Dividing and conquering the fastest–growing genus: Towards a natural sectional classification of the mega–diverse genus Begonia (Begoniaceae)

Abstract

The pantropical genus Begonia is the sixth-largest genus of flowering plants, including 1870 species. The sections of Begonia are used frequently as analogues to genera in other families but, despite their taxonomic utility, few of the current sections have been examined in the light of molecular phylogenetic analyses. We present herein the largest, most representative phylogeny of Begonia published to date and a subsequent provisional sectional classification of the genus. We utilised three plastid markers for 574 species and 809 accessions of Begonia and used Hillebrandia as an outgroup to produce a dated phylogeny. The relationships between some species and sections are poorly resolved, but many sections and deeper nodes receive strong support. We recognise 70 sections of Begonia including 5 new sections: Astrothrix, Ephemera, Jackia, Kollmannia, and Stellandrae; 4 sections are reinstated from synonymy: Australes, Exalabegonia, Latistigma and Pereira; and 5 sections are newly synonymised. The new sectional classification is discussed with reference to identifying characters and previous classifications.

Begonia puerensis sp. nov. (Begoniaceae), a new tuberous species from Yunnan, China

“…The number of Begonia species in China has been predicted to be between 250 and 300, but many new taxa remain to be discovered and described (Tian et al 2018). In China, the tuberous species have been referred to two sections (Gu et al 2007, Moonlight et al 2018: Begonia sect. In China, the tuberous species have been referred to two sections (Gu et al 2007, Moonlight et al 2018: Begonia sect.…”

“…The tuberous species is a polyphyletic group of Begonia. However, according to recent phylogenetic reconstructions (Moonlight et al 2018), B. sect. Diploclinium (Lindl.)…”

“…Diploclinium (Lindl.) Moonlight et al (2018) revised this section, and split off the rhizomatous Malaysian and Sumatran species into the new section Jackia M. Hughes. In 2018, the first author saw pictures of a wild tuberous Begonia species from Ren-Kun Li and considered it to be a potential new species. and B. sect.…”

“…The tuberous species is a polyphyletic group of Begonia. In China, the tuberous species have been referred to two sections (Gu et al 2007, Moonlight et al 2018: Begonia sect. Diploclinium (Lindl.)…”

Begonia medogensis, a new species of Begoniaceae from Western China and Northern Myanmar

“…Besides this new species, there are 171 other species of Begonia section Platycentrum (Klotzsch) A.DC. distributed in Asia (Moonlight et al 2018), of which 4 caulescent species are distributed in Himalayan areas (Doorenbos et al 1998), i.e. Begonia goniotis C.B.…”