Banksia prionotes

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Acorn Banksia
Banksia prionotes, Reabold Hill, Bold Park Floreat, WA
Scientific classification
Kingdom: Plantae Division: Magnoliophyta Class: Magnoliopsida Order: Proteales Family: Proteaceae Genus: Banksia Subgenus: Banksia subg. Banksia Section: Banksia sect. Banksia Series: Banksia ser. Crocinae Species: B. prionotes
Binomial name
Banksia prionotes Lindl.

Banksia prionotes, commonly known as Acorn Banksia or Orange Banksia, is a species of woody shrub or tree of the genus Banksia in the Proteaceae family. It is native to the southwest of Western Australia. It can reach up to 10 m (30 ft) in height, though can be much smaller in more exposed areas or in the north of its range. It has serrated, dull green leaves and large, bright flower spikes, initially white then opening to a bright orange. It gains its common name as the partly opened inflorescences resemble acorns. These make it a popular garden plant, and also of importance to the cut flower industry.

It was first described in 1840 by John Lindley, probably from material collected by James Drummond the previous year. There are no recognised varieties though it has been known to hybridise with Banksia hookeriana. Widely distributed, B. prionotes is found from Shark Bay in the north, south as far as Kojonup. It grows exclusively in sandy soils, and is usually the dominant plant in scrubland or low woodland. The Acorn Banksia is pollinated by and provides food for a wide array of vertebrate and invertebrate animals in the autumn and winter months, and is an important source of food for honey-eaters, and is critical to their survival in the Avon Wheatbelt region, where it is the only nectar-producing plant in flower at some times of the year.

[edit] Description

It grows as a tree up to 10 m (30 ft) high in southern parts of its distribution, but in northern parts is usually a smaller, spreading shrub or small tree, reaching about 4 m (13 ft) in height.^[1] It has thin grey smooth or grooved bark, and tomentose young stems. The leaves are from 15–27 cm (6–11 in) long, and 1–2 cm (⅓–⅔ in) width, with dentate leaf margins made up of triangular lobes, and often an undulate surface. Flowers occur in a typical Banksia flower spike, an inflorescence made up of hundreds of flowers densely packed around a cylindrical axis. B. prionotes has cream flowers with an orange limb. This creates the effect of a cream inflorescence that progressively turns bright orange as anthesis sweeps through the inflorescence. Af the conclusion of flowering, the old flower parts fall away, revealing the axis, which may be embedded with up to 60 follicles.^[2][3]

[edit] Taxonomy

B. prionotes was first published by John Lindley in the January 1840 issue of his A Sketch of the Vegetation of the Swan River Colony; hence the species' full name is Banksia prionotes Lindl..^[4] Lindley did not specify the type material upon which he based the species, but A Sketch is based primarily upon the collections of James Drummond.^[5] A sheet at B. prionotes at CGE, labelled "Swan River, Drummond, 1839", has since been designated the lectotype.^[2] Lindley also made no mention of the etymology of the specific epithet "prionotes"; George has confirmed the obvious, however: it is from the Greek prion ("saw") and -otes ("quality"), in reference to the serrated leaf margins.^[6]

The species has had a fairly uneventful taxonomic history. No subspecies or variety have been published, and it has no taxonomic synonyms. Its only nomenclatural synonym is Sirmuellera prionotes (Lindl.) Kuntze, which arose from Otto Kuntze's unsuccessful 1891 attempt to transfer Banksia into the new name Sirmuellera.^[4][7]

young follicles

When Carl Meissner published his infrageneric arrangement of Banksia in 1856, he placed B. prionotes in B. sect. Eubanksia because its inflorescence is a spike rather than a domed head, and in series B. ser. Salicinae,^[8] a large series that is now considered quite heterogeneous.^[2] This series was discarded in the 1870 arrangement of George Bentham; instead, B. prionotes was placed in B. sect. Orthostylis, which Bentham defined as consisting of those Banksia species with flat leaves with serrated margins, and rigid, erect styles that "give the cones after the flowers have opened a different aspect".^[9]

In 1981, Alex George published a revision arrangement that placed B. prionotes in B. subg. Banksia because of its flower spike, B. sect. Banksia because its styles are straight rather than hooked, and B. ser. Crocinae, a new series of consisting of four closely related species, all with bright orange perianths and pistils.^[2]

George's arrangement remained current until 1996, when Kevin Thiele and Pauline Ladiges published an arrangement informed by a cladistic analysis of morphological characteristics. Their arrangement maintained B. prionotes in B. subg. Banksia, but discarded George's sections and his series Crocinae. Instead, B. prionotes was placed at the end of B. ser. Banksia, subser. Cratistylis.^[10]

In 1999, George overturned Thiele and Ladiges' arrangement, publishing a slightly modified version of his 1981 arrangement in his treatment of Banksia for the Flora of Australia series of monographs. To date, this remains the most recent, and therefore current, arrangement. The placement of B. prionotes in this arrangement may be summarised as follows:^[3]

Genus Banksia

Subgenus Isostylis

Subgenus Banksia

Section Oncostylis

Section Coccinea

Section Banksia

Series Grandes

Series Banksia

Series Crocinae

B. prionotes - B. burdettii - B. hookeriana - B. victoriae

Series Prostratae

Series Cyrtostylis

Series Tetragonae

Series Bauerinae

Series Quercinae

Series Salicinae

Since 1998, Austin Mast has been publishing results of ongoing cladistic analyses of DNA sequence data for the subtribe Banksiinae, which is comprised of Banksia and Dryandra. With respect to B. prionotes, Mast's results are fairly consistent with those of both George and Thiele and Ladiges. Series Crocinae appears to be monophyletic, and B. hookeriana is confirmed as B. prionotes' closest relative. Overall, however, the inferred phylogeny is very greatly different from George's arrangement, and provides compelling evidence for the paraphyly of Banksia with respect to Dryandra.^[11][12][13] Early in 2007, Mast and Thiele initiated a rearrangement of Banksia by transferring Dryandra into it, and publishing B. subg. Spathulatae for the species having spoon-shaped cotyledons; in this way they also redefined the autonym B. subg. Banksia. 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. prionotes is placed in B. subg. Banksia.^[14]

[edit] Hybrids

A number of presumed natural hybrids have been identified. Hybrids with Banksia hookeriana (Hooker's Banksia) may be induced by artificial means,^[15] and occur naturally on occasion; in fact the registered cultivar B. 'Waite Orange' is known to have arisen from a natural hybrid of this parentage.^[16] The same situation applies to hybrids with B. menziesii (Firewood Banksia): hybrids may be produced by artificial means,^[16] and presumed natural hybrids have been recorded.^[17]

During data collection for The Banksia Atlas project, a single presumed natural hybrid between B. prionotes and B. lindleyana (Porcupine Banksia), with fruit like B. lindleyana but leaves intermediate between the two parents, was found north of Kalbarri National Park. At the time this was considered an important discovery, as the parent species were thought to be not closely related.^[17] Mast's analyses, however, place them in a clade of eight species.^[12]

[edit] Distribution and habitat

Distribution of B. prionotes

It is widespread and locally common through much of the Southwest Botanical Province, occurring from Shark Bay in the north, south as far as Perth in coastal areas. Inland population extend further still, with populations as far south as Kojonup and as far east as Jerramungup. It grows amongst tall shrubland or low woodland, and shows a very strong preference for deep white or yellow sand, virtually never being found in heavier soils.^[18][3][17]

[edit] Ecology

See also: Ecology of Banksia

B. prionotes after bushfire. Fire has killed the maternal tree, but has also triggered the release of seed, ensuring population recovery.

Like most other Proteaceae, B. prionotes has proteoid roots, roots with dense clusters of short lateral rootlets that form a mat in the soil just below the leaf litter. These enhance solubilisation of nutrients, allowing nutrient uptake in low-nutrient soils such as the phosphorus-deficient native soils of Australia. It also has a single tap root that extends down to the water table. As the species has neither thick bark nor a lignotuber, it is usually killed by fire, although it may resprout from epicormic buds following a low intensity fire.^[17] Like most Banksia species, however, it is adapted to release its aerial bank of seeds following a bushfire, so populations regenerate rapidly.^[2] Plants senesce if still alive after about 40 years, but this does not mean that the plant is dependant on a suitable fire regime for survival, as it is one of the few Banksia species that is not entirely serotinous: some of its follicles release seed spontaneously, allowing recruitment of seedlings in non-fire years.^[19]

The main pollinators of B. prionotes are honeyeaters, including the New Holland Honeyeater, Brown Honeyeater, Singing Honeyeater, White-cheeked Honeyeater, Tawny-crowned Honeyeater and Red Wattlebird. The pollination relationship between these birds and B. prionotes has been well studied.^[20] Other recorded pollinators include lories and lorikeets and bees.^[17] Pollination by mammals has not been recorded, and it has been suggested that this species may require pollination by birds in order to set seed.^[20]

Surveys of putative hydrids of B. prionotes with B. hookeriana have shown that these occur almost exclusively in areas that have been disturbed by humans, such as on road verges. In 2003, a study by Byron Lamont et al. showed that these disturbed areas offered plants more resources and less competition. This allowed for prolonged flowering seasons, resulting in an overlap in flowering season which would not otherwise occur. It also allowed for greater overall flower production, resulting in more pollen and the presence of more pollinators. Thus the gene flow between the plants was greatly increased, and hybridisation resulted.^[21]

[edit] Conservation

B. prionotes is susceptible to a number of threatening processes. It is highly susceptible to Phytophthora cinnamomi dieback,^[22][23] it is exploited commercially by the cut flower industry,^[6] and some of its range is subject to land clearing for urban or agricultural purposes. It is not considered particularly vulnerable to these factors, however, as it is so widely distributed and common. Western Australia's Department of Environment and Conservation do not consider it to be rare, and have not given it a priority code under their system of Conservation Codes for Western Australian Flora.^[18]

It nonetheless has high conservation importance in at least one context: it has been shown than B. prionotes is the only source of nectar in the Avon Wheatbelt region during a critical period of the year when no other nectar-producing plant is in flower, meaning that the loss of B. prionotes from the region would mean the loss of all the honey-eaters as well.^[24][19]

[edit] Cultivation

Described as "an outstanding ornamental species",^[1] its brightly coloured, conspicuous flower spikes make B. prionotes a popular garden plant. It is good for attracting honey-eaters to the garden, and sometimes flowers twice a year. It is fairly easy to grow in areas with a Mediterranean climate, but does not do well in areas with high summer humidity. It requires a sunny position in well-drained soil, and tolerates at least moderate frost. It should be pruned lightly, not below the green foliage, as it tends to become straggly with age otherwise. Seed is easily germinated.^[6][1]

The species is also considered ideal for cut flower production, as its flowers fulfill the commercial criteria of terminal blooms and a long stem length.^[25]

[edit] References

Close-up of inflorescence, with a western honey bee feeding at the plane of anthesis

[edit] Further reading

• Keighery, Greg (1985). "Possible hybrids between Banksia hookeriana and B. prionotes (Proteaceae)". Western Australian Naturalist 16: 87–90. 

[edit] External links

Wikispecies has information related to:

Banksia prionotes

Wikisource has original text related to this article:

A Sketch of the Vegetation of the Swan River Colony/​Proteaceae​#Banksia prionotes

Wikisource has original text related to this article:

Flora Australiensis/​Volume V/​CIV. Proteaceae/​28. Banksia#Banksia prionotes

• Banksia prionotes Lindl.. Flora of Australia Online. Department of the Environment and Heritage, Australian Government.
• Banksia prionotes Lindl.. FloraBase. Department of Environment and Conservation, Government of Western Australia.
• Banksia prionotes Lindl.. Australian Plant Name Index (APNI), IBIS database. Centre for Plant Biodiversity Research, Australian Government.