Resumo Eleocharis (Cyperaceae) inclui mais de 300 espécies de ervas perenes ou anuais, frequentemente encontradas em solos pouco drenados. As espécies são morfologicamente semelhantes e a taxonomia é difícil devido às estruturas vegetativas e reprodutivas reduzidas. Estudo anterior sobre a arquitetura do caule no subgênero Limnochloa mostrou que as características anatômicas ajudam na interpretação da evolução, taxonomia e aspectos ecológicos do grupo. Nossos objetivos foram adicionar novos caracteres da estrutura do caule (= colmo), explorar os caracteres em um número maior de espécies de Eleocharis, com representantes de outros subgêneros, e adicionar esses dados em uma nova análise filogenética com dados moleculares. O estudo abrangeu 68 espécies obtidas de herbários e material fixado. Além da arquitetura do caule, foram incluídas na análise morfológica a organização interna dos tecidos, o formato da seção transversal, a presença ou ausência de células estiradas nos espaços de aerênquima e o porte da planta. Nossos dados confirmam que o padrão de aerênquima esponjoso é a condição ancestral, enquanto os padrões misto e septados ocorreram independentemente e pontualmente. Somente o formato da seção transversal foi variável entre as amostras, enquanto os demais caracteres foram uniformes e relevantes para o uso taxonômico.

Abstract Eleocharis (Cyperaceae) includes more than 300 species of perennial or annual herbs, frequently found on poorly drained soils. The species are morphologicaly similar, and the taxonomy is difficult because their vegetative and reproductive structures are very reduced. Previous study on the stem architecture in the subgenus Limnochloa showed that anatomical features help in the interpretation of the evolution, taxonomy and ecological aspects of the group. Our objectives were to add new characters from the stem (= culm) structure, to explore the characters in a greater number of Eleocharis species, representatives of the other subgenera, and add these data in a new phylogenetic analysis with molecular data. The study covered 68 species obtained from herbaria and fixed material. In addition to the stem architecture, the internal organization of the tissues, the cross-section format, the presence or absence of stretched cells in aerenchyma air gaps and the plant size were included in the morphological analysis. Our data confirm that spongy aerenchyma pattern is the ancestral condition while the mixed and septate patterns occurred independent and punctually. Only the cross-section format was variable among specimens while the other characters were uniform and relevant for taxonomic use.

ABSTRACT Aquatic ecosystems support species diversity, and knowledge of plant communities is essential for wetland conservation programs. This study provides a checklist of aquatic vascular plants of South Brazil and establishes their floristic affinities with bordering South America phytogeographical domains. The checklist was based on 52 sources, including 35 floristic lists, 17 regional taxonomic studies, and information from an electronic database on wetlands of South Brazil. Floristic similarities with published checklists for neighbouring regions were assessed. A total of 780 species distributed in 277 genera and 85 families of vascular plants were reported for South Brazil. Families with higher species richness were Cyperaceae (128), Poaceae (102), Asteraceae (69), Plantaginaceae (21), Lentibulariaceae (20), and Onagraceae (20). The most represented genera were Eleocharis (41) and Cyperus (24). A cluster analysis revealed high similarity with Iberá (Argentinian Chaco), Pampa and Atlantic Forest, and low similarity with Pantanal, Caatinga and the Amazon Rainforest. The high number of aquatic plant families recorded relative to temperate and tropical climates suggests a zone of biogeographical overlap in Southern Brazil. The compiled data set reveals high biodiversity of wetlands of South Brazil, provides a baseline for future research, and highlights the need for regional conservation planning.

ABSTRACT Dialypetalanthus is a monospecific genus that occurs in the Amazon Basin of Brazil, Bolivia and Peru and occupies a controversial position among the Rubiaceae. We continue this taxonomic discussion with the overall aim of clarifying the systematic position of D. fuscescens within the Rubiaceae. To accomplish this, we analyzed the ontogeny of its gynoecium, in particular the floral meristem, as well as the development of the carpels and cauline placentation. Gynosporogenesis and the differentiation of the carpellary septa and ovules were also described. Dialypetalanthus fuscescens was classified according to evolutionary diagrams found in the literature. The following characteristics were observed in D. fuscescens: 1) permanence of the floral meristem in the central basal part of the early flower bud; 2) dual origin of carpellary septum; 3) trizonate ovular primordia with only one fertile gynospore per ovule; and 4) cellular proliferation in the chalazal region. Embryological results confirm the classification of D. fuscescens in the subfamily Ixoroideae. These results are distinct from any others previously proposed in the evolutionary diagram. Therefore, we conclude that this study has presented evidence strongly suggesting that Dialypetalanthus possesses new morphological-type of ovule we refer to as the Dialypetalanthus-type.