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.

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Question How reliable is the process of delimiting plant species by morphotyping sterile specimens from a highly diverse Amazonian forest plot? Location Biological Dynamics of Forest Fragments Project (BDFFP), Central Amazon, Manaus, Brazil. Methods A taxonomic exercise was conducted during a Center for Tropical Forest Science (CTFS) Taxonomy Workshop held in Manaus in April 2011, using specimens collected in a 25‐ha forest plot. The plant species from this plot had been previously delimited by morphotyping of ca. 80 000 sterile specimens, a process that resulted in the recognition of 115 cases (accounting for 38% of all trees) in which species delimitation was problematic. For the workshop, we selected a subsample of specimens for eight of these difficult cases (taxonomic groups/complexes) and asked 14 participants with different levels of botanical training to independently sort these specimens into morphospecies. We then compared the classifications made by all participants and explored correlations between botanical training and plant classification. Results The classification of specimens into morphospecies was highly variable among participants, except for one taxonomic group/complex, for which the median pair‐wise similarity was 95%. For the other seven taxonomic groups/complexes, median pair‐wise similarity values ranged from 52% to 67%. Training did not increase the similarity in the definition of morphospecies except for two taxonomic groups/complexes, for which there was higher congruence between the classifications made by participants with a high level of botanical training than in comparisons that included less‐experienced participants. The total number of morphospecies defined by participants was highly variable for all taxonomic groups/complexes, with the total number varying from 12 to 46 (a 383% difference). Conclusions Local plant species delimitation by morphotyping sterile specimens is prone to large uncertainties, and botanical training may not reduce them. We argue that uncertainty in species delimitation should be explicitly considered in plant biodiversity inventories as diversity estimates may be strongly affected by such uncertainties. We recommend that species delimitation and identification be treated as separate processes and that difficulties be explicitly recorded, so as to permit error estimates and the refinement of taxonomic data.

We describe here two new species: Magnolia chiguila and M. mashpi and a new subsection, Magnolia subsect. Chocotalauma, sect. Talauma (Magnoliaceae). Magnolia chiguila is morphologically similar to M. calimaensis, but differs from the latter in having larger and broadly elliptic leaves with larger number of lateral veins and larger flowers with more numerous stamens and carpels. Magnolia mashpi is morphologically similar to M. striatifolia, but differs from the latter in having wider and broadly elliptic to obovate leaves with strongly arched lateral veins that are bullate and abaxially pubescent, more numerous stamens, carpels with a prominent apicule, longer sepals, larger outer and inner petals and glabrous peduncular internodes. The new species are found in the Pacific lowlands of western Ecuador, and all species of the new subsection are restricted to the Chocó biogeographic region of western Colombia and Ecuador. A key to the species of Magnolia subsects. Chocotalauma and Dugandiodendron is provided.

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