Banksia hookeriana

Species of shrub in the genus Banksia native to Western Australia

speciesbox
|name = Hooker's banksia
|image = Banksia hookeriana 01 gnangarra. jpg
|genus = Banksia
|parent = Banksia subg. Banksia
|species = hookeriana
|authority = Meisn. |synonyms ref = and high. It has smooth bark. The Latin specific epithet hookeriana refers to Sir Joseph D. Hooker. In his infrageneric arrangement of Banksia in 1856, Meissner placed B. hookeriana 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. In 1891, Otto Kuntze, in his Revisio Generum Plantarum, rejected the generic name Banksia L. f., on the grounds that the name Banksia had previously been published in 1776 as Banksia J. R. Forst & G. Forst, referring to the genus now known as Pimelea. Kuntze proposed Sirmuellera as an alternative, referring to this species as Sirmuellera hookeriana. This application of the principle of priority was largely ignored by Kuntze's contemporaries, and Banksia L. f. was formally conserved and Sirmuellera rejected in 1940. In 1981, Alex George published a revised arrangement that placed B. hookeriana in the subgenus Banksia because of its flower spike, section Banksia because its styles are straight rather than hooked, and the series Crocinae, a new series of four closely related species, all with bright orange perianths and pistils. 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. hookeriana in George's 1999 arrangement may be summarised as follows:
Banksia
B. subg. Banksia
B. sect. Banksia
B. ser. Crocinae
B. prionotes
B. burdettii
B. hookeriana
B. victoriae

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. hookeriana, Mast's results are fairly consistent with those of both George and Thiele and Ladiges. Series Crocinae appears to be monophyletic, and B. prionotes is confirmed as B. hookerianas closest relative. Overall, however, the 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. hookeriana is placed in subgenus Banksia. It is commonly known as Hooker's banksia or acorn banksia.

Banksia hookeriana readily hybridises with B. prionotes under experimental conditions, indicating that these species have highly compatible pollen. The cultivar B. 'Waite Orange' is believed to be such a hybrid, having arisen by open pollination during a breeding experiment conducted at the Waite Agricultural Research Institute of the University of Adelaide in 1988. Banksia prionotes × hookeriana has also been verified as occurring in the wild, but only in disturbed locations. The two parent species have overlapping ranges and are pollinated by the same honeyeater species; and though preferring different soils, they often occur near enough to each other for pollinators to move between them. It therefore appears that the only barrier to hybridisation in undisturbed areas is the different flowering seasons: B. prionotes has usually finished flowering by the end of May, whereas flowering of B. hookeriana usually does not begin until June. In disturbed areas, however, the increased runoff and reduced competition mean extra nutrients are available, and this results in larger plants with more flowers and a longer flowering season. Thus the flowering seasons overlap, and the sole barrier to interbreeding is removed. The resultant F1 hybrids are fully fertile, with seed production rates similar to that of the parent species. There is no barrier to backcrossing of hybrids with parent species, and in some populations this has resulted in hybrid swarms. This raises the possibility of the parent species gradually losing their genetic integrity, especially if the intermediate characteristics of the hybrid offer it a competitive advantage over the parent species, such as a wider habitat tolerance. Moreover, speciation might occur if the hybrid's intermediate characteristics allow it to occupy a habitat unsuited to both parents, such as an intermediate soil type. Banksia prionotes × hookeriana hybrids have characteristics intermediate between the two parents. For example, the first putative hybrids studied had a habit "like that of gigantic B. hookerana [sic]", having inherited the size of B. prionotes, together with B. hookerianas tendency to branch from near the base of the trunk. Similarly, the infructescences were like B. prionotes in size, but had persistent flowers like B. hookeriana. Inflorescences and leaves were intermediate in size and shape, and bark was like that of B. prionotes.

It occurs on sandplain shrubland between Arrowsmith and Eneabba and specifically on the Gingin scarp and Dandaragan plateau in Western Australia, It is also serotinous, in that it holds its seeds in seed pods of old spikes in the plant canopy. As plants take 5 years to begin producing seeds and gradually accumulate more seeds over the coming decades, fire intervals around 15 to 18 years give the best chance of seedling recruitment, while intervals of less than 11 years result in reduced seedlings and ultimately possible extinction. Changing climate conditions and more frequent fire intervals have impacted on the species' reproductive rate. Plants can live up to 40 years old, though are generally killed by fire long before this. B. hookeriana has been shown to be highly susceptible to dieback from the soil borne water mould Phytophthora cinnamomi, unlike many Western Australian banksias. The flowers are visited and pollinated by honeyeaters such as the white cheeked honeyeater (Phylidonyris nigra) and brown honeyeater (Lichmera indistincta).