中间偃麦草(Thinopyrum intermedium)18S-5.8S-26S rDNA位点在染色体上的分布及对其核ITS序列异质性的分析

中间偃麦草(Thinopyrum intermedium(Host)Barkworth et Dewey)是禾本科小麦族植物中的一个异源六倍体物种,是重要的牧草植物,在小麦的抗病育种中发挥了重要作用.利用荧光原位杂交(FISH)技术,在体细胞中期染色体上,对18S-5.8S-26S rDNA位点进行了物理定位,发现该物种有3～4对染色体携带18S-5.8S-26S rDNA主位点.结合基因组原位杂交(GISH)分析,证明中间偃麦草的St基因组中有一对同源染色体短臂末端携带一个主位点,其余2～3对主位点位于E基因组染色体上.对不同来源的材料研究表明:18S-5.8S-26S rDNA位点的数目(包括主位点和小位点)、位置、拷贝数在不同收集材料之间的差异较大,甚至在同一个体的不同细胞中也存在差异.讨论了rDNA物理作图数据在分析系统发育问题中的局限性.结合中间偃麦草的三个可能的二倍体基因组供体(Th.bessarabicum、Th.elongatum和Pseudoroegneria stipifolia)rDNA位点分析的结果,对中间偃麦草进化过程中rDNA位点的变化进行了分析,同时,对其中一份材料的核ITS序列进行了克隆、测序和系统发育分析,发现在中间偃麦草中,ITS序列具有很高的异质性.     

Chromosomal organization of ribosomal genes and NOR-associated heterochromatin, and NOR activity in some populations of Allium commutatum Guss. (Alliaceae)

The position and the number of 18S-5.8S-26S and 5S rDNA loci, characterization of nucleolar organizing region (NOR)-associated heterochromatin and NOR activity assessment are given for six south-eastern Adriatic populations of Allium commutatum Guss. The karyotype characteristics were identical for all the populations studied, even those of distant islands. Diploid karyotypes (2 n = 16) always possessed two NOR-bearing chromosome pairs with pericentric and median secondary constrictions (SCs) on the short arm of the chromosomes VII and VIII. Fluorescent in situ hybridization (FISH) confirmed that these were the only sites of 18S-5.8S-26S rRNA genes. NOR-associated heterochromatin was of the constitutive character as shown after C-banding. Differential fluorochrome banding with Chromomycin A3 (CMA) and 4,6-diamidino-2-phenylindole (DAPI) revealed that this heterochromatin comprises both GC- and AT-rich DNA segments. Heteromorphism of C- and CMA-bands was noticed between homologous NOR-bearing chromosomes. The maximum number of four active NORs was correlated with the maximum number of four nucleoli in interphase. Variability of NOR-activity, expressed as number and size of silver stained NORs, existed between cells and between individuals of the same population. The different size of homologous and nonhomologous silver stained NORs was correlated with the extension of SCs. The only 5S rDNA locus was in an intercalary position on short arm of the chromosome VI, at the region of AT-rich constitutive heterochromatin. Dimorphism of C-bands and DAPI/Hoechst(H)-fluorescent bands was noticed between homologous chromosomes VI. © 2002 The Linnean Society of London, Botanical Journal of the Linnean Society , 2002, 139 , 99–108.     

Cytogenetic studies in South American species of Serjania (Sapindaceae: Paullinieae)

Abstract

Serjania Mill. (Paullinieae) is considered the most important neotropical genus of Sapindaceae due to species number and its widespread distribution. In this study, 14 species belonging to three sections were analyzed using conventional staining, C/CMA/DAPI banding, and fluorescence in situ hybridization (FISH) with a 18S-5.8S-26S rDNA probe. New chromosome counts are reported for Serjania crassifolia, Serjania platycarpa, and Serjania regnellii, all with 2n = 24, which is remarkably constant for Serjania. The karyotypes are moderately asymmetric, and variations observed in A1 and A2 indices show resemblances between S. platycarpa, Serjania hebecarpa, and S. crassifolia, and between Serjania communis, Serjania gracilis, and S. regnellii. The banding pattern was homogeneous in Serjania. C/DAPI bands (AT-rich sites) were not clearly evidenced, but changes in the number and position of GC-rich sites (CMA bands) were observed. These segments were associated with 18S-5.8S-26S rDNA sites. The significance of the results is discussed in relation to chromosomal data available for the genus and in regard to the infrageneric treatment of Serjania.     

Physical mapping of rDNA sequences in four karyotypes of Ranunculus silerifolius (Ranunculaceae)

The chromosomal locations of the 18S-5.8S-26S rDNA and 5S rDNA sequences were examined in four cytotypes of Ranunculus silerifolius (the Matsuyama, Mugi, Otaru, and Karatsu types) using fluorescence in situ hybridization (FISH). Using the 18S-5.8S-26S rDNA probe, one pair of probe hybridization sites was detected by FISH in the interstitial region corresponding to the secondary constriction on the short arm of a satellite chromosome (chromosome pair 6) in all four karyotypes. FISH using 5S rDNA identified one pair of sites. The 5S rDNA locus was on different chromosomes in the four karyotypes: in the interstitial region of the short arm of the largest metacentric chromosome (chromosome pair 1) in the Matsuyama type, in the interstitial region of the short arm of the subtelocentric chromosome (pair 2) in the Mugi and Otaru types, and in the interstitial region of the short arm of the metacentric chromosome (pair 2) in the Karatsu type. This physical mapping of the 5S rDNA provides valuable information about karyotype evolution in R. silerifolius. Possible mechanisms of chromosome evolution are discussed.     

Nuclear DNA content,base composition,heterochromatin and rDNA in Picea omorika and Picea abies

Two closely related spruces, Picea abies and Picea omorika, a Balkan paleoendemic species, often share habitats, yet never hybridize in nature. The present study adresses their characteristics such as nuclear DNA content, base composition, heterochromatin and rDNA pattern. The genome size of P. abies was 10% larger than that of P. omorika when assessed by flow cytometry, respectively 2C=37.2 pg and 33.8 pg; although when estimated as total chromosome length it was virtually the same. The heterochromatin Chromomycin-A (CMA)/ DAPI fluorochrome banding patterns of both P. abies and P. omorika are given here for the first time. Simultaneous FISH (fluorescent in situ hybridization) using 18S-26S and 5S rDNA probes revealed 16 18S rDNA sites in P. omorika, 12 18S rDNA sites in P. abies, and a single 5S rDNA locus in both species. The genomes have about 41% GC. The number and position of CMA/DAPI bands and rDNA loci provide good chromosome markers to clarify the karyotypes of the two species. Received: 18 October 2000 / 14 June 2001     

Scale evolution in Paraphysomonadida (Chrysophyceae): Sequence phylogeny and revised taxonomy of Paraphysomonas,new genus Clathromonas,and 25 new species

Heterotrophic chrysomonads of the genus Paraphysomonas are ubiquitous phagotrophs with diverse silica scale morphology. Over 50 named species have been described by electron microscopy from uncultured environmental samples. Sequence data exist for very few, but the literature reveals misidentification or lumping of most previously sequenced. For critically integrating scale and sequence data, 59 clonal cultures were studied light microscopically, by sequencing 18S ribosomal DNA, and recording scale morphology by transmission electron microscopy. We found strong congruence between variations in scale morphology and rDNA sequences, and unexpectedly deep genetic diversity. We now restrict Paraphysomonas to species with nail-like spine scales, establishing 23 new species and eight subspecies (Paraphysomonadidae). Species having base-plates with dense margins form three distinct subclades; those with a simple margin only two. We move 29 former Paraphysomonas species with basket scales into a new genus, Clathromonas, and describe two new species. Clathromonas belongs to a very distinct rDNA clade (Clathromonadidae fam. n.), possibly distantly sister to Paraphysomonas. Molecular and morphological data are mutually reinforcing; both are needed for evaluating paraphysomonad diversity and confirm excessive past lumping. Former Paraphysomonas species with neither nail-like nor basket scales are here excluded from Paraphysomonas and will be assigned to new genera elsewhere.     

A single species,two basic chromosomal numbers: case of Lygeum spartum (Poaceae)

Abstract

The existence of two chromosome numbers (2n?=?16 and 2n?=?40) in Lygeum spartum is confirmed in the Algerian steppe populations of Oran region. Chromosome counts were established for 11 Algerian populations and three supplementary populations from Italy, Spain and Greece. The karyotypes were characterized by chromosome markers obtained using fluorescence in situ hybridization and fluorochrome bandings. The organization of 5S and 18S-5.8S-26S (35S) rDNA was studied in both cytotypes. Six signals of 35S and 2 signals of 5S were observed in 2n?=?16 population, while 10 signals of 35S and 4 signals of 5S were detected in the population with 2n?=?40. All 35S loci were also strongly marked by chromomycin, but negatively stained by Hoechst, which indicates the presence of GC rich DNA in rDNA regions. The B chromosomes were found in both cytotypes, bearing a 35S locus in 2n?=?16 population. Genome size, determined by cytometry of 10 populations, ranged from 9.27?pg for 2n?=?16 to 26.63?pg for 2n?=?40 populations. The sequencing of plastid and nuclear DNA markers did not reveal major differences among 2n?=?16 and 2n?=?40 populations. However, given the differences between two cytotypes and based on their morphological and cytogenetic characteristics, the 2n?=?16 cytotype merits novel taxonomic treatment.     

Towards the phylogeny of the Curculionoidea (Coleoptera): Reconstructions from mitochondrial and nuclear ribosomal DNA sequences

With about 60,000 described species, Curculionoidea represent the most species-rich superfamily in the animal kingdom. The immense diversity apparently creates difficulties in the reconstruction of the phylogenetic relationships. Independent morphological studies have led to very different classifications. This study is based on molecular data from two independent molecular sources, the 16S and 18S rDNA. Sensitivity analyses were conducted for the sequence alignment (gap costs were varied) as well as the phylogenetic reconstruction algorithms and some of their parameters. The higher-level relationships reconstructed within Curculionoidea are sensitive to alignment and reconstruction method. Nemonychidae or Oxycorynidae+Belidae were found to be sister to all remaining Curculionoidea in many analyses. The 16S rDNA sequence data (obtained from 157 species) corroborate many tribes and genera as monophyletic. It is observed that the phylogenetic reconstruction of genera with specific genetic features such as polyploidy and parthenogenetic reproduction is difficult in weevils. The curculionid subfamily Lixinae appears monophyletic. A new monophylum consisting of Entiminae, Hyperinae, Cyclominae, Myllorhinus plus possibly the Cossoninae is distinguished and we call it Entiminae s.l. For most other subfamilies and families homoplasy concealed the phylogenetic signal (due to saturation of the 16S sequences), or the species sampling was insufficient, although our sampling scheme was rather broad. We observed that although data from one source can easily be misleading (16S) or hardly informative (18S), the combination of the two independent data sets can result in useful information for such a speciose group of organisms. Our study represents the most thorough analysis of molecular sequence data of the Curculionoidea to date and although the phylogenetic results appear less stable than expected, they reflect the information content of these sequence data realistically and thus contribute to the total knowledge about the phylogeny of the Curculionoidea.     

Molecular cytogenetic insights into the evolution of the epiphytic genus Lepismium (Cactaceae) and related genera

Changes in chromosome structure and number play an important role in plant evolution. This was investigated in the Neotropical epiphytic cacti: all Lepismium spp. and some related Rhipsalis spp. Both genera have species with disjunct distributions between the paranas of south‐eastern Brazil and north‐eastern Argentina and the yungas forests of the eastern Andes. Karyotypes, fluorescent banding and fluorescence in situ hybridization (FISH) studies using rDNA probes were performed. A time‐calibrated phylogenetic tree was generated to place the karyological information and biogeographical history in an explicit evolutionary context. All species were 2n = 22 and showed symmetrical karyotypes comprising only metacentric chromosomes of similar sizes. The heterochromatin bands were always associated with chromosome satellites coinciding with the location and number of the 18S–5.8S–26S rDNA loci. The 5S rDNA loci had more heterogeneous profiles with one or two loci per haploid genome. Phylogenetic analysis suggested an ancient duplication event of the 5S rDNA loci and more recent post‐speciation translocation and deletion events. These genome restructurings are estimated to have occurred approximately 13.98 Mya in the middle Miocene, after Lepismium and Rhipsalis diverged. The ancestor of Lepismium may have had a similar karyotype to L. lumbricoides and the Rhipsalis spp. (i.e. one 5S locus on chromosome 2). Both genera hypothetically originated in the yungas (north‐eastern Argentina and southern Bolivia), but diversification of the Lepismium crown group probably originated from populations with duplicated 5S loci in the parana forests of south‐eastern Brazil (8.70 Mya in the late Miocene). Two migration events between the yungas and parana forests were suggested to explain the extant distribution of Lepismium spp. These results make Lepismium a model system for the study of the complex chromosomal evolution in plants. © 2015 The Linnean Society of London, Botanical Journal of the Linnean Society, 2015, 177 , 263–277.     

Karyotype variation, evolution and phylogeny in Borago (Boraginaceae), with emphasis on subgenus Buglossites in the Corso-Sardinian system

BACKGROUND AND AIMS: Karyological variation in the Mediterranean genus Borago and cytogeography of subgenus Buglossites in Corsica, Sardinia and the Tuscan Archipelago were investigated in combination with a molecular phylogenetic analysis aimed at elucidating relationships between subgenera and taxa with different chromosome features. METHODS: Karyotype analysis was performed on population samples of B. pygmaea, B. morisiana, B. trabutii and B. officinalis. Phylogenetic analyses were based on ITS1 nrDNA and matK cpDNA sequences. KEY RESULTS: Four base numbers were found, x = 6, 8, 9 and 15, and three ploidy levels based on x = 8. In subgenus Buglossites the Sardinian endemic B. morisiana is diploid with 2n = 18, while B. pygmaea includes three allopatric cytotypes with 2n = 30 (Sardinia), 2n = 32 (southern Corsica) and 2n = 48 (central northern Corsica and Capraia). In subgenus Borago, the Moroccan endemic B. trabutii and the widespread B. officinalis have 2n = 12 and 2n = 16, respectively. Molecular data support the monophyly of Borago, while relationships in subgenus Borago remain unclear. Borago trabutii appears as the earliest divergent lineage and is sister to a clade with B. officinalis, B. morisiana and B. pygmaea. Subgenus Buglossites is also monophyletic, but no correspondence between ITS1 phylogeny and B. pygmaea cytotypes occurs. CONCLUSIONS: Chromosome variation in Borago is wider than previously known. Two base numbers may represent the ancestral condition in this small genus, x = 6 or x = 8. An increase in chromosome number and karyotype asymmetry, a decrease in chromosome size and heterochromatin content, and the appearance of polyploidy are the most significant karyological changes associated with the divergence of the Buglossites clade. High ITS1 variation in the tetra- and hypotetraploid races of B. pygmaea suggests a multiple origin, while the lower polymorphism of the hexaploid race and its allopatric distribution in the northernmost part of the range is better explained with a single origin via union of unreduced and reduced gametes.     

Ribosomal RNA evolution by fragmentation of the 23S progenitor: Maturation pathway parallels evolutionary emergence

Summary The eukaryotic 5.8S and the chloroplast 4.5S ribosomal RNAs were proposed to have arisen from the 5 and 3 ends respectively of prokaryotic 23S ribosomal RNA by the introduction of new processing sites during evolution. This hypothesis was supported by comparison of previously published primary sequences; in addition we can draw models of secondary structure in accord with this notion. Finally, we further noted that the sequence of processing cuts in the maturation pathway of ribosomal RNA reflects the probable order in which they arose during evolution.     

FISH mapping of 35S and 5S rRNA genes in Artemisia subgenus Dracunculus (Asteraceae): changes in number of loci during polyploid evolution and their systematic implications

Fluorescence in situ hybridization (FISH) with 35S and 5S rDNA probes was used to characterize cytogenetically representatives of Artemisia subgenus Dracunculus and allied species and to explore their evolution following polyploidization. At the diploid level two rDNA loci were observed in most species belonging to the A. dracunculus complex, a pattern considered to be the ancestral state for diploid Artemisia. In contrast, representative species from the Eurasian grade which belong to the other major lineage of the subgenus had more heterogeneous rDNA profiles, with three to five loci at the diploid level. Divergent patterns of locus evolution were also detected in polyploids, with the number and distribution of rDNA loci broadly fitting the two main diversification lineages in the subgenus. In the polyploid complex of A. dracunculus, the number of rDNA loci was almost proportional to ploidy, although monoploid genome size was shown to decrease with increasing ploidy. However, in polyploids from the Eurasian grade we found a remarkable reduction in the number of rDNA sites, suggesting that these species might have experienced either a complete loss of loci or a significant reduction in the number of repeats following polyploid formation. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013 , 171 , 655–666.     

Chromosomal localization of 5S and 18S rDNA in five species of subgenus Strobus and their implications for genome evolution of Pinus

BACKGROUND AND AIMS: Studying the genome structure of pines has been hindered by their large genomes and uniform karyotypes. Consequently our understanding of the genome organization and evolutionary changes in different groups of pines is extremely limited. However, techniques are now available that can surmount these difficulties. The purpose of this study was to exploit some of these techniques to characterize the genome differentiation between the two subgenera of Pinus: Pinus and Strobus. METHODS: Double-probe fluorescence in-situ hybridization (FISH) was used to localize the 5S and 18S rDNA loci on chromosomes of five species from the subgenus Strobus: P. bungeana, P. koraiensis, P. armandii, P. wallichiana and P. strobus. * KEY RESULTS: The rDNA FISH pattern varied considerably among the five species, with P. bungeana being the most distinct. By comparing the results obtained with those of previous rDNA FISH studies of members of the subgenus Pinus, several general features of rDNA loci distribution in the genus Pinus can be discerned: (a) species of subgenus Strobus generally have more rDNA loci than species of subgenus Pinus, correlating with their larger genomes in the subgenus Strobus; (b) there is a clear differentiation in 5S and 18S rDNA loci linkage patterns between the two subgenera; (c) variations in the rDNA FISH pattern correlate with phylogenetic relationships among species within the subgenus; (d) P. bungeana has fewer 18S rDNA sites than other pines investigated to date, but they give intense signals, and may reflect the primary distribution of the 18S-25S rDNA loci in the genus. CONCLUSIONS: The stable differentiation in rDNA FISH pattern between the subgenera suggests that chromosomal rearrangements played a role in the splitting of the two subgenera, and transpositional events rather than major structural changes are likely responsible for the variable rDNA distribution patterns among species of the same subgenus with conserved karyotypes.     

18-26S rDNA在4种重楼属植物中的定位

为探讨rDNA在重楼属Paris L.中的分布规律,利用荧光原位杂交（FISH）对4种重楼属植物 的18-26S rDNA进行了定位。所有植物均为二倍体,基因组由A、B、C、D和 E5条染色体构成。（1）滇重楼P.polyphylla var.yunnanensis:2n=10=6m+4t,C和D染色体的 短臂上各有1个18-26S rDNA位点;（2）长柱重楼P.forrestii:2n=10=6m+4t,B染色体的长臂 、C和D染色体的短臂上各有1个位点;（3）五指莲P.axialis:2n=10=6m（2sat）+4t（2sat） +1-2B,C和D染色体的短臂上各有1个位点;在有1个B染色体的细胞中,B染色体没有信号点, 而有2个B染色体的细胞中,只有1个B染色体上有信号点,表明B染色体上有基因存在且其分裂 不均等;（4）大理重楼P.daliensis:2n=10=4m+2sm+2st+2t,C染色体的短臂上有1个位点。1 8-26S rDNA位点不仅出现在染色体的次缢痕上,也出现在非次缢痕位点。另外,4个种中C染 色体短臂末端均有18-26S rDNA。     

Physical mapping of 18S-5.8S-26S and 5S ribosomal RNA gene families in three important vetches (Vicia species) and their allied taxa constituting three species complexes

The most-important vetch species, Vicia narbonensis (narbon vetch, section Faba), Vicia villosa (hairy vetch, section Cracca) and Vicia sativa (common vetch, section Vicia) and their close relatives (often difficult to circumscribe into distinct taxa) constitute respectively, Narbonensis, Villosa and Sativa species complexes in the genus Vicia. The distribution of the 18S-5.8S-26S (18S-26S) and 5S ribosomal RNA (rRNA) gene families on the chromosomes of 19 (2n=2x=10,12,14) of the 24 species and subspecies belonging to the three species complexes, and Vicia bithynica (2n=12, section Faba) and Vicia hybrida (2n=12, section Hypechusa) was studied by fluorescence in situ hybridization (FISH) with pTa 71 (18S-26S rDNA) and pTa 794 (5S rDNA) DNA clones. Computer – aided chromosome analysis was performed on the basis of chromosome length, the arm-length ratio and the position of the hybridization signals. The positions of the four (2+2) signals of the two rRNA gene families were similar between each of the three, as well as two subspecies of V. narbonensis and Vicia johannis, respectively. Two major 18S-26S rDNA loci were found in the nucleolus organiser regions (NORs) of each of the species except V. hybrida, where it was present in two out of four SAT chromosomes. In addition to major NORs, two minor loci have been physically mapped at the centromeric regions of chromosomes of group 1 in Vicia amphicarpa, Vicia macrocarpa and V. sativa, and two NORs of group 5 in V. hybrida, and on the long arms of group 4 in V. bithynica. Two or four 5S rDNA loci, observed in the short arms of groups 2–4 and 5, and 18S-26S rDNA loci were located in different chromosomes of all the species within the Narbonensis and Villosa species complexes, and Vicia angustifolia of the Sativa species complex. In the remaining six species of the Sativa species complex, and V. bithynica and V. hybrida, the two or four 5S rDNA sites were present in chromosomes which harbor 18S-26S rRNA genes. The tandemly repeated 5S rDNA sites, located at the proximal part of the long arm of groups 3–5, were diagnostic for V. angustifolia, Vicia cordata, Vicia incisa, V. macrocarpa, Vicia nigra and V. sativa of the Sativa species complex. In V. amphicarpa of the same complex, the tandem repeats were located at the distal part of the long arms of group 3. Variability in the number, size and location of two ribosomal DNA probes could generally distinguish species within the Narbonensis and Sativa species complex, V. bithynica and V. hybrida. With respect to the four species of the Villosa species complex the karyotypes could not be identified individually on the basis of the distribution of two ribosomal gene families in three out of seven pairs of chromosomes. Received: 18 October 2000 / Accepted: 20 March 2001     

中间偃麦草(Thinopyrum intermedium)18S-5.8S-26S rDNA位点在染色体上的分布及对其核ITS序列异质性的分析(英文)

中间偃麦草(Thinopyrum intermedium(Host)Barkworth et Dewey)是禾本科小麦族植物中的一个异源六倍体物种,是重要的牧草植物,在小麦的抗病育种中发挥了重要作用。利用荧光原位杂交(FISH)技术,在体细胞中期染色体上,对18S-5.8S-26S rDNA位点进行了物理定位,发现该物种有3～4对染色体携带18S-5.8S-26S rDNA主位点。结合基因组原位杂交(GISH)分析,证明中间偃麦草的St基因组中有一对同源染色体短臂末端携带一个主位点,其余2～3对主位点位于E基因组染色体上。对不同来源的材料研究表明:18S-5.8S-26S rDNA位点的数目(包括主位点和小位点)、位置、拷贝数在不同收集材料之间的差异较大,甚至在同一个体的不同细胞中也存在差异。讨论了rDNA物理作图数据在分析系统发育问题中的局限性。结合中间偃麦草的三个可能的二倍体基因组供体(Th.bessarabicum、Th. elongatum和Pseudoroegneria stipifolia)rDNA位点分析的结果,对中间偃麦草进化过程中rDNA位点的变化进行了分析,同时,对其中一份材料的核ITS序列进行了克隆、测序和系统发育分析,发现在中间偃麦草中,ITS序列具有很高的异质性。     

Molecular phylogeny of solitary shell-bearing Polycystinea (Radiolaria)

The phylogeny of the Family Spongodiscidae (polycystine Radiolaria), which includes Dictyocoryne profunda Ehrenberg, Dictyocoryne truncatum (Ehrenberg) and Spongaster tetras Ehrenberg, was examined using 18S ribosomal DNA (small-subunit ribosomal DNA) sequence analysis. Three types of tree construction methods, the neighbor joining (NJ), maximum parsimony (MP), and maximum likelihood (ML) methods, were used to infer the phylogenetic relationships of the polycystine and acantharian Radiolaria among eukaryotes. The obtained 18S rDNA molecular phylogenetic tree argues for the monophyly of the two groups. Furthermore, the Polycystinea is divided into at least two distinct lineages consisting of: (1) colonial and skeletonless Polycystinea, including Thalassicollidae, Collospaeridae, and Sphaerozoidae; and (2) shell-bearing solitary Polycystinea, including Spongodiscidae. The Polycystinea thus show a paraphyly among Radiolaria. Moreover, the monophyly of the clade including the acantharians and the spongodiscid polycystines was supported by bootstrap values, which were 94%, 53%, and 59% in the NJ, MP, and ML analyses, respectively. This lineage is characterized by having latticed or spongy skeletons of different chemical composition, namely SiO₂ (Class Polycystinea) or SrSO₄ (Class Acantharea). According to the present taxonomic scheme, the Acantharea and the Polycystinea have not been placed in different classes, but the results of our molecular study show the opposite. We therefore suggest, based on the monophyly of the two clades, that a new taxonomic group of Radiolaria can be established. Our molecular data also suggest that the currently used radiolarian taxonomic system may need serious revisions.     

Cytogenetic and phylogenetic studies of diploid and polyploid members of tribe Anemoninae (Ranunculaceae)

The ancestry, phylogenetic differentiation and systematic classification of the worldwide-distributed genus Anemone have been debated for many years. In this paper 11 Anemone, three Pulsatilla species and Hepatica nobilis were subjected to detailed karyotype analysis with the aim of obtaining new cytogenetic data that will contribute to karyotype evolutionary studies of the tribe Anemoninae. The results are interpreted in a phylogenetic context, established from the intergenic nontranscribed spacer (NTS) of 5S rDNA and internal transcribed spacer (ITS) of 35S rDNA. One to three 35S and one to three 5S rDNA loci are present in diploid and polyploid taxa. The 35S rDNA loci are located terminally on the short arm of acrocentric chromosomes, while for 5S rDNA there is no preferential chromosomal position as it exhibits terminal, subterminal, interstitial or pericentromeric positions, and is located either on acrocentric or metacentric chromosomes. The karyotype of hexaploid A. baldensis (2n = 6x = 48) is presented for the first time, and A. sylvestris is proposed as one of its putative parental species. Chromosome fusion/translocation is proposed as the key mechanism involved in reduction of the basic chromosome number from 8 in the Anemone subgenus to 7 in the Anemonidium subgenus. The cytogenetic data obtained are mainly supported by ITS and NTS phylogeny. Diversification of the genus Anemone was accompanied by a large reduction of heterochromatin, from the Mediterranean anemones that have large amounts of heterochromatin to the New World anemones without any detectable heterochromatic blocks.