Revision of Nymphaea candida range - new data on the distribution and habitat preferences of the species in southern Poland

The paper presents results of geobotanical and taxonomic studies on the distribution and habitat requirements of Nymphaea candida in southern Poland. The researches were conducted in southern Poland in 2003-2009, in the provinces of Lower Silesia, Lublin, Małopolska, Opole, Silesian province as well as, in southern parts of Mazowieckie and Lubuskie. Flowers, leaves and fruits of Nymphaea species were collected from 27 locations. Altogether pollens from 73 populations of N. candida and 18 of N. alba from all the researched area were measured. The trophic level of an ecosystem was evaluated according to the results of the total nitrogen, total phosphorus, chlorophyll a, transparency and biological parameters. As the result of the studies of more than 200 water bodies, 57 localities of N. candida were documented within the investigation area. The populations of N. candida occupy mid-forest water bodies and river ox-bow lakes. A significant number of populations was also found in artificial reservoirs - fish ponds. The most suitable habitat conditions for N. candida occur in shallow waters in the shore zone with the amplitude of the water column vary from 0.5 to 2 m. Regarding the trophy level, N. candida occupies different habitats, mainly mesotrophic and also eutrophic with high content of organic matters. Considering the 15 checked morphological parameters, especially the stigma diameter, the number of carpellary teeth, flower and pollen diameters, the found and collected specimens of N. candida significantly differ from N. alba. The study confirms that N. candida ocurrs in whole lowland Poland without any regional distribution gaps. According to the IUCN guidelines to species assessment the data gathered during the presented study do not allow to classify N. candida as a vulnerable species in Poland. Still existing populations for more than 150 years, numerous stable locations, abundant populations, a habitat accessibility, a biotope extent, an ecological amplitude against the trophy level and direct human impacts suggest, that the species should be regarded as a least concern (LC) taxon