Inventory of the alien flora of Slovakia.

This is the first complete inventory of alien vascular plant taxa for the Slovak Republic. The presented database contains information on family affiliation, residence status, invasion status, time of introduction, mode of introduction, planting purpose, abundance and distribution within phytogeographic regions, types of invaded habitats and syntaxa, and life forms and geographical origin of the alien taxa. In total, 21.5% of the total flora is made of up of alien taxa, comprised of 282 archaeophytes that make up 6.6% and 634 neophytes 14.9% of the total number of taxa, respectively. The majority of the alien taxa are casuals (57.6%), 39.1% are naturalized and 3.3% invasive. Most of them come from Europe (32.8%) and Asia (32.8%), followed by Africa (12.2%) and North America (10.8%). The database contains members of 98 families of which the Asteraceae, Brassicaceae, Fabaceae, Poaceae, Amaranthaceae and Rosaceae are the most represented. Almost 50% of the alien taxa are therophytes. Hemicryptophytes (26.3%) and phanerophytes (15.6%) are also abundant. More of the alien taxa were introduced deliberately (49.0%) than unintentionally (43.9%), and the majority were introduced as ornamental plants (55.9%). Of the total number of alien taxa, 45.2% are recorded from less than five localities. Most of them prefer human-made habitats; they are found in 137 phytosociological alliances, with those richest in alien taxa categorized as synanthropic vegetation.