Agapanthus - Relationships

Relationships

Four valid botanical names have Agapanthus as their basionym.

In 1985, Dahlgren, Clifford, and Yeo placed Agapanthus in Alliaceae, close to Tulbaghia. Their version of Alliaceae differed from any that are recognized today in that it included Agapanthus and in that it included several genera that would later be transferred to Themidaceae.

In 1996, in a phylogenetic analysis of DNA sequences of the gene rbcL, Themidaceae was resurrected and Agapanthus was removed from Alliaceae. The authors found Agapanthus to be sister to Amaryllidaceae and transferred it to that family. This was not accepted by the Angiosperm Phylogeny Group when they published the APG system in 1998, because the clade consisting of Agapanthus and Amaryllidaceae had only 63% bootstrap support. The APG system recognized the families Agapanthaceae, Alliaceae, and Amaryllidaceae. Agapanthaceae consisted of Agapanthus only, and Dahlgren's idea that it is close to Tulbaghia was rejected. The APG circumscriptions of the latter two families would eventually become known as Alliaceae sensu stricto, and Amaryllidaceae sensu stricto.

When the APG II system was published in 2003, it offered the option of combining Agapanthaceae, Alliaceae sensu stricto, and Amaryllidaceae sensu stricto to form a larger family, Alliaceae sensu lato. When the name Amaryllidaceae was conserved by the ICBN for this larger family, its name was changed from Alliaceae to Amaryllidaceae, but its circumscription remained the same. When APG II was replaced by APG III in 2009, Agapanthaceae was no longer accepted, but was treated as subfamily Agapanthoideae of the larger version of Amaryllidaceae. Also in 2009, Armen Takhtajan recognized the three smaller families allowed by APG II, instead of combining them as in APG III.

Molecular phylogenetic analysis of DNA sequences has shown that Agapanthus is sister to a clade consisting of subfamilies Allioideae and Amaryllidoideae of the family Amaryllidaceae (sensu APG III). These two subfamilies are equivalent to the families Alliaceae sensu stricto, and Amaryllidaceae sensu stricto, respectively.