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The ecological niche of Vallonia pulchella (Muller, 1774) was investigated by means of the general factor analysis of GNESFA. It was revealed that the ecological niche of a micromollusk is determined by both edaphic factors and ecological features of vegetation. Ecological niche optima may be presented by integral variables such as marginality and specialization axes and may be plotted in geographic space. The spatial distribution of the Vallonia pulchella habitat suitability index (HSI) within the Technosols (sod-lithogenic soils on red-brown clays) is shown, which allows predicting the optimal conditions for the existence of the species.
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Ecologica Montenegrina, 17, 2018, 29-45
Analysis of the spatial organization of Vallonia pulchella (Muller,
1774) ecological niche in Technosols (Nikopol manganese ore basin,
Ukraine)
NADIA YORKINA1, KATERINA MASLIKOVA2, OLGA KUNAH3,
OLEXANDR ZHUKOV3
1Bohdan Khmelnitsky Melitopol State Pedagogical University, Department of Chemistry and Biology, ul. Hetmanska
20, Melitopol, Zaporizhzhia oblast, 72312 Ukraine;
E-mail: nadyayork777@gmail.com
2Dnipro Agrarian and Economy University, Serhii Efremov Str., 25, 49600 Dnipro, Ukraine;
E-mail: mkaterina@ukr.net
3Oles Honchar Dnipro National University, pr. Gagarina, 72, 49010 Dnipro, Ukraine;
E-mail: zhukov_dnipro@ukr.net, olga-kunakh@rambler.ru
*Corresponding author: Nadia Yorkina. E-mail: nadyayork777@gmail.com
Received 10 Febuary 2018 Accepted by V. Pešić: 1 April 2018 Published online 4 April 2018.
Abstract
The ecological niche of Vallonia pulchella (Muller, 1774) was investigated by means of the general factor analysis of
GNESFA. It was revealed that the ecological niche of a micromollusk is determined by both edaphic factors and
ecological features of vegetation. Ecological niche optima may be presented by integral variables such as marginality
and specialization axes and may be plotted in geographic space. The spatial distribution of the Vallonia pulchella
habitat suitability index (HSI) within the Technosols (sod-lithogenic soils on red-brown clays) is shown, which allows
predicting the optimal conditions for the existence of the species.
Key words: mollusks, marginality, biodiversity, ecological niche, spatial organization, Ukraine.
Introduction
Much of the research on the selection of habitat by land mollusks is based on the comparison of mollusk
communities from geographically different sampling points that differ in plant cover, soil type, and moisture
level (Millar, Waite, 1999, Martin, Sommer, 2004, Müller et al., 2005; Weaver et al., 2006). Of the edaphic
factors that affect molluscs, the most significant one is the content of calcium in the soil, pH and soil texture
(Ondina et al., 2004), as well as the content of exchangeable cations and aluminum (Ondina et al., 1998).
The moisture content of soils plays an important role (Nekola, 2003), however, Ondina et al. (2004) note the
limited data on the role of soil moisture at a given time in view of the significant variability of this
parameter. To solve this problem, it is appropriate to use phytoindication data to assess the autecological
features of mollusks and the structure of their communities (Horsák et al., 2007; Dvořáková, Horsák, 2012).
Ecologica Montenegrina 17: 29-45 (2018)
This journal is available online at: www.biotaxa.org/em
ANALYSIS OF THE SPATIAL ORGANIZATION OF VALLONIA PULCHELLA
30
For describing habitat preferences of the mollusk Vertigo geyeri Lindholm, 1925, the Ellenberg
phytoindication scales were successfully used in Poland and Slovakia (Schenková et al., 2012).
Studies at a large scale level have made it possible to determine the role of edaphic factors in the
spatial distribution, abundance, and diversity of mollusks communities (Nekola, Smith, 1999; Juřičková et
al., 2008; Szybiak et al., 2009). Particular attention is drawn to the problem of spatial scale and hierarchy of
factors affecting mollusks (Nekola, Smith, 1999, Bohan et al., 2000, McClain, Nekola, 2008, Myšák et al.,
2013). The habitat is characterized by the presence of resources and conditions for given species in some
territory, as a result of which the colonization of this territory becomes possible, including its survival and
reproduction (Hall et al., 1997). The purpose of studying the choice of habitats for species is to identify the
characteristics of the environment that make the place suitable for the existence of the species (Calenge,
2005). Ecological niche models are useful for describing the choice of habitat by species. Hutchinson
(1957) proposed a formal, quantitative concept of the ecological niche as a hyper volume in a
multidimensional space, defined by ecological variables delimiting where stable populations can be
maintained (Kearney et al., 2010). Methodologically, an ecological niche can be described by means of a
General niche-environment system factor analysis (GNESFA) (Calenge, Basille, 2008).
The factor analysis of ecological niches is based on the assumption that species are not randomly
distributed with respect to ecogeographic variables (Hirzel et al., 2002). The species can be characterized by
marginality (which is expressed in the difference between the species mean and the global mean of the
ecogeographic variable) and by specialization (which manifests itself in the fact that the species variance is
smaller than the global variance).
GNESFA can be implemented in the form of three versions FANTER, ENFA and MADIFA.
Factor analysis of the ecological niche, taking the environment as the reference (FANTER) considers the
deformation of the ecological niche relative to the ecological space, which is accepted as referential, i.e. the
axes of this space lead to such a state that the ecological space has an ideal spherical shape. On the contrary,
the spherical shape is attached to the ecological niche in the analysis of MADIFA (Mahalanobis distances
factor analysis), and the curvature of the ecological space indicates the degree of difference in environmental
properties from the ecological optimum of the species. Based on the results of MADIFA, the most correct
habitat preference map for this species can be constructed (Calenge et al., 2008).
A special point of view is possible in which two distributions (an ecological niche and an ecological
space) are considered as focal and referential. This symmetrical viewpoint has an advantage beyond the
choice of the reference distribution. This special case is the basis of the ecological niche factor analysis
(ENFA). In ENFA, the first axis completely corresponds to marginality, and the subsequent axes describe the
specialization of the species. Integration of these axes also makes it possible to build a habitat preference
map, but unlike MADIFA, this result within ENFA is not mathematically well-founded.
Caruso et al. (2015) note that, despite the benefits of GNESFA, this type of analysis is not well
represented in scientific literature. Even after the publication of the paper (Calenge, Basille, 2008), a number
of articles continue to use the ENFA approach not only as a research tool, but also for building habitat
preferences maps (De Angelo et al., 2011; Galparsoro et al., 2009; Valle et al., 2011). A number of authors
use only MADIFA to describe the distribution of species (Halstead et al., 2010; Hemery et al., 2011; Thiebot
et al., 2011). Along with the original work (Calenge, Basille, 2008) in the article by Caruso et al. (Caruso et
al., 2015) the environmental niche of a cougar in South America is described using all of the GNESFA
techniques.
Mollusks Vallonia pulchella (Muller, 1774) is Holarctic species found around the world at high
latitudes. In Europe it reported from wetter habitats such as wet meadows and marshes, as well as dry dunes
and grasslands (Kerney, Cameron, 1979). In Ukraine it prefers moderately dry and wet meadow habitats.
Calciphilic appearance (Gural-Sverlova, Gural, 2012). The population density of V. pulchella in alder and
oak forests of Belarus was 4-8 individuals/m2 (Zemoglyadchuk, 2005), in ash-elm forests in Poland it did not
exceed the average of 0.13 individuals/m2 (Koralewska-Batura, Błoszyk, 2007), and in floodplain forests of
Slovakia it was 0.07 individuals/m2 (Čejka, Hamerlik, 2009). On the other hand, J. Hermida et al. (1993)
estimated the average density for three studied populations of V. pulchella in Spain (meadow and forest
habitats, as well as near the river bank) to be 5.9-10.1 individuals/m2, reaching on separate test plots values
of the order of 200 individuals/m2. In bush willow depressions in Kazakhstan K. Uvalieva (1990) a density
YORKINA ET AL.
Ecologica Montenegrina, 17, 2018, 29-45 31
of 224 individuals/m2 was estimated. There are no evidence about ecological properties of the V. pulchella
population in artificial soils.
The aim of our work is to describe the ecological niche of the micromollusk Vallonia pulchella
(Muller, 1774) in terms of the edaphic properties and properties of the vegetation cover and to show the
spatial features of the variation of the habitat preference index within the artificial soil body Technosols
(soddy-lithogenic soils on red-brown clays) using GNESFA.
Material and Methods
The research was carried out at the Research Centre of the Dnipro Agrarian and Economic University in
Pokrov (Fig. 1). The experimental site for the study of optimal regimes of agricultural recultivation was
established in 19681970. Sampling was carried out on a variant of artificial soil (technozems) formed on
red-brown clays (the geographic coordinates of the southwestern corner of the test site are 47°38'55.24"N.L.,
34°08'33.30"E.L.). According to WRB 2007 (IUSS Working group WRB, 2007), examined soil belong to
the RSG Technosols. Examined profile, also, satisfies the criterion for Spolic prefix qualifier having 20
percent or more artefacts (consisting of 35 percent or more of mine spoil) in the upper 100 cm from the
soil surface. From 1995 to 2003, a long-term legume-cereal agrophytocenosis grew on the site, after which
the process of naturalization of the vegetation began.
The test site within which sampling was made consists of 7 transects of 15 samples each. Test points
form a regular grid with a mesh size of 3 m. Thus, the total test point number is 105. In each test point 10
samples of 10 g weight of dry soil were collected. In each sample molluscs were extracted by sorting with
dissecting needle.
Soil mechanical impedance was measured in the field using the Eijkelkamp manual penetrometer at
a depth of up to 50 cm with an interval of 5 cm. The average error in the instrument measurement results is ±
8%. For the measurement, a cone with a cross-sectional dimension of 1 cm2 was used. Within each cell, soil
mechanical impedance measurements were made in one-fold replication.
Determination of the aggregate-size distribution was carried out by means of dry sieving
(Vadyunina, Korchagina, 1986).
To measure the electrical conductivity of soil in situ the HI 76305 sensor (Hanna Instruments,
Woodsocket, R. I.), working in conjunction with the portable instrument HI 993310 were used. The tester
estimates the total electrical conductivity of the soil, i.e. combined conductivity of soil air, water and
particles. The results of measurements of the device are presented in units of saturation of the soil solution
with salts - g/l. Comparison of the measurement results with the instrument HI 76305 with laboratory data
allowed estimating the conversion factor of units as 1 dS/м = 155 mg/l.
The humus content was determined by «wet chemistry» method. The essence of the method lies in
the determination of organic carbon by oxidation with a mixture of potassium dichromate and sulphuric acid.
The organic carbon values obtained can be recalculated into humus or organic matter using the mean
coefficient (1.724) (Nelson & Sommers, 1982; Slepetiene et al., 2008). The content of humus is determined
by the method of Tyurin. Shrinkage of the soil upon drying was measured according to Vadyunina &
Korchagina (1986). Sifted soil samples were brought to a humidity of 31.17 ± 0.35%. After gradual drying in
the laboratory, the samples were further dried in an oven at 105°C for 5 hours. The size of the soil samples
after shrinkage was measured with a caliper.
The vegetation cover was described within squares with a lateral side of 3 m. The material was
collected in June 2012. The physiognomic characteristics of the vegetation cover were established by the
results of decoding the digital photographs of the surface of the experimental plot made from a height of 1.5
m (Fig. 2). The main physiognomic types of vegetative cover were singled out visually: 1 cereals (Bromus
squarrosus L.); 2 Seseli tortuosum L.; 3 Lactuca tatarica (L.) C.A. Mey.; 4 legumes (Medicago sativa
L.); 5 dead plant residue; 6 open soil cover. The most typical fragments for the corresponding species
were chosen for the images, according to which their color characteristics in RGB format were set. They
were used as a testing sample for discriminant analysis. After that, all pictures were decoded, which allowed
us to estimate the share that each of the physiognomic types in the cover occupies.
Ecomorphic analysis of vegetation was carried out according to Bel'gard (1950). Biological and
ecological characteristics of plants were used according to the work by Tarasov (2012). In the plant
community of the studied type of technosoils, the hygromorphs are mainly represented by xeromesophiles
ANALYSIS OF THE SPATIAL ORGANIZATION OF VALLONIA PULCHELLA
32
(KsMs) and mesoxerophiles (MsKs) (98.89% of the number of samples). Therefore, as a quantitative
measure of the hygromorphic structure of the vegetation, the proportion of xeromesophiles in the plant
community was chosen. Plant trophomorphs are represented by mesotrophs and megatrophs. The
trophomorphic structure is characterized by the proportion of megatrophs. In the ceonomorphic structure,
mainly the stepants (steppe species) (82.37%) and the pratant (meadow species) (17.53%) are represented.
Quantitatively, the cenomorphic structure is described with the help of stepants ratio. Heliomorphs are
represented by heliophytes (59.88%) and scioheliophytes (40.12%). The adaptation of plants to the light
regime is characterized by the proportion of heliophytes (Hel).
In the work the phytoindication scales of Tsiganov (1983) were used (Database of “Flora of vascular
plants of Central Russia”, http://www.jcbi.ru/eco1).
Statistical calculations were performed with the help of the Statistica 7.0 program and the project for
statistical computations R (www.r-project.org) using adehabitat libraries (Calenge, 2006) and vegan
(Oksanen, 2011), two-dimensional mapping, estimation of geostatistics and creation of asc-files with data of
spatial variability of the environment indicators - using the programs Surfer 8.0 and ArcGis 10.0. The
coefficient of spatial correlation of I-Moran was calculated using the Geoda 1.6.6 program (Anselin et al.,
2006).
Figure 1. Research Centre of the Dnipro Agrarian and Economic University in Pokrov (Ukraine). A satellite image of
the study area (1 reclaimed land; 2 mining quarry); B technosoils profile; C quarry panorama view.
YORKINA ET AL.
Ecologica Montenegrina, 17, 2018, 29-45 33
Results
In total air-dry soil weighing 10.5 kg were examined, in which 193 specimens of Vallonia pulchella (Muller,
1774) were found. Thus, the average density of this species in sod-lithogenic soils on red-brown clays during
the study period was 1.84 ind./m2. In the spatial distribution of individuals, it manifests itself in the formation
of “hotspots” - localities with a high concentration of mollusks (Fig. 1, 3).
Figure 2. Soil surface and physiognomic characteristics of the vegetation cover. 1 type_1 (Bromus sguarrosus L.); 2
type_2 (Seseli tortuosum L.); 3 type_3 (Lactuca tatarica (L.) C.A. Mey.); 4 type_4 (Medicago sativa L.); 5 type_5
(dead plant residue); 6 type_6 (open soil cover).
ANALYSIS OF THE SPATIAL ORGANIZATION OF VALLONIA PULCHELLA
34
Figure 3. Spatial placement of Vallonia pulchella molluscs along the site on sod-lithogenic soils on red-brown clays.
The coordinates are in meters.
In order to describe the dependence of the mollusk population of Vallonia pulchella on environmental
factors, along with the Pearson correlation coefficients (not taking into account the spatial context), I-Moran
statistics were calculated (Table 1).
The Pearson and I-Moran correlation coefficient reflects various aspects of the relationship between
the mollusc population and environmental factors. Thus, the Pearson correlation coefficient does not indicate
a correlation between the density of the mollusc population and the content of humus in the soil. Pearson
correlation coefficient reflects the presence of a linear connection. The I-Moran coefficient takes into
account the spatial context, since it indicates the correlation of spatially averaged indicators of the compared
features. We established a positive and reliable correlation between the number of molluscs and the content
of humus by the I-Moran coefficient.
According to soil mechanical impedance indicators, statistically significant Pearson correlation
coefficients were established in the absence of statistically significant I-Moran coefficients (except for the 0-
5 cm layer). It is obvious that the mechanical impedance indices at the investigated depth of up to 50 cm
reflect the state of the soil structure as combination of the density and soil pore space composition. The
measurement range extends beyond the area within which animals were selected. It is likely that the
variability of the technosoil structure is of a local nature and is not characterized by spatial patterns at a
selected scale level. Variations in the composition of clay soil are due to the processes of swelling and
shrinkage, as a result of which the soil fissuration is appeared. These processes largely determine the
variability of soil mechanical impedance. These processes, being by their nature physico-mechanical, do not
form significant spatial patterns.
The aggregate structure of the artificial soil is also a consequence of the physical and mechanical
processes of swelling and shrinkage, but in addition to these processes biological processes also affect the
soil aggregation. The root systems of plants form the soil structure, as well as the trophic and pedoturbational
activity of soil animals. The spatial variability of the vegetation cover, its continuity in time and space lead to
the formation of spatially regular structures. As a consequence, we observe a correlation between the number
of Vallonia pulchella mollusk populations and aggregate structure indices according to two correlation
coefficients. Also the correlation with the characteristics of vegetation (physiognomic types and
phytoindication indicators) should be noted.
Thus, we found that the mollusks Vallonia pulchella are sensitive to the soil aggregate structure. The
number of Vallonia pulchella increases with an increase in the proportion of aggregates 3-5, 5-7 and 7-10
mm in size and decreases with the growth of the components of small aggregates - <0.25, 0.25-0.5, 0.5-1
YORKINA ET AL.
Ecologica Montenegrina, 17, 2018, 29-45 35
mm. Obviously, interaggregate porosity, which is formed in the soil in the presence of aggregates of
appropriate size, is an essential condition for the life of these mollusks for their breathing and migration.
Small aggregates form a system of pores of small dimensions, which are unfavorable for the life of the
micromollusks studied.
Table 1. Correlation of the number of Vallonia pulchella with soil characteristics and vegetation properties (only
correlation measures are shown that are significant for p <0.05)
Characteristics
Mean. ± st. error
CV, %
Correlations
coefficients
r-
Pearson
I-Moran
Humus content and physical properties of soil
Humus, % (Hum)
0.78±0.01
15.36
0.18
Conductivity, dSm/m (EC)
0.55±0.01
18.43
Maximum hygroscopic humidity,% (MGM)
8.51±0.16
18.78
0.21
0.18
Shrinkage,% (Comp)
20.73±0.35
17.51
0.44
0.16
The soil layer temperature in 0-5 cm
03.05.12, °C (Temp1)
22.61±0.10
4.65
0.26
0.16
The soil layer temperature is 0-5 cm
20.06.12, °C (Temp2)
33.07±0.25
7.63
0.10
Aggregate structure, size of fractions, mm
>10
23.15±0.99
43.98
710
7.81±0.24
31.05
0.37
0.23
57
8.33±0.32
39.04
0.37
0.25
35
14.39±0.46
32.53
0.32
0.22
23
13.33±0.46
35.68
12
18.54±0.60
33.43
0.13
0,51
4.19±0.20
48.16
0.31
0,250,5
6.07±0.30
50.89
0.33
0.16
<0,25
3.33±0.18
56.90
0.35
0.16
Soil penetration resistance in MPa at depth, cm
05
3.26±0.08
25.01
0.29
0.14
510
4.49±0.16
35.37
0.37
1015
5.47±0.18
34.13
0.39
1520
6.18±0.21
35.35
0.38
2025
6.80±0.23
34.86
0.33
2530
7.17±0.25
36.10
0.29
3035
7.59±0.26
35.14
0.32
3540
7.80±0.28
36.47
0.31
4045
8.01±0.30
37.78
0.31
4550
8.16±0.31
39.31
0.32
Physiognomic types of vegetation
Type_1
0.07±0.003
51.17
0.26
Type_2
0.28±0.004
15.69
Type_3
0.19±0.007
35.77
0.16
Type_4
0.03±0.002
78.47
0.09
..continued on the next page
ANALYSIS OF THE SPATIAL ORGANIZATION OF VALLONIA PULCHELLA
36
TABLE 1.
Type_5
0.09±0.004
41.68
0.28
Type_6
0.35±0.009
26.89
0.10
Tsyganov phytoindicator values
Tm
9.73±0.007
0.72
Kn
10.54±0.008
0.80
Om
6.94±0.006
0.85
0.20
Cr
9.12±0.006
0.71
Hd
7.83±0.005
0.68
0.18
Tr
6.38±0.006
0.93
Nt
5.31±0.016
3.07
Rc
9.92±0.009
0.97
Lc
2.21±0.015
0.98
0.13
Bellagard ecomorphs
Hygromorphs (KsMs ratio)
2.48±0.011
4.50
0.32
0.26
Trophomorphs (MgTr ratio)
2.46±0.016
6.47
0.21
0.18
Cenomorphs (St ratio)
0.70±0.004
6.08
Cenomorphs (Pr ratio)
0.12±0.005
43.99
0.12
Heliomorphs (Hel ratio)
3.61±0.009
2.69
0.41
Symbols: * values weighted by V. pulchella density
It should be noted that mollusks prefer more xerophilic microstations within the test site with
increased mineralization (trophicity) of the soil solution.
Information on the spatial distribution of animals allows comparing the distribution of resources
within the site, as well as their particular distribution at the points where mollusks were found (Fig. 2, 4).
Obviously, the fact that the general and partial distributions do not coincide indicates the structuring role of
the corresponding variable in determining the shape of the ecological niche.
Estimation of the shape of the ecological niche, if the distribution of the availability of resources is
set as reference, can be obtained by means of the FANTER analysis (Fig. 3, 5). The largest eigenvalues of
the axes identified as a result of this analysis indicates that the marginality described by the axis is the largest
and the specialization is the smallest. The smallest eigenvalue indicates a strong specialization and/or low
marginality. Thus, both the first and the last axes by the eigenvalues value play an important role in the
framework of the FANTER analysis.
The statistical significance of the axes allocated in the FANTER analysis was verified by a
randomized test (999 random samples were generated for which the corresponding indices were calculated).
The test showed that the first axis statistically significantly differs from the random alternative (γ1 = 4.64, p
<0.046, the alternative hypothesis is less), and the second and last two axes of the ecological niche of
Vallonia pulchella differ significantly from the random distribution (γ2 = 3,.36, p <0.19, the alternative
hypothesis is less, γ44 = 0.12, p = 0.93, γ45 = 0.09, p = 0.86, alternative hypothesis is greater). This result
suggests that within the studied area the distribution of molluscs is characterized by both marginality and
specialization.
Marginality and specialization are determined both by edaphic factors and ecological features of
vegetation (Table 2).
The ecological niche of Vallonia pulchella is characterized by marginality, which is characterized by
shrinkage of soil, indicators of aggregate structure, and soil mechanical impedance. Of all the properties of
vegetation in the definition of marginality, only the fraction of heliophytes and the ratio in the physiognomic
structure of cereals (type 1) play a role. The specialization is determined by the humus content, the maximum
hygroscopic humidity, the temperature of the upper soil layer, the aggregate structure, soil mechanical
impedance at a depth of more than 25 cm, a wide range of physiognomic types, nitrogen content in soil
according to phytoindication estimates.
YORKINA ET AL.
Ecologica Montenegrina, 17, 2018, 29-45 37
Table 2. Results of analysis of the ecological niche of Vallonia pulchella by GNSFA methods (only correlation
measures are shown that are significant for p <0.05)
Ecological factors
FANTER
ENFA
MADIFA
Marginality
Specialization
M
Sp1
Sp2
C1
C2
C1
C2
C44
C45
Physiognomic type of vegetation cover
Hum
0.26
0.22
0.24
0.25
EC
MGM
0.21
0.47
0.22
Comp
0.24
0.57
Temp1
0.25
0.47
0.33
Temp2
0.22
0.24
Aggregate structure, aggregate dimensions, mm
>10
0.23
0.20
0.27
710
0.59
0.20
0.23
57
0.60
35
0.21
0.46
23
0.21
0.08
0.24
12
0.26
0.37
0.23
0.27
0,51
0.27
0.29
0.39
0,250,5
0.23
0.54
<0,25
0.51
Soil mechanical impedance at depth, cm
05
0.58
0.21
510
0.71
1015
0.28
0.23
0.76
1520
0.24
0.20
0.72
2025
0.71
2530
0.20
0.66
3035
0.65
3540
0.20
0.64
4045
0.20
0.20
0.62
4550
0.24
0.20
0.61
Physiognomic type of vegetation cover
Type_1
0.28
Type_2
0.25
0.26
0.27
Type_3
0.32
Type_4
0.33
0.27
0.28
0.41
0.33
Type_5
0.24
0.35
0.23
0.27
Type_6
0.28
0.35
0.28
0.25
Phytoindication values of environmental factors
Tm
Kn
0.21
0.22
0.23
Om
0.40
0.40
0.32
0.27
Kr
Hd
0.22
Tr
0.23
Nt
0.44
0.19
0.52
0.30
..continued on the next page
ANALYSIS OF THE SPATIAL ORGANIZATION OF VALLONIA PULCHELLA
38
TABLE 2.
Rc
0.34
0.41
0.25
Lc
0.52
Bellgard ecomorphs
KsMs
0.53
0.21
0.19
MgTr
0.25
0.54
0.32
St
0.31
0.20
0.27
Pr
0.22
0.24
0.25
Hel
0.24
0.48
0.20
0.27
Figure 4. An histogram of the available resource units. Resource allocation (black bars) and an histogram of the used
resource units distribution of resource use (gray bars) of Vallonia pulchella. Type_1 - type_6 - the proportion of
physiognomic types of vegetation cover; temp_05 - top soil temperature (3-5 cm) May 3, 2012; temp_06 - temperature
of the top layer of soil (3-5 cm) June 20, 2012; Tm - thermoclimate; Kn - continentality; Om - ombroclimate; Kr -
cryoclimate; Hd - humidity; Tr - salt regime; Nt - nitrogen nutrition; Rc - acidity; Lc - lighting; St - stepants; Pr -
pratants; Humus humus comtant; EC soil electrical conductivity, imp_05 - imp_50 - soil mechanical impedance at a
depth of 5, ..., 50 cm, Agr_10 - Agr_025 - aggregate fractions of size> 10, ..., <0.25 mm, g_Vlag - hygroscopic
humidity,%; Compact soil shrinkage, in %.
YORKINA ET AL.
Ecologica Montenegrina, 17, 2018, 29-45 39
Figure 5. Correlation between the environment variables and the axes selected as a result of FANTER analysis. A
marginality axes 1 and 2; B - specialization axes 44 and 45. Type_1 - type_6 - the proportion of physiognomic types of
vegetation cover; temp_05 - top soil temperature (3-5 cm) May 3, 2012; temp_06 - temperature of the top layer of soil
(3-5 cm) June 20, 2012; Tm - thermoclimate; Kn - continentality; Om - ombroclimate; Kr - cryoclimate; Hd - humidity;
Tr - salt regime; Nt - nitrogen nutrition; Rc - acidity; Lc - lighting; St - stepants; Pr - pratants; Humus humus comtant;
EC soil electrical conductivity, imp_05 - imp_50 - soil mechanical impedance at a depth of 5, ..., 50 cm, Agr_10 -
Agr_025 - aggregate fractions of size> 10, ..., <0.25 mm, g_Vlag - hygroscopic humidity,%; Compact soil shrinkage,
in %.
Thus, the FANTER-approach allowed establishing the marginality and specialization of the
ecological niche of Vallonia pulchella molluscs within the studied territory.
The ENFA-approach allows distinguishing the axis of marginality and the axis of specialization (Fig.
4, 6). The test for statistical significance showed that an axis of marginality of the ecological niche of
Vallonia pulchella (γmarg = 4.30, p = 0.001) and two axes of specialization (γspec1 = 10.85, p <0.003;
γspec2 = 6.71, p <0.006) are significantly different from the random distribution. According to the results of
the ENFA-approach, it can be argued that molluscs prefer sites with a high content of humus in the soil, with
higher maximum hygroscopic humidity and shrinkage, but a lower temperature of the upper soil layer. The
marginality of the ecological niche of Vallonia pulchella is closely related to the variability of the aggregate
structure: molluscs prefer sites with a larger proportion in the aggregate structure with sizes ranging from 2-
3 to 10 mm and avoid areas where the share of smaller aggregates increases. Marginality indicators also
point to the fact that molluscs avoid areas with increased soil mechanical impedance throughout the profile.
An important role in the characteristic of marginality is played by indicators of the properties of the
vegetation cover.
The analysis of MADIFA reflects the degree of difference in the observed ecological conditions
from the ecological optimum of the species. The statistical significance test showed that the axes 1 and 2
isolated in the MADIFA analysis differed significantly from the random distribution (γ1 = 11.60, p = 0.16,
γ2 = 6.71, p <0.006), but usually established the significance level which is not considered to be statistically
significant. The main aspects of the difference of the ecological situation in the studied test site from the
ecological optimum Vallonia pulchella are the humus content and soil temperature, the content of some
aggregate fractions, the features of the vegetation cover, expressed with the help of indicators of the
physiognomic structure and phytoindication scales (Fig. 5, 7).
ANALYSIS OF THE SPATIAL ORGANIZATION OF VALLONIA PULCHELLA
40
Figure 6. Results of ENFA-mapping of Vallonia pulchella ecological niche.
The GNESFA variants reveal the various aspects of linking the ecological niche of an animal with
the ecological situation. The analysis of the correlation coefficients between the ENFA and FANTER axes
shows that the marginality presented in the ENFA approach by one axis is divided into two axes within the
framework of the FANTER approach (Table 3).
Table 3. Comparison of the results of ENFA, FANTER and MADIFA spatial analyzes of placement of Vallonia
pulchella molluscs within the test site on sod-lithogenic soils on red-brown clays (only significant correlation
coefficients p <0.05 are shown).
Analysis
ENFA
Marginality
Specialization 1
Specialization 2
FANTER
Component 1
0.35
Component 2
0.23
Component 44
0.86
Component 45
1.00
MADIFA
Component 1
0.15
0.78
0.35
Component 2
0.65
0.48
It should be noted that the ENFA marginality is statistically significant, whereas the FANTER
marginality only differs significantly from the random alternative, taking into account some arbitrariness of
the boundary criterion p = 0.05. Thus, the partition of marginality within the framework of the FANTER
approach leads to a decrease in the statistical validity of the allocation of the corresponding axes. Axes of
specialization, identified in both approaches, are highly correlated.
YORKINA ET AL.
Ecologica Montenegrina, 17, 2018, 29-45 41
Figure 7. Results of MADIFA-mapping of Vallonia pulchella ecological niche.
Correlation of the ENFA and MADIFA axes indicates that the differences in the ecological situation
within the studied range from the ecological optimum Vallonia pulchella (MADIFA axis) reflect the aspect
of specialization of the ecological niche of this species to the greatest degree.
The weighted mean of a give environmental variable with respect to species abundance provides a
computationally simple and reliable estimate of the taxon’s optimum (Biggs, 1990). Ecological niche optima
of the snail studied may be characterized by the ecological parameters values which most important for
marginality and specialization axes identification. Ecological parameters correlated with axes show that
species optimal conditions are possible if optimal value for all corresponding parameters occur
simultaneously. Thus, ecological niche optima may be presented by integral variables such as marginality
and specialization axes and may be plotted in geographic space by means of Habitat Preference Index (HSI)
reproduction.
As noted by the creators of FANTER, the most correct habitat preference map for this species can be
constructed according to the results of MADIFA (Calenge et al., 2008). The correlation coefficient of the
HSI obtained with the help of two approaches is r = 0.60, p = 0.00. This indicates a high degree of
consistency of the results that can be obtained with the help of MADIFA and ENFA procedures. This is also
evidenced by consideration of the spatial variability of the HSI index (Fig. 6, 8). The features of the maps are
due to the different accents that make approaches for assessing habitat preferences. In the framework of the
ENFA-approach, marginality and specialization are taken into account, and within the framework of the
MADIFA approach, the specialization of the ecological niche is taken into account.
Discussion
To describe the ecological niche as a hypervolume within the framework of GNESFA, there are several
points of view: the niche side (FANTER allocates several axes of marginality and specialization, the
separation of the latter is not clear), the environment (MADIFA allows making a mathematically correct
ANALYSIS OF THE SPATIAL ORGANIZATION OF VALLONIA PULCHELLA
42
estimate of the preference index habitats), and also their combination (ENFA allocates one axis of
marginality and several axes of specialization). Another important problem is the choice of measured
environmental parameters, in terms of which the ecological niche is described. Here, along with the
ecological relativity of the parameters, the scale proportionality and instrumental feasibility of collecting the
necessary amount of information is also of great importance. As a rule, the mapping of ecological space is
associated with its mapping in the geographic space (Kunakh, Kolyada, 2010).
Figure 8. Spatial distribution of the habitat preference index (HSI) for Vallonia pulchella within the experimental site
on red-brown clays based on ENFA (top) and MADIFA (bottom) procedures. The arrow indicates the zones of greatest
difference.
Scale proportionality acts as a hierarchy of factors that determine and regulate the dynamics of the
population (Begon et al, 1989). In relation to the mollusks Vallonia pulchella, the characteristics of the
habitat can be divided into two categories: commensurate with the habitat of molluscs and superior to it. The
first group includes characteristics that are measured directly in the same soil samples, of which the molluscs
themselves are selected. These are the content of humus, electrical conductivity, temperature and shrinkage
of the soil, its aggregate structure and soil mechanical impedance in the 0-5 cm layer. The second group can
be referred to the soil mechanical impedance at a depth of more than 5 cm, as well as the characteristics of
the plant. Soil mechanical impedance measurements go beyond the soil layer from which the molluscs are
taken in the vertical direction, and the characteristics of the vegetation cover are 3 × 3 m in the horizontal
YORKINA ET AL.
Ecologica Montenegrina, 17, 2018, 29-45 43
direction, which also significantly exceeds the dimensions of the space within which one individual Vallonia
pulchella presumably lives.
With a significant geographical extension of the study area, the indicators that determine the level of
the mollusc population acquire importance - the moisture gradients, the calcium content and the acidity of
the soil, as well as their phytoindication estimates (Millar, Waite, 1999; Martin, Sommer, 2004; Müller et al.,
2005; Weaver et al., 2006; Schenková et al., 2012). On a large scale, chemical indicators, such as the
availability of food elements or the characteristics of leaf litter, also usually attract attention. As our research
shows, the indexes of the physical state of the soil - aggregate structure, shrinkage, temperature, play an
important role for the Vallonia pulchella geobiont micro-mollusks. An important role of humus in soil is its
value for the formation of soil structure (Medvedev, 2009). These indicators mainly determine the
marginality of the ecological niche.
Conclusion
Local trends, as well as the mosaic nature of the organization of the soil body determine the structure of the
vegetation cover. This explains the role of indicators in the organization of ecological niche of mollusk
Vallonia pulchella, the dimension of which exceeds the size of the ecological space of an individual of this
species. Soil mechanical impedance, as well as phytoindication indicators of vegetation, determine the
peculiarities of marginality and specialization of the ecological niche of Vallonia pulchella. It is the
measurement of these indicators that makes it possible to draw a map of habitat preferences for Vallonia
pulchella.
Thus, ecological niche optima may be presented by integral variables such as marginality and
specialization axes and may be plotted in geographic space by means of habitat suitability index
reproduction.
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The study examined the possibility of using the phytoindication technique to describe habitat preferences of red deer in a relatively homogeneous area. Two alternative hypotheses were tested. Hypothesis 1 suggests that the relationship between red deer and vegetation is due to a trophic factor, so preferences for individual plant species cause vegetation to influence the distribution of animal numbers. Hypothesis 2 suggests that environmental factors influence vegetation, structuring and determining the productive level of the community as a whole. Therefore, environmental factors, rather than individual plant species, cause vegetation-animal interactions. The research was conducted on Biryuchiy Island Spit, where the Azov-Sivash National Nature Park is located. The geobotanical surveys were performed in three types of ecosystems: sandy steppe (vegetation class Festucetea vaginatae), saline meadows (vegetation class Festuco–Puccinellietea), and artificial forest plantation (vegetation class Robinietea). 250 releves were recorded according to the Brown-Blanquet approach. The number of fecal pellets and the number of groups of pellets of red deer was recorded together with geobotanical surveys in the same sample plots. The pellet groups counted in the field were converted to deer densities in specific vegetation classes taking into account the number of pellet groups on the site and the decay rate of the fecal pellets. The vegetation types were distinguished by the number of deer fecal pellets per unit area. The highest number of fecal pellets was found for the plant class Festucetea vaginatae, somewhat fewer fecal pellets were in the plant class Robinietea, and the lowest number was in the plant class Festuco-Puccinellietea. A geometric distribution model is adequate for explaining the experimental data on the number of fecal pellets. A total of 59 species of flowering plants were found. Based on the species composition and projective cover of species, the ecological regimes of ecotopes were identified by phytoindication. The correspondence analysis of the vegetation revealed two ordination axes. The ordination axis 1 (CA1) was able to explain 11.3% of community inertia, and the ordination axis 2 (CA2) was able to explain 5.2% of community inertia. The maximum excretory activity of animals was recorded for the central part of the ordination space, indicating the presence of an optimum zone in the gradient of environmental factors that structure plant communities. The forward selection procedure allowed the Nutrients Availability variable to be selected as the most important variable to explain variation in the plant community structure. The number of deer fecal pellets exhibited different patterns of response in the Nutrients Availability gradient. The response within the plant class Festucetea vaginatae could best be explained by Model III from the list of HOF-models. The response of the excretory activity of deer within the class Festuco-Puccinellietea could best be fitted by the model IV, which represents a symmetric Gaussian curve. The response of excretory activity in the Robinietea vegetation class was asymmetrical bimodal. The ecological properties of the red deer ecological niche in both the drier and less mineralized part of the range of ecological conditions and the wetter and more mineralized part should be assessed in the context of the prospects for future studies.
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The patterns of terrestrial gastropod richness within two species-rich carbonate cliff habitats in eastern Wisconsin were analyzed at two differing sample scales. Up to 23 taxa were found in 1 m 2 quadrats, and 21 taxa in 0.04 m 2 quadrats. These observations are among the highest reported globally for 1 ha or smaller samples. At the 1 m 2 scale, samples collected within 5 m of bedrock outcrops had higher richness than more distant sites. At this scale, only soil pH (not Ca, Mg, N, P, K, percent organic matter, vascular plant species richness, or surface and 20 cm depth soil temperatures) was found to significantly correlate with species richness. At the 0.04 m 2 scale, the richest sites were restricted to areas within 0.5 m of cliff bases. Comparison of maximum richness levels across varying spatial scales demonstrate that up to a third of the total fauna may co-exist in <0.04 m 2 regions (alpha diversity), up to half of the fauna may coexist in <100 m 2 regions (beta diversity), while the remainder of the taxa (gamma diversity) occurs between regions separated by at least 10 km.
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Resource managers often have little information regarding the habitat requirements and distribution of rare species. Factor analysis-based habitat suitability models describe the ecological niche of a species and identify locations where these conditions occur on the landscape using existing occurrence data. We used factor analyses to assess the suitability of habitats for Thamnophis gigas (Giant Gartersnake), a rare, threatened species endemic to the Central Valley of California, USA, and to map the locations of habitat suitable for T. gigas in the Sacramento Valley. Factor analyses indicated that the niche of T. gigas is composed of sites near rice agriculture with low stream densities. Sites with high canal densities and near wetlands also appeared suitable, but results for these variables were sensitive to potential sampling bias. In the Sacramento Valley, suitable habitats occur primarily in the central portion of the valley floor. Based upon the results of the factor analyses, recovery planning for T. gigas will require an on-the-ground assessment of the current distribution and abundance of T. gigas, maintaining the few remaining natural wetlands and the practice rice agriculture in the Sacramento Valley, and studying the effects of agricultural practices and land use changes on populations of T. gigas.
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We studied snail assemblages at 39 plots in hay meadows of the White Carpathians, Czech Republic. We recorded snails quantitatively in 1 m² quadrats, along with vegetation and several measured variables in the same plots in order to investigate the influence of selected environmental factors on meadow snail species composition and richness. The study aimed to determine the extent to which it is possible to use vegetation as a predictor of land snail composition by comparing the predictive power of three groups of variables: (i) measured variables and climatic factors, (ii) vegetation, and (iii) Ellenberg indicator values for plants estimated from plant composition. Detrended correspondence analysis revealed that both snail and plant assemblages were strongly affected by the main environmental gradient running from calcium-poor, wet and cool upland sites to calcium-rich, dry and warm lowland sites. The main changes of vegetation and snail species composition were highly correlated (rs = 0.77, p < 0.001). Soil calcium content and moisture were the most important factors, which explained most of the variation both in the snail and plant assemblages. The interaction of these two factors was even stronger but it was not possible to separate the influence of particular variables on snail species composition and to determine which of these variables made the greatest contribution to the observed pattern. Using the variance partitioning approach, we found that most variation in snail species data was jointly explained by all three groups of variables (i.e., measured variables and climatic factors, vegetation, and Ellenberg indicator values for plants). Even so, the net effects of both vegetation and measured variables were significant. This indicates that vegetation could describe important environmental controls of land snail distribution, even those that are difficult or even impossible to measure directly. We conclude that vegetation composition can be very useful predictor in snail community ecology studies.