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ИСТИНА ЦЭМИ РАН |
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In 2014, we performed further molecular survey for a complete revision of sect. Oreiprason. For most samples, the nuclear DNA ITS region was amplified using ITS-SF and ITS-SR primers. We mainly worked with DNA material from herbarium specimens, some of them were dated back to the first half of 20th century. Once we were lucky to make a successful amplification of ITS from an 88-years old specimen, but this is somewhat exceptional. Success rate in amplification and further sequencing for specimens collected in 1920–30s was 26% growing gradually up to 94% for specimens collected in 2000s. All together, we sampled DNA from 89 specimens and made 351 ITS amplifications with varying level of DNA in order to find appropriate conditions of PCR for old specimens. As a result, we got complete ITS sequences from 50 specimens and two partial sequences. 275 amplifications and 22 sequences failed. Almost all specimens with successful ITS sequences were appropriate for cpDNA fragments sequencing. We used rpl32–trnL and trnL–trnF regions for phylogeny reconstruction (44 successful amplifications for each fragment). Key results 1. Recircumscription of sect. Oreiprason. Surprisingly, many slender species of sect. Oreiprason known to occur in Middle Asia are definitely closely related to robust species from sect. Falcatifolia N. Friesen. This section was introduced for A. carolinianum DC. and A. platyspathum Schrenk with large flat falcate leaves. Later on, Fritsch and Friesen (2009) transferred tall A. hymenorrhizum Ledeb. and similar A. kaschianum Regel to sect. Falcatifolia on genetic ground. Species like A. filifolium Regel, A. kokanicum Regel, A. caricoides Regel, A. alexandrae Vved. are more or less similar to «A. globosum» in their gross-morphology, but show similar ITS and cpDNA fragments with abovementioned species from sect. Falcatifolia. The most intricate issue that sect. Oreiprason and sect. Falcatifolia are not closely related in the general tree of the genus Allium (Friesen et al., 2006). Thereby, monophyletic sect. Oreiprason s. str. includes two groups – large A. saxatile group as circumscribed by Seregin et al. (2015, in press) (i.e. including A. petraeum and A. obliquum) and its probable sister A. tianschanicum Rupr. s. l. All other species should be excluded from this section. Form of leaf cross-sections should not be considered as a phylogenetically important character, because there are plants with terete, hollowed and wide flat leaves both in sections Oreiprason and Falcatifolia. 2. New species in sect. Oreiprason s. str. Further sampling made us sure that we need recognition and formal description of several new entities in sect. Oreiprason s. str. For instance, at least three clear genetic entities of monophyletic origin exist in A. petraeum Kar. et Kir. We confirmed yellow-flowered A. petraeum s. str. from Dzungarian Alatau and Trans-Ili Alatau. Red-flowered plants of A. petraeum s. l. were reported earlier by Egorova (1977), but she did not recognize them taxonomically. Such plants grow in Dzungarian Alatau only and form a monophyletic clade. Yellow-flowered plants of the southern lineage were sampled from several localities in Central Tian Shan (Kazakhstan and China). We splitted A. dshungaricum Vved. into two species earlier. The second member of this lineage was described from a single locality in Eastern Tian Shan, China. Now we confirmed this species from another locality in Central Tian Shan (Kazakhstan). Plants from Tarbagatai and Dzungarian Alatau may represent different groups (additional material is needed). Also, we discovered the third member in the A. cretaceum – A. montanostepposum complex which is a rare species formed on SE fringes of A. montanostepposum range. We sampled two specimens of this entity from Tarbagatai and Sary Chelek Lake. A. tianschanicum Rupr. was described from Tian Shan, but consequently reported from Pamiro-Alai. It has purplish flowers whereas plants from Alai and adjacent ridges have somewhat yellowish flowers. Their monophyletic origin and clear genetic delimitation confirmed that they represent a previously neglected species new to science (known as A. pamiri Vved. ined.). Relations of A. tianschanicum and A. saxatile M. Bieb. are unresolved. 3. Genetic differentiation in sect. Falcatifolia. ITS variation within newly circumscribed sect. Falcatifolia is fairly low comparing with such in sect. Oreiprason. All species are forming tight core clade with two early diverged sister clades – A. talassicum sensu Vved. and A. platyspathum s. l. Within the core clade there are both widely distributed species and narrow endemics. Species with large ranges like A. hymenorrhizum (from Altai to Turkey), A. carolinianum (from Nepal to Mongolia), and A. kokanicum (from Pamiro-Alai to Dzungarian Alatau) have been sampled from many localities and has almost no ITS variation. Lineages with narrow endemics are notably variable and need further sampling, proper morphological characterization, and perhaps further splitting on both morphological and genetic ground (A. alexandrae, A. filifolium, etc.). Some rare species were sampled only once. Allium kastekii Vved., A. clausum Vved. and one unknown species show uncertain positions within sect. Falcatifolia. They might represent separate sections or intersectional hybrids, but for proper decision additional sampling is vitally important. Tobias Herden (University of Osnabrück) performed in BEAST age analysis of sect. Oreiprason ITS tree in order to reveal time of splitting of proposed ancestors (only mean figures are given below). The first splitting in sect. Oreiprason probably happened ca. 12,0 Mya; splitting of the European clade in the A. saxatile group took place ca. 8,4 Mya, while splitting within A. tianschanicum s. l. occurred ca. 4,8 Mya. In contrast, the core clade of sect. Falcatifolia is certainly younger. Age of speciation within it could be estimated as 1,4 Mya. Genetic uniformity and striking morphological variability of younger sect. Falcatifolia contrast with long genetic distances between morphologically similar “old” species in sect. Oreiprason. Unfortunately, we know little about chromosome numbers in sect. Falcatifolia, although A. carolinianum is reported to be a tetraploid. We suppose that in the latter section other evolutionary mechanisms (like hybridization and probably polyploidization) are employed in speciation rather than clear geographical isolation within sect. Oreiprason.