Alien flora of the Czech Republic is presented. In Appendix 1, 1378 alien taxa (33.4% of the total flora) are listed with information on the taxonomic position, origin, invasive status (casual, naturalized, invasive; a new category post-invasive is introduced), time of immigration (archaeophytes vs. neophytes), habitat type invaded (natural, seminatural, human-made), vegetation invaded (expressed as occurence in phytosociological alliances), mode of introduction into the country (accidental, deliberate), and date of the first record. Number of phytogeographical as well as biological and ecological attributes were compiled for each species in the database; its structure is presented in Appendix 2 as a suggestion for similar work elsewhere. Czech alien flora consists of 24.1% of taxa which arrived before 1500 (archaeophytes) and 75.9% neophytes. There are 891 casuals, 397 naturalized and 90 invasive species. Of introduced neophytes, 21.9% became naturalized, and 6.6% invasive. Hybrids contribute with 13.3% to the total number of aliens, and the hybridization is more frequent in archaeophytes (18.7%) than in neophytes (11.7%). If the 184 hybrids are excluded from the total number of aliens, there are 270 archaeophytes and 924 neophytes in the Czech flora, i.e. total of 1195 taxa. Accidental arrivals account for 53.4% of all taxa and deliberate introduction for 46.6%; the ratio is reversed for neophytes considered separately (45.5 vs. 54.5%). Majority of aliens (62.8%) are confined to human- made habitats, 11.0% were recorded exclusively in natural or seminatural habitats, and 26.2% occur in both types of habitat. Archaeophytes and neophytes occur in 66 and 83 alliances, respectively, of the phytosociological system. Flora is further analysed with respect to origin, life histories, life forms and strategies. Only 310 species (22.4% of the total number of all alien taxa) are common or locally abundant; others are rare, based on a single locality or no longer present. The following 19 taxa are reported as new for the Czech alien flora: Agrostis scabra, Alhagi pseudalhagi, Allium atropurpureum, Bromus hordeaceus subsp. pseudothominii, Carduus tenuiflorus, Centaurea ×gerstlaueri, Centaurea nigra ×phrygia, Cerastium ×maureri, Gilia capitata, Helianthus strumosus, Hieracium pannosum, Hordeum leporinum, Oenothera coronifera, Papaver atlanticum subsp. mesatlanticum, Parietaria pennsylvanica, Polypogon fugax, Rodgersia aesculifolia, Sedum pallidum var. bithynicum, Sedum stoloniferum; these represent results of our own field research as well as of herbaria search, and unpublished data from colleagues. Other 44 taxa are reported as escaping from cultivation for the first time. Twenty two archaeophytes are listed in the Red List of the Czech flora.
A complete list of all alien taxa ever recorded in the flora of the Czech Republic is presented as an update of the original checklist published in 2002. New data accumulated in the last decade are incorporated and the listing and status of some taxa are reassessed based on improved knowledge. Alien flora of the Czech Republic consists of 1454 taxa listed with information on their taxonomic position, life history, geographic origin (or mode of origin, distinguishing anecophyte and hybrid), invasive status (casual; naturalized but not invasive; invasive), residence time status (archaeophyte vs neophyte), mode of introduction into the country (accidental, deliberate), and date of the first record. Additional information on species performance that was not part of the previous catalogue, i.e. on the width of species’ habitat niches, their dominance in invaded communities, and impact, is provided. The Czech alien flora consists of 350 (24.1%) archaeophytes and 1104 (75.9%) neophytes. The increase in the total number of taxa compared to the previous catalogue (1378) is due to addition of 151 taxa and removal of 75 (39 archaeophytes and 36 neophytes), important part of the latter being the reclassification of 41 taxa as native, mostly based on archaeobotanical evidence. The additions represent taxa newly recorded since 2002 and reported in the national literature; taxa resulting from investigation of sources omitted while preparing the previous catalogue; redetermination of previously reported taxa; reassessment of some taxa traditionally considered native for which the evidence suggests the opposite; and inclusion of intraspecific taxa previously not recognized in the flora. There are 44 taxa on the list that are reported in the present study for the first time as aliens introduced to the Czech Republic or escaped from cultivation: Abies concolor, A. grandis, A. nordmanniana, Avena sterilis subsp. ludoviciana, A. ×vilis, Berberis julianae, B. thunbergii, Bidens ferulifolius, Buddleja alternifolia, Buglossoides incrassata subsp. splitgerberi, Buxus sempervirens, Corispermum declinatum, Cotoneaster dielsianus, C. divaricatus, Euphorbia myrsinites, Gleditsia triacanthos, Helleborus orientalis, Hieracium heldreichii, Koelreuteria paniculata, Lonicera periclymenum, Lotus ornithopodioides, Malus baccata, M. pumila, Miscanthus sacchariflorus, Morus alba, Muscari armeniacum, Paeonia lactiflora, Pennisetum alopecuroides, Pinguicula crystallina subsp. hirtiflora, P. grandiflora subsp. rosea, Podophyllum hexandrum, Pyracantha coccinea, Rhodotypos scandens, Rumex patientia × R. tianschanicus ‘Uteuša’, Salix cordata, Sarracenia purpurea, Sasa palmata ‘Nebulosa’, Scolymus maculatus, Spiraea japonica, Tagetes tenuifolia, Thuja occidentalis, Trifolium badium, Vaccinium corymbosum and Viburnum rhytidophyllum. All added and deleted taxa are commented on. Of the total number of taxa, 985 are classified as casuals, 408 as naturalized but not invasive, and 61 as invasive. The reduction in the number of invasive taxa compared to the previous catalogue is due to a more conservative approach adopted here; only taxa that currently spread are considered invasive. Casual taxa are strongly overrepresented among neophytes compared to archaeophytes (76.7% vs 39.4%), while naturalized but non-invasive taxa follow the reversed pattern (18.8% vs 57.4). However, these two groups do not significantly differ in the proportion of invasive taxa. Of introduced neophytes, 250 taxa (22.6%) are considered vanished, i.e. no longer present in the flora, while 23.3% became naturalized, and 4.5% invasive. In addition to the traditional classification based on introduction–naturalization–invasion continuum, taxa were classified into 18 population groups based on their long-term trends in metapopulation dynamics in the country, current state of their populations, and link to the propagule pressure from cultivation. Mapping these population groups onto the unified framework for biological invasions introduced by Blackburn et al. in 2011 made it possible to quantify invasion failures, and boom-and-busts, in the Czech alien flora. Depending on inclusion criteria (whether or not extinct/vanished taxa and hybrids are considered), alien taxa ever recorded in the Czech Republic contribute 29.7–33.1% to the total country’s plant diversity; taking into account only naturalized taxa, a permanent element of the country’s flora, the figure is 14.4–17.5%. Analysis of the dates of the first record, known for 771 neophytes, indicates that alien taxa in the flora have been increasing at a steady pace without any distinct deceleration trend; by extrapolating this data to all 1104 neophytes recorded it is predicted that the projected number would reach 1264 in 2050. Deliberate introduction was involved in 747 cases (51.4%), the remaining 48.6% of taxa are assumed to have arrived by unintentional pathways. Archaeophytes are more abundant in landscapes, occupy on average a wider range of habitat types than neophytes, but reach a lower cover in plant communities. The alien flora is further analysed with respect to representation of genera and families, origin and life history. and Nevejdou se dvě poslední jména autorů