Angiosperm Phylogeny Group
After the 1980s, detailed genetic evidence analysed by phylogenetic methods became available and while confirming or clarifying some relationships in existing classification systems, it radically changed others.
This genetic evidence created a rapid increase in knowledge that led to many proposed changes; stability was "rudely shattered".
The impetus came from a major molecular study published in 1993[3] based on 5000 flowering plants and a photosynthesis gene (rbcL).
Independent researchers, including members of the APG, continue to publish their own views on areas of angiosperm taxonomy.
[11]) The initial 1998 paper by the APG made angiosperms the first large group of organisms to be systematically re-classified primarily on the basis of genetic characteristics.
[2][1] In 1998 only a handful of families had been adequately studied, but the primary aim was to obtain a consensus on the naming of higher orders.
[13] The classification continued the tradition of seeking broad circumscriptions of taxa, for example trying to place small families containing only one genus in a larger group.
[13] APG II continued and indeed extends the use of alternative 'bracketed' taxa allowing the choice of either a large family or a number of smaller ones.
The broad outline of the system remains unchanged, but the number of previously unplaced families and genera is significantly reduced.
[17] The other paper gives, for the first time, a classification of the families in APG III which uses formal taxonomic ranks; previously only informal clade names were used above the ordinal level.
[5] In particular Peter Stevens questioned the validity of discussions regarding family delimitation in the absence of changes of phylogenetic relationships.
[19] Further progress was made by the use of large banks of genes, including those of plastid, mitochondrial and nuclear ribosomal origin, such as that of Douglas Soltis and colleagues (2011).
[12] It arose from an international conference hosted at the Royal Botanical Gardens in September 2015[4] and also an online survey of botanists and other users.
Due to nomenclatural issues, the family name Asphodelaceae is used instead of Xanthorrhoeaceae, and Francoaceae is used instead of Melianthaceae (and now also includes Vivianiaceae).
[21] Peter Stevens, one of the authors of all four of the APG papers, maintains a web site, the Angiosperm Phylogeny Website (APWeb), hosted by the Missouri Botanical Garden, which has been regularly updated since 2001, and is a useful source for the latest research in angiosperm phylogeny which follows the APG approach.
