Abstract: We present here a revision of the APG classification that considers the extensive recent analyses of hundreds of nuclear and plastid genes for many angiosperm species. Although previous versions of the APG classification were largely based on uniparentally inherited markers (plastid DNA, typically maternally inherited), there has emerged since APG IV extensive evidence of widespread hybridization and inheritance of ancestral polymorphisms. Despite this evidence of gene-tree discordance, most of the APG IV classification is supported by both plastid and nuclear analyses, and only a few revisions are required in this update to make the classification parallel phylogenetic results in the literature. At the ordinal level, few changes in circumscription are required relative to the last APG version, although the fabids now comprise only the four nitrogen-fixing orders (Cucurbitales, Fabales, Fagales, and Rosales) and the malvids now include the former COM clade (Celastrales, Malpighiales, and Oxalidales), which, in nuclear DNA analyses, is no longer monophyletic. Oncothecales (with only Oncothecaceae) and Cardiopteridales (with Cardiopteridaceae and Stemonuraceae) are newly recognized, and Icacinales are restricted to Icacinaceae. Restriction of Aquifoliales and Bruniales to just Aquifoliaceae/Helwingiaceae and Bruniaceae, respectively, is also proposed. Huaceae and Columelliaceae are unplaced to order among the malvids and campanulids, respectively. At the family level, expanded circumscriptions include Tecophilaeaceae (including Ixioliriaceae, Asparagales), Frankeniaceae (including Tamaricaceae, Caryophyllales), Phytolaccaceae (including Agdestidaceae and Sarcobataceae, Caryophyllales), Helwingiaceae (including Phyllonomaceae, Aquifoliales), Gesneriaceae (including Calceolariaceae and Peltantheraceae, Lamiales), Pentaphylacaceae (including Sladeniaceae, Ericales), and Orobanchaceae (including Mazaceae, Paulowniaceae, Phrymaceae, and Wightiaceae, Lamiales). In Santalales, the limits of Santalaceae and Olacaceae are revised, and Erythropalaceae and Strombosiaceae are recognized as distinct from Olacaceae; Balanophoraceae are maintained as distinct from Santalaceae, but this is a tentative placement. Generic relationships in Dioscoreales require more analyses before a revised family classification can be proposed, so we maintain the APG IV families of this order.

Key words: angiosperms, classification, molecular systematics, nuclear DNA, organellar DNA