Distributions of vascular plants in the Czech Republic. Part 3.
The third part of the publication series on the distributions of vascular plants in the Czech Republic includes grid maps of 105 taxa of the genera Acorus, Amelanchier, Asplenium, Calla, Cerastium, Ceratophyllum, Eichhornia, Hieracium, Hippuris, Hottonia, Lemna, Limosella, Peplis, Pistia, Pontederia, Sorbus, Spirodela, Symphytum, Trapa, Valerianella and Wolffia. The maps were produced by taxonomic experts based on all available herbarium, literature and field records. Three of the studied genera include Czech endemics, which are confined to small geographic areas, mostly have small population sizes and thus are of conservation concern. These maps resulted from detailed fieldwork and herbarium revisions by monographers of the respective groups and for many of these endemics they are first available maps. The endemic species of Hieracium occur mainly in the subalpine habitats in the Krkonoše, Králický Sněžník and Hrubý Jeseník Mts. By contrast, a great majority of Sorbus endemics are found mainly in thermophilous open broad-leaved and pine forests on rocky habitats at middle altitudes. Cerastium alsinifolium is confined in its total distribution to serpentine outcrops in western Bohemia. Asplenium is another ecologically specialized group, which includes petrophytes, some of which are restricted to specific substrates, such as siliceous, limestone, basalt or serpentine rocks. The plants studied include 53 taxa classified in the Red List of vascular plants of the Czech Republic, some of which have shown remarkable declines. Symphytum bohemicum, distributed mainly in central Europe, is confined to calcareous fens in the lowlands. There are many endangered and vulnerable species amongst aquatic plants, which are threatened mainly by fish-farming intensification, eutrophication and habitat destruction. Populations of some of the most endangered and attractive aquatics, including Hippuris vulgaris and Trapa natans, have been lost and locally replaced by plants of unknown provenance purchased in garden stores, which causes a potential threat of genetic erosion of native populations. Attractive appearance is the reason why alien aquatics, such as Eichhornia crassipes, Pistia stratiotes and Pontederia cordata, are sometimes planted not only in garden pools but also in wetlands in the countryside; each has been recorded at about a dozen such sites during the past 25 years. Lemna turionifera, by contrast, has been introduced and dispersed by waterfowl and is now widespread in the country. The histories of the introduction and subsequent spread are also described and analysed for the widespread neophyte Acorus calamus and for the alien species of Amelanchier and Symphytum. Spatial distributions and temporal dynamics of individual species are shown in maps and documented by records included in the Pladias database and available in electronic appendices. The maps are accompanied by comments, which include additional information on the distribution, habitats, taxonomy and biology of the species.