Systematics
The taxonomy of the group has varied widely. In the APG III system of 2009, adopted here, the Agavoideae is defined very broadly to include the former family Agavaceae along with other formerly separate families such as Anemarrhenaceae, Chlorogalaceae, Hostaceae, Yuccaceae, Anthericaceae, Hesperocallidaceae and Chlorogalaceae. This is based on data from molecular systematics. Stevens comments that "The broad concept of Agavoideae may not seem very satisfactory" but that none of the alternatives is better. Sources prior to 2009 will still have Agavaceae (in varying circumscriptions) as a separate family and may contain varying numbers of other families included in Agavoideae in the APG III system.
Some genera formerly placed in this group (under whatever name) have been separated off; e.g. Dracaena, which superficially resembles some species of Agave, is currently placed in the subfamily Nolinoideae.
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