Banksia Attenuata - Taxonomy

Taxonomy

Banksia attenuata was first collected by Robert Brown from King George Sound in December 1801, and published by him in 1810. The specific epithet is the Latin adjective attenuatus "narrowed", and refers to the leaves narrowing towards the base. The species has had a fairly uneventful taxonomic history. It has only two synonyms, and no subspecies or varieties have been published; George reviewed the variation in form in the species, and felt that the tree and shrub forms differed only in size and hence were not distinct enough to represent separate taxa. In 1840, John Lindley published a putative new species, Banksia cylindrostachya, in his A Sketch of the Vegetation of the Swan River Colony; this has now be shown to be a taxonomic synonym of B. attenuata. In 1891, Otto Kuntze made a failed attempt to transfer Banksia to the new generic name Sirmuellera. In the process he published the name Sirmuellera attenuata, which is now considered a nomenclatural synonym of B. attenuata. Common names include slender banksia, candle banksia and candlestick banksia. Piara (alternately spelled biara) is an aboriginal name from the Melville region of Perth.

The relationships of Banksia attenuata within the genus are unclear. When Carl Meissner published his infrageneric arrangement of Banksia in 1856, he placed B. attenuata in section Eubanksia because its inflorescence is a spike rather than a domed head, and in series Salicinae, a large series that is now considered quite heterogeneous. This series was discarded in the 1870 arrangement of George Bentham; instead, B. attenuata was placed in section Cyrtostylis, a group of species which did not fit easily into one of the other sections.

In 1981, Alex George published a revised arrangement that placed B. attenuata in the subgenus Banksia because of its flower spike, section Banksia because its styles are straight rather than hooked, and the series Cyrtostylis, a large and rather heterogenous series of twelve species. He conceded its large emarginate cotyledons (having a notch in their apex) were quite different from other members, and that it had similarities in flower architecture to another anomalous member B. elegans. He felt B. attenuata to have affinities to B. lindleyana and B. media.

George's arrangement remained current until 1996, when Kevin Thiele and Pauline Ladiges published an arrangement informed by a cladistic analysis of morphological characteristics. They calculated B. attenuata to lie at the base of a large B. attenuata – B.ashbyi clade, but conceded further work was needed before its relationships could be determined, and left it as incertae sedis (i.e. Its exact placement is unclear.). 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. attenuata in George's 1999 arrangement may be summarised as follows:

Banksia

B. subg. Banksia

B. sect. Banksia

B. ser. Cyrtostylis

B. media

B. praemorsa

B. epica

B. pilostylis

B. attenuata

B. ashbyi

B. benthamiana

B. audax

B. lullfitzii

B. elderiana

B. laevigata

B. laevigata subsp. laevigata

B. laevigata subsp. fuscolutea

B. elegans

B. lindleyana

Since 1998, American botanist Austin Mast and co-authors have been publishing results of ongoing cladistic analyses of DNA sequence data for the subtribe Banksiinae, which then comprised genera Banksia and Dryandra. Their analyses suggest a phylogeny that differs greatly from George's taxonomic arrangement. Banksia attenuata resolves as a basal member of and next closest relative, or 'sister', to a clade containing B. elegans and, within that, a monophyletic B. subg. Isostylis. An Eocene fossil cone named Banksia archaeocarpa, around 50 million years old, resembles that of B. attenuata.

Early in 2007, Mast and Thiele rearranged the genus Banksia by merging Dryandra into it, and published B. subg. Spathulatae for the taxa having spoon-shaped cotyledons; thus B. subg. Banksia was redefined as encompassing taxa lacking 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. attenuata is placed in B. subg. Banksia.