TAXONOMIC COMPOSITION AND CHANGES IN SYSTEM OF AMELANCHIER MEDIK. GENUS

A brief history of studying Amelanchier Medik. genus is represented in a retrospec­ tive discourse. Besides, the analysis of current state of its taxonomic and systematic studies. The reasons that complicate the identification of plants, as well as the structure of the genus system, are defined. The most convenient taxonomic features of the genus are named. The controversial issues of the genus system are discussed, based on the classical, molecular and genetic positions. The analysis of the available publications and electronic databases on the taxonomy of species Amelan chier enabled us to state their ambiguous interpretation and, in effect, reduce the number of recognized species of the excepted status in the genus composition. We can assume that the revealed tendencies concerning the clarifying status of the species indicate the change of views on the taxonomy of the Juneberry. In terms of the concept of the species, its converted rank as a monotypic species to the polytypic (monophyletic) species is evident with the smallest number of distinctive features. A more thorough study shows manifestation of the species variability in its process of adaptation to environmental factors. Differences on species and intraspecies classification of the genus found in various publications point to incompleteness of its system and the necessity for further research using both modern and traditional methods.


INTRODUCTION
The Amelanchier Medik. (Juneberry) genus is considered to be complicated for iden tifying plants by themselves, and for genus system construction [14]. Difficulties related to its study are connected first of all with morphological variation of features of vegetative and generative organs [14], a large number of divergent and intermediate forms [3], polyploidy, spontaneous hybridization and detected just recently [5] a tendency to apomixis causing so-called occurring agamospecies [6] which determines some taxonomic difficulties.
One of the first reccords about Juneberry dates back to the year 1581 [17]. Before singling out Amelanchier as a separate genus in 1789 by Friedrich Casimir Medicus [18], Joseph Pitton de Tournefort [28] and Carl Linnaeus [16] reffered its species to the genus Mespilus, though first Linnaeus defined its place in the genus Chionanthus [15].
As a monograph of George Neville Jones mentions [14], during the following taxo nomic revisions, its representatives were united under many generic names, including as a separate genus: Amelanchus Rafinesque (1834), Merrill (1942) (1753,1767,1768,1774,1787,1790,1803,1810,1818,1834,1859) and Pyrus (1781,1787,1793,1796,1799,1803,1809,1813,1814,1824,1825,1838 ), but the clear position of Amelanchier is caused by the morphological features of its leaves (being its most variable feature, it is dependent on the condition of the vegetation, the period of the growing season and its ontogeny), its multifloral racemous buds and flowers, and fruits with special leathery carpels -each of which have incomplete membranes starting from the back wall (this feature is observed only in two genera of the family Rosaceae -Peraphyllum Nutt. and Malacomeles (Decne.) Engl.).
Taking into consideration the mentioned taxonomic difficulties, the aim of our re search was to specify the taxonomic composition of the genus Amelanchier representa tives, and to analyze current views on the systematic position of these plants in the genus system and make lists of their synonymous names.

MATERIALS AND METHODS
Taking into account the data obtained from analyzing the experimental and theo retical studies performed in different countries of the world over a long historical period by scientists from different scientific schools [1; 4; 8; 10; 11; 14-16; 21], the attempt to generalize available information is made. In addition, the method of group selection was applied, which allowed the dispelling of dubious publications using citing criteria in peerreviewed publications and giving priority to research that is carried out by international programs. In the process of preparing the article, works on the domestication of the genus Amelanchier and their nearest families published in different years, were ana lyzed, summarized and supplemented with their own experiences [1; 4; 20-23; 30].

RESULTS AND DISCUSSION
The Amelanchier genus in classical phylogenetic, as well as in the molecular phy logenetic (cladistic) classification system of plants, is defined as a component of the family Rosaceae Juss. of the range Rosales Bercht. et J.Presl. [2; 10; 25].
Numerous "microspecies" are distinguished in many genera of Rosaceae, morpho logical differences between which are slight (for example, details of pubescence), but they are considered stable. Microspecies appear in groups where free interbreeding in populations is limited because of apomixis spread or other reasons. Therefore, if coun ting microspecies, the number of Rosaceae species can significantly increase [27].
Traditionally, on the basis of differences, mainly in fruit morphology and in basic chromosome numbers, the family Rosaceae were separated into 4 subfamilies: Spirae oideae (Meadowsweet) -fruit -follicles, rarely capsule, basic chromosome numbers 8 and 9; Rosoideae (Rose) -fruit -hip, aggregate fruit, aggregateaccessory fruit, the hypanthium often takes part in the fruit formation, basic chromosome numbers 7, 9,  [11]. The other authors, depen ding on the occurrence of stipules, calyx structure, hypanthium, gynoecium, fruit, and other signs in the family Rosaceae distinguish from 3 to 12 subfamilies [8].
The genus Amelanchier, since the times of Adolf Engler (1903), was defined within the subfamily Pomoideae (later Maloideae) [10]. Formed at the beginning of the last century [24], synopsis of the genera of the subfamily Maloideae as a part of the family Rosaceae with certain deviations [29] in his nearclassical state is supported by many authors [1; 22]. However, more evidence is provided concerning the revision of the fa mily Rosaceae appropriateness on regrouping subfamilies, supertribes, tribes, subtribes, some particular genera and species with the simultaneous elimination of the subfamily Maloideae [4; 9; 23].
The revision of the family Rosaceae was supported by Armen Takhtajan, who sug gested a new version of flowering plant systems, revised according to the latest results of molecular phylogenetics in the book "Flowering Plants" reissued in 2009 [25].
Armen Takhtajan highlights the subfamily Pyroideae (formerly Maloideae) in the family Rosaceae, combining in it 27 genera in 4 tribes, defining the genus Amelanchier among the families of the tribe Maleae.
According to the analysis of the subfamilies from the family Rosaceae, performed by a group of scholars of different universities in the USA, Canada and Sweden after six nuclear (18S, gbssi1, gbssi2, ITS, pgip, ppo) and four chloroplastic (matK, ndhF, rbcL, and trnLtrnF) segments of DNA sequences [4; 9; 23], only the subfamily Rosoideae (Juss.) Arn. turned out monophyletic, with the basic chromosome number x = 7 or 8, except for the tribe Dryadeae (x = 9). Instead, the subfamilies Prunoideae and Malo ideae in the traditional sense were paraphyletic, and Spiraeoideae -polyphyletic group. On this basis, the rank of the first two subfamilies is proposed to reduce to the tribe and together with the other related tribes to combine into one monophyletic (in a very broad sense) subfamily Spiraeoideae C. Agardh, with x = 8, 9, 15 or 17. Therefore, the super tribe Pyrodae Camp., Ev., Morg. et Dick. with the tribe Pyreae Baill. were included into the subfamily Spiraeoideae (x = 17, with the exception of the genus Vauquelinia Correa ex Humb. Et Bonpl. with x = 15), the subtribe of which Pyrinae absorbed most of the genera of the subfamily Maloideae, including the genus Amelanchier.
However, due to the Melburnian Code, the current variant of the International Code of Nomenclature for algae, fungi, and plants [13], the priority name for the subfamily, which combines Spiraeoideae, Maloideae and Amygdaloideae is the name Amygdaloideae; for the tribe Pyreae -name Maleae Small; for the subtribe Pyrinae -name Malinae Rev. (Article 19.5, ex. 5). This is a reason to define the genus Amelanchier among the corresponding groups.
While comparing the systematic position of the genus Amelanchier, according to the different classification systems of plants, different in time of creation and research level, the relative stability of the placement of the genus Amelanchier can be observed within major taxa of higher ranks (Table 1). We find it appropriate to consider the systematic position of the genus Amelanchier according to the A. L. Takhtadzhyan system (2009) [25], arguing such a position be cause this system takes into account the latest results of molecular phylogenetic stu dies, yet reveals and demonstrates those obvious synapomorphies, morphological or other features that unite or divide taxa of different ranks, and which takes note of some aspects of the analysis of the main features of modern angiosperm phylogenetic sys tems that were suggested by S. L. Mosyakin [19].
Until recently it was considered that the genus Amelanchier comprises about 25-33 species [22; 30]. Herewith the number of species names used by different authors is nearly ten times as much. Most of these names are now considered unresolved (semiand/or temporarily accepted), synonyms, intraspecies taxa or interspecific hybrids [7; 26].
Here is a list of the names of 33 species plants of the genus Amelanchier according to the subfamily Maloideae (Rosaceae) checklist, 1990 [22]  Summarized data on the taxonomy of the genus Amelanchier, presented by scien tists of the Royal Botanic Gardens in Kew (UK) and the Missouri Botanical Garden (USA) (The Plant List..., 2013) combine together 243 species name of this genus repre sentatives. Of them, 28 have acquired an accepted status (11.5 %), the rest is consid ered synonymous -122 (50.2 %) and unassessed -93 (38.3 %). Besides, 89 names of infraspecific names are included to this list, which increases the number of accepted species to 37 (11.1 %), synonyms to 197 (59.3 %) and unassessed to 98 (29.5 %) [26].
Here is a list of the names of 28 species and 9 infraspecific taxa of plants belonging The analysis of the available lists of plants, which belonged to the genus Amelanchier at various times, demonstrates their ambiguous interpretation and shows the gene ral tendency for thorough review of their status.
The dynamics of this process is well illustrated by a comparative list of the names of species of the genus Amelanchier of the accepted status according to the checklists of the subfamily Maloideae (Rosaceae), 1990 [22] lists The Plant List., 2013 [26] and the Catalogue of Life., 2015 [7] (Table 2). It can be mentioned reducing the number of species of the accepted status in the genus Amelanchier composition, due to its specification (change), and the transfer of certain species names of species rank to the rank of infraspecific taxon or synonym with accepted or unresolved status.

CONCLUSION
Concerning relative stability of the placement of Amelanchier representatives with in the main taxa of higher rank, the place of the genus within the particular subfamily, namely: within the subfamily Pyroideae (former Maloideae) or in the subfamily Amygda loideae, uniting former subfamilies Amygdaloideae, Spiraeoideae and Maloideae, re mains debatable.
Tendencies concerning specifying the status of the species that once belonged to the genus Amelanchier, indicate changing views on the taxonomy of the Juneberry in the perspective of a certain concept, in particular the transition from monotypic to poly typic species concept, when a certain amount (one-two) of distinctive features, at a more detailed study, are the manifestation of variability in the species to adapt to en vironmental factors.
The end of the Table 2