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Oxalis subg. Thamnoxys is a mostly South American group of Oxalis encompassing almost 80 species from tropical habitats that are currently separated into nine sections based on morphology and geographic distributions. In this study, we investigated whether Oxalis subg. Thamnoxys and its sections are monophyletic. DNA sequences of the nrITS, trnL-trnL-trnF , and petA-psbJ from 92 specimens of Oxalis (55 from O. subg. Thamnoxys , 37 from O. subg. Oxalis , and five outgroup taxa) were used to investigate phylogenetic relationships among its nine sections. Nuclear and plastid molecular markers were subjected to maximum likelihood and Bayesian inference analyses individually and in a combined data matrix. Our phylogenetic trees recovered O. subg. Thamnoxys as monophyletic only if O. praetexta , previously included in O. sect. Robustae , is transferred to O. subg. Oxalis. The remaining samples of the subgenus emerged in a clade with full bootstrap and posterior probability support. Within it, O. sect. Holophyllum was the only section that was recovered as monophyletic, whereas the remaining sections were not, either because of sampling a single species of each (O. sect. Foliosae , Hedysaroideae , and Phyllodoxys), to the unexpected placement of O. goyazensis (O. sect. Robustae) in O. sect. Psoraleoideae , or to the sister relationship between O. densifolia (O. sect. Foliosae) with O. pyrenea var. macrochaeta (O. sect. Thamnoxys), suggesting the need of revaluating some specific affinities and updating sectional circumscriptions. This phylogenetic study with an improved sampling of O. subg. Thamnoxys is the first step towards an updated classification of the subgenus and for interpreting both its morphological diversification and biogeographic history in South America. [ABSTRACT FROM AUTHOR]

Myrcia capixaba and M. forzzae, two new species from the large Neotropical genus Myrcia, are here proposed, described, and illustrated. Both species belong to Myrcia sect. Aguava and are morphologically quite distinct from the other species of the section. Myrcia capixaba occurs in the Atlantic Forest of Espírito Santo and presents a set of features that do not overlap with any other species within M. sect. Aguava: dibrachiate trichomes on the branches, leaves, and inflorescences and externally on the flowers, broadly elliptic to ovate leaves with flat, barely visible secondary venation adaxially, and subterminal panicles. Myrcia forzzae occurs in the Amazon Forest of Mato Grosso and resembles M. gigas, differing in the shorter internodes, vegetative branches and inflorescence rachises densely covered with trichomes (vs. with scattered trichomes or glabrous), and calyx lobes bearing trichomes externally (vs. glabrous). [ABSTRACT FROM AUTHOR]

Two new species of Myrcia sect. Reticulosae, M. carassana and M. revoluta are here described and illustrated. Myrcia carassana was firstly recognized in 1908 by A. F. M. Glaziou but never validly published. This species is similar to M. venosissima but differs by reddish trichomes, inflorescences botryoid or reduced to simple dichasia with longer peduncles, obconic floral buds and calyx lobes internally densely pilose. Myrcia revoluta resembles M. reticulosa but differs by leaves strongly revolute, densely pilose abaxially when mature, and subterminal inflorescences subtended by reduced leaves. [ABSTRACT FROM AUTHOR]

• Our results highlight the importance of the number of locules in Myrcia classification. • The widespread and taxonomically complex Myrcia guianensis is non-monophyletic. • Myrcia sect. Aguava appears to have originated in the Cerrado. • Transitions from Cerrado to humid forests occurred in the evolution of M. sect. Aguava. • Combination of NGS and Sanger data is possible and generates robust phylogenetic trees. Myrcia is one of the largest exclusively Neotropical angiosperm genera, including ca. 800 species divided into nine sections. Myrcia sect. Aguava is one of most complex sections of Myrcia due to high morphological variation and wide distribution range of some species, including M. guianensis , with distribution throughout South America and a complex taxonomic history. We used complete plastid DNA sequences data generated using next-generation sequencing of 45 terminals, mostly from Myrcia sect. Aguava. These data were combined with five target DNA regions (ITS, psbA-trnH , trnL-trnF , trnQ-rps16 , ndhF) of additional terminals to increase taxonomic coverage. Phylogenetic analyses were conducted using a maximum likelihood approach, and divergence times and ancestral range distributions were estimated. Myrcia sect. Aguava is monophyletic and exclusively comprises species with trilocular ovaries but has no relationship with other groups within Myrcia that possess trilocular ovaries. Three main lineages that correspond to geographical distribution are recognized within Myrcia sect. Aguava. Multiple accessions reveal a non-monophyletic Myrcia guianensis and stress the biogeographical structure inside the group. Myrcia sect. Aguava had a probable mid-Miocene origin in the Cerrado, but lineages that persisted there diversified only more recently, when the present-day vegetation started to stabilize. Posterior migrations to Atlantic Forest, Amazon and Caribbean occurred at the end of Miocene, evidencing transitions from open and dry to forested and more humid areas that are less frequent in the Neotropics. Overall, it is observed that related lineages remained in ecologically similar environments. Future perspectives on Myrcia and Myrteae in the phylogenomic era are also discussed. [ABSTRACT FROM AUTHOR]