361
Abstract
We have analyzed structural and dynamic characteristics (production, 
morphometric parameters, phytocoenotic features and invasive behavior) of two 
locations with the alien species Pistia stratiotes L. in different types of water bodies, 
by origin, use and trophic status (a drainage canal and oxbow lake) in the outskirts 
of Kyiv. It is possible that in the case of increased anthropogenic eutrophication 
due to inorganic nitrogen, mother plants become smaller and more compact. The 
variability of morphological features increases. We also have distinguished growth 
of invasive potential of the species in the conditions of the water bodies of the 
region.
Izvleček
V članku smo analizirali strukturne in dinamične značilnosti (proizvodnja, 
morfometrični parametri, fitocenološke značilnosti in invazivnost) na dveh 
lokacijah, kjer uspeva tujerodna vrsta Pistia stratiotes L., v različnih vodnih telesih 
glede na nastanek in trofičnost (odvodni kanal in mrtvica) na obrobju Kijeva. 
Mogoče je, da v primeru povečane antropogene evtrofikacije s strani anorganskega 
dušika materinske rastline postanejo manjše in bolj kompaktne rasti, poveča se 
raznolikost morfoloških značilnosti. Prav tako smo opazili povečanje potenciala 
invazivnosti vrste v vodnih telesih preučevane regije. 
Ecological features of the alien species 
Pistia stratiotes L. in different habitats of 
the secondary distribution range (Ukraine)
Key words: invasive species, 
macrophytes, aquatic ecosystems, 
morphometric parameters.
Ključne besede: invazivne vrste, 
makrofiti, vodni ekosistemi, 
morfometrični parametri.
Corresponding author:
Mariana Prokopuk
E-mail:  
maryanaprokopuk406@gmail.com
Received: 20. 10. 2021
Accepted: 4. 2. 2022
1 Institute for Evolutionary Ecology, National Academy of Sciences of Ukraine, Kyiv, Ukraine.
Mariana Prokopuk1, Lesya Zub1
DOI: 10.2478/hacq-2022-000121/2 • 2022, 361–370
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Ecological features of the alien species Pistia stratiotes L. in different habitats
Introduction
During the twentieth century, the basic climatic con-
ditions of Europe have undergone significant changes. 
Thus, in Ukraine, the average annual air temperature in-
creased in the eastern region by 2.7–2.8 ºC, in the north-
western region by 1.1–1.7 ºC (FCCC, 2009). The effects 
of such climate change are the spread of thermophilic 
invasive species. Convenient corridors for the invasions 
of southern alien species are aquatic ecosystems: they are 
azonal, open to intrusion due to the network structure, 
have free ecological niches owing to significant anthro-
pogenic transformation.
Pistia stratiotes L. is one of pantropic invasive hydrobi-
onts in the Europe’s hydrographic networks. It is a poten-
tially dangerous alien species which responds positively 
to the gradual increase in average annual water tempera-
tures and has been on the EPPO list of invasive plants 
since 2012 (Chapman at al., 2017). In 2016, P. stratiotes 
was identified as a priority for risk assessment in accor-
dance with the requirements of Regulation 1143/2014 
(Branquart et al., 2016; Tanner et al., 2017). P. stratiotes 
presents a high phytosanitary risk for the endangered 
area within the EPPO region with a low uncertainty. The 
overall probability that P. stratiotes will continue to enter 
the EPPO region is high, as this species is widely cul-
tivated and constantly traded within the EPPO region 
(EPPO, 2018).
Pistia stratiotes is a member of a monotypic genus of 
the Araceae family. It is a free-floating macrophyte whose 
biological and ecological features contribute to its rapid 
development and ability to expand (Aston, 1973; Cook 
et al., 1974; Holm et al., 1977; Sainty & Jacobs, 1981; 
Neuenschwander et al., 2009). 
Invasions of this species in European water bodies be-
gan at the end of the previous century. The facts of nu-
merous finds in Europe of this period are determined in 
the Netherlands, Denmark, Germany; in France, Spain, 
Italy – one-time finds are known (Mennema, 1977; 
Diekjobst, 1984; Pilipenko, 1993; Murillo et al., 2005; 
Verloove, 2006; Šajna et al., 2007; Brundu et al., 2012; 
Hussner, 2012; Boršić & Rubinić, 2018; Jaklič at al., 
2020). These are cases of successful naturalization of the 
species in thermal waters (Šajna et al., 2007). The plant 
appears in shallow and warm urban water bodies of more 
continental regions (Eastern Europe) during abnormally 
hot summers or water bodies which receive technically 
heated water (Barmin & Kuzmina, 1993; Prokopuk & 
Zub, 2020). The facts of naturalization of the species in 
Eastern Europe are unknown.
Ways of penetration of the species into secondary range 
were different. i.e. escape from confinement (the species is 
popular in aquaria, in outdoor garden pools and other or-
namental ponds), and release in nature (deliberate intro-
duction by amateurs) (Scalera & Genovesi, 2016). Inter-
connected waterways are excellent penetration corridors. 
The plant is also spread by water flows and wind over long 
distances in slow-flowing rivers and stagnant waters. 
The species can be transmitted by birds, which en-
ables vegetative and generative diasporas of P. stratiotes 
to overcome significant distances between isolated water 
bodies (Adebayo et al., 2011). One of the mechanisms 
of invasive dominance of the species in aquatic phyto-
coenoses is considered to be allelopathic interaction with 
representatives of the local aquatic flora (Aliotta et al., 
1991). In the secondary range, P. stratiotes is able to pro-
duce seeds (Šajna et al., 2007; Neuenschwander et al., 
2009; Buzgo, 2015; Jaklič et al., 2020), but more often P. 
stratiotes reproduces vegetatively. It forms small colonies 
with daughter plants attached to the mother plant with 
stolons, developing in the axils of the lower leaves. Dis-
tribution is enhanced by separation of daughter plants, 
which form new colonies.
It is due to the intentional release of P. stratiotes that it 
entered the water bodies and water streams of Ukraine. 
Phytoinvasion of P. stratiotes in natural water bodies is fa-
cilitated by a high concentration of man-made objects in 
the region with water use with the subsequent return of 
its to natural reservoirs (Dubyna & Ustymenko, 2014). 
There are general trends towards further invasive spread 
of water lettuce in Ukraine and adjacent territories (Mo-
syakin & Kazarinova, 2014). This fact makes it relevant 
to study the biology and ecology of the species in the re-
gional conditions.
The basis of the distribution management of P. stratiotes 
is a comprehensive study of the distribution patterns of 
this species within the secondary range and determina-
tion of key factors in enabling invasive potential. Indi-
cators of the viability of the invasive species in the new 
conditions are its structural and dynamic characteristics: 
reproduction rate, density, phytomass produced, mor-
phometric parameters, the ability to form adapted eco-
morphs in variable environmental conditions and others. 
Our research is aimed to determine the regional fea-
tures of morphology, phenotypic variability and produc-
tion indicators of the species depending on the habitat of 
distribution. We want to show that in the conditions of 
the secondary range the type of biotope determines the 
invasive properties of P. stratiotes and the potential ability 
to naturalization.
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Material and methods
Study area
The research was conducted on the southern border of 
Kyiv within the left-bank floodplain of the Dnipro River 
(Figure 1). Kyiv is located on the border of forest and 
forest-steppe physiographic areas. The area of the city is 
836 km2. The Dnipro and its floodplain are the natural 
axis of the city. The urban areas along the coast are over 
20 km long. The climate is moderately continental, with 
mild winters and warm summers. The average monthly 
temperatures in January are −3.5 °C, in July +20.5 °C. 
The average annual precipitation is 649 mm, with the 
maximum precipitation in July (88 mm) and the mini-
mum one in October (35 mm). In winter, snow covers 
Kyiv with the average snow height in February of 20 cm 
and the maximum one of 440 cm (Osadchyy et al., 2010).
During 2013–2021, we monitored the spread of alien 
macrophytes in water bodies of the city and its outskirts 
(Prokopuk & Zub, 2020). Two locations of the species 
were selected for the structural analysis: (i) in the lothic 
artificial water body – the drainage canal of the Bortny-
tchy protective dam; (ii) in the lentic natural water body 
– a floodplain water body of the Dnipro River – Zoloche 
Lake. 
In order to hydrotechnically protect the suburban resi-
dential areas of the Dnipro River left bank from floods of 
the Kaniv water body, the Bortnytchy protective dam was 
built, with a drainage canal. It is nearly 16 km long, and 
it is connected through 5 cross regulators with the Dnipro 
River down the city of Kyiv.
Zoloche Lake is an oxbow 
lake of the Dnipro River 
floodplain. Today it is trans-
formed in the process of ur-
ban planning, it is deepened, 
and one of the components of 
the drainage hydraulic system 
and has a hydraulic connec-
tion with the Dnipro River 
through the cross regulator. 
Field sampling
The materials were the results 
of population studies with two 
locations of P. stratiotes in hab-
itats characterized by different 
hydrological and trophic con-
ditions:
– drainage canal (two  research 
sites – 50° 17' 05.5" N, 
30° 41' 16.5" E; 50° 17' 
58.5" N, 30° 40' 09.8" E) 
– lotic type, mesotrophic 
waters.
– floodplain water body (three 
research sites – 50° 18' 
29.6" N, 30° 42' 18.2" E; 
50° 18' 34.9" N, 30° 42' 
19.0" E; 50° 18' 25.0" N, 
30° 41' 56.5" E) – lentic 
type, eutrophic waters.
Locations were selected ac-
cording to the criterion where 
the peak of P. stratiotes devel-
opment was the largest dur-
Figure 1: Location of the studied territory in Ukraine (A – on the map of Europe; B – the outskirts of 
Kyiv; C – drainage canal and oxbow lake. Red dots indicate Pistia stratiotes locations).
Slika 1: Lokacija znotraj območja raziskav v Ukrajini (A – na zemljevidu Evrope; B – obrobje Kijeva; 
C – odvodni kanal in mrtvica. Rdeče točke označujejo lokacije z vrsto Pistia stratiotes.
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Ecological features of the alien species Pistia stratiotes L. in different habitats
ing the studied period, as well as where the reappear-
ance of the species was confirmed. There were exactly 5 
of them. The research was conducted during the grow-
ing seasons in October 2019–2021 by general hydrobot-
anical methods (Fasset, 1969; Wood, 1975). Phytomass 
samples were selected at the end of the growing season 
(October 2020), when the species reached its maximum 
distribution, and local populations – the maximum den-
sity and phytomass. Samples were selected at all research 
sites from the test plots with an area of 0.25 m² in sites 
with the highest density of mats with subsequent drying 
to air-dry phytomass. The sample for the calculation of 
morphometric data was taken from the same samples. 
Morphometric indicators of 351 maternal and 57 filial 
plants in the floodplain have been analyzed; 150 mater-
nal and 270 filial plants – in the drainage channel. The 
number of adult and filial plants, rosette leaves and veins 
on the leaf surface was counted. Evaluation of morpho-
metric parameters included measurements of the size of 
roots, rosettes, leaves of maternal, and filial plants. The 
presence of flowers in plants was recorded.
The research was performed with recording water tem-
perature, basic hydrochemical and tropho-saprobiological 
characteristics. Hydrochemical measurements were per-
formed using a PH-meter/OVP-meter/conductometer/
TDS-meter EZODO 8200M. We measured conductiv-
ity, ion content of dissolved salts, total mineralization 
and pH. Water was studied for nutrient content by the 
colorimetric method using the DR/890 Colorimeter. We 
measured concentration of NO2
–, NO3
–, NH4
+, PO4
3- in 
water. Water samples were taken from the near-surface 
layer once in the period of sampling Pistia phytomass. 
Tropho-saprobiological type of water bodies was deter-
mined according to Romanyuk et al. (1998).
Data analysis
The results of the research were processed by the Princi-
pal component analysis PCA performed using the ‘ade4’ 
package (Dray & Dufour, 2007) in R software (R Core 
Team, 2020). Considering different units of variables, 
e.g. length and number, we have chosen a normed PCA 
that bases on scored and centered variables. Two pairs of 
coordinates obtained in the PCA were used to draw a cor-
relation circle, or variables scores, that is a superposition 
of principal components and column scores, and factor 
map that is the superposition of principal axes or variable 
loadings and row scores. Factor map was plotted for (i) 
individual plants, (ii) maternal and filial plants, (ii) and 
two studied water bodies.
We used nested analysis of variance ANOVA to assess 
the effect of two factors, a plant type and water body, on 
plants’ morphological traits. The plant type factor was 
nested within the water body factor and six plants’ traits 
were the response variables. The analysis was performed 
using ‘stats’ package for R (R Core Team, 2020).
Scientific names of plant species are given in accord-
ance with the International Plant Names Index (IPNI, 
2021).
Results
Until 2020, macrophytes in the drainage canal in the 
areas without engineering shore protection and with 
shallow water, were represented by coastal fragmentary 
mats of Phragmites australis (Cav.) Trin. et Steud., Glyce-
ria maxima (C. Hartm.) Holmberg, Typha angustifolia L. 
and, occasionally – Typha latifolia L. Among the mats of 
helophytes there are synusia of duckweeds (Lemna mi-
nor L., Spirodela polyrhiza (L.) Schleiden, Hydrocharis 
morsus-ranae L. and Salvinia natans L. The next vegeta-
tion belt, also fragmentary, is formed by communities of 
Nuphar lutea (L.) J.E. and Trapa natans L. In some places 
there are separate curtains of Sparganium erectum L. The 
basis of hydrophytes in early summer are co-dominant 
communities of Elodea canadensis Michx. and Cerato-
phyllum demersum L., Najas marina L., Myriophyllum spi-
catum L., Potamogeton perfoliatus L., Stuckenia pectinata 
(L.) Borner, and Caulinia minor (All.) Coss. Stratiotes 
aloides L. coenoses have developed in the areas protected 
by emergent plants. Since 2015, the canal has witnessed 
Elodea nuttallii (Planch.) H. St. John, which sometimes 
replaced Elodea canadensis. At the end of summer, one 
can see single specimens of Egeria densa (Planch.) Casp.
Until 2020, vegetation of Zoloche Lake was typical 
for floodplains of the region: after the belt of helophytes 
composed of P. australis, G. maxima and T. angustifolia, a 
belt of plants with floating leaves forms dominated by N. 
lutea and N. alba L., with separate rosettes of T. natans 
and among submerged macrophytes there are coenoses 
of P. perfoliatus, M. spicatum, and E. canadensis. In 2014-
2015 there was a boom of E. densa, in subsequent years 
there were only a few specimens of the plant.
At the end of the growing season (September-October) 
in 2020, both water bodies underwent a complete change 
in the phytocoenotic pattern of vegetation: P. stratiotes 
formed dense monodominant mats with a total cover per-
centage of 100%. Its growth covered the water surfaces 
with a continuous mat (Figure 2), with other hydrophytes 
occurring not often.
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Ecological features of the alien species Pistia stratiotes L. in different habitats
Mass development of P. stratiotes was accompanied by 
low concentrations of inorganic nitrogen in the waters of 
the drainage canal (Table 1). Excess of organic matter here 
determined the content of inorganic phosphorus, with an 
excess of nitrates and phosphates within the oxbow lake.
In the studied locations, large amounts of phytomass 
of mats of the species are formed. In the canal they were 
6.16 kg/m² (raw phytomass)/0.319 kg/m² (air-dried), 
and in the floodplain Zoloche Lake these indicators were 
lower – 5.53/0.278 kg/m², respectively. On average, 222 
plants in the canal and 231 in the floodplain water body 
were recorded per 1 m².
The largest maternal plant was recorded in the flood-
plain lake with a rosette size of 49 cm in diameter and 
with 13 leaves and the root of 18 cm in length. The larg-
est plant in the canal was a plant of 30 cm in diame-
ter with 14 leaves and the root of 35 cm in length. The 
Figure 2: General view of the surface of the studied water objects with mats of P. stratiotes: a drainage canal in the area of gateway-regulator № 3 
(August, 2020) (left); Zoloche floodplain Lake (October, 2020) (right); Kyiv, Ukraine.
Slika 2: Pogled na površino raziskovanih vodnih teles, prekritih z vrsto P. stratiotes: odvodni kanal na območju uravnalnih vrat št. 3 (avgust 2020) 
(levo); jezero na poplavni ravnici Zoloche (oktober 2020) (desno); Kijev, Ukrajina.
Table 1: Physico-chemical and tropho-saprobiological charac-
teristics of the studied habitats 
Tabela 1: Fizikalno-kemične in trofično-saprobiološke značil-
nosti raziskovanih habitatov.
Habitat type Drainage canal Floodplain water 
body
pH 7.6 8.8
Conductivity, µS 416 231
Total mineralization, ppm 269 308
Salt, (mg\dm³) 207 186
NO2
– (mgN\dm³) 0.001 0.041
NO3
– (mgN\dm³) 0.1 3.4 
NH4
+(mgN\dm³) 0.01 0.21 
PO4
3–(mgP\dm³) 0.34 2.75 
Temperature (°C) +9 +9
Saprobity β' – mesosaprobic β" – mesosaprobic
Trophicity mesotrophic eutrophic 
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Ecological features of the alien species Pistia stratiotes L. in different habitats
smallest ones were 6 cm in diameter in the canal and 
2.5 cm in the floodplain lake. 
The average morphometric parameters of P. stratiotes 
were higher in the drainage canal (Table 2): plants with 
rosette diameter by 20% larger were formed here, with 
longer leaves and roots which produced more filial plants.
Table 2: Morphometric characteristics of P. stratiotes in differ-
ent habitats (average value and standard deviation).
Tabela 2: Morfometrične značilnosti vrste P. stratiotes v 
različnih habitatih (povprečna vrednost in standardni odklon).
Morphometric 
 characteristics
Drainage canal Floodplain lake
Maternal  
plants
Filial  
plant
Maternal  
plants
Filial  
plant
Rosette 
diameter, cm
16.33±8.06 3.68±1.64 12.82±7.12 10.49±5.19
Number of  
veins
7.00±0.87 5.87±1.01 6.96±1.25 6.95±0.93
Number of  
leaves
8.67±3.00 4.47±1.08 8.79±2.85 6.19±2.49
Leaf length, 
cm
6.57±4.59 1.76±1.25 5.15±3.48 4.51±3.09
Root length,  
cm
17.89±8.77 4.53±1.72 14.61±9.74 12.77±9.46
However, larger filial plants formed in the floodplain 
lake (almost three times larger) with more and much 
longer leaves and three times longer roots. Variability of 
features in filial plants in this water body was much great-
er than in those of the drainage canal.
Flowers and buds were recorded on 8% of the plants 
collected (the floodplain lake).
In both locations, the species successfully overwintered. 
And although in 2021 we did not notice such a massive 
boom of plants, both locations exhibited abundant mats 
of P. stratiotes at the end of summer.
To evaluate the relationship of plants morphometric 
parameters from two studied populations with the char-
acteristics of habitats factor analysis was used (Table 3).
The variables were assessed by constructing a correlation 
circle of morphometric data. There is a group of three al-
most horizontal and much related indicators (Figure 3A): 
number of leaves, the diameters of rosettes and number 
of veins correlate with each other in both habitats. Longer 
roots lead to an increased number of leaves.
Figure 3 (B, C, D) shows the factor maps (sample val-
ues) for individual plants (B), maternal and filial plants 
(C) and water bodies (D). Ellipses represent standard de-
viations. Points depicted close together have similar val-
ues. In the floodplain lake (Zoloche Lake) maternal plants 
predominate, in the drainage channel – filial plants.
Trait Factor
Model
Sum-of-
squares 
(SS)
Degrees 
of 
freedom
Mean 
squares 
(MS)
p
Rosette
diameter,  
cm
water body 1350 1 1350 <0.001
plant type 1385 2 693 <0.001
residuals 19850 443 45
Root  
length, cm
water body 1781 1 1781 <0.001
plant type 1426 2 713 <0.001
residuals 38829 443 88
Number  
of leaves
water body 344 1 344 <0.001
plant type 455 2 227 <0.001
residuals 3281.0 443 7
Number  
of veins
water body 26 1 26 <0.001
plant type 9 2 4 <0.05
residuals 631 443 1
Leaf  
length, cm 
water body 33 1 33 <0.05
plant type 139 2 69 <0.001
residuals 3204 443 7
Leaf length/  
Root length 
water body 3 1 3 <0.001
plant type 0.210 2 0.1050 <0.001
residuals 443 443 0.0753 >0.1
Table 3: Nested design ANOVA results examining the effect of 
plant type and water body (plant types nested in a water body) 
on plants morphological traits.
Tabela 3: Rezultati testa ANOVA z gnezdasto zasnovo, ki 
oceni vpliv tipa rastline in vodnega telesa (tip rastline gnezden 
znotraj vodnega telesa) na morfološke znake rastlin.
Discussion
Coenopopulations of P. stratiotes in the region are com-
mon for meso-eutrophic and eutrophic waters (Lushpa, 
2009; Kazarinova at al., 2014; Afanasyev & Savitskiy, 
2016). Analysis of species preferences based on the results 
of our own research has shown that P. stratiotes is charac-
terized by a wide ecological valence in terms of phosphate 
content in water (occurred in water bodies with phosphate 
concentration of 0.01–2.75 mgP/dm³) (Zub & Prokopuk, 
2020). The species prefers habitats which are rich in min-
eral phosphorus compounds. At high values of phosphates 
content (0.30 mgP/dm³ and more) populations with high 
abundance are formed (Zub & Prokopuk, 2020).
Deficiency and excess of mineral nitrogen can be con-
sidered as a limiting factor for the development of P. stra-
tiotes coenopopulations. Ecological preferences of the spe-
cies for this indicator are within the limits characteristic 
of meso-eutrophic waters, P. stratiotes disappeared in the 
case of increasing the concentration of mineral nitrogen 
to 4.3 mgN/dm³ and reducing the content of phospho-
rus in phosphates to 0.01 mgR/dm³ (Zub & Prokopuk, 
2020). We assume that lower rates of the produced phy-
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Ecological features of the alien species Pistia stratiotes L. in different habitats
tomass and average size of P. stratiotes in Zoloche Lake can 
be explained by the influence of high content of nitrate 
nitrogen in water (see Table 1). Probably, this fact has pre-
determined a smaller number of filial plants in this local 
population.
In the drainage canal, where the waters correspond to 
the meso-eutrophic type were formed – young vegetative 
individuals predominated (see Figure 3C). Accordingly, 
this local population is characterized by higher invasive 
potential. Invasive potential, or invasiveness of alien 
plants (Burda & Pridatko, 2005) is the ability of alien 
species to spread in new local conditions and to create in 
disturbed or natural phytocoenoses stable local popula-
tions, well adapted to the new environment.
Figure 3: The results of Principal component analysis: correlation circle of the morphological data, i.e. scores of the morphological variables (A); 
factor maps, i.e. sample scores, for individual plants (B), maternal and filial plants (C), and water bodies (D). Letter d denotes the size of the grid. 
Ellipses have standard deviations.
Slika 3: Rezultati analize glavnih komponent: korelacijski krog podatkov o morfologiji, t.j. vrednosti morfoloških spremenljivk (A); faktorski zem-
ljevidi, t.j. vrednosti vzorcev za posamezne rastline (B), materinske in hčerinske rastline (C), in vodni telesi (D). Črka “d” označuje velikost mreže. 
Elipse predstavljajo standardne odklone.
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Ecological features of the alien species Pistia stratiotes L. in different habitats
P. stratiotes can be used to indicate the conditions of 
water bodies: in case of increased water trophism (mainly, 
manifestations of anthropogenic eutrophication due to 
inorganic nitrogen), maternal plants become smaller and 
more compact (see Table 2). Variability of morphological 
features of plants increases (see Figure 3D). The modern 
literature confirms bioindication properties of the spe-
cies: P. stratiotes is an organism that responds sensitively 
to changes in the aquatic environment by growth and 
density of stands (Ružičková et al., 2020).
The research localities were characterized by much less 
average length of leaves and roots of both maternal and 
filial plants than the data provided in the literature for 
earlier invasions (Kazarinova et al., 2014; Ružičková et 
al., 2020). This indicates that populations are in the early 
stages of species invasion (Thompson, 2000). However, 
the maximum size of plants (30 cm in diameter – the 
drainage canal and 49 cm – floodplain water body) is 
comparable to those given in the literature: the param-
eters of the rosettes of the largest maternal plants from 
the Seversky Donets River (Kharkiv region, Ukraine) 
were 40-45 cm in diameter (Kazarinova et al., 2014); in 
the rivers of Slovakia, the largest maternal plant had a ro-
sette with the diameter of 47 cm (Ružičková et al., 2020). 
Sampling was realized in the same period in the end of 
vegetation period and the same climatic zone.
The morphological changes of P. stratiotes are primarily 
influenced by environmental conditions and population 
density (Thompson, 2000; Ružičková et al., 2020), but 
morphological parameters may indicate the degree of nat-
uralization of the species. Plants that were first recorded in 
the urban ornamental ponds of Kyiv were much smaller 
in size, with the diameter of the rosettes of 5.8–17.5 cm 
(Prokopuk, 2017). For comparison, in the ponds of the 
Republic of Adygea, the first plants also had lower values: 
the diameters of large rosettes reached 26 cm (Shapovalov 
& Saprykin, 2016). We can assume that for regions with 
a moderate climate and natural temperatures in autumn-
winter period, the small size of the rosettes is evidence 
of the first invasions of the species. Over time, the size 
of plants (average and maximum values) becomes larger, 
and we can consider this being a feature of naturalization 
of the species.
Unfortunately, there are no data concerning study of 
P. stratiotes wintering in Ukraine. Wintering of P. stra-
tiotes in Europe is noted in Germany for the Erft River 
(Hussner & Heiligtag, 2013). They point out that in 
the winter months the number of P. stratiotes plants de-
creases due to low growth rates, and mostly young plants 
dominate. However, at next summer phytomass stocks 
increased, and in the summer months plants up to 60 
cm in diameter.
Since 2012, we have observed permanent coenopopu-
lations of the species in a number of localities of the city. 
Until 2020, P. stratiotes behaved as a distinct edificator, 
but did not manifest itself as a transformer species; ac-
cording to the degree of naturalization we evaluated it 
as an ephemerophyte (casual alien plants) (Zub & Pro-
kopuk, 2020).
The results of the 2020–2021 study enable us to make 
slightly different general conclusions. The full-fledged 
structure of populations with a predominance of young 
plants, active vegetative propagation, the ability to form 
generative organs, as well as the ability to survive adverse 
winter conditions indicates the formation of normal pop-
ulations (plants are fully developed) and according the 
degree of naturalization today show the features of colo-
nophyte (naturalized plants) (term according to Thellung, 
1918–1919).
Higher produced phytomass can be considered as a 
feature of naturalization of P. stratiotes. For example, 
for one of the first invasions of the species in the region 
(Sviatoshynsky pond, Kyiv), 2.47–4.38 kg/m² of raw 
phytomass was produced within the period of the most 
massive development (air-dry – 0.24–0.38 kg/m2) (Pro-
kopuk, 2017). For the local populations of P. stratiotes of 
the drainage canal, this value is twice as high. We have 
witnessed formation of extremely huge reserves of phyto-
mass – for example, for Zoloche Lake, the total reserves 
of phytomass for the research period can be estimated at 
more than 345 tons.
The features of P. stratiotes as a transformer species are 
also noting. We have witnessed that 100% of the flood-
plain water body, with nearly 80% of the drainage ca-
nal covered with mats of plants. Even 50% of the water 
surface area covered by Pistia stratiotes is a real threat to 
the immersed species, sensitive to light, oxygen content 
and pH level (Olkhovich et al., 2017). Such mats limit 
development of macrophytes through shading and a 
mechanical barrier which prevents enriching water with 
oxygen due to atmospheric aeration. Due to development 
of phytocoenosis of P. stratiotes, in 2014 in the valley of 
the Siversky Donets (about 70% of floodplain areas were 
covered with a continuous layer of plants of the species), 
there were changes in the degree of water trophism from 
meso-eutrophic to eutrophic (in lotic hydroecosystems – 
to hypereutrophic) (Kazarinova at al., 2014).
The transition of phytomass of P. stratiotes to detritus 
delayed regeneration of natural trophic conditions for 
several years (Kazarinova at al., 2014). We are to investi-
gate the influence of the mass development of the species 
on the ecosystems of floodplain water bodies in the mid-
dle reaches of the largest river in Ukraine – the Dnipro.
21/2 • 2022, 361–370
369
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Ecological features of the alien species Pistia stratiotes L. in different habitats
Conclusions
P. stratiotes is a known invasive species which responds 
to various conditions and spreads rapidly in a vegetative 
and generative way. In mesotrophic lotic conditions, the 
species forms more productive populations, dominated 
by young vegetative individuals and is characterized by 
higher invasive potential. Conditions of lentic floodplain 
water bodies contribute to formation of larger plants, the 
ability to form generative organs, aging of the coeno-
population and formation of significant reserves of phy-
tomass within one water body.
In the case of increased anthropogenic eutrophication 
due to inorganic nitrogen, mother plants become smaller 
and more compact. The variability of morphological fea-
tures increases. Mineral nitrogen deficiency and excess 
can be considered as a limiting factor for development of 
local populations of P. stratiotes. Ecological preferences of 
the species with regard to the type of trophism are within 
the meso-eutrophic waters.
Mass development of the species on drainage canals 
and a number of floodplain lakes of the left bank of the 
Dnipro River on the southern border of Kyiv in 2019-
2021 enables to make assumptions about the increased 
degree of naturalization of P. stratiotes in Ukraine (from 
ephemerophyte to colonophyte) and invasive status (from 
Casual alien plants to Naturalized plants).
Acknowledgements
Special thanks to the Doctor of Biological Sciences Nets-
vetov M.V. for assistance in statistical data analysis.
Mariana Prokopuk  https://orcid.org/0000-0001-7739-0068
Lesya Zub  https://orcid.org/0000-0003-4539-080X
Funding
This work was supported by the grant from the National 
Academy of Sciences for young scientists in priority 
areas of science and technology (№ of state registration 
0121U110322)
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