Providing tools for the reassessment of Eupatorieae (Asteraceae): Comparative and statistical analysis of reproductive characters in South American taxa

• Published in: Perspectives in plant ecology, evolution and systematics Vol. 46; p. 125566
• Main Authors: Grossi, Mariana A., Viera Barreto, Jessica N., Plos, Anabela, Rodríguez-Cravero, Juan F., Forte, Noelia B., Gutiérrez, Diego G., Sancho, Gisela
• Format: Journal Article
• Language: English
• Published: Elsevier GmbH 01-10-2020
• Subjects: Clustering analysis; Comparative morphology; Compositae; Eupatorieae; South America; South America; Clustering analysis; Comparative morphology; Compositae; Eupatorieae
• ISSN: 1433-8319; 1618-0437
• DOI: 10.1016/j.ppees.2020.125566

•This work is the most extensive morphological study at the species level of Eupatorieae.•The sampled Eupatorieae species showed most of the variability of the reproductive characters found in the tribe.•The cluster analysis partly supports the traditional subtribe classification of Eupatorieae.•The circumscription of many of the subtribes and genera of Eupatorieae should be re-evaluated.
The Eupatorieae represent nearly 10 % of the Asteraceae, including about 187 genera and 2500 species. With close to 116 genera, South America is one of the richest areas for Eupatorieae diversity. Understanding of the taxonomy of the tribe has been hindered by the morphological variation of its genera and by the partly incongruent circumscription of genera and subtribes yielded by morphological and molecular characters. Furthermore, to date, no clustering analyses based on morphological characters have been done to explore the degree of agreement between the resulting groupings and those provided by molecular analyses. To contribute to the morphological definition of the clades obtained by ongoing molecular studies, the goals of this study are 1. To describe, characterize, compare, and assess the variability of reproductive characters in representative genera of South American Eupatorieae and, 2. To carry out a clustering analysis using reproductive morphological characters of these taxa. Additionally, we also aim to provide a standardized terminology of features for use by specialists and detailed drawings of reproductive structures to help elucidate the complex morphology of Eupatorieae. A total of 123 species belonging to 42 South American genera and 14 subtribes of Eupatorieae were studied. Twenty-eight characters of the involucre, receptacle, corolla, stamen, style, pappus and cypsela were morphologically and anatomically analyzed and compared. All these characters were included in the clustering analysis. A dendrogram was built using UPGMA method. Our work provides a comparative study of reproductive morphology at the species level, involving 14 of the 19 subtribes of Eupatorieae. The South American species studied showed high variability in reproductive characters. According to our statistical results, the representative genera of Alomiinae, Ayapaninae, Critoniinae, Disynaphiinae, Eupatoriinae, and Gyptidinae did not cluster together. These outcomes agree with molecular studies that found out these subtribes as either polyphyletic or paraphyletic. The genera of subtribes Adenostemmatinae, Fleischmanniinae, and Mikaniinae clustered together in our statistical analysis as well as in molecular studies that have found these subtribes to be monophyletic. At the genus level, our results found that the sampled species of many genera e.g. Barrosoa, Campuloclinium, Mikania, Ophryosporus, and Stevia, were grouped, in agreement with molecular studies that found these genera to be monophyletic. At the same time, the species of some genera that appeared as para- or polyphyletic in molecular studies, e.g. Chromolaena and Heterocondylus, were also distributed in different clusters in our study. In contrast, in other cases, e.g. Kaunia and Praxelis, our results did not agree with previous molecular studies. Interestingly, our statistical analysis showed clustering of genera from different subtribes, similarly to the findings of molecular studies: e.g. Austrobrickellia and Stomatanthes, Malmeanthus close to members of Disynaphiinae. Moreover, our results supported the exclusion of Stevia from Ageratinae, as shown by molecular studies. All these findings should be corroborated by the addition of more species to both statistical and molecular analyses. In light of our results, and despite some potential bias related to the sampling of species and the election and codification of characters, we conclude that, as proven by recent molecular studies, the circumscription of many of the traditionally defined subtribes and numerous genera should be re-evaluated to describe monophyletic entities.