A new Centaurea species (Asteraceae) from Mt Sakar,South-eastern Bulgaria

A new species of Centaurea, C. sakarensis, known from a single locality north-east of the village of Lessovo on Mt Sakar, is described and illustrated. It belongs to C. sect. Acrolophus, and its morphologically closest relative is C. cariensis Boiss., a Turkish endemic from western and south-western Anatolia. The new species is currently known from a single population of about 1000 individuals, growing on open stony calcareous places, at 475 m a.s.l., and should be classified as Critically Endangered, (B1ab[i, ii, iii]+2ab [i, ii, iii]).     

Differential spreading of HinfI satellite DNA variants during radiation in Centaureinae

Background and Aims

Subtribe Centaureinae appears to be an excellent model group in which to analyse satellite DNA and assess the influence that the biology and/or the evolution of different lineages have had on the evolution of this class of repetitive DNA. Phylogenetic analyses of Centaureinae support two main phases of radiation, leading to two major groups of genera of different ages. Furthermore, different modes of evolution are observed in different lineages, reflected by morphology and DNA sequences.

Methods

The sequences of 502 repeat units of the HinfI satellite DNA family from 38 species belonging to ten genera of Centaureinae were isolated and compared. A phylogenetic reconstruction was carried out by maximum likelihood and Bayesian inference.

Key Results

Up to eight different HinfI subfamilies were found, based on the presence of a set of diagnostic positions given by a specific mutation shared by all the sequences of one group. Subfamilies V–VIII were mostly found in older genera (first phase of radiation in the subtribe, late Oligocene–Miocene), although some copies of these types of repeats were also found in some species of the derived genera. Subfamilies I–IV spread mostly in species of the derived clade (second phase of radiation, Pliocene to Pleistocene), although repeats of these subfamilies exist in older species. Phylogenetic trees did not group the repeats by taxonomic affinity, but sequences were grouped by subfamily provenance. Concerted evolution was observed in HinfI subfamilies spread in older genera, whereas no genetic differentiation was found between species, and several subfamilies even coexist within the same species, in recently radiated groups or in groups with a history of recurrent hybridization of lineages.

Conclusions

The results suggest that the eight HinfI subfamilies were present in the common ancestor of Centaureinae and that each spread differentially in different genera during the two main phases of radiation following the library model of satellite DNA evolution. Additionally, differential speciation pathways gave rise to differential patterns of sequence evolution in different lineages. Thus, the evolutionary history of each group of Centaureinae is reflected in HinfI satellite DNA evolution. The data reinforce the value of satellite DNA sequences as markers of evolutionary processes.     

Flavonoids in Subtribe Centaureinae (Cass.) Dumort. (Tribe Cardueae,Asteraceae): Distribution and 13C‐NMR Spectral Data

This review reports the occurrence of flavonoids in subtribe Centaureinae of Asteraceae family. It extensively covers the literature up to 2010 and collects all available ¹³C‐NMR data.     

New chromosome counts in the Centaurea Jacea group (Asteraceae, Cardueae) and some related taxa

Twenty-seven chromosome counts are reported in 23 species of the genus Centaurea , mostly eastern endemic species of the Jacea group, which has become the core of the re-defined genus Centaurea . Twenty reports are new, one is a correction of a previous count, one is a confirmation of limited previous data and one represents a new basic number in the Centaureinae. The prevalence of the basic chromosome number x  = 9 among the Eastern sections of the Jacea group is confirmed, together with the close correlation between karyological data and classification of the genus. Two alternative hypotheses on the aberrant chromosome number (for the Centaureinae) found in C. behen are proposed. One of them, if verified, would confirm that a cycle of polyploidy and descending dysploidy is a key mechanism in the speciation of the group.  © 2004 The Linnean Society of London, Botanical Journal of the Linnean Society , 2004, 145 , 345–352.     

New chromosome counts in the genus Centaurea (Asteraceae) from Turkey

Twenty‐two chromosome counts are reported in 16 species, four subspecies and two varieties of the genus Centaurea. These are mostly Turkish local endemics of section Cheirolepis, a complicated group from the Eastern clade of the Jacea group. Twenty‐one reports are new. Prevalence of the basic chromosome number x = 9 among the eastern sections of the Jacea group is confirmed. © 2009 The Linnean Society of London, Botanical Journal of the Linnean Society, 2009, 159 , 280–286.     

Karyological evolution in Rhaponticum Vaill. (Asteraceae, Cardueae) and related genera

Chromosome counts are reported in 29 populations representing 20 species and one subspecies of the genera Callicephalus (one sp.), Klasea (seven spp.), Myopordon (two spp.), Oligochaeta (one sp.), and Rhaponticum (nine spp., one ssp.). Eleven reports are new, the others supplement limited previous data. New and published cytological data are summarized and evaluated critically in light of current taxonomic treatments and evolutionary hypotheses. Basic chromosome numbers are a valuable source of taxonomic information and relate well to the phylogeny. They are quite conserved in Klasea (only x  = 15), the sister group of the remaining genera, and in the early branching genera of the Rhaponticum group ( x  = 14 for Centaurothamnus and Callicephalus ). However, a more complex pattern of genome evolution is present among the more derived clades, Oligochaeta plus Myopordon ( x  = 12, 14) and the genus Rhaponticum ( x  = 12, 13). The occurrence of x  = 12 in Oligochaeta divaricata and Rhaponticum carthamoides seems to be the result of a recent event of chromosome fusion, as suggested by the fragility of particularly long pairs of chromosomes. The use of chromomycin staining, including an enzymatic digestion step that facilitates spreading and permits a reduction of potential fragmentation, only partially resolves this problem.  © 2007 The Linnean Society of London, Botanical Journal of the Linnean Society , 2007, 153 , 193–201.     

Flavonoids from the Turkish endemic plant Rhaponticoides mykalea (Hub.-Mor.) M.V.Agab. & Greuter (Asteraceae)

The genus Rhaponticoides, recently segregated from the genus Centaurea, belongs to the family Asteraceae (tribe Cardueae). Rhaponticoides mykalea (Hub.-Mor.) M.V.Agab. & Greuter is an endemic species narrowly distributed in the Aegean part of Turkey. Owing to the existing anthropogenic impacts (such as urbanization and road construction) throughout its distribution range, the species has been the subject of several conservation studies. Phytochemical research on the aerial parts of R. mykalea led to the isolation of a new flavonoid, namely patuletin 7-O-(6″-E-sinapyl)-β-glucopyranoside, together with four known flavonoids from n-butanol extract. The structures of all isolated compounds were elucidated by spectroscopic analysis (1D and 2D NMR, HR-ESI-MS), as well as by comparison with the relevant literature data. All of the compounds have been isolated from the genus Rhaponticoides for the first time.     

Systematics and biogeography of Klasea (Asteraceae–Cardueae) and a synopsis of the genus

Klasea , traditionally treated as a section in Serratula , is now widely accepted at the generic level. A classification of the genus is presented here, accommodating the 46 species in ten sections based on nuclear ribosomal DNA external and internal transcribed spacer sequence data and morphology. New combinations for five species and ten subspecies are published, and a new hybrid species is described. The genus ranges from the Iberian Peninsula and north Africa through southern and eastern Europe, west and central Asia to the Himalayas, and the Far East of Russia and China. The ancestral area is in west Asia, most probably eastern Anatolia and northern and western Iran. In this region, representatives of all sections are present. The largest section Klasea diversified most likely in the mountains of central Asia. A key to all Klasea species is provided.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 152 , 435–464.     

Lessons from Plectocephalus (Compositae, Cardueae-Centaureinae): ITS disorientation in annuals and Beringian dispersal as revealed by molecular analyses

Background and Aims

The geographic distribution of the genus Plectocephalus comprises a single species in Ethiopia, two in North America and possibly four more in South America, in a striking disjunction that is exceptional for genera of the tribe Cardueae. The enormity of this disjunction cast doubts on the precise taxonomic delineation of the genus, which is not unanimously recognized as a natural entity. The aims of this study were to define the generic boundaries of Plectocephalus and to formulate a hypothesis that would explain its natural range.

Methods

A combined molecular approach, using nuclear internal transcribed spacers (ITS) and external transcribed spacers (ETS), and plastid trnL-trnL-F, rpl32-trnL^UAG and ndhF markers, was chosen for phylogenetic reconstruction by maximum parsimony and Bayesian inference.

Key Results

Phylogenetic analysis shows that Plectocephalus is a natural genus that includes the African species P. varians, together with all the native South American species, currently classified as Centaurea, C. cachinalensis, C. floccosa and C. tweediei. The recognition of Centaurodendron as an independent genus, which we consider appropriate, would make Plectocephalus paraphyletic. Affinities of Plectocephalus should lie with eastern representatives of Centaureinae. Geographic disjunction is explained as a consequence of dispersal via the Bering Land Bridge during the Miocene–Pliocene. The phylogeny of the basal grade of Centaureinae differs from previous phylogenies, and artefacts resulting from differences in mutation rates of annual and perennial taxa are confirmed. Sensitivity of ITS to these differences was the highest observed for all DNA regions used in this study.

Conclusions

The natural status of the genus Plectocephalus is confirmed and several nomenclatural combinations are proposed. New evidence contributes to the debate concerning problems posed by the use of ITS in the phylogenetic reconstruction of groups that differ in terms of their life cycles. Dispersal from Caucasus and Anatolia along the Siberian route and then across the Bering Land Bridge follows a route previously proposed for other taxonomic groups.