karst area of Český kras in central Bohemia. About 25 populations of Jurinea cyanoides were known in the past in the Labe river basin in central Bohemia. Of these, only one population has survived but it is declining despite intensive conservation management. The facultative halophyte Lactuca saligna has been recorded at more than a hundred sites in the past but was observed at only nine sites in 2020. In contrast, the previously rare Draba muralis and D. nemorosa have spread along railways during the past decades. Several neophytes, including Dracocephalum thymiflorum and Lactuca tatarica, have accidentally been introduced with grain or iron ore from the former USSR during the second half of the 20th century. Some archaeophytes, such as Lactuca serriola and Onopordum acanthium, are naturalized and widespread in this country, others, such as Xanthium strumarium, used to be established and rather frequent in the past but have declined sharply due to changes in land use. Two species are reported here as new for the Czech flora. Carex agastachys was identified as a result of examination of herbarium specimens formerly assigned to C. pendula; it is distributed mainly in the Carpathian part of this country. The Mediterranean species Petrorhagia dubia is reported here as a new alien species in the Czech Republic, identified based on revision of a herbarium specimen collected in 1934 in the city of Brno. In contrast, examination of herbarium specimens of Xanthium revealed that X. orientale was reported erroneously from the Czech Republic, based on misidentification of X. saccharatum. Spatial distributions and often also temporal dynamics of individual taxa are shown in maps and documented by records included in the Pladias database and available in electronic appendices. The maps are accompanied by comments that include additional information on the distribution, habitats, taxonomy and biology of the taxa.