Banksia Violacea - Taxonomy

Taxonomy

The type specimen of Banksia violacea was collected by West Australian botanist Charles Gardner on 14 December 1926 in the vicinity of Lake Grace. The following year, he published a description of the species in Journal and Proceedings of the Royal Society of Western Australia. He placed it in section Oncostylis of Bentham's taxonomic arrangement of Banksia, giving it the specific epithet violacea in reference to the violet flowers. Thus the full name of the species, with author citation, is Banksia violacea C.A.Gardner. The species has been considered a variety of B. sphaerocarpa (Fox Banksia); this view was published by William Blackall in his 1954 How to know Western Australian wildflowers. He considered B. violacea to be a variety of B. sphaerocarpa with violet flowers. This description was an invalid publication, however, and a nomen nudum. In 1981 Alex George declared Banksia sphaerocarpa var. violacea Blackall a nomenclatural synonym of B. violacea.

In George's 1981 arrangement, B. violacea was placed in subgenus Banksia because its inflorescence is a typical Banksia "flower spike"; section Oncostylis because of its hooked styles; and series Abietinae because its inflorescence is roughly spherical. It was placed in taxonomic sequence between B. incana (Hoary Banksia) and B. meisneri (Meissner's Banksia).

In 1996, Kevin Thiele and Pauline Ladiges published the results of a cladistic analysis of morphological characters of Banksia. They retained George's subgenera and many of his series, but discarded his sections. B. ser. Abietinae was found to be very nearly monophyletic and so it was retained. It further resolved into four subclades, so Thiele and Ladiges split it into four subseries. B. violacea appeared in the last of these:

This clade became the basis of B. subseries Longistyles, which Thiele defined as containing those taxa with very long and slender styles, smoothly convex perianth limbs without a costal ridge, and thickened margins. In accordance with their cladogram, their arrangement placed B. violacea first in taxonomic sequence, followed by B. laricina (Rose-fruited Banksia). However, Thiele and Ladiges' arrangement was not accepted by George, who, questioning the emphasis on cladistics, rejected most of their changes in his 1999 arrangement, restored B. series Abietinae to his broader 1981 definition, and abandoned all of Thiele and Ladiges' subseries. George commented that the species has no close relatives, being "loosely allied" to B. sphaerocarpa (Fox Banksia) and B. telmatiaea (Swamp Fox Banksia). Despite this, the sequence of the series was altered so that B. violacea fell between B. scabrella (Burma Road Banksia) and B. incana, and its placement in George's arrangement may be summarised as follows:

Banksia

B. subg. Banksia

B. sect. Banksia (9 series, 50 species, 9 subspecies, 3 varieties)

B. sect. Coccinea (1 species)

B. sect. Oncostylis

B. ser. Spicigerae (7 species, 2 subspecies, 4 varieties)

B. ser. Tricuspidae (1 species)

B. ser. Dryandroideae (1 species)

B. ser. Abietinae

B. sphaerocarpa (3 varieties)

B. micrantha

B. grossa

B. telmatiaea

B. leptophylla (2 varieties)

B. lanata

B. scabrella

B. violacea

B. incana

B. laricina

B. pulchella

B. meisneri (2 subspecies)

B. nutans (2 varieties)

B. subg. Isostylis (3 species)

Since 1998, American botanist Austin Mast has been publishing results of ongoing cladistic analyses of DNA sequence data for the subtribe Banksiinae. His analyses suggest a phylogeny that is very greatly different to George's arrangement, and somewhat different to Thiele and Ladiges'. With respect to B. violacea, Mast's results agree with its placement near B. laricina and B. incana, placing it in a clade with these two species and B. sphaerocarpa var. dolichostyla (treated at species rank as B. dolichostyla). However, Thiele's B. subseries Longistyles appears to be polyphyletic, as do both definitions of B. ser. Abietinae—that is, none form a natural grouping.

Early in 2007, Mast and Thiele initiated a rearrangement of Banksia by merging Dryandra into it, and publishing B. subgenus Spathulatae for the taxa having spoon-shaped cotyledons. They foreshadowed publishing a full arrangement once DNA sampling of Dryandra was complete; in the meantime, if Mast and Thiele's nomenclatural changes are taken as an interim arrangement, then B. violacea is placed in B. subgenus Spathulatae.