The evolution of the inflorescence head in Asteraceae is important in the diversification of this largest angiosperm family. The aggregation of heads into higher-order capitulescences (secondary heads or syncephalia) is considered evolutionarily advanced. The genera Moscharia, Nassauvia, Polyachyrus, and Triptilion of the subtribe Nassauviinae (Mutisieae) have syncephalia with differing degrees of capitula condensation. ITS and plastid trnL-trnF regions were analyzed separately and together using maximum parsimony and maximum likelihood to examine the evolution of syncephalia in the Nassauviinae. The four genera displaying syncephalia do not form a clade minus taxa without syncephalia, indicating that secondary heads in Nassauviinae have either convergently evolved twice in the subtribe (or, very unlikely) once with multiple reversions. Strong support was obtained for a sister relationship between Leucheria (without syncephalium) and Polyachyrus, and both sister to Moscharia. Nassauvia and Triptilion form a distinct clade but are sister to other genera, Perezia and Panphalea, without syncephalium. Previous hypotheses postulated the evolution from simple to more complex secondary heads. We show that the ancestor of Moscharia, Polyachyrus, and Leucheria, in a more arid habitat, had a complex type of secondary head, and loss of complexity occurred in response to a shift from arid to mesic conditions.

Subfamily Gochnatioideae is the sister group of ∼96% of the species in Compositae (Asteraceae). It is of particular interest not only because of its position in the phylogeny, but also because, in recent molecular studies, the node it occupies is not strongly supported making difficult any inferences on the direction of character evolution in the family. The recognition of tribe Gochnatieae was one of the results of a comprehensive molecular analysis of the family that showed the traditional circumscription of the Mutisieae to be non–monophyletic. The four genera of Gochnatieae (Cnicothamnus, Cyclolepis, Gochnatia, Richterago) were defined by the presence of apiculate anther appendages and dorsally smooth style branches. Gochnatia, which contained about 70 species, was the largest and most complex genus and in the last decade some of its sections have been moved (or returned) to the rank of genus. This study includes a large selection of potential outgroups and over 60% of all species in the tribe, including all the genera and all but one of the sections of Gochnatia, to examine evolutionary relationships among the taxa. Both cpDNA and nrDNA were used in a phylogenetic analysis using parsimony, likelihood, and Bayesian approaches. The results suggest a non–monophyletic Gochnatia that is here resolved by the recognition of segregate genera. Morphological characters support these new genera and allow the adoption of a new classification for the Gochnatieae. A biogeographic analysis shows a possible southern South American/Andean origin followed by movement in three directions: into the Central Andes, into central and northern Brazil, and into Mexico and the Caribbean. The dating analysis gives an age of the split of the core Gochnatieae from the Wunderlichieae–Cyclolepis clade, and hence the age of the tribe, of 36–45 Ma and an age of 23–25 Ma for the first split within the core Gochnatieae (Andean vs. Brazil–Mexico–Caribbean). Cnicothamnus remains in Gochnatieae but Cyclolepis is designated incertae sedis.

Although three New World Menthinae genera occur in both North and South America, none exhibit an amphitropical disjunction. However, three clades exhibit amphitropical disjunctions, all dating to the early Pliocene, and all involve jump dispersals to either southeastern or southwestern South America from southeastern North America.

No abstract

The classification of the family Compositae (Asteraceae) has been much improved in the last decades by the application of molecular methods culminating in the recompilation published in 2009, Systematics, evolution, and biogeography of Compositae. Additional evidence of relationships has come from the use of high-throughput sequencing methods. Our late colleague Vicki Ann Funk (1947-2019) was a pioneer in this line of research. Together with her team, she contributed to the achievement of a mature classification of the family, which she left outlined. In this paper, we contribute this classification including all of the recent advances at the subtribal level and review in depth all contributions to Compositae classification made since the 2009 compilation.

A revision and a morphological analysis of the Uruguayan species of Stevia (Compositae, Eupatorieae) were performed. Leaf, inflorescence, pubescence and pappus traits were identified as key to separate species. Stevia entreriensis, S. entreriensis var. minor, and Dissothrix hassleriana were considered synonyms of S. hirsuta, and S. ophryodonta and S. oxylaena synonyms of S. veronicae. Lectotypes for the names Stevia cinerascens, S. megapotamica, S. linariifolia, S. selloi, S. selloi var. yparacayensis, S. oxylaena and S. veronicae were designated. Stevia burkartii was excluded from the Uruguayan flora. As a result, 10 Uruguayan species are considered: S. aristata, S. cinerascens, S. congesta, S. gratioloides, S. hirsuta, S. multiaristata, S. sabulonis, S. satureiifolia, S. selloi, and S. veronicae. A key to the Uruguayan species, descriptions, photographs and distribution maps are provided.

South American Microgyne Less. is resurrected from the synonymy of Microgynella. Microgyne Cass. is a nomen nudum and therefore not validly published. The replacement generic name Microgynella, a homotypic synonym of Microgyne Less., is illegitimate and superfluous. A revision is presented for the two species of Microgyne, one herein described as new. The new species, Microgyne marchesiana, is described from Uruguay and is diagnosed by pinnatifid leaves, whitish pappus, and a thick testa. A neotype is designated for Microgyne trifurcata Less. Detailed descriptions and illustrations are provided for the two species, together with additional data on anatomy.

The genus Bidens (Compositae) comprises c. 230 species distributed across five continents, with the 41 Polynesian species displaying the greatest ecomorphological variation in the group. However, the genus has had a long and complicated taxonomic history, and its phylogenetic and biogeographic history are poorly understood. To resolve the evolutionary history of the Polynesian Bidens, 152 individuals representing 91 species were included in this study, including 39 of the 41 described species from Polynesia. Four chloroplast and two nuclear DNA markers were utilized to estimate phylogenetic relationships, divergence times, and biogeographic history. Bidens was found to be polyphyletic within Coreopsis, consistent with previous assessments. The Polynesian radiation was resolved as monophyletic, with the initial dispersal into the Pacific possibly from South America to either the Hawaiian or Marquesas Islands. From the Marquesas, Bidens dispersed to the Society Islands, and ultimately to the Austral Islands. The initial diversification of the crown group in the Pacific is estimated to have occurred 1.63 mya (0.74-2.72, 95% HPD), making Polynesian Bidens among the youngest and most rapid plant diversification events documented in the Pacific. Our findings suggest that relatively rare long-distance dispersal and founder-event speciation, coupled with subsequent loss of dispersal potential and within-island speciation, can explain the repeated and explosive adaptive radiation of Bidens throughout the archipelagoes of Polynesia.