On the occurrence and naturalization of Amaranthus hypochondriacus (Amaranthaceae) in some European countries, with notes on its climatic features

The occurrence and invasion status of Amaranthus hypochondriacus in Belarus, Estonia, Italy, the Netherlands, and the North Caucasus were discussed. For Italy, we change the status from casual to naturalized based on living populations which are able to sustain themselves for 5 and over 20 years. Concerning the other countries, we clarified the invasion status of the species (inconsistently reported in literature) indicating it as a casual alien in Belarus, Estonia, and the North Caucasus and naturalized in the Netherlands. Climatic data of the European stations in which Amaranthus hypochondriacus was found were compared with those referring to the native distribution area (Mexico and southeastern regions of the US). The occurrence of the species in Europe appears to be facilitated by the temperate climate (Dutch and Italian localities), which also characterizes the native distribution area (N-America). The occurrence of the species in Estonia, the Netherlands, and the North Caucasus is interesting. In fact, although the types of climates (“Cold, Dfb” and “Temperate, Cfb”) occur in America (northeastern US and central Mexico), there are some differences in precipitation and temperature values, i.e. lower mean precipitation [644.1 mm (Estonia) vs. 1119 mm (N-America); climate Dfb] and lower mean temperature [9.7–11.1 °C (Netherlands and North Caucasus) vs. 15.3 °C (Mexico); climate Cfb].