Zoltán Barina

In the present study, species were selected from the new Red List of the vascular flora of Hungary which can be regarded as a weed. For each species, current conservation status and the most important traits were assessed. Altogether 149 weed species were found to be at risk according to the International Union for Conservation of Nature (IUCN) categories: 11 species are extinct, 11 are critically endangered, 27 are endangered, 26 are vulnerable, 62 are near threatened and 12 are data deficient. These species belong to 37 plant families, from which the most important are Caryophyllaceae, Brassicaceae, Asteraceae, Scrophulariaceae, Chenopodiaceae, Poaceae and Fabaceae. The most significant chorological elements are Mediterranean (28%) and Eurasian (27%); endemic (Pannonian) taxa constitute only 5.4%. Over 90% of these species are of native or archaeophyte origin, according to their residence time. Considering the main habitat types, 46% of the species are originated from dry habitats, 23% from arable lands, 17.5% from wet habitats and 13.5% from ruderal habitats. In the life form spectra, a pronounced dominance of therophytes (81%) is represented. The factor that currently offers the greatest conflict to the conservation of endangered weed species in Hungary are side effects of strong eradication campaigns against the invasive Ambrosia artemisiifolia.

The introduction and early spread of common ragweed (Ambrosia artemisiifolia L.) in Central and Eastern Europe were reconstructed based on a study of all herbarium specimens of common ragweed deposited at six herbaria in Austria, Hungary and Serbia. More than 450 specimens were examined and the oldest ones, collected from 1907 to 1927, were used to map the historical spread of this highly allergenic invasive weed in this region. The herbarium records back-date the first known introduction of this noxious weed to Central and Eastern Europe as well as its early spread on the Danube-Tisza Plain, and in the North-Eastern part of Hungary. The data also confirm that the introduction of common ragweed to Central and Eastern Europe took place later than its introduction to the Western part of the continent.