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Despite long-term research, the aquatic genus Nymphaea still possesses major taxonomie challenges. High phenotypic plasticity and possible interspecific hybridization often make it impossible to identify individual specimens. The main aim of this study was to assess phenotypic variation in Nymphaea taxa sampled over a wide area of Eastern Europe and temperate Asia. Samples were identified based on species-specific genome sizes and diagnostic morphological characters for each taxon were then selected. A total of 353 specimens from 32 populations in Poland, Russia and Ukraine were studied, with nine biometric traits being examined. Although some specimens morphologically matched N. xborealis (a hybrid between N. alba and N. Candida) according to published determination keys, only one hybrid individual was revealed based on genome size data. Other specimens with intermediate morphology possessed genome size corresponding to N. alba, N. Candida or N. tetragona. This indicates that natural hybridization between N. alba and N. Candida is not as frequent as previously suggested. Our results also revealed a considerably higher variation in the studied morphological traits (especially the quantitative ones) in N. alba and N. Candida than reported in the literature. A determination key for the investigated Nymphaea species is provided, based on taxonomically-informative morphological characters identified in our study.
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.
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