ABSTRACT The Chromolaena congesta complex (Asteraceae, Eupatorieae) presents a difficult challenge for biodiversity researchers due to the intertwined connections of its species and the difficulty of establishing morphological boundaries. In this study, we aimed to use morphometric analyses to evaluate the delimitation of the taxa belonging to the C. congesta complex, identify informative morphological traits and to understand the identity of several “atypical” specimens morphologically related to the complex. To achieve this, we used cluster and principal component analysis to evaluate 50 morphological traits from a total of 210 specimens throughout the geographic distribution of the species complex. We found support for the recognition of at least six species - Chromolaena ascendens, C. gentianoides, C. hirsuta, C. latisquamulosa, C. rhinanthacea and C. squarrulosa - according to a phenetic species concept and to corroborate the restoration of three species from synonymy. Furthermore, our results provide a morphological recircumscription of C. congesta and C. elliptica and indicate two taxonomic novelties, including a new combination and a new species. Despite the answers provided by morphology, many taxonomic issues remain to be solved, and further studies with other types of evidence should be carried to contribute towards a more stable classification.

Resumo Moquiniastrum, originalmente descrito por Cabrera como uma seção de Gochnatia, após análises moleculares e morfológicas mais detalhadas foi elevado à categoria de gênero. Moquiniastrum diferencia-se de Gochnatia pela presença de ginodioicia, indumento de tricomas com 2-5-raios e capitulescências paniculiformes. Atualmente é constituído por 21 espécies, distribuídas principalmente no Brasil. Pouco se conhece sobre a taxonomia do gênero Moquiniastrum e ainda há escassez de estudos sobre o arranjo sexual das flores no capítulo, necessitando de análises aprofundadas destas estruturas. O objetivo geral deste trabalho foi realizar um estudo taxonômico de Moquiniastrum na Região Sul do Brasil, além de avaliar e enquadrar os táxons em categorias de ameaça de extinção. Este estudo foi realizado através de revisões de herbários e expedições de campo nos três estados da Região Sul do Brasil. Foram encontradas 10 espécies de Moquiniastrum, além de três subespécies de M. polymorphum. São fornecidos chave de identificação para os táxons confirmados, descrições morfológicas, comentários sobre habitats, conservação e períodos de floração e de frutificação das espécies, além de observações taxonômicas e imagens.

Abstract Moquiniatrum, originally described by Cabrera as a section of Gochnatia, was raised to the category of genus after detailed molecular and morphological analysis. Moquiniastrum differs from Gochnatia by the presence of gynodioecy, indumentum of 2-5-armed hairs and the paniculate capitulescences. Moquiniastrum consists of about 21 species and occurs mainly in Brazil. Studies on the taxonomy and morphology of the genus are sparse, especially regarding the sexual disposition of capitula, thus requiring more studies. The aim of this paper was to produce a taxonomic study of Moquiniastrum in Southern Brazil, as well as to classify the species in categories of threat. This study was conducted through review of herbarium specimens and field expeditions to the Southern Brazilian states. We found 10 species of Moquiniastrum, besides three subspecies of M. polymorphum. We provide an identification key, morphological descriptions, comments on habitats, conservation and flowering and fruiting periods of the species, as well as taxonomic observations and images.