Taxonomy ofCarminatia (Asteraceae,Eupatorieae)

A taxonomic study of the largely Mexican genusCarminatia is rendered. It is comprised of three closely related species:C. tenuiflora, C. recondita andC. anomala spec. nova. Illustrations, dot maps, keys to species and complete synonymy are presented.     

A new species of Ageratina (Asteraceae: Eupatorieae) from northwestern Oaxaca

Fieldwork in connection with the project to document the flora of the Mixteca Alta region, northwestern Oaxaca, Mexico, has resulted in the discovery of a new species, Ageratina pendula.     

Geographical distribution of Eupatorieae (Asteraceae) in South-eastern and South Brazilian Mountain Ranges

This study deals with the geographical distribution of Eupatorieae species in South-eastern and Southern Brazilian mountain ranges, with special emphasis on the Mantiqueira range (Serra da Mantiqueira). In the Mantiqueira range, five localities were sampled for two years during the flowering period of the plants. Species composition in the Mantiqueira localities was then compared to data from a central range (the Espinhaço) and a southern coastal range. Cluster and ordination analyses showed clear floristic differences among the three ranges. Nearer localities were more similar floristically only within the Espinhaço range and across all ranges, as shown by Mantel tests. The dendrogram in the Mantiqueira range clustered Itatiaia and Campos do Jordão, two non-adjacent localities with similar environment, landscape and topography. Different processes may be influencing the structure and composition of the Eupatorieae flora at different geographical scales. Historical and biogeographical processes may be more important in determining community composition of different mountain ranges, whereas factors such as climate and human impact may be determining differences among localities within each mountain range.     

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.     

A comparative study of latex-producing tissues in genera of Liabeae (Asteraceae)

Laticifers are highly specialized living plant cells which produce and contain latex. Occurrence of latex was used to establish morphological affinities (i) between Liabeae and other Asteracean tribes, (ii) among the Liabean genera, and (iii) in order to obtain phylogenies within Liabeae. However, structures and types of latex-producing tissues in this tribe have not yet been studied anatomically. In the present paper latex-producing structures of aerial parts in species of Microliabum, Munnozia, and Paranephelius (Liabeae), from open areas in mid-elevation Andean forests and in Andean high-elevation habitats, were studied. In all the analyzed species, latex secretion was easily observed in stem and leaf blade hand sections. Laticifers accompanied vascular tissues in all the cases, throughout stems and leaves, and they were of the articulated anastomosed type, at least in fully developed stages. Laticifers were found facing both, the xylem and the phloem, except for Paranephelius stems, in which they occur merely next to the phloem. Leaf laticifers form a reticulum accompanying the vein system. The type of latex-producing tissue shared by Microliabum and Munnozia could be a character shared by common ancestry whereas the laticifer system of Paranephelius stems could represent an evolutionary novelty for this genus. The laticifer type described in this study in aerial parts of Liabeae may allow establishing morphological affinities with tribes Cichorieae and Arctoteae.     

Meiotic behavior and pollen fertility in triploid and tetraploid natural populations of Campuloclinium macrocephalum (Eupatorieae,Asteraceae)

Campuloclinium macrocephalum DC. is a perennial herb widely distributed in the New World and introduced in South Africa, where it is commonly called “pompom weed”. This species is considered one of the most important weeds of Brazil and one of the problematic invasive plants of South Africa. The meiotic system can be studied to assess the ability of a weed to spread, but only few studies on C. macrocephalum have been realized. In this study, we examined the meiotic behavior and pollen fertility of 14 natural populations of C. macrocephalum from Argentina and Uruguay. Meiotic analysis revealed 2 triploid (2n = 3x = 30), 11 tetraploid (2n = 4x = 40) and 1 mixed population (2n = 2x = 20, 2n = 4x = 40). Both, triploid and tetraploid specimens showed a widely variable meiotic behavior with irregular chromosome pairing showing univalents, bivalents, trivalents (in triploids) and tetravalents (in tetraploids) at diacinesis of first meiotic division. Different abnormalities were observed, such as: laggard chromosomes, chromatin bridges, and out of plate chromosomes at metaphase I. During meiosis I (prophase), some cells showed the phenomenon of cytomixis or chromatin transfer between pollen mother cells. The meiotic indexes suggest that only four populations were normally fertile (over 90 % of fertile pollen), indicating meiotically stable plants. The remaining populations share variable pollen fertility, with triploids ranging from 46.64 to 54.83 % and tetraploids varying from 3.54 to 45.30 %. We suggest that polyploidy seems to be recurrent in C. macrocephalum, promoting partial sterility of pollen grains, generating large numbers of individuals by apomixis promoting invasion of crop fields. This study presents the meiotic behavior of this weed, these could be useful for future studies of biological control in areas with no natural enemies.     

Stylotrichium glomeratum (Asteraceae, Eupatorieae), a new species from Chapada Diamantina, Bahia, Brazil

Stylotrichium glomeratum (Asteraceae, tribe Eupatorieae, subtribe Gyptidinae) is described from Chapada Diamantina (Bahia, Brazil), where the genus is endemic. A key to the five species ofStylotrichium is presented.

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Descreve-seStylotrichium glomeratum (Eupatorieae, Asteraceae), uma nova espécie da Chapada Diamantina (Bahia, Brasil), onde este gênero é endêmico. é apresentada uma chave para as cinco espécies deStylotrichium.

     

中国菊科泽兰族的一个新归化属——裸冠菊属

报道了在华南地区广西发现的菊科Asteraceae泽兰族EuPatorieae一个新归化属——裸冠菊属GymnDcDmnis DC．。它在形态上接近于下田菊属Adenostemma J．R．Forst．＆G.Forst．,但区别在于裸冠菊属无冠毛。依据在中国所采集的标本详细描述了该属在中国的唯一代表种裸冠菊Gymnocoronis spilanthoides （D．Don ex Hook．＆Arn.）DC．的形态特征,并讨论了其地理分布和进入中国的可能途径。     

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     

Self-fertility and associated flower head traits in the Iberian taxa ofLactuca and related genera (Asteraceae: Lactuceae)

Sexual reproduction is the main reproduction mechanism among the 14 wild Iberian taxa ofLactuca, Prenanthes, Cicerbita, andMycelis. High levels of self-fertilization occur inLactuca, as well as facultative and obligate xenogamy. Xenogamy is strongly correlated with large capitula having blue or bright yellow colouration, high P/O ratios, and long anthesis, whereas self-fertilization is correlated with smaller capitula having pale yellow colouration, small P/O ratios, and short anthesis. Large variations occur in P/O index among taxa showing similar fertilization mechanism, probably in relation to the number of florets included in flower heads. Interesting differences in reproductive systems have been detected between subspecies ofLactuca viminea.     

Pollen morphology of some related genera of Vernonieae (Asteraceae) and its taxonomic significance

Pollen morphology is an important source of information to increase systematic resolution in Asteraceae, especially in Vernonieae. Aiming to investigate if palynological traits give support to Caatinganthus, Strophopappus and Xiphochaeta as separate genera from Stilpnopappus, we used cluster analysis followed by a test of group sharpness. Further, ordination analysis was applied to detect informative pollen traits associated with the revealed groups. The analyses evidenced five groups: (G1) Caatinganthus rubropappus as a single-species group; (G2) species of Stilpnopappus; (G3) Xiphochaeta aquatica as a single-species group; (G4) Strophopappus bicolor, S. glomeratus, S. villosus, S. ferrugineus, S. pohlii and S. speciosus; (G5) Strophopappus bullatus and S. regnelli. The interruption in the middle of the muri in apertural lacunae explains the single-species group Caatinganthus rubropappus. The thickness of sexine, the type of apertures (porate or colporate), and spine dimensions (length, thickness and distance from each other) are the traits explaining differences between species of Stilpnopappus and Strophopappus. Equatorial lacunae give support to Xiphochaeta aquatica as a single-species group, despite the smaller size of pollen grains of this species as compared to the others species analyzed. The differences among pollen morphology give support to Caatinganthus, Stilpnopappus, Strophopappus and Xiphochaeta as genera according to the taxonomic classification currently accepted. The used approach was efficient to reveal individual pollen traits informative to explain the sharp groups, and was an effective alternative to the use of “pollen types”.     

Metastevia (Compositae: Eupatorieae): A new genus from Mexico

A new genus and species from Mexico,Metastevia hintonii, is described. The genus, considered to be closely related to and derived fromStevia, differs in seven morphological features from all known species ofStevia. The reasons for recognizing the new genus are discussed in detail.     

Molecular Phylogeny of Eupatorieae (Asteraceae) Estimated from cpDNA RFLP and its Implication for the Polyploid Origin Hypothesis of the Tribe

Neomirandea (x=17 and 25), Ageratina (x=17) and Sclerolepis (x=15) with the higher chromosome base numbers, and the other includes Mikania (x=17) and the remaining genera with lower chromosome base numbers (x=10–11). However, the monophyly of the former clade is supported with a low bootstrap value. In the latter clade, Mikania (x=17) diverged first, then Stevia (x=11), and finally eight genera with x=10 diverged in succession. This result supports the hypothesis that the genera in the tribe Eupatorieae with x =10 evolved from an ancestor with a higher base number, and the tribe is of polyploid origin. Received 13 September 1999/ Accepted in revised form 20 January 2000     

New taxa of compositae (Eupatorieae) from Brazil

A new genus and speciesMonogereion carajensis and a new species ofAgeratum, A. glomemtum, are described from Para, Brazil. The relationships of the new genus and species are discussed.