Iris pumila L. and the State of Its Populations in the Samara Region (Southeast of the European Part of Russia)

Abstract

The current state of the coenotic populations of Iris pumila L. (Iridaceae) were studied in the southeast of the European part of Russia (Samara Region). The phytocenotic confinement and population structure of the species were assessed. I. pumila preferred growing in steppe zonal communities. In total, 118 species of vascular plants were found in the communities, where I. pumila has been registered, and of which 34 (28.8%) were included into the Red List of the Samara Region and 8 species into the Red List of the Russian Federation. In the study area, populations of I. pumila were represented by a significant number of individuals and were in a stable state. According to the “delta-omega” criterion, the populations were mature (47.0%), transitional (23.5%), maturing (17.6%), and aging (11.9%), which testified to the diversity of population structure and thus to a satisfactory state of the species in the Samara Region. The populations recovered mainly due to individuals of vegetative origin, but this process was rather slow. Under unfavorable conditions, I. pumila populations were characterized by a vegetative settled way of life. Fires, grazing, and destruction of habitats had a significant impact on the population structure and absolute abundance in the Samara Region.

1. Introduction

The conservation of biological diversity on a planetary scale is impossible without identifying and further considering the ecological, biological, and population features of specific representatives of the biota as well as taking into account the ecological and coenotic conditions of their habitats. The comparison of the features of the development of certain individuals and their populations throughout the range seems interesting and reasonable; however, it is impossible without initial and very important stage of such work, which is the study of the species and its phytocenotic environment at specific loci. The accumulation of data on various aspects of the biology and ecology of species makes it possible to compare and to analyze various characteristics in the future, in particular, to identify features and patterns of development at the organismal, species, population, and coenotic levels. Generally, studying the features of biology and ecology of rare species (including plants) makes it possible to assess their state in various environmental conditions, including under anthropogenic load, and thus to conclude on their protection status. Iris pumila L., which has a rather extensive range, due to its reducing number in many regions, may be named as one of such species. The data obtained in our study are important for revealing the mechanisms of adaptation of the species to changing environmental conditions.

I. pumila L. is a short-rhizome herbaceous polycarpous hemiephemeroid growing in the south of Central Europe, the Balkan Peninsula, in Moldova, Ukraine, Crimea, the Caucasus and Transcaucasia, north-west Kazakhstan, and Asia Minor [1,2,3,4] (Figure A1). In Russia, it may be found in almost all black earth regions and reaches of the Southern Urals, where it is replaced by a closely related species I. glaucescens Bunge, in the lower reaches of the Volga and Eastern Ciscaucasia, by I. scariosa Willd. ex-Link. [2]. However, despite the wide distribution, populations of I. pumila isolated from each other due to intensive plowing of the steppe and forest-steppe zones [4]. It is believed that steppe plants may not be adapted to habitat fragmentation since the steppe originally covered vast continuous areas [5]. In this regard, population studies of steppe plants are of significant interest, which make it possible to assess their current state [6,7,8].

Phytocenotically, I. pumila is associated primarily with forb-bunch-grass, sod-grass and sagebrush-bunch-grass steppes and, to a lesser extent, with their halophytic and petrophytic varieties. Currently, it is reported that the species has a fairly wide resistance to the effects of such factors as soil moisture and acidity, its salt regime, soil carbonate content, humidity, frost, and average annual precipitation [9,10]. The factors limiting the distribution of the species are habitat disturbances, such as road construction, trampling, lack of grazing, and competition, with invasive alien species [11] as well as the illumination, air regime of the soil, and its nitrogen content [9].

I. pumila is included into European Red List of Vascular Plants as Data Deficient [11]; in the Red List of the Russian Federation [12], it has the status 3b (rare), as well as in the regional Red Lists of the subjects, where it grows, including the Red List of the Samara Region with status 5, a recovering species [13].

The species was studied for a long time by a number of researchers [4,14,15,16,17,18,19,20,21,22]. In particular, the species morphology was described in detail [18,23,24,25,26,27,28] along with its seed productivity [29] and phytocenotic confinement [30]. I. pumila is a diagnostic species for a number of steppe vegetation associations [31,32,33]. Information about the structure of I. pumila populations is still scarce [23,34,35].

The study aims to describe the population of I. pumila and the phytocenotic conditions of the species habitat in the central part of the range (Samara Region, Russia). The originality of the topic is associated with the replenishment of data on the species using various research methods (population ecology, geobotanical description, and floristics). The research novelty covers the comprehensive approach in studying the species populations and its phytocenotic confinement in the Middle Volga Region, where such work has not been performed earlier.

The study contributes to the issues of population biology and ecology, including the assessment of the direction, duration, intensity, and causes of successional changes in the communities with the species participation, and the identification of a variety of living conditions and responses of I. pumila at the population level to anthropogenic impact.

2. Materials and Methods

Samara Region is located in the southeast of the European part of Russia in the middle reaches of the Volga River (51.394780–54.678116° N; 47.927147–52.566598° E). Botanically and geographically, the territory is located on the border of the European broad-leaved forest and Eurasian steppe regions. The climate is temperate continental with an average monthly temperature of −13.8 °C in January and 20.7 °C in July. The average annual temperature is 3.8 °C, and the average annual precipitation is 372 mm [36].

The study of steppe plant communities, where I. pumila has been registered, was carried out in the Samara Region in 2017–2020 (Figure A2). The processing and interpretation of the obtained geobotanical descriptions was performed from the standpoint of the dominant approach [37,38,39]. All geobotanical descriptions were carried out within the natural contours of plant communities; the projective cover was estimated according to the Drude abundance scale.

Latin plant names are assigned in accordance to the ‘Plants of the World Online’ database (POWO, URL: http://www.plantsoftheworldonline.org/ (accessed on 15 May 2023)). Soil types are given according to the Classification and Diagnostics of Soils of the USSR [40]. Plants were identified using taxonomic keys [1,41,42]. Coordinates of the loci, where geobotanical descriptions were performed, were determined with the Gauss–Krüger system using a GPS device.

Ontogenetic and spatial structure of coenotic populations was assessed according to accepted methods of population ecology [43,44,45,46,47,48,49,50]. When describing the population structure, main ontogenetic stages of the analyzed individuals were taken into account. Based on the data obtained on the quantitative ratio of individuals of different ages in populations, ontogenetic (age) spectra were constructed. For a detailed description of the ontogenetic structure of populations, the main demographic indicators were used: the replenishment index (I_Rep), the recovery index (I_Rec)_, and the aging index (I_Age). The state of the populations was assessed using the ‘delta-omega’ criterion [51].

3. Results and Discussion

1.

Phytocenotic features of Iris pumila habitats

I. pumila is a rather drought-resistant species and phytocenotically most closely related to the subzonal types of true (forbs-bunch-grass), arid (bunch-grass), and desert-like (sagebrush-bunch-grass) steppes. Due to current mass plowing of zonal steppes, I. pumila is more common in their edaphic (petrophytic, psammophytic, and halophytic) habitats and in non-zonal communities of steppe ravines and river valleys. In the ravines and on the slopes of the valleys, the populations of I. pumila are confined to more or less gently sloping watersheds, upper and middle parts of the steppe slopes, as well as to the edges of low-growing shrubs.

In total, eight steppe communities with I. pumila L. are described in the Samara Oblast: Stipa pulcherrima + herbae stepposae [+ Iris pumila]; Festuca valesiaca + herbae stepposae [+ Iris pumila]; Stipa capillata + herbae stepposae [+ Iris pumila]; Festuca valesiaca + Artemisia marschalliana [+ Iris pumila]; Festuca valesiaca + Stipa pennata [+ Iris pumila]; Galatella villosa + Festuca valesiaca [+ Iris pumila]; Helictotrichon desertorum + herbae stepposae [+ Iris pumila], and Agropyron desertorum + Iris pumila + Gypsophila altissima. Their ecological and phytocenotic features are given below.

Community Stipa pulcherrima + herbae stepposae [+ Iris pumila] (loci nos. 1 and 9;

Table A1. Geobotanical descriptions of steppe phytocenoses that include Iris pumila L. in the Samara Region, Russia.

Locus No.	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20
Date (dd.mm.yyyy)	07.06.2017	07.06.2017	07.06.2017	30.04.2017	02.05.2017	30.04.2017	01.05.2017	02.05.2017	26.07.2017	26.07.2017	11.06.2018	25.07.2018	25.07.2018	25.07.2018	21.05.2019	16.08.2019	16.08.2019	15.06.2019	15.06.2019	11.05.2020	Occurrence
GPS coordinates of the locus (N)	53°53.762′	53°55.589′	53°53.511′	51°57.490′	51°57.644′	51°57.614′	51°53.747′	51°57.639′	53°53.039′	53°53.043′	54°02.003′	53°56.236′	53°5 6.571′	53°56.579′	53°55.001′	53°54.458′	53°54.455′	53°55.591′	53°53.513′	53°19.102′
GPS coordinates of the locus (E)	051°06.847′	051°16.157′	051°17.301′	050°45.960′	050°46.035′	050°46.014′	050°44.558′	050°46.059′	050°50.012′	050°50.007′	050°54.003′	051°33.288′	051°35.250′	051°35.263′	050°28.420′	050°24.161′	050°24.550′	051°16.159′	051°17.303′	050°11.402′
Locus size, m2	100	20	20	25	25	70	30	70	100	100	100	100	100	100	100	100	100	25	25	25
Total projective cover, %	90	90	90	90	80	90	70	80	70	60	40	50	40	60	90	80	80	90	90	90
Number of species at the locus	47	17	22	13	15	16	18	22	44	34	31	28	25	30	40	28	28	21	25	28
Species composition
Iris pumila	sp.	cop1	sp.	sp.	sp.	sp.	sp.	sp.	sp.	sp.	sp.	sp.	sp.	sp.	sp.	sp.	sp.	cop1	sp.	cop2	100
Festuca valesiaca	sp.	cop3	sp.	cop3	cop3	cop3	cop3	cop3	sp.	cop3	cop3	cop2	cop2	cop2	.	sol.	sol.	cop3	sp.	.	90
Galatella villosa	sp.	.	sol.	sol.	sol.	sol.	.	sol.	.	.	sol.	cop3	cop3	cop3	sol.	sol.	sol.	sol.	sol.	.	75
Euphorbia seguieriana	sp.	.	sol.	.	.	.	.	.	sol.	sol.	sol.	sol.	sol.	sol.	sol.	sol.	sol.	sol.	sol.	sol.	70
Artemisia marschalliana	.	.	sp.	cop2	cop2	sol.	sp.	sol.	.	.	.	sol.	.	sol.	sol.	.	sol.	.	sp.	sol.	60
Allium strictum	.	.	cop1	.	.	.	sol.	sol.	sol.	sol.	.	sol.	.	sol.	.	sol.	sol.	sol.	cop1	.	55
Gypsophila altissima	sol.	sp.	sol.	.	.	.	.	.	sp.	.	.	sol.	.	.	sol.	sol.	sol.	sp.	sol.	cop1	55
Rhaponticoides ruthenica	.	.	.	.	.	sol.	.	sol.	sol.	sp.	sol.	sol.	sol.	sol.	sol.	.	.	.	.	sol.	50
Psephellus sumensis	sol.	.	.	.	.	.	.	.	sol.	sol.	sol.	sol.	sol.	sol.	sol.	sol.	.	.	.	sp.	50
Eremogone procera	sol.	.	.	sol.	sol.	.	.	.	sol.	.	sol.	sol.	.	sol.	sol.	sol.	sol.	.	.	.	50
Rostraria cristata	sp.	.	.	.	.	.	.	.	.	sol.	sol.	sol.	sol.	sol.	sol.	sol.	sol.	.	.	sp.	50
Potentilla incana	sol.	.	sol.	.	.	.	.	.	sp.	.	.	sol.	sol.	sol.	sol.	sol.	sol.	.	sol.	.	50
Thymus marschallianus	.	.	sp.	.	.	.	.	.	sol.	sol.	sol.	sol.	sol.	sol.	sol.	.	.	.	sp.	sol.	50
Asparagus officinalis	sol.	.	sol.	.	.	.	.	.	.	.	sol.	.	sol.	sol.	sol.	sol.	sol.	.	sol.	.	45
Echinops ritro subsp. meyeri	sol.	.	sol.	.	.	.	.	.	sol.	sol.	sol.	.	.	.	sol.	sol.	sol.	.	sol.	.	45
Prunus tenella	.	.	.	.	.	sol.	sol.	sol.	sol.	sol.	.	.	sol.	sol.	.	.	.	.	.	sp.	40
Chamaecytisus ruthenicus	sol.	.	sol.	.	.	.	.	.	sol.	.	.	.	.	.	sol.	.	sol.	sol.	sol.	sp.	40
Ephedra distachya	.	.	.	.	.	.	sol.	sol.	.	sol.	.	sol.	sol.	sol.	sol.	.	.	.	.	sol.	40
Onosma simplicissima	sol.	.	sp.	.	.	.	.	.	sp.	sol.	sol.	.	.	.	sol.	.	sol.	.	sp.	.	40
Salvia stepposa	sol.	.	.	.	.	.	.	.	sol.	.	sol.	.	sol.	sol.	sol.	sol.	sol.	.	.	.	40
Hedysarum grandiflorum	sol.	.	.	.	.	.	.	.	sp.	.	sol.	sol.	sol.	sol.	sol.	.	.	.	.	.	35
Medicago falcata subsp. romanica	sol.	sp.	sol.	.	.	.	.	.	sol.	.	.	sol.	.	.	.	.	.	sp.	sol.	.	35
Scorzonera austriaca	sol.	sol.	.	.	.	.	.	.	sol.	.	sol.	.	.	.	.	.	.	sol.	sol.	sol.	35
Adonis volgensis	sol.	.	.	.	sol.	sol.	.	sol.	.	sol.	.	.	.	.	.	.	.	.	.	sol.	30
Agropyron desertorum	.	.	.	sol.	.	.	.	sol.	.	.	.	sol.	sol.	sol.	.	.	.	.	.	cop3	30
Bromus inermis	.	sp.	sol.	sp.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	sol.	.	30
Galium ruthenicum	sol.	.	.	.	.	.	.	.	sol.	sol.	.	.	.	.	sol.	sol.	sol.	.	.	.	30
Galium verum	.	sol.	sol.	.	.	.	sol.	.	.	.	.	sol.	.	.	.	.	.	sol.	sol.	.	30
Jurinea ewersmannii	sol.	.	.	.	.	.	.	.	sol.	.	sol.	.	.	.	.	sol.	sol.	.	.	sol.	30
Lomelosia isetensis	.	.	.	.	.	.	.	.	sp.	sp.	sol.	sol.	sol.	sol.	.	.	.	.	.	.	30
Spiraea crenata	.	.	.	.	.	sol.	sol.	sol.	.	.	.	.	.	.	sol.	sol.	.	.	.	sp.	30
Stipa pennata	cop1	.	.	.	.	cop2	cop2	cop2	.	cop2	cop2	.	.	.	.	.	.	.	.	.	30
Stipa pulcherrima	cop3	.	.	.	.	.	.	.	cop3	.	sol.	.	.	.	sol.	sp.	sp.	.	.	.	30
Tanacetum kittaryanum subsp. sclerophyllum	sol.	.	.	.	.	.	.	.	.	.	sol.	sol.	sol.	sol.	.	sol.	.	.	.	.	30
Tulipa biebersteiniana	.	.	.	sol.	sol.	sol.	sol.	sol.	.	.	.	.	.	.	.	.	.	.	.	sol.	30
Alyssum lenense	.	.	.	.	.	.	.	.	sol.	.	.	sol.	sol.	sol.	sol.	.	.	.	.	.	25
Ferula tatarica	.	.	.	sol.	sol.	sol.	sol.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	25
Genista tinctoria	sol.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	sol.	sol.	sol.	.	.	.	25
Hedysarum razoumowianum	sol.	.	.	.	.	.	.	.	sp.	sp.	sol.	.	.	.	sol.	.	.	.	.	.	25
Nepeta ucranica	sol.	.	.	.	.	.	.	.	.	.	.	sol.	sol.	sol.	sol.	.	.	.	.	.	25
Nonea pulla	.	sol.	sol.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	sol.	sol.	.	25
Jacobaea erucifolia	.	.	.	sol.	sol.	.	sol.	sol.	.	.	.	.	.	.	.	.	.	.	.	sol.	25
Achillea setacea	.	sol.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	sol.	.	20
Allium rotundum	.	sol.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	sol.	sol.	.	20
Alyssum gymnopodum	.	.	.	.	.	.	.	.	sp.	.	.	sol.	sol.	sol.	.	.	.	.	.	.	20
Artemisia salsoloides	.	.	.	.	.	.	.	.	.	.	sol.	.	sol.	sol.	sol.	.	.	.	.	.	20
Filipendula vulgaris	sol.	.	sol.	.	.	.	.	.	.	.	.	.	.	.	sol.	.	.	.	sol.	.	20
Gagea minima	.	.	.	.	.	sol.	sol.	sol.	.	.	.	.	.	.	.	.	.	.	.	sol.	20
Galatella angustissima	.	.	.	.	.	.	.	.	sol.	sol.	.	.	.	.	.	sol.	sol.	.	.	.	20
Goniolimon elatum	.	.	.	.	.	.	.	.	.	.	sol.	sol.	sol.	sol.	.	.	.	.	.	.	20
Jurinea ledebourii	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	sol.	sol.	.	.	.	20
Linum flavum	sol.	.	.	.	.	.	.	.	sol.	.	sol.	.	.	.	sol.	.	.	.	.	.	20
Origanum vulgare	.	.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	sol.	.	sol.	.	20
Polygala comosa	sol.	.	.	.	.	.	.	.	.	.	sol.	.	.	.	sol.	.	sol.	.	.	.	20
Scorzonera hispanica	sol.	.	.	.	.	.	.	.	.	.	sol.	.	.	.	sol.	sol.	.	.	.	.	20
Stipa capillata	.	.	soc.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	sol.	.	soc.	.	20
Taraxacum serotinum	sol.	.	.	.	.	.	.	.	.	.	sol.	.	.	.	.	sol.	sol.	.	.	.	20
Thalictrum simplex	.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	sol.	sol.	.	.	.	sol.	20
Verbascum chaixii subsp. orientale	sol.	.	.	.	.	.	sol.	sol.	.	sol.	.	.	.	.	.	.	.	.	.	.	20
Vincetoxicum hirundinaria subsp. stepposum	sol.	.	.	.	.	.	.	.	sol.	.	sol.	.	.	.	sol.	.	.	.	.	.	20
Viola ambigua	.	.	.	.	.	.	.	.	sol.	sol.	.	.	.	.	sol.	.	.	.	.	sol.	20
Anemone sylvestris	sol.	.	.	.	.	.	.	.	sol.	sol.	.	.	.	.	.	.	.	.	.	.	15
Artemisia austriaca	.	.	.	.	sol.	sol.	.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	15
Aster alpinus	sol.	.	.	.	.	.	.	.	.	.	sol.	.	.	.	sol.	.	.	.	.	.	15
Astragalus macropus	.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	sol.	sol.	.	.	.	15
Astragalus onobrychis	.	sol.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	sol.	.	.	15
Astragalus wolgensis	.	.	.	.	.	.	sol.	sol.	.	.	.	.	.	.	sol.	.	.	.	.	.	15
Bassia prostrata	.	.	.	.	.	.	sol.	sol.	.	.	.	sol.	.	.	.	.	.	.	.	.	15
Campanula sibirica	sol.	.	.	.	.	.	.	.	sol.	.	sol.	.	.	.	.	.	.	.	.	.	15
Centaurea scabiosa	sol.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	sol.	.	.	.	15
Prunus fruticosa	.	.	.	.	.	.	.	.	sol.	sol.	.	.	.	.	.	.	.	.	.	sp.	15
Helictotrichon desertorum	.	.	.	.	.	.	.	.	.	.	.	.	.	.	cop3	cop3	cop3	.	.	.	15
Oxytropis spicata	.	.	.	.	.	.	.	.	.	.	.	.	sol.	sol.	sol.	.	.	.	.	.	15
Rindera tetraspis	.	.	.	.	.	sol.	sol.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	15
Tulipa suaveolens	.	.	.	.	.	sol.	sol.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	15
Veronica incana	.	.	.	.	.	.	.	.	.	.	.	sol.	sol.	sol.	.	.	.	.	.	.	15
Veronica prostrata	.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	sol.	.	15
Astragalus danicus	.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	.	.	10
Astragalus testiculatus	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	10
Cephalaria uralensis	.	.	.	.	.	.	.	.	.	.	.	sol.	.	sol.	.	.	.	.	.	.	10
Cichorium intybus	.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	.	.	10
Erysimum cuspidatum	.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	.	.	10
Fritillaria ruthenica	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	10
Globularia bisnagarica	.	.	.	.	.	.	.	.	sp.	sp.	.	.	.	.	.	.	.	.	.	.	10
Pentanema hirtum	.	.	.	.	.	.	.	.	sol.	sol.	.	.	.	.	.	.	.	.	.	.	10
Pentanema salicinum	sol.	.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	.	.	10
Knautia arvensis	.	.	.	sol.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	10
Lappula squarrosa	.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	.	.	10
Ornithogalum fischerianum	.	.	.	sol.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	10
Oxytropis floribunda	.	.	.	.	.	.	.	.	.	.	.	.	sol.	sol.	.	.	.	.	.	.	10
Oxytropis pilosa	sol.	.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	.	.	10
Pedicularis kaufmannii	sol.	.	.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	.	10
Phlomis herbaventi subsp. pungens	.	.	.	sol.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	10
Reseda lutea	.	.	.	.	.	.	.	.	.	.	.	sol.	.	sol.	.	.	.	.	.	.	10
Seseli libanotis	.	.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	.	10
Valeriana tuberosa	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	10
Caragana frutex	.	sp.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	.	.	10
Achillea nobilis	.	.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	.	.	5
Aster amellus	.	.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	.	.	5
Astragalus tenuifolius	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	5
Astragalus zingeri	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	sp.	5
Centaurea diffusa	.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	.	.	.	5
Cotoneaster laxiflorus	.	.	.	.	.	.	.	.	.	sp.	.	.	.	.	.	.	.	.	.	.	5
Euphorbia semivillosa	.	.	.	.	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	5
Hieracium virosum	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	5
Hypericum perforatum	.	.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	.	.	5
Krascheninnikovia ceratoides	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	5
Onobrychis arenaria	.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	.	.	.	5
Phlomoides tuberosa	.	.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	.	.	5
Pimpinella tragium	.	.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	.	.	5
Tanacetum corymbosum									.	sol.	.	.	.	.	.	.	.			.	5
Rosa majalis	.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	.	.	.	5
Serratula coronata	sol.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	5
Seseli tortuosum	.	.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	.	.	5
Silenebaschkirorum	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	5
Stipa korshinskyi	cop1	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	5
Thesium ramosum	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	.	sol.	5
Trinia multicaulis	.	.	.	.	.	.	.	.	sol.	.	.	.	.	.	.	.	.	.	.	.	5

, Figure A3). The descriptions were performed on 7 June 2017 at the right bank of the Kozak River, on the top of a hill located 1.7 km southwards off the village Sok and 5.6 km southwestwards off the village Sergievsk, PA, “Mountains on the Kazachka River” and on 26 July 2017 on the left bank of the Elkha River on the hill slope, 4 km westwards off the village Chekalino, valley-drainage geosystem of the Sok River (Sergievsky District). Total projective cover (hereinafter, TPC) varied from 70 to 90%. The number of species per locus was 47. The aspect was variegated pale green. The grassing was weak. The soil was dry, loose, chernozem type, with medium and coarse gravel. The herbage was composed of three sub-tiers. Loci nos. 25–28 were characterized by similar parameters (

Table A2. Features of the demographic structure of the Iris pumila L. populations.

Locus No.	IRep	IRec	IAg	∆	ω	Type of Population	Geographical Area	GPS Coordinates of the Locus (N)	GPS Coordinates of the Locus (E)
21	0.26	0.28	0.08	0.50	0.71	mature	Natural monument “Kamenny Dol”	53°17.105′	050°35.312′
22	0.25	0.29	0.11	0.44	0.70	transitional		53°17.314′	050°35.423′
23	0.38	0.47	0.16	0.39	0.64	transitional	Natural monument “Gora Kopeika”	53°40.425′	052°09.246′
24	0.17	0.18	0.08	0.55	0.71	aging		53°40.386′	052°10.240′
25	0.24	0.26	0.08	0.48	0.72	mature	Natural monument “Zelenaya Gora”	53°53.147′	050°25.569′
26	0.23	0.28	0.17	0.51	0.71	mature	Natural monument “Syrnovodny Shikhan”	53°53.519′	051°17.404′
27	0.64	0.64	0.00	0.33	0.61	maturing		53°54.150′	051°17.508′
28	0.10	0.12	0.16	0.58	0.74	aging		53°53.354′	051°17.229′
29	0.35	0.35	-	0.41	0.74	mature	Natural monument “Mulin Dol”	52°05.529′	051°20.262′
30	0.66	0.70	0.04	0.30	0.65	maturing		52°06.160′	051°19.532′
31	0.33	0.47	0.25	0.48	0.62	transitional		52°07.146′	051°22.282′
32	0.09	0.10	0.10	0.52	0.81	mature	Natural monument “Kamenny Log-1, 2, 3”	52°13.408′	051°08.098′
33	0.15	0.15	-	0.50	0.76	mature		52°14.369′	051°11.458′
34	0.26	0.28	0.07	0.47	0.73	mature	Mount Mogutova, Samarskaya Luka National Park	53°25.182′	049°29.206′
35	0.47	0.48	0.02	0.37	0.67	transitional		53°25.018′	049°31.112′
36	0.54	0.55	0.02	0.34	0.66	maturing		53°25.081′	049°29.236′
37	0.19	0.19	-	0.45	0.81	mature	Gubinskie Vysoty Heights	53°17.468′	048°43.227′

Note. ∆ is the age index; ω, the efficiency index; I_Rep, replenishment index; I_Rec, recovery index; I_Ag, aging index.

).

In the sub-tier I (1-2 m), along with sparse tall grass (Asparagus officinalis L., Centaurea diffusa Lam., C. scabiosa L., Echinops ritro subsp. meyeri (DC.) Kouharov, Rhaponticoides ruthenica (Lam.) M.V. Agab. and Greuter, and Verbascum chaixii subsp. orientale Hayek), there were single shrubs: Chamaecytisus ruthenicus (Fisch. ex Wol.) Klásk., Krascheninnikovia ceratoides (L.) Gueldenst., Prunus fruticosa Pall., P. tenella Batsch, and Rosa majalis Herrm.

Sub-tier II (35—70 cm) was formed by the main edificator of the community, Stipa pulcherrima K.Koch (cop₃). The other grasses were characterized by minor abundance and did not even act as a co-edificator (Stipa korshinskyi Roshev., S. pennata L., Festuca valesiaca Schleich. ex Gaudin (sp.), and Rostraria cristata (L.) Tzvelev (sp.)). Motley grasses were represented by Medicago falcata subsp. romanica (Prodán) Hayek, Hedysarum grandiflorum Pall. (sp.-sol.), and H. razoumowianum Helm and Fisch. ex DC. (sp.-sol.), and forbs by Centaurea scabiosa, Filipendula vulgaris Moench, Galium ruthenicum Willd., Genista tinctoria L., Gypsophila altissima L. (sp.-sol.), Jurinea ewersmannii Bunge, Salvia stepposa Des.-Shost. and Verbascum chaixii subsp. orientale.

In sub-tier III (up to 30 cm), species characterized by high occurrence and abundance were Iris pumila, Euphorbia seguieriana Neck., Onosma simplicissima L. and Potentilla incana P.Gaertn., B.Mey. and Scherb. Species of short grasses that were found scarcely: Anemone sylvestris L., Campanula sibirica L., Eremogone procera (Spreng.) Rchb., Linum flavum L., Psephellus sumensis (Kalen.) Greuter, Scorzonera austriaca Willd. and Vincetoxicum hirundinaria subsp. stepposum (Pobed.) Markgr. Species found only once were Adonis volgensis Steven ex DC., Allium rotundum L., A. strictum Schrad., Alyssum gymnopodum P.A. Smirn., A. lenense Adams, Aster alpinus L., Astragalus onobrychis L., A. tenuifolius L., A. testiculatus Pall., Fritillaria ruthenica, Galatella angustissima (Tausch) Novopokr., G. villosa (L.) Rchb.f., Globularia bisnagarica L., Jurinea ledebourii Bunge, Lomelosia isetensis (L.) Soják, Nepeta ucranica L., Nonea pulla (L.) DC., Onobrychis arenaria (Kit.) DC., Oxytropis pilosa (L.) DC., Pedicularis kaufmannii Pinzger, Pentanema hirtum (L.) D.Gut.Larr., Santos-Vicente, Anderb., E.Rico and M.M.Mart.Ort., P. salicinum (L.) D.Gut.Larr., Santos-Vicente, Anderb., E.Rico and M.M.Mart.Ort., Polygala comosa Schkuhr, Scorzonera hispanica L., Serratula coronata L., Tanacetum kittaryanum subsp. sclerophyllum (Krasch.) Tzvelev, Taraxacum serotinum (Waldst. and Kit.) Poir., Thalictrum simplex L., Thymus marschallianus Willd., Trinia multicaulis (Poir.) Schischk. and Viola ambigua Waldst. and Kit.

Community Festuca valesiaca + Herbae stepposae [+ Iris pumila] (loci nos. 2 and 18; Table A1, Figure A4). The descriptions were made on 7 June 2017 and 15 June 2019, 1 km northeastwards off Sernovodsk town, on the top of the Sernovodsk Upland, the valley-drainage geosystem of the Surgut River (Sergievsky district). Locus size 20–25 m². TPC 90%. The average number of species in the descriptions was 19. The aspect variegated green. Average grassing. The soil was dry, crumbly, chernozem type, dusty, fine to coarsely gravel. Loci nos. 21, 23, 29, 34 were characterized by similar parameters (Table A2).

The herbage was composed of three sub-tiers. Sub-tier I (100–120 cm) was presented by sparse shrubs Caragana frutex (L.) K.Koch (sp.-sol.) and Chamaecytisus ruthenicus (once).

Sub-tier II (35–70 cm) was formed by Festuca valesiaca (cop₃), the main edificator of the community. Astragalus danicus Retz., A. onobrychis, Bromus inermis Leyss., Cichorium intybus L., Galium verum L., Gypsophila altissima, and Medicago falcata subsp. romanica were characterized by high occurrence but low abundance.

I. pumila dominated in the III sub-tier (up to 30 cm). Low-grass species such as Achillea setacea Waldst. and Kit., Allium rotundum, Erysimum cuspidatum (M.Bieb.) DC., Lappula squarrosa (Retz.) Dumort., Nonea pulla, Scorzonera austriaca, and Veronica prostrata L.; Allium strictum, Galatella villosa, and Euphorbia seguieriana were found only once each.

Community Stipa capillata + Herbae stepposae [+ Iris pumila] (loci nos. 3 and 19; Table A1, Figure A5). Descriptions made on 7 June 2017 and 15 June 2019, on the top of the slope of the western exposure of the hill, 3 km southeastwards off Sernovodsk and 3.5 km eastwards off the village Sukhodol, PA “Sernovodsky Shikhan” (Sergievsky District). Locus size 20–25 m². TPC 90%. The average number of species in the descriptions was 24. The aspect variegated pale green. The grassing was weak. The soil was dry, loose, chernozem type, with medium and coarse gravel. Loci nos. 22, 24, 33, 35 were characterized by similar parameters (Table A2).

The herbage was composed of three sub-tiers. In sub-tier I (100–120 cm), single Chamaecytisus ruthenicus shrubs were noted along with sparse tall grasses (Asparagus officinalis, Echinops ritro subsp. meyeri, and Seseli libanotis (L.) W.D.J.Koch).

Sub-tier II (35–70 cm) was formed by Stipa capillata L. (soc.), the main edificator of the community. Cereals were presented by Festuca valesiaca and Bromus inermis, legumes, by Medicago falcata subsp. romanica, forbs, by Artemisia marshalliana Spreng., Filipendula vulgaris, Galium verum, Gypsophila altissima, and Origanum vulgare L. Allium strictum dominated in sub-tier III (up to 30 cm), and I. pumila was also presented with high occurrence and abundance, as well as Onosma simplicissima and Thymus marschallianus (sp.). Lower abundance was inherent to Achillea setacea, Allium rotundum, Euphorbia seguieriana, Galatella villosa, Nonea pulla, Potentilla incana, Scorzonera austriaca, and Veronica prostrata.

Community Festuca valesiaca + Artemisia marschalliana [+ Iris pumila] (loci nos. 4 and 5; Table A1). Descriptions were performed on 30 April–2 May 2017, 7 km northwestwards off the village Polyakov, on the margin of the right slopes of the PA “Balka Kladovaya”, the valley-drainage geosystem of the Talovka River (Bolshechernigovsky District). Locus sizes 25 m². TPC 80–90%. The average number of species was 14. The aspect brown-greenish. The grassing is average. The soil was dry, crumbly, chernozem type, dusty, fine to coarse gravel. Loci nos. 30–32 were characterized by similar parameters (Table A2).

The herbage was composed of two sub-tiers. Sub-tier I (35–70 cm) was formed by Festuca valesiaca (cop₃) and Artemisia marshalliana. Agropyron desertorum (Fisch. ex Link) Schult., Bromus inermis, Euphorbia semivillosa (Prokh.) Krylov, Jacobaea erucifolia (L.) G.Gaertn., B.Mey. and Scherb. and Knautia arvensis (L.) Coult. were characterized by high occurrence and low abundance.

Sub-tier II (up to 30 cm) was sparse, represented by I. pumila and Adonis volgensis, Artemisia austriaca Jacq., Eremogone procera, Ferula tatarica Fisch. ex Spreng., Galatella villosa, Ornithogalum fischerianum Krasch., Phlomis herba-venti subsp. pungens (Willd.) Maire ex DeFilipps, Tulipa biebersteiniana Schult. and Schult.f.

Community Festuca valesiaca + Stipa pennata [+ Iris pumila] (loci nos. 6–8, 10, 11, Table A1, Figure A6). Descriptions were performed on 30 April–2 May 2017, 7 km northwestwards off the village Polyakov, on the margin of the right slopes of the PA “Balka Kladovaya”, the valley-drainage geosystem of the Talovka River and 5 km south-westwards off the village Polyakov “Urochishche Bastandyk” (Bolshechernigovsky District); on 26 July 2017, on the left bank of the Elkha River on the slope of a hill, 4 km westwards off the village Chekalino, valley-drainage geosystem of the Sok River; and on 11 June 2018, on the southern slope of the Soksky Yars in the vicinity of the village Krasnoselskoe (Sergievsky District). Locus sizes were 30–70 m². TPC from 70 to 90%. The average number of species was 19. The aspect variegated green. The grassing was weak. The soil was dry, loose, chernozem type, coarse gravel with traces of fallen, almost no rags. The vertical structure of communities was two-tiered.

The shrub tier, 100–120 cm, TCP 10–15%, formed by Bassia prostrata (L.) Beck, Cotoneaster laxiflorus J.Jacq. ex Lindl., Prunus fruticosa, P. tenella(sp.), and Spiraea crenata L.

The herbage was represented by two or three sub-tiers. Sub-tier I (100–120 cm) was sparse, formed by Rhaponticoides ruthenica (sp.-sol.) and Verbascum chaixii subsp. orientale.

Sub-tier II (35–70 cm) was formed by Festuca valesiaca (cop₃) and Stipa pennata (cop₂). Artemisia marschalliana (sp.-sol.), Ferula tatarica, and Jacobaea erucifolia were characterized by high occurrence; less common were Echinops ritro subsp. meyeri, Galatella angustissima, Galium ruthenicum, Phlomoides tuberosa (L.) Moench, Tanacetum corymbosum (L.) Sch.Bip. and Seseli tortuosum L.

Sub-tier III (up to 30 cm) was formed by Adonis volgensis, Allium strictum, Artemisia austriaca, Astragalus wolgensis Bunge, Ephedra distachya L., Gagea minima (L.) Ker Gawl., Galatella villosa, Rindera tetraspis Pall., Tulipa biebersteiniana, and T. suaveolens Roth. Less often, by Achillea nobilis L., Anemone sylvestris, Aster amellus L., Euphorbia seguieriana, Galium verum, Globularia bisnagarica, Hedysarum razoumowianum, Hypericum perforatum L., Onosma simplicissima, Oxytropis pilosa, Pentanema hirtum, P. salicinum, Pimpinella tragium Vill., Psephellus sumensis, Lomelosia isetensis, Thymus marschallianus, Valeriana tuberosa L. and Viola ambigua. I. pumila formed small clumps, and its projective cover in pinnate-feather grass-fescue communities ranged from 10 to 15%.

Community Galatella villosa + Festuca valesiaca [+ Iris pumila] (loci nos. 12–14, Table A1, Figure A7). The descriptions were made on 25 July 2018 on the right bank of the Sukharka River on the slopes of a hill, 2 km northwards off the village Sukhar Matak, 4.3 km eastwards off the village Novoe Yakushkino, PA “Isaklinskaya Upland Forest-Steppe” (Isaklinsky District). Locus size 30–70 m². TPC 70–90%. The average number of species was 19. The aspect variegated green. The grassing was weak. The soil was dry, loose, chernozem type, with coarse gravel, almost no rags. Loci nos. 36 and 37 were characterized by similar parameters (Table A2).

The vertical structure is single-tier. The herbaceous tier was represented by three sub-tiers.

Sub-tier I (100–120 cm) was sparse, represented by Artemisia salsoloides Willd., Asparagus officinalis, Cephalaria uralensis (Murray) Schrad. and Rhaponticoides ruthenica. In addition to herbaceous species, Bassia prostrata and Prunus tenella shrubs take part in the formation of this sub-tier.

Sub-tier II (35–70 cm) was formed by the co-edificator, Festuca valesiaca. Agropyron desertorum, Artemisia marschalliana, Goniolimon elatum (Fisch. ex Spreng.) Boiss., Rostraria cristata, and Lomelosia isetensis were noted with high occurrence in addition to fescue.

Sub-tier III (up to 30 cm) was formed by Galatella villosa. Allium strictum, Alyssum gymnopodum, A. lenense, Ephedra distachya, Eremogone procera, Euphorbia seguieriana, Hedysarum grandiflorum, Nepeta ucranica, Oxytropis floribunda (Pall.) DC., O. spicata (Pall.) O.Fedtsch. and B.Fedtsch., Potentilla incana, Psephellus sumensis, Reseda lutea L., Salvia stepposa, Tanacetum kittaryanum subsp. sclerophyllum, Thymus marschallianus, and Veronica incana L. were also present with high occurrence but low abundance. I. pumila had high occurrence, and its projective cover varied from 10 to 20%.

Community Helictotrichon desertorum + Herbae stepposae [+ Iris pumila] (loci nos. 15–17, Table A1). Descriptions were made from 21 May–16 August 2019 at the top of the southeastern slope of the hill, 1.5 km southeastwards off the village Tukshum, the Pustynovka natural landmark, PA “Mountain Lysaya” and in the vicinity of the village of Zelenogorsky (Elkhovsky District). Locus size 20 m². TPC 90%. The number of species was 21. The aspect variegated pale green. The grassing was weak. The soil was dry, loose, calcareous gray chernozem, with medium to coarse gravel. The vertical structure was single-tiered. The herbage was represented by three sub-tiers.

Community Agropyron desertorum + Iris pumila + Gypsophila altissima (locus no. 20, Table A1). The description was made on 11 May 2020. The upper part of the slope in the Sokol’iy Gory massif, the Kozeyrog natural landmark, PA “Sokol’i Gory and the Volga River bank between the Studyony and Koptev ravines (Samara city)”. Locus size 25 m². TPC 90%. The number of species was 28. The aspect variegated bright green. The grassing was average. The soil was dry, loose, calcareous chernozem of a gray-whitish hue, with medium to coarse gravel. The vertical structure of communities was two-tiered.

Shrub tier, 100–120 cm, with up to 20% projective cover represented by Chamaecytisus ruthenicus, Prunus fruticosa, P. tenella, and Spiraea crenata.

The herbaceous tier occupied up to 80% of the coenosis area and was represented by two sub-tiers. Sub-tier I, 35–70 cm, formed by Agropyron desertorum, the edificator of the community. Agropyron desertorum, Artemisia marshalliana, Gypsophila altissima, Jurinea ewersmannii, Rostraria cristata, and Jacobaea erucifolia had high occurrence, but low abundance.

In the second sub-tier (20–30 cm), I. pumila dominated, and its projective cover reached 55% of TCP. Astragalus zingeri Korsh. and Psephellus sumensis also had high abundance. Other registered species had a relatively low abundance (Adonis volgensis, Ephedra distachya, Euphorbia seguieriana, Fritillaria ruthenica Wikstr., Gagea minima, Hieracium virosum Pall., Scorzonera austriaca, Silene baschkirorum Janisch., Thalictrum simplex, Thesium ramosum Hayne, Thymus marshallianus, Tulipa biebersteiniana, Valeriana tuberosa, and Viola ambigua).

In total, 118 species of vascular plants are found in the communities, where I. pumila is registered, and of which 34 (28.8%) are rare and are included in the Red List of the Samara Region [13]: Adonis volgensis, Alyssum lenense, Astragalus macropus, A. tenuifolius, A. volgensis, Aster alpinus, Cephalaria uralensis, Ephedra distachya, Eremogone procera, Ferula tatarica, Galatella angustissima, Goniolimon elatum, Jurinea ewersmannii, J. ledebourii, Linum flavum, Nepeta ucranica, Ornithogalum fischerianum, Oxytropis floribunda, Rindera tetraspis, Lomelosia isetensis, Silene baschkirorum, Stipa korshinskyi, Tanacetum sclerophyllum, Tulipa biebersteiniana, T. suaveolens, and Valeriana tuberosa; Artemisia salsoloides, Astragalus zingeri, Fritillaria ruthenica, Globularia bisnagarica, Hedysarum grandiflorum, H. razoumowianum, Stipa pennata, and S. pulcherrima, which are also included into the Red List of Russian Federation [12].

Data obtained during our studies when analyzing the phytocenoses, where I. pumila is presented, allow to characterize this species as stenobiont in relation to climatic conditions and as hemistenobiont in relation to soil and phytocenotic conditions, which generally corresponds to previous results presented in the monograph by L.A. Zhukova et al. [51]. Climate is a limiting environmental factor for the development and conservation of I. pumila populations; this suggestion is also consistent with the data by A.V. Kryukova and L.M. Abramova [29], who have revealed the dependence of various parameters of I. pumila specimens on weather conditions.

As a rule, I. pumila does not reach high abundance in communities, and it is an assectator. Similar data have been obtained by other researchers, for example, in the Rostov Region [52]. In the habitats under anthropogenic pressure, vegetative sedentary life is characteristic of this species, noted also by other authors as the ability to stay for a long time in a certain area with weakly expressed vegetative reproduction [19]. Under optimal conditions, Iris populations are characterized by vegetative mobility (i.e., the ability to reproduce vegetatively).

2.

Population features of Iris pumila

In habitats, where conditions are optimal or close to optimal, the surveyed populations of I. pumila have full-membered ontogenetic spectra (at the time of the study, senile individuals and seedlings may be absent in the population). Under stress conditions, the populations are incomplete (most often there are no individuals in the initial stages of ontogenesis: seedlings, juveniles, and immature ones), so their ontogenetic spectra are fragmentary unimodal centered or right-handed.

Demographic features of surveyed I. pumila populations are presented in Table A2. Some differences in the aging index (0.0–0.25) indicate the unequal rate of aging of individuals in different coenotic populations. A recovery index ranging as 0.10–0.70 and a slightly smaller replenishment index both indicate the species stability in studied plant communities and generally favorable conditions for the populations’ renewal in the region.

According to the ‘delta-omega’ classification of populations [50], 47.0% of the studied populations of I. pumila are mature, 23.5%, transitional, 17.6%, maturing, and 11.9%, aging. Different types of populations have been recorded at some loci: maturing, mature, and aging (Sernovodny Shikhan, nos. 26–28); maturing, mature, and transitional (Mulin Dol, nos. 29–31, and Mountain Mogutova, nos. 34–36). In our opinion, this is associated with different habitats (a variety of phytocenotic conditions), quantitative parameters of the population (the number of individuals and the total number of coenotic populations at particular locus), and the difference in the degree of anthropogenic load in different population loci. For example, at Sernovodny Shikhan (nos. 26–28) and Mulin Dol (nos. 29–31), the studied loci are subject to grazing, recreation, and steppe burns; on Mountain Mogutova (nos. 34–36), these are quarrying, recreation, and camping. All maturing coenotic populations (nos. 27, 30, 36) are characteristic of areas that have been traversed by steppe fires. Most of mature coenotic populations (nos. 21, 25, 26, 32, 33, and 37) are found in phytocenoses affected by cattle grazing. Only the mature coenotic population no. 34 (Mountain Mogutova) grows under the influence of recreational load. The transitional type of populations (nos. 22, 23, 31, and 35) is noted in habitats with low grazing and weak recreational use. However, the coenotic population no. 31 is characterized by the presence of a high proportion of sub-senile individuals, which may be associated with fires in 2006, 2012, and 2019. Aging coenotic populations (nos. 24 and 28) are recorded in the areas with low or no anthropogenic load, the development of turf grasses, the accumulation of steppe felt, and a high projective soil cover with herbage.

Similar to other range loci, I. pumila populations in the Samara Region are characterized by the dependence of the types of ontogenetic spectra (and, accordingly, the type of population) on the anthropogenic load intensity. For example, an increase of the pasture load on the populations of I. pumila causes an increase of the number of generative individuals (g1–g3), exhibiting disappearance of young individuals (j–im), and a practical absence of seed renewal in the Republic of Kalmykia [29]. The vulnerability of the plants to grazing due to the superficial position of its rhizomes is also noted in the Rostov Region [17]. Similar tendency is characteristic of I. pumila populations in the Samara Region.

I. pumila populations are stable in most of the surveyed loci. Demographic features indicate a rather low efficiency of renewal in populations, and both recovery and replenishment indices are less than 1.0. The replenishment is generally sufficient to maintain the absolute abundance; as the anthropogenic load increases, the populations are steadily aging, and the population recovery is significantly reduced.

The spatial distribution of individuals in the Iris population is most often aggregated. The average population density of generative specimens is 2.3 individuals per 1 m²; in total for entire population and all age groups, 2.8 individuals per 1 m².

Currently, I. pumila populations are in satisfactory condition in the study area. As the anthropogenic load increases in the habitats of I. pumila, the share of generative individuals in populations increases, young individuals are eliminated, seed productivity decreases, seed renewal is practically absent, and vegetative reproduction is recorded but at low rates (3–4% of young individuals are found out in the total abundance per year). They also reported that the vegetative propagation of Iris is more significant for its stable position in phytocenoses than seed propagation, for example, in the Republic of Kalmykia [29]. At the same time, seed reproduction occurs rather randomly.

According to our data, population characteristics of I. pumila in the Samara Region are quite similar to that in the Volgograd Region [53]. However, there are differences in the parameters of the demographic structure when comparing with the populations of the Saratov Region [34], where a left-sided ontogenetic spectrum with a predominance of the initial stages of ontogeny prevails, which indicates a fairly high diversity of ontogenetic spectra of populations within the range. However, the authors agree that the populations of the species are unstable under the influence of grazing, fires, and recreation.

4. Conclusions

In the Samara Region, the intensity of anthropogenic disturbance of habitats is not the only limiting factor for I. pumila populations. In general, factors such as significant fragmentation of the range, small absolute abundance of most populations, vulnerability to grazing, and low and highly fluctuating seed productivity over the years pose a potential threat to the species.

Local populations of I. pumila grow in various associations that differ in the degree of development, vertical and horizontal structure, and floristic composition. As a rule, I. pumila does not reach high abundance in communities, and it is an assectator. In the Samara Region, I. pumila is a part of eight steppe zonal communities: (Stipa pulcherrima + herbae stepposae [+ Iris pumila]; Festuca valesiaca + herbae stepposae [+ Iris pumila]; Stipa capillata + herbae stepposae [+ Iris pumila]; Festuca valesiaca + Artemisia marschalliana [+ Iris pumila]; Festuca valesiaca + Stipa pennata [+ Iris pumila]; Galatella villosa + Festuca valesiaca [+ Iris pumila]; Helictotrichon desertorum + herbae stepposae [+ Iris pumila]; and Agropyron desertorum [+ Iris pumila + Gypsophila altissima]). In these communities, its populations are represented by a significant number of individuals, and they are in a stable state, with a variety of ontogenetic spectra. Populations growing in relatively favorable conditions are characterized by satisfactory indicators of absolute abundance, population density, and plant vitality, which together ensure the possibility of its long-term stable existence.

However, it has been found that I. pumila populations even characterized by high abundance and population density still need protective measures and reduction of agricultural and recreational use in their habitats. Population features indicate sufficient stability of the species in plant communities under low and medium anthropogenic pressure on the soil and vegetation cover. As the anthropogenic pressure increases, the Iris population disappears from the communities due to its low reproductive rates, when seed reproduction is practically absent, and individuals of vegetative origin make a small contribution to the population replenishment (less than 4% of new individuals are formed annually). Under optimal conditions, Iris populations are characterized by vegetative mobility; under unfavorable conditions, vegetative sedentarization appears.

The data obtained may serve as additional scientific information, for example, for the 2nd edition of the Green List of the Samara Region. In addition, the results of this study indicate that it is necessary to carry out monitoring and implementation of additional measures for the protection of natural territorial complexes, identifying new territories as natural monuments of regional significance in the steppe communities, where I. pumila grows.