Yoko Kita

Nuclear ribosomal ITS sequences and phylogeny in East AsianAconitum subgenusAconitum (Ranunculaceae), with special reference to extensive polymorphism in individual plants

Internal transcribed spacer (ITS) sequences of nuclear ribosomal DNA (nrDNA) were used to examine the phylogeny of East Asian aconites. Individual aconites were discovered to contain as many as eight different ITS sequences after cloning and PCR-SSCP (single-stranded conformational polymorphisms) analysis. We identified eight putative ITS pseudogenes from four taxa with low predicted secondary structure stability and high substitution rates. Maximum likelihood (ML) and neighbor-joining (NJ) methods were used for phylogenetic reconstruction. The ITS trees agree with the previous chloroplast DNA (cpDNA) tree for the vast majority of the taxa. We found two East Asian clades in the ITS trees: 1) a clade with the Chinese diploid,Aconitum volubile and East Asian tetraploids, and 2) a clade of East Asian diploids and Siberian tetraploids. In the former clade, most tetraploid taxa appear to be polyphyletic; sequences from individual plants did not correspond to recognized taxonomic units. This indicates a recent divergence of the East Asian tetraploids.

Evolution of rbcL group IA introns and intron open reading frames within the colonial Volvocales (Chlorophyceae)

Mobile group I introns sometimes contain an open reading frame (ORF) possibly encoding a site-specific DNA endonuclease. However, previous phylogenetic studies have not clearly deduced the evolutionary roles of the group I intron ORFs. In this paper, we examined the phylogeny of group IA2 introns inserted in the position identical to that of the chloroplast-encoded rbcL coding region (rbcL-462 introns) and their ORFs from 13 strains of five genera (Volvox, Pleodorina, Volvulina, Astrephomene, and Gonium) of the colonial Volvocales (Chlorophyceae) and a related unicellular green alga, Vitreochlamys. The rbcL-462 introns contained an intact or degenerate ORF of various sizes except for the Gonium multicoccum rbcL-462 intron. Partial amino acid sequences of some rbcL-462 intron ORFs exhibited possible homology to the endo/excinuclease amino acid terminal domain. The distribution of the rbcL-462 introns is sporadic in the phylogenetic trees of the colonial Volvocales based on the five chloroplast exon sequences (6021 bp). Phylogenetic analyses of the conserved intron sequences resolved that the G. multicoccum rbcL-462 intron had a phylogenetic position separate from those of other colonial volvocalean rbcL-462 introns, indicating the recent horizontal transmission of the intron in the G. multicoccum lineage. However, the combined data set from conserved intron sequences and ORFs from most of the rbcL-462 introns resolved robust phylogenetic relationships of the introns that were consistent with those of the host organisms. Therefore, most of the extant rbcL-462 introns may have been vertically inherited from the common ancestor of their host organisms, whereas such introns may have been lost in other lineages during evolution of the colonial Volvocales. In addition, apparently higher synonymous substitutions than nonsynonymous substitutions in the rbcL-462 intron ORFs indicated that the ORFs might evolve under functional constraint, which could result in homing of the rbcL-462 intron in cases of spontaneous intron loss. On the other hand, the presence of intact to largely degenerate ORFs of the rbcL-462 introns within the three isolates of Gonium viridistellatum and the rare occurrence of the ORF-lacking rbcL-462 intron suggested that the ORFs might degenerate to result in the spontaneous intron loss during a very short evolutionary time following the loss of the ORF function. Thus, the sporadic distribution of the rbcL-462 introns within the colonial Volvocales can be largely explained by an equilibrium between maintenance of the introns by the intron ORF and spontaneous loss of introns when the introns do not have a functional ORF.

Phylogeny and Phytogeography of Eupatorium (Eupatorieae, Asteraceae): Insights from Sequence Data of the nrDNA ITS Regions and cpDNA RFLP

Eupatorium were examined by sequencing the internal transcribed spacers (ITS) of nuclear ribosomal DNA and restriction site analysis of chloroplast DNA. Molecular data provided strong evidence that (1) this genus originated in North America, (2) the genus diverged into three morphological species groups, Eutrochium, Traganthes and Uncasia in North America, and (3) one of the North American Uncasia lineages migrated into temperate Europe and eastern Asia over the Bering land bridge. The estimated divergence times support a late Miocene to early Pliocene migration from North America to Eurasia via the Bering land bridge. A European species was sister to all of the eastern Asian species examined. The disjunct distribution pattern of the genus Eupatorium is incongruent with the classical Arcto-Tertiary geoflora concept.

Seedling developmental anatomy of an undescribed Malaccotristicha species (Podostemaceae, subfamily Tristichoideae) with implications for body plan evolution

The seedling development of an undescribed Malaccotristicha species was observed by using seedling culture and microtomy to infer the evolution of body plan with a focus on the root, which is a developmentally leading organ of most Podostemaceae. The young seedling has a small primary shoot apical meristem and a primary root apical meristem. The shoot meristem develops into a plumular ramulus, and the root meristem, into a cylindrical radicle with no root cap. The radicle transforms to a dorsiventral, flattened, capped primary root. An adventitious root develops endogenously on the lateral side of the hypocotyl and is similar to the primary root. This is a new pattern in Podostemaceae. Comparison of this and described patterns of Podostemaceae (and the sister-group Hypericaceae) suggests that the radicle was lost in the early evolution of Podostemaceae and instead adventitious roots replaced it as a leading organ.

Molecular Phylogeny of Cladopus and Hydrobryum (Podostemaceae, Podostemoideae) with Implications for their Biogeography in East Asia

Abstract Molecular data from Cladopus and Hydrobryum, members of the aquatic angiosperm family Podostemaceae, were analyzed phylogenetically using the chloroplast matK gene and internal transcribed spacer (ITS) regions of the nuclear ribosomal RNA (nrRNA) gene to infer the species relationships and the biogeographic history of the East Asian species. The phylogenies based on matK and ITS were incongruent for relationships in a northern clade of Cladopus, but the pattern of root morphologies (ribbon vs. linear) agreed with the matK phylogeny. The matK phylogeny revealed that all East Asian temperate species of each genus form a monophyletic group that is derived from tropical/subtropical species. A clock-constrained maximum-likelihood tree suggests that the divergence events of the temperate lineages from their tropical sisters occurred coevally in the two genera. Dispersal-vicariance analysis (DIVA) suggests that distribution at the middle latitudes was formed by a wide primary distribution covering tropical and temperate areas and a secondary dispersal event in Cladopus, and by a dispersal event in Hydrobryum. Two Kyushu-Fujian groups are found in Cladopus, one consisting of Japanese C. austro-osumiensis and Chinese C. fukiensis and another consisting of Japanese C. japonicus, C. austrosatsumensis, and C. doianus and Chinese C. chinensis, each of which shows little genetic differentiation between species from Kyushu, southern Japan, and Fujian, China, suggesting parallel biogeographic histories. Disjunct populations of Hydrobryum japonicum from Kyushu in southern Japan and from northern Thailand show little genetic differentiation, whereas a plant from Yunnan, China, diverged earlier than did the Japanese or Thai plants. The DIVA results suggest that the disjunctive distribution of Hydrobryum japonicum was formed by two dispersal events from Kyushu to Yunnan and to northern Thailand.

Molecular phylogeny, taxonomy and biogeography of Malaccotristicha australis comb. nov. (syn. Tristicha australis) (Podostemaceae)

The systematic relationship of Tristicha australis C.Cusset & G.Cusset in northern Australia was investigated by comparative morphology and molecular phylogeny. Both lines of evidence show that it is most closely related to Malaccotristicha malayana (J.Dransf. & Whitmore) C.Cusset & G.Cusset and distinct from Tristicha trifaria (Bory ex Willd.) Sprengel and consequently the nomenclatural combination of Malaccotristicha australis is made. It is suggested that M. australis rapidly gained its characteristic morphology that is distinct from Malaccotristicha and resembles Tristicha. Phylogeographically, Australian Podostemaceae with two species, M.xa0australis and Cladopus queenslandicus (Domin) C.D.K. Cook & Rutishauser, are probably derived, compared with the tropical Asian sisters. A key is provided to the species of Tristichoideae to distinguish M. australis and the other species.

Molecular phylogenetic analyses and systematics of the genus Saussurea and related genera (Asteraceae, Cardueae)

The phylogenetic relationships of the genus Saussurea DC. and Hemistepta lyrata Bunge were analyzed using the nuclear ribosomal ITS and chloroplast matK gene. Phylogenetic analyses revealed that Saussurea ceratocarpa Decne. of subg. Jurinocera (Baill.) Lipsch. and the species assigned to sect. Elatae Hook.f. of subg. Saussurea were separated from all other members of the genus Saussurea. The species of subgen. Jurinocera and subgen. Saussurea sect. Elatae form a monophyletic unit along with a group including genus Jurinea Cass. The species of subg. Jurinocera and sect. Elatae share 4-5-gonal cypselas and apical pericarpal crowns bearing sharp horns or sharp teeth. The Saussurea s.s. group is comprised of representatives of six sections of the subg. Saussurea and morphologically distinctive subgenera [Amphilaena (Stschegl.) Lipsch., Eriocoryne (DC.) Hook.f., and Theodorea (Cass.) Lipsch.]. Two frigid-adapted forms, the snowball plants of subg. Eriocoryne and the glasshouse plants of subg. Amphilaena, were confirmed as members of Saussurea s.s. Hemistepta lyrata and Saussurea s.s. show a close sister relationship, which is supported by the pappus dimorphism involving free, short, scabrid outer bristles or tiny outer scales and basally connate in a ring, with much longer, plumose inner bristles.