Systematics of Helieae Gilg (Gentianaceae) / Sistemática de Helieae Gilg (Gentianaceae)

AUTOR(ES)
DATA DE PUBLICAÇÃO

2009

RESUMO

Helieae, one of the six Gentianaceae tribes, comprises about 23 genera and over 200 species found exclusively in the Neotropics. It is a highly diverse assemblage of plants, which have traditionally been problematic regarding generic circumscriptions. Several Helieae genera were understudied and phylogenetic relationships within the tribe were unclear. On these grounds, the present seven-chapter Thesis aimed to provide solid hypothesis on the phylogenetic relationships of the tribe, focusing primarily on the study of four of these poorly known genera, specifically, Calolisianthus Gilg, Helia Mart., Prepusa Mart. and Senaea Taub., which occur mainly in Brazil. In the first chapter, a morphologybased phylogeny and taxonomic revision of Prepusa and Senaea are presented. Based on studies of herbarium collections, five species of Prepusa and two species of Senaea are recognized. All are endemic to montane habitats in the Brazilian states of Bahia, Espírito Santo, Minas Gerais and Rio de Janeiro. Morphological descriptions, identification keys, illustrations and distribution maps for each species are provided. Prepusa and Senaea are morphologically, geographically, and phylogenetically isolated within Helieae, and their close relationship is supported by 6-merous flowers. Phylogenetic analyses of 33 morphological characters using both parsimony and Bayesian methods provide a consistent picture of the relationships of Prepusa and Senaea. The two genera are monophyletic and sister to one another. Parsimony-based phylogenetic analyses including 22 genera and 60 species of the tribe Helieae are presented in the second chapter. This study is based on data from morphology, palynology, and seed micromorphology (127 structural characters), and DNA sequences (matK, trnL intron, ITS). Phylogenetic reconstructions based on ITS and morphology provided the greatest resolution. Celiantha, Prepusa and Senaea together appear as the sister clade to the rest of Helieae. The remainder of Helieae is largely divided into two large subclades, the "Macrocarpaea" subclade and the "Symbolanthus" subclade. The first subclade includes Macrocarpaea, sister to Chorisepalum, Tachia, and Zonanthus. Irlbachia and Neblinantha are placed as sisters to the "Symbolanthus" subclade, which includes Aripuana, Calolisianthus, Chelonanthus, Helia, Lagenanthus, Lehmanniella, Purdieanthus, Rogersonanthus, Roraimaea, Sipapoantha, and Symbolanthus. Generic-level polyphyly is detected in Chelonanthus and Irlbachia. Evolution of morphological characters is discussed, and new pollen and seed characters are evaluated for the first time in a combined morphological-molecular phylogenetic analysis. In the third chapter, phylogenetic relationships in Helieae were studied based on new data and larger sampling in particular clades. DNA sequences from two nuclear regions (ITS and 5S-NTS) and morphological data were analyzed separately and in combination using parsimony and Bayesian inference. A 184 total of 86 specimens representing 17 and 51 Helieae genera and species, respectively, were included in the phylogenetic analyses; 47 specimens are sequenced for both regions, and eight have only morphological data. The complete data set produced topologies largely congruent with the ones obtained from two subsets, one without missing data, and another including taxa without data for one molecular partition. The use of new information led to a consistent result in the relative position of some clades and allowed defining new generic circumscriptions for Calolisianthus, Chelonanthus, Helia, and, to a lesser extent, Symbolanthus. The genus Calolisianthus formerly encompassed 610 species. As a result of these molecular and morphological phylogenetic studies, in the fourth chapter a new circumscription is presented and the existing lectotypification of Calolisianthus is questioned. It is proposed that this lectotype is rejected and superseded by the designation of a new lectotype, based chiefly on the conflict with the protologue. The genus Calolisianthus in its new circumscription, revised in the fifth chapter, comprises 4 species (one new to science) endemic to campos rupestres and cerrados in Brazil. The genus is characterized by herbaceous to subshrubby habit, by pink, red, purple-blue or lilac flowers, and by shedding pollen in reticulate tetrads with islands of coarse reticulum. Taxonomic key, morphological descriptions, illustrations, distribution maps, and comments about conservation status are provided. Moreover, two former Calolisianthus species are transferred to Chelonanthus. Morphological descriptions, illustrations and geographic distribution maps of these species are presented in the sixth chapter. Finally, it is proposed that Adenolisianthus and the "green-flowered Chelonathus", which are not closely related to the type species, be included in a largely circumscribed Helia. In the final chapter, the existing lectotypification of Helia is questioned based on the difficulties in recognizing the material identity. It is proposed that this lectotype is rejected and superseded by the designation of a new lectotype. Helia sensu stricto comprises 2 species that occur in swamps and wet fields in Brazil and Paraguay. They are characterized by their herbaceous habit and greenish-yellow, cream or white, salverform corollas. Morphological descriptions, identification keys, illustrations, and distribution maps are provided for both of them.

ASSUNTO(S)

filogenia helieae taxonomia plant taxonomy gentianaceae helieae phylogeny gentianaceae

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