Banksia Petiolaris - Taxonomy

Taxonomy

Banksia petiolaris was first described by Victorian state botanist Ferdinand von Mueller in 1864, its specific name Latin for "with petioles". The type specimen was most likely collected in 1861 by G. Maxwell between Cape Le Grand and Cape Arid and is housed in Melbourne. No further subspecies or varieties of B. petiolaris have been described, and it has no taxonomic synonyms. Its only nomenclatural synonym is Sirmuellera petiolaris, which arose from Otto Kuntze's unsuccessful 1891 attempt to transfer Banksia into the new name Sirmuellera.

It is one of six closely related species in section Banksia ser. Prostratae, all endemic to Western Australia, and all with a prostrate habit. George holds it as closely related to B. blechnifolia.

In 1996, botanists Kevin Thiele and Pauline Ladiges published an arrangement informed by a cladistic analysis of morphological characteristics. Their arrangement maintained B. petiolaris in B. subg. Banksia and series Prostratae. They found it to be basal (the earliest offshoot) to the other prostrate banksias. Questioning the emphasis on cladistics in Thiele and Ladiges' arrangement, George published a slightly modified version of his 1981 arrangement in his 1999 treatment of Banksia for the Flora of Australia series of monographs. To date, this remains the most recent comprehensive arrangement. The placement of B. petiolaris in George's 1999 arrangement may be summarised as follows:

Banksia

B. subg. Banksia

B. sect. Banksia

B. ser. Salicinae (11 species, 7 subspecies)

B. ser. Grandes (2 species)

B. ser. Banksia (8 species)

B. ser. Crocinae

B. ser. Prostratae (6 species, 3 varieties)

B. goodii

B. gardneri

B. gardneri var. gardneri

B. gardneri var. brevidentata

B. gardneri var. hiemalis

B. chamaephyton

B. repens

B. blechnifolia

B. petiolaris

B. ser. Cyrtostylis (13 species)

B. ser. Tetragonae (3 species)

B. ser. Bauerinae (1 species)

B. ser. Quercinae (2 species)

B. sect. Coccinea (1 species)

B. sect. Oncostylis (4 series, 22 species, 4 subspecies, 11 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, which includes Banksia. With respect to B. petiolaris, Mast's results have some semblance to George and Thiele's. It is somewhat basal in a group with the other prostrate species as well as species in series Tetragonae, and B. elderiana, B. baueri, and B. lullfitzii. However, B. repens, B. chamaephyton and B. blechnifolia form a closely knit group within this group, and the overall inferred phylogeny is very different from George's arrangement. Early in 2007, Mast and Thiele initiated a rearrangement of Banksiinae by publishing several new names, including subgenus Spathulatae for the species of Banksia that have spoon-shaped cotyledons; in this way they also redefined the autonym B. subgenus Banksia. They have not yet published a full arrangement, but if their nomenclatural changes are taken as an interim arrangement, then B. petiolaris is placed in subgenus Banksia.