Ambrosia artemisiifolia in the Czech Republic: history of invasion, current distribution and prediction of future spread.

We analyse the dynamics of invasion of Ambrosia artemisiifolia (common ragweed), one of the most noxious invasive species in Europe with a great impact on human health. We investigate the habitats and factors that shape its current distribution and specify areas in the Czech Republic endangered by the further spread of this species. The analysis is based on a total of 281 records in 164 grid cells, recorded up to 2016, of which 37 harbour naturalized populations and 127 casual populations. The majority of records (49%) was from railway corridors, followed by human settlements (11%), and there was a recent increase in records from roadsides. A conditional inference tree revealed factors shaping the species distribution with the effect of the proportional area of industrial, commercial and transport units as the most important, highly significant variable, further fine-tuned by factors related to human-related dispersal and climate, such as density of railway network and temperature, respectively. The prediction model indicated that many suitable grid cells are unoccupied. Many of these grid cells are in the proximity of currently occupied ones but there are also some cells rather far from current populations. Further spread of A. artemisiifolia in the Czech Republic is thus highly probable.