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Hypochaeris is thought to have arrived in South America by dispersal over the Atlantic Ocean from NW Africa during the Pliocene or Pleistocene. We used amplified fragment length polymorphism (AFLP) to unravel specific limits and relationships in the South American group of Hypochaeris (c. 45 species). The Moroccan endemic Hypochaeris angustifolia, which is sister to the entire South American group, was used as outgroup. Our AFLP analysis comprises 415 individuals from 32 South American species and is based on six primer combinations with 670 fragments scored. It provides important information for the delimitation of species and detection of closely related species pairs or groups. Most species are monophyletic and supported with > 90% bootstrap proportion. Hybridization is suggested between Hypochaeris chillensis and H. microcephala in Brazil. The internal nodes (or "backbone") of the tree are not highly supported, but six major phylogenetic groups (also showing similarity in distribution and growth form) center around Hypochaeris apargioides, H. chondrilloides, H. microcephala, H. pampasica, H. sessiliflora, and H. tenuifolia. These results suggest that rapid migration into different geographical regions played an important role in the initial diversification of Hypochaeris in South America.

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The association of cytogenetic and molecular techniques has contributed to the analysis of chromosome organization and phylogeny in plants. The fluorochrome GC-specific CMA 3 , fluorescent in situ hybridization (FISH) and RAPD (Random Amplified Polymorphic DNA) markers were used to investigate chromosome structure and genetic relationships in Hypochaeris (Asteraceae). Seven species native to South America, and two species introduced from Europe (H. glabra and Hypochaeris sp) were studied. FISH with rDNA probes identified one or two loci of 18S-5.8S-25S rDNA in the South American Hypochaeris species and one locus in the European species. Only one 5S rDNA locus was seen in all species studied. Blocks of GC-rich heterochromatin (CMA-positive bands) associated to 18S-5.8S-25SrDNA loci were detected in all species investigated. Co-location of 5S rDNA and CMA bands was also observed, except for three South American species and Hypochaeris sp. In two South American species, additional CMA bands not related to rDNA were observed on the long arm of chromosome 2, near to the centromere. Hypochaeris glabra exhibited additional CMA-positive signals distributed at pericentromeric regions, on the short arms of all chromosomes. A total of 122 RAPD markers were used to determine the genetic relationships among species. The level of polymorphism was very high, revealing two genetic groups comprising the South American and the European species, thus supporting a previous hypothesis of monophyly of the South American Hypochaeris species. The coefficients of genetic similarity between European and South American species were 0.35, on average. Polymorphism was also high within the two groups. The genetic associations observed with RAPD markers were consistent with chromosome characteristics. Species carrying similar distribution of 45S rDNA loci and CMA-positive signals were included in the same group revealed by RAPDs. Cytogenetic and molecular data support the view that not only chromosome rearrangements, but also changes in DNA sequence took place during the diversification of the South American Hypochaeris species.

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RESUMO:Os óleos voláteis das folhas e infl orescências de Eupatorium polystachyum DC. (Asteraceae), coletado no Rio Grande do Sul, Brasil, foram caracterizados por CG-EM e sua atividade antioxidante foi avaliada utilizando-se o método de DPPH. Foram obtidos rendimentos de 1,6 e 0,9% de óleo em relação às folhas e infl orescências frescas, sendo identifi cados 34 compostos, correspondendo a 99,1 e 99,5% do óleo volátil, respectivamente. Os óleos apresentaram exclusivamente compostos terpênicos, sendo que as folhas contêm grande quantidade de monoterpenos (66,4%) enquanto que as infl orescências apresentaram quantidades equivalentes de mono e sesquiterpenos (51,8 e 47,7%, respectivamente). As amostras apresentaram-se qualitativamente muito semelhantes sendo constituídas majoritariamente por: β-pineno (14,7 e 9,8%), β-mirceno (15,3 e 10,8%) e limoneno (22,8 e 20,5%) entre os monoterpenos e β-cariofi leno (10,4 e 15,4%), germacreno D (7,2 e 9,4%) e biciclogermacreno (12,0 e 19,2%) entre os sesquiterpenos. As diferenças entre as amostras foram basicamente quantitativas. Os óleos apresentaram atividade antioxidante pelo ensaio com DPPH por bioautografi a na diluição de 1:10 em éter etílico (v/v). Unitermos: Eupatorium polystachyum, óleos voláteis, atividade antioxidante, DPPH.ABSTRACT: "Chemical composition and antioxidant activity of the volatile oil from Eupatorium polystachyum DC". The essential oil obtained from leaves and fl owers of Eupatorium polystachyum DC. (Asteraceae) collected in Rio Grande do Sul State, Brazil, was characterized by GC-MS and its antioxidant activity was assessed by DPPH assay. The yield of essential oil, relative to fresh material, was 1.6 and 0.9% for leaves and fl owers, respectively. Both oils are constituted exclusively by terpenic compounds. Leaf oil contains great quantity of monoterpenes (66.4%); on the other hand, infl orescence oil contains comparable quantities of mono-and sesquiterpenes (51.8 and 47.7%, respectively). The same compounds are majority in both oils: β-pinene (14.7 and 9.8%), β-myrcene (15.3 and 10.8%) and limonene (22.8 and 20.5%) among monoterpenes and β-caryophyllene (10.4 and 15.4%), germacrene D (7.2 and 9.4%) and bicyclogermacrene (12.0 and 19.2%) among sesquiterpenes. The oils had antioxidant activity by DPPH assay in 1:10 dilution in ethyl ether (v/v).