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. Received 13 September 1999/ Accepted in revised form 4 January 2000     

Thirteen new species and two new combinations of Stevia (Asteraceae: Eupatorieae) from Mexico

Thirteen new species of the genusStevia are described and illustrated from Mexico:S. chilapensis, S. coahuilensis, S. crassifolia, S. ecatepecana, S. filodecaballoana, S. mascotensis, S. mexicana, S. oaxacana, S. oligophylla, S. potosina, S. rotundifolia, S. scabrelloides, andS. viejoana. In addition, two varieties,Stevia aschenborniana Sch. Bip. ex Klotzsch var.occidentalis Grashoff andS. palmeri A. Gray var.constricta Grashoff are herein redefined as being distinct species,S. occidentalis andS. constricta stat. nov.Stevia mexicana resemblesStevia trifida Lagasca but differs in the habit.     

Chloroplast DNA restriction site data support a narrowed interpretation ofEupatorium (Asteraceae)

Chloroplast DNA (cpDNA) restriction site analysis was used to assess relationships among samples of Eupatorieae from eastern North America. A total of 270 cpDNA variants was recorded from 35 species using 13 restriction enzymes. Phylogenetic analysis usingGalinsoga, Flaveria, andHelianthinae as outgroups indicated that samples ofAgeratina, Hofmeisteria, Mikania, andStevia, each of which have relatively high base chromosome numbers, formed an unresolved basal polytomy. The remaining samples examined formed a well-supported clade, within which there was a split betweenBrickellia, which hasx = 9, and a number of genera withx = 10. Within thex = 10 clade, there was an unresolved trichotomy, with one group ofAgeratum, Conoclinium, Fleischmannia, andCritonia, a second ofLiatris andTrilisa, and a third ofEupatorium s.s. Within theEupatorium s.s. clade there were three further clades, withE. sect.Verticillata diverging first, and a subsequent split between species originating from North America and those from Asia. The cpDNA restriction site data provided support for a relatively narrow interpretation ofEupatorium, and indicated that a high chromosome base number is plesiomorphic for Eupatorieae.     

Principal features of the cpDNA evolution in Taraxacum (Asteraceae, Lactuceae): a conflict with taxonomy

Phylogenetic relationships based on the chloroplast genome of Taraxacum were studied. Representative samples of 44 sections or species groups and a number of isolated species were analyzed. On the basis of the sequence variation in psbA–trnH and in trnL–trnF, mutations associated with RFLPs were monitored. Five RFLPs without homoplasy were recognized and used to reconstruct four main cpDNA groups (haplotypes); Group I is ancestral and, contrary to the information in the primary sequences, the RFLPs were not distinct from those of the outgroup species of Agoseris and Prenanthes. This group corresponds to dandelions believed to be ancestral on the basis of morphological data and previous studies of the chloroplast genome. A comparison of parsimony analysis of morphological and chloroplast data showed an overall lack of congruence. The conflict can most probably be accounted for as a consequence of reticulation.     

Chromosomal Evolution in the Genus Brachyscome (Asteraceae, Astereae): Statistical Tests Regarding Correlation Between Changes in Karyotype and Habit Using Phylogenetic Information

Brachyscome and 8 taxa of its allied genera, Australian Astereae. Statistical tests regarding correlations between changes in chromosome number, total chromosome length, mean chromosome length, karyotypic asymmetry and chromosome length heterogeneity and changes in habit were performed based on the matK molecular phylogenetic tree. The reductions in chromosome number and total chromosome length, and the increases in mean chromosome length, chromosome length heterogeneity and karyotypic asymmetry were found to be correlated with the change in habit from perennial to annual. A reduction in total chromosome length is favored to shorten the mitotic cell cycle and to produce smaller cells conducive to more rapid development of smaller annuals under the time-limited environment. Stepwise dysploidal reductions in chromosome number were achieved through the translocation of large chromosome segments onto other chromosomes, followed by the loss of a centromere, resulting in one fewer linkage group and one fewer haploid chromosome. The correlations between the dysploidal reduction in chromosome number and the increases in mean chromosome length, length heterogeneity and asymmetry in karyotype can be attributed to this mode of chromosomal change. These changes occurred independently in several different lineages in Brachyscome. Received 27 May 1998/ Accepted in revised form 18 January 1999     

Pollen morphology and its relation with meiotic irregularities in ten species of Campuloclinium (Eupatorieae,Asteraceae)

Pollen grains of ten species of Campuloclinium (Eupatorieae, Asteraceae) are described and illustrated using light and scanning electron microscopy. The species included in this study are C. burchelli, C. campuloclinioides, C. chlorolepis, C. hirsutum, C. irwinii, C. macrocephalum, C. megacephalum, C. parvulum, C. purpurascens and C. riedelli. Pollen grains of Campuloclinium are typically radially symmetric, echinate, tectate, oblate-spheroidal to prolate-spheroidal (P/E ratio: 0.94–1.10). Pollen is mostly triaperturate, but tetraaperturate or biaperturate pollen also occurs in some species. The pollen diameter was highly variable ranging from 10.54 µm to 36.18 μm. The significance of the variation in type and size of pollen is discussed in relation to diverse meiotic abnormalities and possible reproductive apomictic processes within the polyploid species.     

江苏铁角蕨的系统位置和多倍体起源

运用分子系统发育分析的方法研究了江苏铁角蕨（Asplenium kiangsuense）的系统位置及其与庐山铁角蕨（Agulingense）的关系,并探讨了该类群可能的多倍体起源方式。结果显示：江苏铁角蕨与庐山铁角蕨可能为同源四倍体,是组成倒挂铁角蕨复合体（Anormale complex）的成员之一;二者在形态特征与基因序列方面均表现一致,接受英文版中国植物志的处理,即把庐山铁角蕨处理为江苏铁角蕨的异名。     

Molecular Phylogeny of Magnolia (Magnoliaceae) Inferred from cpDNA Sequences and Evolutionary Divergence of the Floral Scents

Magnolia (disjuncts), however, have similar chemical profiles. A molecular phylogeny of Magnoliaceae was constructed to reveal phylogenetic relationships of taxa by sequencing the trnK intron (including the matK coding region), psbA-trnH, and atpB-rbcL intergenic spacer regions of chloroplast DNA from 25 Magnolia, two Michelia, and two Liriodendron taxa. The psbA-trnH spacer region showed twice the sequence divergence (0.0157) of the trnK intron (0.0073) or the matK coding region (0.0077). The strict consensus tree constructed from the combined data set (ca. 3,700 bp) indicated the genus Magnolia was polyphyletic containing Michelia species as ingroup. The clade of Magnolia liliifera var. obovata, M. coco, and M. delavayi formed the first branch. Among the remaining species, two additional large clades were recognized, i.e., one comprised of American evergreen Magnolia species and another of subgenus Yulania. The relationship among sect. Rytidospermum taxa was not clearly resolved. Parsimonious mapping of the floral scent chemical characters was performed onto the molecular phylogenetic tree to discuss evolutionary trends of the floral scent chemistries. Received 7 December 1998/ Accepted in revised form 18 May 1999     

Polyploidy and new chromosome counts in Anaphalis(Asteraceae:Gnaphalieae) from the Qinghai-Tibet Plateau of China

Anaphalis is one of the largest genera of the Asian Gnaphalieae (Asteraceae) and is most diversified on the Qinghai-Tibet Plateau. The chromosome numbers and karyomorphology of six species from seven populations were investigated for the first time for this region. Chromosome numbers have been newly documented for four species: Anaphalis deserti (2n = 56 = 24 median [m] + 24 submedian [sm] + 8 acrocentric [st]); Anaphalis plicata (2n = 56 = 26m + 30sm); Anaphalis xylorhiza (2n = 28 = 2 median point [M] + 14m + 12sm); and Anaphalis rhododactyla (2n = 56 = 32m + 24sm). Two further counts are in agreement with the previously reported numbers, that is, Anaphalis royleana (2n = 28 = 4M + 6m + 18sm) and Anaphalis margaritacea (2n = 28 = 12m + 16sm). A new polyploid cytotype (2n = 56 = 26m + 30sm) was found in the Zougong population of A. margaritacea. Polyploidy is for the first time reported for Anaphalis, with four out of seven counts being tetraploid. Our cytological results suggest that polyploids might have played an important role in the evolution of Anaphalis on the Qinghai-Tibet Plateau.     

Cytogeography and chromosome evolution of subgenus Tridentatae of Artemisia (Asteraceae)

The subgenus Tridentatae of Artemisia (Asteraceae: Anthemideae) is composed of 11 species of various taxonomic and geographic complexities. It is centered on Artemisia tridentata with its three widespread common subspecies and two more geographically confined ones. Meiotic chromosome counts on pollen mother cells and mitotic chromosome counts on root tips were made on 364 populations ( = 3.1 plants per population). These population counts are ～60% of all Tridentatae counts. Some are first records for taxa. The Tridentatae are a polyploid complex (x = 9) with ploidy levels from 2x to 8x, but mostly 2x (48%) and 4x (46%). Polyploidy occurs in nine of the 11 species and in many subspecies as well. Supernumerary or b chromosomes are present only at a low frequency. In the principal species, A. tridentata, 2x plants are larger than 4x ones, which are adapted to drier conditions, probably in consequence of their slower growth rates. Gigas diploidy is a phenomenon shared by some other woody genera, but is in contrast to the gigas polyploid nature of many herbaceous genera. Polyploidy occurs within populations and is essentially autoploid. Hybridization sometimes occurs at taxa interfaces in stable hybrid zones. Stable Tridentatae hybrid zones coupled with the group's inherent propensity for polyploidization has led to the establishment of a geographically and numerically large and successful complex of species.     

Phylogeny of Barnadesioideae (Asteraceae) inferred from DNA sequence data and morphology

Subfamily Barnadesioideae (Asteraceae) consists of nine genera and 91 species endemic to South America. They include annual and perennial herbs, arching shrubs and trees up to 30 m tall. Presumed sister to all other Asteraceae, its intergeneric relationships are key to understanding the early evolution of the family. Results of the only molecular study on the subfamily conflict with relationships inferred from morphology. We investigate inter- and intrageneric relationships in Barnadesioideae with novel DNA sequence data and morphological characters using parsimony, likelihood and Bayesian inference. All results verify Barnadesioideae as monophyletic and sister to the rest of the family. A basal split within the subfamily is recognized, with Chuquiraga, Doniophyton and Duseniella in one clade, and Arnaldoa, Barnadesia, Dasyphyllum, Fulcaldea, Huarpea and possibly Schlechtendalia in another. The largest genus, Dasyphyllum, is revealed as biphyletic with the two clades separating along subgeneric and geographic lines. Schlechtendalia, suggested as the earliest diverging lineage of the subfamily by morphological studies and parsimony analyses, is found in a more derived position under model-based inference methods. Competing phylogenetic hypotheses, both previous and present, are evaluated using likelihood-based tests. Evolutionary trends within Barnadesioideae are inferred: hummingbird pollination has developed convergently at least three times. An early vicariance in the subfamily’s distribution is revealed. X = 9 is supported as the ancestral base chromosome number for both Barnadesioideae and the family as a whole.     

Polyploidy and new chromosome counts in Anaphalis (Asteraceae: Gnaphalieae) from the Qinghai‐Tibet Plateau of China

Abstract Anaphalis is one of the largest genera of the Asian Gnaphalieae (Asteraceae) and is most diversified on the Qinghai‐Tibet Plateau. The chromosome numbers and karyomorphology of six species from seven populations were investigated for the first time for this region. Chromosome numbers have been newly documented for four species: Anaphalis deserti (2n = 56 = 24 median [m]+ 24 submedian [sm]+ 8 acrocentric [st]); Anaphalis plicata (2n = 56 = 26m + 30sm); Anaphalis xylorhiza (2n = 28 = 2 median point [M]+ 14m + 12sm); and Anaphalis rhododactyla (2n = 56 = 32m + 24sm). Two further counts are in agreement with the previously reported numbers, that is, Anaphalis royleana (2n = 28 = 4M + 6m + 18sm) and Anaphalis margaritacea (2n = 28 = 12m + 16sm). A new polyploid cytotype (2n = 56 = 26m + 30sm) was found in the Zougong population of A. margaritacea. Polyploidy is for the first time reported for Anaphalis, with four out of seven counts being tetraploid. Our cytological results suggest that polyploids might have played an important role in the evolution of Anaphalis on the Qinghai‐Tibet Plateau.     

中国特有蕨属扇蕨属（水龙骨科）的系统学研究

扇蕨属（Neocheiropteris）为中国蕨类植物4个特有属之一。自Christ建属以来,不同的分类学者对本属的范畴以及系统位置一直存有争议。本研究对扇蕨属和盾蕨属进行了形态解剖观察,并对扇蕨属及其近缘类群共14个种的4个叶绿体DNA片段：rbcL、rpS4 ＆ rpS4-trnS IGS、trnL intron ＆ trnL-trnF IGS以及atpB ＆ atpB-rbcL IGS进行测序,应用最大简约法（Maximum-parsimony）、最大似然法（Maximum-likeli-hood）和贝叶斯推断（Bayesian inference）对序列进行联合矩阵分析,并构建系统树。该研究从形态学和分子系统学方面都提出了支持扇蕨属和盾蕨属分立的证据。形态学研究显示扇蕨属和盾蕨属叶片分裂方式、叶被和侧脉特征迥异,支持扇蕨属和盾蕨属的分立;但两属根状茎鳞片的共同特征则反映了两属问的紧密联系。分子系统学研究表明扇蕨属与毛鳞蕨属和鳞果星蕨属构成姐妹群,其集合与盾蕨属构成姐妹群。综合形态学和分子系统学的证据,对扇蕨属的系统位置以及范畴进行了深入探讨,扇蕨属包括扇蕨和三出扇蕨,结合形态学和分子系统学证据对三出扇蕨的系统位置进行了初步探讨。     

DNA evidence for multiple origins of intergeneric allopolyploids in annualMicroseris (Asteraceae)

Seventy populations of North American annualMicroseris, Stebbinsoseris, andUropappus species were examined for chloroplast and nuclear ribosomal DNA restriction site variability to determine the origin of the allotetraploid speciesS. heterocarpa andS. decipiens. Previously identified chloroplast DNA restriction site variants were used in concert with restriction site variation forNco I in the nuclear-encoded ribosomal DNA repeat. The presence of two, mutually exclusive restriction site gains were observed in diploid populations ofM. douglasii; these same variants were also found in populations of allotetraploidS. heterocarpa, indicating mutiple origins of this species from different maternal diploid populations ofM. douglasii. Variation in the rDNA repeat between the diploid annual species and the putative paternal genome ofU. lindleyi was found to be additive inS. heterocarpa. A similar relationship was observed for the origin ofS. decipiens; cpDNA restriction site variants found inM. bigelovii andM. douglasii were present inS. decipiens. The rDNANco I variants also were additive in this purported allotetraploid. These results confirm the reticulate evolutionary pattern inStebbinsoseris and provide another example of multiple origins of intergeneric allopolyploids.     

Molecular evidence for multiple polyploidization and lineage recombination in the Chrysanthemum indicum polyploid complex (Asteraceae)

The Chrysanthemum indicum polyploid complex comprises morphologically differentiated diploids, tetraploids and hybrids between C. indicum and C. lavandulifolium. The relationships between species and cytotypes within this complex remain poorly understood. Random amplified polymorphic DNAs (RAPDs), intersimple sequence repeats (ISSRs) and chloroplast SSR markers were used to elucidate the genetic diversity and relationships of the C. indicum polyploid complex. Molecular analysis of three diploid and nine tetraploid populations provided strong evidence for recurrent origins and lineage recombination in the C. indicum polyploid complex. The high similarity in molecular marker profiles and cpDNA haplotypes between the diploids and tetraploids distributed in the Shen-Nong-Jia Mountain area of China suggested an autopolyploid origin of the tetraploids, while the tetraploids from other populations may have originated via allopolyploidization. Lineage recombination was revealed by the extensive sharing of chloroplast haplotypes and genetic markers among the tetraploid populations with different origins. Multiple differentiation and hybridization/polyploidization cycles have led to an evolutionary reticulation in the C. indicum polyploid complex, and resulted in the difficulties in systematic classification.     

Molecular phylogenetic analyses of nuclear and plastid DNA sequences support dysploid and polyploid chromosome number changes and reticulate evolution in the diversification of Melampodium (Millerieae, Asteraceae)

Chromosome evolution (including polyploidy, dysploidy, and structural changes) as well as hybridization and introgression are recognized as important aspects in plant speciation. A suitable group for investigating the evolutionary role of chromosome number changes and reticulation is the medium-sized genus Melampodium (Millerieae, Asteraceae), which contains several chromosome base numbers (x = 9, 10, 11, 12, 14) and a number of polyploid species, including putative allopolyploids. A molecular phylogenetic analysis employing both nuclear (ITS) and plastid (matK) DNA sequences, and including all species of the genus, suggests that chromosome base numbers are predictive of evolutionary lineages within Melampodium. Dysploidy, therefore, has clearly been important during evolution of the group. Reticulate evolution is evident with allopolyploids, which prevail over autopolyploids and several of which are confirmed here for the first time, and also (but less often) on the diploid level. Within sect. Melampodium, the complex pattern of bifurcating phylogenetic structure among diploid taxa overlain by reticulate relationships from allopolyploids has non-trivial implications for intrasectional classification.