First record of Pistia stratiotes L. (Araceae) in Croatia, with the consideration of possible introduction pathways

Background and Purpose: The species Pistia stratiotes L. (Araceae) is South American (or pan-tropical) free-floating, aquatic macrophyte, present on all continents, except Antarctica, today. In Europe it occurs occasionally and casually in many countries, but it is established only in thermally abnormal waters in Slovenia, France and Germany. Although it was found in different European countries, even in Slovenia, it has never been recorded in Croatia. Materials and Methods: Floristic research in the Sava-Strmec Special reserve (Zagreb County) was carried out during autumn (September and November) of 2017, using GPS Receiver to determine investigated localities. Results: The species Pistia stratiotes was firstly recorded on 9th September 2017 on one locality in the Sava-Strmec Special reserve (Zagreb County). On 24th and 27th November 2017 several other localities in the vicinity were found. On each locality a small colony of plants was found. Although exact introduction pathway is not known, several possible pathways were taken into consideration and discussed. Conclusion: A first record of the macrophyte Pistia stratiotes for Croatia is reported here. For now, it should be treated as a casual alien species.