Amaranthus emarginatus - a new species to the flora of the Czech Republic and notes on its occurrence in Slovakia, Hungary and Austria

Amaranthus emarginatus, a species of the A. blitum agg. was found new to the flora of the Czech Republic, where it occurs in two subspecies - A. e. subsp. emarginatus and A. e. subsp. pseudogracilis. The subsp. emarginatus is reported here as a taxon also new to Slovakia, Hungary and Austria. Amaranthus emarginatus has become a naturalized species in the Central European countries investigated over the past 30 years, colonizing mainly river banks and alluvial deposits. The majority of reported and studied individuals belong to subsp. pseudogracilis, which was documented from all these countries as early as in the 1980s. The first specimen of subsp. emarginatus was collected in 1994 and is very rare here. It grows mainly on banks of the Morava River in the Czech Republic, Slovakia and Austria, and was also discovered on the banks of the Danube River at a single site in Hungary. It is mostly found co-occurring with subsp. pseudogracilis, but slightly differs in its ecological requirements and has not been found in agricultural habitats. None of the mature specimens studied showed morphological transitions between A. blitum and A. emarginatus, neither between subspecies A. e. subsp. emarginatus and subsp. pseudogracilis.