Banksia violacea

From Wikipedia, the free encyclopedia

Violet Banksia
Inflorescence of Banksia violacea
Inflorescence of Banksia violacea
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Proteales
Family: Proteaceae
Genus: Banksia
Species: B. violacea
Binomial name
Banksia violacea
C.A.Gardner

Banksia violacea, commonly known as Violet Banksia, is a species of small shrub in the plant genus Banksia. Found in southern regions of Western Australia from Esperance in the east to Narrogin in the west, it is best known for its unusually coloured dark purple-violet inflorescences.

Contents

[edit] Description

It grows as a shrub up to 1.5 metres tall, with narrow leaves, one to two centimetres long and about 1.5 millimetres wide. Flowers occur in typical Banksia "flower spikes", inflorescences make up of hundreds of pairs of flowers densely packed in a spiral around a woody axis. B. violacea's flower spike is roughly spherical, with a diameter of two to three centimetres. Unusually for Banksia species, the inflorescences are often violet in colour, ranging anywhere from a dark violet-black through various combinations of violet and greenish-yellow in less pigmented blooms. Each flower consists of a tubular perianth made up of four fused tepals, and one long wiry style. The styles are hooked rather than straight, and are initially trapped inside the upper perianth parts, but break free at anthesis. The fruiting structure is a stout woody "cone", with a hairy appearance caused by the persistence of old withered flower parts.[1] The follicles, when young are greenish in colour and covered in fine white hairs, fading to tan or grey with age.

[edit] Taxonomy

See also: Taxonomy of Banksia

[edit] Discovery and naming

The type specimen of B. violacea was collected by 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.[2] 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 is Banksia violacea C.A.Gardner.[3]

William Blackall omitted the species from his 1954 How to Know Western Australian Wildflowers, instead including under B. sphaerocarpa (Fox Banksia) the text "Fls violet = var violacea".[4] This was an invalid publication, however, and a nomen nudum to boot. In 1981 Alex George declared Banksia sphaerocarpa var. violacea Blackall a nomenclatural synonym of B. violacea.[5][6]

[edit] Infrageneric placement

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 phyletic order between B. incana (Hoary Banksia) and B. meisneri (Meissner's Banksia).[5]

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 retained. It further resolved into four subclades, so Thiele and Ladiges split it into four subseries. B. violacea appeared in the last of these:[7]

B. violacea




B. laricina



B. incana


B. tricuspis





B. pulchella



B. meisneri var. meisneri


B. meisneri var. ascendans




This clade became the basis of B. subser. Longistyles, which Thiele defined as containing those taxa with very long and slender styles, and with smoothly convex perianth limbs without a costal ridge and with thickened margins. In accordance with their cladogram, their arrangement placed B. violacea first in phyletic order, followed by B. laricina (Rose-fruited Banksia).[7]

Thiele and Ladiges' arrangement was not accepted by George, and was largely discarded by him in his 1999 arrangement. B. ser. Abietinae was restored to George's 1981 circumscription, and all of Thiele and Ladiges' subseries were abandoned. 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 phyletic ordering of the series was altered so that B. violacea fell between B. scabrella (Burma Road Banksia) and B. incana. [1]

Young follicles of B. violacea
Young follicles of B. violacea

B. violacea's placement in George's arrangement may be summarised as follows:[1]

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, 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 someone 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. dolichostyla (alternately known as B. sphaerocarpa var. dolichostyla):

B. dolichostyla (alternately known as B. sphaerocarpa var. dolichostyla)


B. violacea



B. laricina


B. incana


However, Thiele's B. subser. Longistyles appears to be polyphyletic, as do both circumscriptions of B. ser. Abietinae.[8][9][10]

Early in 2007, Mast and Thiele initiated a rearrangement of Banksia by merging Dryandra into it, and publishing B. subg. 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. subg. Spathulatae.[11]

[edit] Distribution and habitat

Distribution of B. violacea, shown on a map of Western Australia's biogeographic regions.
Distribution of B. violacea, shown on a map of Western Australia's biogeographic regions.[12]

B. violacea occurs in southern regions of Western Australia, from Woodanilling to Esperance and as far north as Hyden.[13][1] This distribution includes areas of the Avon Wheatbelt, Esperance Plains and Mallee biogeographic regions.[12] It favours white sandy soils, often overlying laterite, clay or quartzite. It usually grows amongst proteaceous-myrtaceous heath and shrublands.

[edit] Ecology

See also: Ecology of Banksia

Like most other Proteaceae, B. violaceae 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, thus allowing nutrient uptake in low-nutrient soils such as the phosphorus-deficient native soils of Australia.

It is one of a small number of Banksia species that has both lignotuberous and non-lignotuberous populations. In both cases, plants are adapted to release their aerial bank of seeds following a bushfire, ensuring seedlings are established on clear and relatively fertile ground; however the possession of a lignotuber makes plants much less reliant on fire regime for population maintenance and regeneration, as maternal plants are not killed by bushfire, but resprout from below ground level. Lignotuberous plants generally occur amongst the north-eastern populations;[5][14] an investigation into the biogeography of these plants failed to find any vegetative, climatic or other environmental factors associated with the possession of a lignotuber.[15]

[edit] Cultivation

B. violacea is rarely cultivated. It is a slow-growing plant that tends to become untidy with age, and probably does not flower until four to five years from seed. Flowers are an unusual colour, but occur within the bush where they are usually obscured by foliage. It tolerates light pruning not below the green foliage, except for the variant with a lignotuber, which may be pruned heavily. George recommends a sunny position in light, sandy soil.[14]

[edit] References

Older follicles of B. violacea
Older follicles of B. violacea
  1. ^ a b c d George, A. S. (1999). "Flora of Australia". 17B: Proteaceae 3: Hakea to Dryandra. Ed. Wilson, Annette. CSIRO Publishing / Australian Biological Resources Study. 175–251. ISBN 0-643-06454-0. 
  2. ^ Gardner, C. A. (1927). "Contributiones florae Australiae occidentalis VI". Journal and Proceedings of the Royal Society of Western Australia 13: 61–68. 
  3. ^ Banksia violacea C.A.Gardner. Australian Plant Name Index (APNI), IBIS database. Centre for Plant Biodiversity Research, Australian Government.
  4. ^ {{cite book | author = Blackall, W. E.; edited by B. J. Grieve | year = 1954 | title = [[How to Know Western Australian Wildflowers | location = Nedlands | publisher = University of Western Australia Press}}
  5. ^ a b c George, Alex S. (1981). "The genus Banksia L.f. (Proteaceae)". Nuytsia 3 (3): 239–473. ISSN 0085-4417. 
  6. ^ Banksia sphaerocarpa var. violacea Blackall C.A.Gardner. Australian Plant Name Index (APNI), IBIS database. Centre for Plant Biodiversity Research, Australian Government.
  7. ^ a b Thiele, Kevin and Pauline Y. Ladiges (1996). "A cladistic analysis of Banksia (Proteaceae)". Australian Systematic Botany 9 (5): 661–733. doi:10.1071/SB9960661. 
  8. ^ Mast, Austin R. (1998). "Molecular systematics of subtribe Banksiinae (Banksia and Dryandra; Proteaceae) based on cpDNA and nrDNA sequence data: implications for taxonomy and biogeography". Australian Systematic Botany 11: 321–342. doi:10.1071/SB97026. 
  9. ^ Mast, Austin R. and Thomas J. Givnish (2002). "Historical biogeography and the origin of stomatal distributions in Banksia and Dryandra (Proteaceae) based on Their cpDNA phylogeny". American Journal of Botany 89 (8): 1311–1323. doi:10.3732/ajb.89.8.1311. ISSN 0002-9122. 
  10. ^ Mast, Austin R., Eric H. Jones and Shawn P. Havery (2005). "An assessment of old and new DNA sequence evidence for the paraphyly of Banksia with respect to Dryandra (Proteaceae)". Australian Systematic Botany 18 (1): 75–88. CSIRO Publishing / Australian Systematic Botany Society. doi:10.1071/SB04015. 
  11. ^ Mast, Austin R. and Kevin Thiele (2007). "The transfer of Dryandra R.Br. to Banksia L.f. (Proteaceae)". Australian Systematic Botany 20: 63–71. doi:10.1071/SB06016. 
  12. ^ a b Banksia violacea C.A.Gardner. FloraBase. Department of Environment and Conservation, Government of Western Australia.
  13. ^ Taylor, Anne and Stephen Hopper (1988). The Banksia Atlas (Australian Flora and Fauna Series Number 8). Canberra: Australian Government Publishing Service. ISBN 0-644-07124-9. 
  14. ^ a b George, Alex S. (1987). The Banksia Book (Second Edition). Kenthurst, New South Wales: Kangaroo Press (in association with the Society for Growing Australian Plants). ISBN 0-86417-006-8. 
  15. ^ Lamont, Byron and Adrienne Markey (1995). "Biogeography of fire-killed and resprouting Banksia species in south-western Australia". Australian Journal of Botany 43 (3): 283–303. doi:10.1071/BT9950283. 

[edit] External links

Wikispecies has information related to: