Aquatic alien plants in Poland
Limnobium laevigatum (Hydrocharitaceae), Pistia stratiotes (Araceae: EPPO A2 List) and Pontederia crassipes (Pontederiaceae: EPPO A2 List) were recently recorded as casual species in an artificial pond in the Bieżanów-Prokocim district, of the eastern part of Kraków, Poland.
Limnobium laevigatum is a free-floating or rooted perennial freshwater plant native to tropical areas of Central and South America. It usually occurs in rivers, lakes, swamps, canals, and ponds. Mature plants grow up to 50 cm tall with emergent leaves and solitary or paired white, unisexual flowers. It reproduces sexually by seeds and vegetatively by fragmentation of stolons. It has been introduced into North America, Europe, Asia, Africa, and Australia, where it is often used as an ornamental plant in aquaria and artificial ponds. In the EPPO region, it is recorded as casual in Belgium and Hungary. This is the first record of L. laevigatum in Poland.
Pontederia crassipes is a free-floating perennial freshwater plant native to tropical areas of South America. It reproduces sexually by seeds and vegetatively by fragmentation of stolons. It has been introduced to North America, Europe, Africa, Asia, and Australia. In the EPPO region, it is invasive in Portugal, Spain, France, and Italy. In many other countries, it is reported as a casual or naturalised species. This is the first record of P. crassipes in Poland.
Pistia stratiotes is a free-floating aquatic species with an ambiguous native range: potentially South America or pan-tropical occupying a native range across the tropical and subtropical regions of Asia, Africa, Australia and South America. It is invasive in Africa, Asia and Australia. It is present in a number of EPPO countries and is regarded as invasive in Italy and France.
All three species can form dense mats which can reduce native species diversity and negatively effect ecosystem services. In the artificial pond, L. laevigatum covered about 35% of the water surface and P. crassipes coupled with P. stratiotes covered approximately 5 % of the water surface. All species were probably dumped in the pond and follow-up surveys should be conducted to check if the population persists.
Sources
Pliszko A, Gόrecki A (2021) First record of Limnobium laevigatum (Humb. & Bonpl. ex Willd.) Heine (Hydrocharitaceae) and Pontederia crassipes Mart. (Pontederiaceae) in Poland. BioInvasion Records 10 (in press). https://www.reabic.net/journals/bir/2021/Accepted/BIR_2021_Pliszko_Gorecki_correctedproof.pdf