Floristic composition of Spiraea hypericifolia ( Rosaceae ) shrubberies of Georgia (Caucasus)

Lachashvili, N., Kereselidze, K., Eradze, N. & Khetsuriani, L.: Floristic composition of Spiraea hypericifolia ( Rosaceae ) shrubberies of Georgia (Caucasus). — Fl. Medit. 33: 131-156. 2023. — ISSN: 1120-4052 printed, 2240-4538 online. The floristic composition of Spiraea hypericifolia shrubberies distributed in Georgia is studied for first time. 256 species of vascular plants, which belong to 172 genera and 49 families, were recorded. Leading families by content number of species are: Poaceae - 28 species (10.9%), Asteraceae – 27 (10.5%), Fabaceae – 20 (7.8%), Rosaceae – 18 (7%), Brassicaceae – 16 (6.3%), Lamiaceae – 16 (6.3%), Apiaceae – 11 (4.3%), Caryophyllaceae – 11 (4.3%), Asparagaceae – 7 (2.7%). Spectrum of life forms is as follows: phanerophytes – 37 species (14.4%), chamaephytes – 8 (3.1%), hemicryptophytes – 109 (42.6%), geophytes – 33 (12.9%), therophytes – 69 (27%). Based on the analysis of the systematic structure of the flora, the composition and ratio of chorotypes and the composition of life forms, 4 main directions of floro-genetic connections were identified: Mediterranea, South-West Asia, Europe and Eurasian steppe. It can be concluded that the formation of the Spiraea hypericifolia shrubberies in Georgia took place under the influence both of the Ancient Mediterranean and Boreal floristic centers. Nevertheless, the Ancient Mediterranean connections are more expressed. The dominance of local (Caucasian) species in the spectrum of chorotypes (14%) emphasizes the originality of the studied shrubberies.


Introduction
The distribution area of the Iberian Spirea (Spiraea hypericifolia L.) extends from southwestern Europe (Iberian Peninsula) to China and Mongolia including southern parts of East Europe and Siberia, Crimea, Caucasus eco-region, Balkan Peninsula (Bulgaria), Middle Asia and partially South-West Asia.
The hypsometric range of the species in the Caucasus extends from the foothills to the subalpine belt.
The spectra of life forms are based on the classifications of Raunkiaer (1934) and Serebryakov (1964).

Results
Description of the study area.-As a result of our research, it was found that the distribution area of the Spiraea hypericifolia formation in Georgia includes the central and western parts of the Iori Plateau, the foothills of the eastern endings of the Trialeti Ridge, the Kverknaki Ridge and the Shida Kartli Plain hills; rare on the northern foothills of the Saguramo Ridge and the southwestern foothills of the Gombori Ridge (Fig. 1).
The physical-geographical conditions of the area are more or less heterogeneous, which is primarily due to the characteristics of the climate and soil.
Distribution area of Iberian Spirea scrubs in Georgia is mainly located in moderately humid subtropical climate region.Nevertheless, different parts of the area belong to various climatic zones and are characterized by more or less different parameters.The central and western parts of the Iori Plateau are characterized by a transitional climate from a moderate warm steppe to a moderate humid with hot summer and two minimums of precipitation per year (BS-Cxa).The average annual temperature is in the range of 10.4°C-12°C, the average annual precipitation -(400) 450-550 (600) mm, evaporability -(800) 900-1000 mm, humidity ratio -(0.4) 0.5-0.6.
Area of different climatic zones (BS-Cxa, Cxa, Cxb, Dxbk') are intersected in the vicinity of Tbilisi.Most part of the Tbilisi area, as well as central and western parts of the Iori Plateau is within the transitional climate zone from a moderate warm steppe to a moderate humid (BS-Cxa).The eastern endings of the Trialeti Ridge entering in the Tbilisi environs are characterized by a moderate humide climate with moderately cold winter and prolonged warm summer and two minimums of precipitation per year (Cxb).Average annual temperature is within 8°C-10°C (11°C), the average annual precipitation is from (570) 600 to 800 (870) mm, evaporability -(700) 800-900 mm, humidity ratio -in the range of 0.6-1.Climatic data of the southwestern foothills of the Gombori Ridge (around the village of Khashmi) and northern foothills of the Saguramo Ridge is similar.Only a small part of the Trialeti Ridge entering in the Tbilisi area (Kojori and etc.) is located in a moderate humid climate zone with modereately cold winter and prolonged cool summer and two minimums of precipitation per year (Dxbk').
The Kvernaki Ridge and the hills of the Shida Kartli Plain are also characterized by a transitional climate from a moderate warm steppe to a moderate humid with hot summers and two minimums of precipitation per year (BS-Cxa).However, the degree of aridity, compared to the Iori plateau and the Tbilisi area, is slightly reduced.In particular, average annual temperature is in the range of 10°C-11°C, the average annual precipitation is from 550 to 650 mm, evaporability -800-900 mm and humidity ratio -in range 0.6-1.
Hypsometric range of Spiraea hypericifolia communities in Georgia is within 600-1000 (1100) m a.s.l. and mostly covers the foothills.They are distributed on the slopes of different inclination (15°-20° to 30°-45°).The macro exposure of the slopes is mostly northern, although they are also found on the southern exposure.They are developed on the various modifications of gray-cinnamonic and cinnamonic soils.In most cases the soil is thin or medium deep.Soils are skeletal.In some cases, bares of the sandstone of marine origin is observed.The inclination of Spiraea hypericifolia plant communities in the Caucasus to northern exposure is also noted by other researchers (Kakulia 1942; Rubtsov 1956; Sakhokia 1961).But the distribution of Spirea communities in the southern part of the South Caucasus (in particularl in Armenia) is different.Here they are common in the subalpine belt mainly on slopes of southern exposure (Fayvush & Aleksanyan 2016).
General regularities of the distribution of Spiraea hypericifolia shrubberies in Georgia.-The area of Iberian Spirea formation in Georgia is included, on the one hand, in the area of steppes and, on the other hand, in the area of deciduous forests of the foothills and lower mountain belt.
S. hypericifolia communities are rare in the natural area of steppe (climate zone BS-Cxa).They are most widespread in the transitional climate zones (Cxa, Cxb, Dxbk'), particularly on the eastern endings of the Trialeti Ridge entering in the Tbilisi environs.Here they are in contact with the deciduous forests, various secondary shrubberies and secondary plant communities of steppes and meadows.
S. hypericifolia communities are mostly developed on the slopes of the northern macroexposure and it is relatively rare on the slopes of the macro-southern exposure.
S. hypericifolia communities are of both primary and secondary origin.The secondary plant communities belong to one of the stages of the digressive succession of the foothill deciduous forests.At present, the structure of primary and secondary communities is, in most cases, identical and it is impossible to draw a line between them (Lachashvili & al. 2015(Lachashvili & al. , 2019)).
Although the Spirea communities in different parts of the area are in direct contact with the deciduous forests of the foothills, as well as with the steppe vegetation, they do not form a connecting "bridge" between them.
Systematic Structure of Flora.-256 species of vascular plants were recorded in Spiraea hypericifolia shrubberies of Georgia.They belong to 172 genera and 49 families (Table 1).
Leading families by contains of genera are represented in form of a table (Table 2).
Crassulaceae, Orchidaceae and Ranunculaceae are represented by 4 genera each.Three families (Caprifoliaceae, Oleaceae and Rubiaceae) contain 3 genera each.10 families are represented by 2 genera each and 22 families -by one genus each.The data makes it clear, that genera are unequally distributed among families.In particular, most of the families (32 families) contain only 24.4% (42 genera) of the total number of genera.
Like genera, species are disproportionately distributed by to families.The spectrum of the top families is given in the form of a table (Table 3).
Leading genera by species content are Alyssum and Euphorbia (Table 4).256 recorded vascular plants were grouped into 36 geographic range types.Proportion of chorotypes is given in the form of a table (Table 5).

Discussion
Systematic structure of flora.-The spectrum of leading families by content of species does not fit into the standard of any floristic center (Mediterranean, South-West Asia, Iran-Turan, Europe, etc.).The influence of various floristic centers is reflected on it.
First of all, a very high position (fourth place) of the family Rosaceae is especially noteworthy.The position of this family in the Mediterranean floras is not clearly defined -it is rarely included in the top ten.Instead it is one of the leading families of submediterranean, nemoral and Boreal floras (Turrill 1929; Tolmachev 1986; Chasapis & al. 2020; Vladimirov & al. 2020, etc.).In addition, its position in the floristic spectrum rises from south to north.A similar situation is observed in the Iran-Turan region of the Ancient Mediterranean, where its place in the floristic spectrum increases from non-forest regions to forests (Turril 1929; Kamelin 1973; Karamysheva & Rachkovskaya 1973; Tolmachev 1986; Lachashvili & al. 2007; Lachashvili & al. 2020).Consequently, in the forest regions of South-West Asia, the family Rosaceae is always included in the top ten, although it is mostly in the second half of the top ten (6-10 places).Judging from the information above, one can conclude that such a high position of the Rosaceae in the Spiraea hypericifolia scrub of Georgia indicates both Boreal and South-West Asian connections.
If not for the very high position of the family Rosaceae in the spectrum, otherwise the main characteristic features of the Ancient Mediterranean floras are clearly visible.Families Brassicaceae, Caryophyllaceae, Apiaceae and Lamiaceae are almost always in the top ten of the floristic spectra of the Ancient Mediterranean regions (Turril 1929; Kamelin & al. 1989; Gagnidze 2000; Asaadi 2009; Aghaei & al. 2013; Dehshiri & Jozipoor 2014; Ghollasimood & al. 2014; Roshan & Heydari 2014: Jafari & al. 2016; Kargar Chigani & al. 2017, etc.).Mentioned families together with Fabaceae, Asteraceae and Poaceae, form the core of the leading families of the Ancient Mediterranean floras.In the context of Ancient Mediterranean connections, we should also consider the presence of Boraginaceae and Rubiaceae in the top of spectrum (10-11 places).
Flora Mediterranea 33 -2023 139 Separately should be noted the families of Monocotyledonae such as Asparagaceae (7 species), Amaryllidaceae (4), Liliaceae (3) and Colchicaceae (1).If we consider these families with the older, larger volume of Liliaceae (s.l.), then the total number of species included in them would be 15 species and Lilaceae (s.l.) would be in the 7th position.Currently the family Asparagaceae ranks 9th, and Amaryllidaceae is in the second echelon of leading families.All this once again underscores Ancient Mediterranean influence (Mediterranean and South-West Asia).The second dozen of the floristic spectrum (Caprifoliaceae, Euphorbiaceae, Iridaceae, Orchidaceae, Ranunculaceae, Amaryllidaceae, Crassulaceae, Geraniaceae) emphasize the transitional nature of the flora.
Composition of chorotypes (Geographical Range Types).-The composition of chorotypes is one of the most important characteristics of any flora and best reflects the main directions of florogenetic connections.The number of Boreal chorotypes is 1.5 times higher than the number of Ancient Mediterranean chorotypes.The so-called "conjunctive" chorotypes are represented by the largest number of species (Fig. 2).
In the spectrum of chorotypes first of all a very high share of Caucasian species (14%) are noteworthy.In addition, 27 out of 36 Caucasian species are endemic of Caucasus.All this emphasizes the originality of Spiraea hypericifolia shrubberies of Georgia.Not only the high share of Caucasian chorotype is noteworthy, but also its diverse composition.Plants of all life forms and different bioecology are presented.However, a significant part of them are hemixerophilous and xerophilous and with their bioecology and systematic connections they are associated rather more with the Ancient Mediterranean region than the Boreal.Prunus georgica (Desf.)Eisenman (Amygdalus georgica Desf.), which is considered as an independent species according to the IPNI (2022), POWO (2022) and WFO (2022), stands out in this respect.This species is closely related to Prunus tenella Batsch, which is widespread in the steppe area of Eurasia, and should be considered as its vicarious species.As in our previous studies (Lachashvili & al. 2020; Lachashvili & al. 2021), we now note that the Caucasian chorotype by some researchers is considered within Ancient Mediterranean region, particularly in Submediterranean (Gagnidze 2004; Gagnidze & Davitadze 2000; Shetekauri & Gagnidze 2000).In such a case, the ratio of Boreal and Ancient Mediterranean chorotypes will change in the opposite direction.
Although European species have not been recorded, connections to Europe are expressed.These connections are mainly reflected in a wide range of "connecting" and European-Caucasian chorotypes.The total number of such species is 49 species (19.1%).
The links with the Eurasian steppes are also strong.The total number of species related to the Eurasian steppes in different ways is 43 (16.8%).It is obvious that in the floristic composition of the Spiraea hypericifolia formation of Georgia there is a kind of a circle of florogenetic connections between the Caucasus and the Eurasian steppes.
Ancient Mediterranean ties have two main directions -Mediterranean and South-West Asia.The main core of the Ancient Mediterranean chorotypes is Mediterranean-South-West Asian species -20 species (7.8%).The number of directly South-West Asian-Turanian (-Central Asian) species is small -6 species (2.4%).There are also few Mediterranean plants (7 species).The florogenetic connections with both the Mediterranea and South-West Asia are supported by a wide range of so-called "conjunctive" chorotypes.In this respect, the European-Mediterranean, European-Mediterranean-South-West Asian and Mediterranean-South-West Asian-Eurasian steppe chorotypes are important in relation to the Mediterranean, and the Caucasian-South-West Asian chorotype in relation to South-West Asia.The latter is the most numerous of the "conjunctive" chorotypes.Here we note that the Caucasus-South-West Asian (-Middle Asian) species form an important circle of florogenetic connections between the Caucasus and South-West Asia.In the direction of the Ancient Mediterranean, the weakest connection is with Turan and Central Asia.This is completely natural, because the hemixerophilous shrubberies of the Caucasus and Turanian deserts will not have a single "root" of origin.
The presented data show that both Boreal and Ancient Mediterranean connections of the most are revealed in a wide range of "connecting" chorotypes.The dominance of "conjunctive" chorotypes and their wide range, in our opinion, indicates the transitional nature of the floristic composition of Spirea shrubberies.
The very high share of widspread species in the spectrum of chorotypes attracts special attention.The most numerous are Palearctic species.They are divided into three groups: Palearctic -25 species, West Palearctic -12 and South Paleractic -6.Palaearctic and Holarctic chorotypes are almost entirely represented by herbaceous plants (mainly with hemicryptophytes and therophytes).Nevertheless, among them socalled weed and ruderal plants are few.
The chorological analysis of the species compositions of the leading families turned out to be important and interesting.As mentioned, most of the top ten leading families are characteristics of the Ancient Mediterranean floras.In the chorological spectrum of all ten leading families mostly dominated are "conjunctive" chorotypes.Their wide range determines the florogenetic connections of different directions and no sharp influence of any floristic center is observed.However, certain tendencies are still evident.All the families of the top ten, except Rubiaceae, contain at least one Caucasian species.Asteraceae (6 species), Fabaceae (5) and Lamiaceae (4) are distinguished by the content of Caucasian species.In the first ten leading families, compared to other connections, the strongest connection is expressed with South-West Asia, which is reflected in a wide range of "connecting" chorotypes.Species linked with South-West Asia dominate almost every family, including family Rosaceae.Compared to South-West Asia, the floristic connection of the European direction is significantly weakened, however, this is manifested to varying degrees in the floristic composition of all ten leading families.This connection is reflected in the " conjunctive" chorotypes.The species associated with the Eurasian steppes are disproportionately distributed.Their concentration is in three widely distributed families -Asteraceae (11 species), Poaceae (8) and Fabaceae (3).Rosaceae also includes three species.Most of the families characteristic of the Ancient Mediterranean floras (Apiaceae, Brassicaceae, Caryophyllaceae, Rubiaceae) do not contain species related to the Eurasian steppes.Only the family Lamiaceae is represented by two species of this group.Such a ratio of species associated with the Eurasian steppes, in our view, is perfectly natural.Almost all of the 10 leading families contain at least one widespread (Palearctic and Holarctic) species.Their highest concentration was observed in the families Poaceae (8 Palearctic and 1 Holarctic species) and Brassicaceae (7 Palearctic species).5 Palearctic species include Rosaceae.At the same time, Palearctic and Holarctic species are negligibly present in the families Asparagaceae, Apiaceae, Caryophyllaceae, and Fabaceae, while Asteraceae does not contain such species at all.
The approximately similar situation is in the second echelon of leading families."Conjunctive" chorotypes are mostly dominant in these families as well and no sharp influence of any floristic center is observed.
Based on the analysis of the systematic and chorological structure of the floristic composition, we can conclude that there is an influence of both Ancient Mediterranean and Boreal centers on the floristic composition of Iberian Spirea scrubs in Georgia and its formation was going through the "struggle" of these two floristic centers.If we do not take into account the local (Caucasian) species, which are considered differently by the researchers, then relatively strong florogenetic connections are expressed in the direction of the Ancient Mediterranean.
Composition of life forms.-The core of the flora consists of herbaceous plants (82.4%).Compared to them, the share of woody and semi-woody plants is much smaller (respectively, 13.7% and 3.9%).
One of the main characteristics of the life forms spectrum is the ratio of the share of hemicryptophytes and therophytes.In the life forms spectrum of Iberian Spirea shrubberies of Georgia the number of hemicryptophytes is almost 1.6 times higher than the number of therophytes.
The share of phanerophytes is high (14.4%).The main core is made up of species characteristic of hemixerophilous shrubberies and arid open woodlands.Among them are also shrubs characteristic of stony, crumbling and rocky ecotopes.The composition of phanerophytes is enriched with the participation of the components of the deciduous forests of the foothills and the lower mountain belt [Acer ibericum M. Bieb., Euonymus verrucosus Scop., Fraxinus excelsior L., Ligustrum vulgare L., Lonicera caprifolium L., Quercus petraea subsp.iberica (Steven ex M. Bieb.)Krassiln., Ulmus minor Mill.], which are uncharacteristic and very rare plants for Iberian Spirea shrubberies.
With respect to life forms the ratio of characteristic (constant) plants is important.Study of Iberian Spirea shrubberies in the Tbilisi area revealed that the core of characteristic species consists of hemicryptophytes and phanerophytes (Lachahsvili & al. 2019).Some species of chamaephytes also belong to the constant species.Despite not that small number, there are no constant species in the composition of therophytes.They belong to the rare (uncharacteristic) plants.The data are also similar in the Iberian Spirea's communities common on the Iori plateau (Lachashvili & Kereselidze 2020).
An important picture is given by the mutual comparison of life forms and chorotypes.The main ties in the phanerophytes are to South-West Asia, Mediterranean and Europe.Caucasian-South-West Asian chorotype is represented by the largest number of species (9 species).Not that small number of local (Caucasian) species (6 species) deserves attention.The link with the Eurasian steppes is very weak -only Spirea hypericifolia belongs to Caucasian-Eurasian steppe chorotype.Local (Caucasian) species (4 species) predominate in chamephytes.The connections to Eurasian steppes and Mediterranean are weak.
The composition and florogenetic connections of hemicryptophytes are diverse.First of all, a large number of Palearctic (24 species) and Caucasian (20 species) species are striking.At the same time, strong connections with the South-West Asia and Mediterranean are pronounced, which is due to the wide range of chorotypes.Connections with Eurasian steppes are also strongly expressed -28 species of hemicryptophytes are associated with the Eurasian steppe area.In relation to the Eurasian steppes the so-called 3 florogenetic circles are well-defined: Mediterranean -South-West Asia -Eurasian steppes, South-West Asia -Caucasus -Eurasian steppes and Caucasus -Eurasian steppes.In addition, in the "conjunctive" chorotypes not so weak ties to direction of Europe are reflected (15 species).It is clear that both Ancient Mediterranean and boreal connections are pronounced in the rich floristic composition of hemicryptophytes.
Both Ancient Mediterranean and Boreal connections are expressed in the composition of geophytes.The most evident is the florogenetic link with South-West Asia.In this direction, the Caucasian-South-West Asian chorotype stands out (8 species).Relatively weak connections are to the direction of Mediterranean, Europe, Eurasian steppes and Euxine.It should be noted that florogenetic connections in geophytes are due to a wide range of "conjunctive" chorotypes.Compared to the life forms discussed above, the participation of local species is small (4 species) and the Caucasian "roots" are mostly reflected in the "connecting" chorotypes.
Unlike other life forms, the role of the Caucasian species in the composition of therophytes is insignificant (only one species).The most widely represented are Palearctic (17) and Mediterranean-Southwest Asian ( 16) species.The links with the Ancient Mediterranean are well expressed (both of Mediterranean and South-West Asia direction).Connections to Europe are relatively weak.The participation of species associated with Eurasian steppes is small.
Based on the reconciled of life forms and chorotypes, the following became evident: Caucasian species are widely represented in all life forms except therophytes, which emphasizes the originality of the Iberian Spirea shrubberies of Georgia; Ancient Mediterranean connections (mainly in the direction of the Mediterranean and South-West Asia) are clearly visible in the composition of all life forms; Connections with Eurasian steppes are formed mainly through hemicryptophytes, although these connections are reinforced by plants of other life forms; The florogenetic link with Europe is represented mainly by hemicryptophytes and therophytes; this connection is reinforced by the corresponding species of phanerophytes and geophytes; The core of the Palaearctic and Holarctic species consist of hemicryptophytes and therophytes.
Bilateral (boreal and ancient Mediterranean) connections are most reflected in the composition of herbaceous plants.

General Conclusion
Based on the analysis of the systematic structure of the flora, compositions of chorotypes and life forms, we can conclude that the formation of the Iberian Spirea shrubberies in Georgia took place under the influence of both the Ancient Mediterranean and the Boreal centers.The florogenetic connection of four main directions is expressed: Mediterranea, South-West Asia, Europe and Eurasian steppe.Florogenic connections of the most are reflected in a wide range of "connecting" chorotypes.If we do not take into account the local (Caucasian) species, which are considered differently by the researchers, then relatively strong florogenetic connections are expressed in the Ancient Mediterranean direction.At the same time, the Mediterranean and South-West Asian connections are strongly reflected in the composition of all life forms, while the florogenetic connections in the direction of the Europe and especially Eurasian steppes are not equally expressed in all life forms.The high share of local (Caucasian) species emphasizes the originality of the Iberian Spirea shrubberies of the Georgia.It is also noteworthy that Caucasian species are present in all leading families, as well as in all life forms except therophytes.
Floristic composition indicating main synonyms, chorotypes and life forms for each species are given below.

Table 2 .
). -The flora of Spiraea hypericifolia shrubberies of Georgia is characterized by a rich composition of chorotypes.Number of genera by the leading families in Spiraea hypericifolia shrubberies of Georgia.

Table 3 .
Number of species by the leading families in Spiraea hypericifolia shrubberies of Georgia.

Table 4 .
Number of species in genera of the vascular flora of Spirea hypericifolia shrubberies of Georgia.

Table 5 .
Proportion of chorotypes in the vascular flora of Spirea hypericifolia shrubberies of Georgia.