Classification and Relationships Within Proteaceae
The framework for classification of genera within Proteaceae was laid by L. A. S. Johnson and Barbara Briggs in their influential 1975 monograph "On the Proteaceae: the evolution and classification of a southern family". Their arrangement has been refined somewhat over the ensuing three decades, most notably by Peter H. Weston and Nigel Barker in 2006. Proteaceae is divided into five subfamilies, with Banksia placed in subfamily Grevilleoideae because the individual flowers in its inflorescence occur in pairs. On the basis of certain characters of the leaf venation, hairs and pollen, it is grouped with three other genera in the tribe Banksieae. Two small genera, Austromuellera and Musgravea, both of which occur only in the rainforests of Queensland, are placed in subtribe Musgraveinae. Banksia is placed subtribe Banksiinae on a number of grounds of which the most obvious and easily recognised is the occurrence of flowers in condensed heads. The placement of Banksia in Proteaceae can be summarised as follows:
- Family Proteaceae
- Subfamily Bellendenoideae
- Subfamily Persoonioideae
- Subfamily Symphionematoideae
- Subfamily Proteoideae
- Subfamily Grevilleoideae
- Tribe Roupalae
- Tribe Banksieae
- Subtribe Musgraveinae
- Subtribe Banksiinae
- Genus Banksia
- Tribe Embothrieae
- Tribe Macadamieae
Although the taxonomic legitimacy of tribe Banksiinae is universally recognised, there has been some debate about the legitimacy of the tribe's resolution into genera Banksia and Dryandra. For a number of years this debate centred on similarities between the inflorescences of Banksia subg. Isostylis species and those of Dryandra. These similarities led to calls for the genera to be merged, or for Isostylis to be moved across to Dryandra. However, Alex George and other supporters of the status quo argued that the similarities between Isostylis and Dryandra were matters of superficial appearance, whereas similarities between Isostylis and other Banksia species were far more important diagnostically. Recent DNA analyses led by Austin Mast have confirmed George's position that Dryandra and Isostylis are not especially closely related, but have also provided powerful evidence that Banksia is paraphyletic with respect to Dryandra (that is, Dryandra is a sub-group of Banksia. Mast suggested that the least disruptive approach to restore monophyly would be to sink Dryandra into Banksia. This has been put into effect in a 2007 paper by Mast & Thiele, in which all existing species of Dryandra were transferred into Banksia.
Read more about this topic: Taxonomy Of Banksia