Taxonomy of Banksia
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As with other flowering plants, the taxonomy of Banksia is based on anatomical and morphological properties of the Banksia flower, fruiting structure and seed, along with secondary characteristics such as leaf structure and growth habit. The genus is placed in family Proteaceae, subfamily Grevilleoideae, tribe Banksieae and subtribe Banksiinae, alongside its close relative Dryandra. The currently accepted infrageneric arrangement is based on Alex George's 1999 monograph for the Flora of Australia book series, and recognises two subgenera, three series, 13 series, around 77 species, 6 subspecies and 18 varieties. Recent cladistic analyses have cast doubt on aspects of this arrangement, but proposed alternative arrangements have not been widely accepted.
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[edit] Background
- See also: Banksia
Banksia is a genus of around 80 species in the plant family Proteaceae. An iconic Australian wildflower and popular garden plant, they are easily recognised by their characteristic flower spikes and fruiting "cones". They grow in forms varying from prostrate woody shrubs to trees up to 35 metres tall, and occur in all but the most arid areas of Australia. As heavy producers of nectar, they are important sources of food for nectariferous animals such as honeyeaters and honey possum, and they are of economic importance to the nursery and cut flower industries. However they are seriously threatened by a number of processes including land clearing, frequent burning, and disease, and a number of species are rare and endangered.
[edit] Taxonomic history
- See also: Timeline of Banksia
Specimens of Banksia were first collected by Sir Joseph Banks and Dr Daniel Solander, naturalists on the Endeavour during Lieutenant (later Captain) James Cook's first voyage to the Pacific Ocean. Cook landed on Australian soil for the first time on 29 April 1770, at a place that he later named Botany Bay in recognition of "the great quantity of plants Mr Banks and Dr Solander found in this place".[1] Over the next seven weeks, Banks and Solander collected thousands of plant specimens, including the first specimens of a new genus that would later be named Banksia in Banks' honour. Four species were present in this first collection: B. serrata (Saw Banksia), B. integrifolia (Coast Banksia), B. ericifolia (Heath-leaved Banksia) and B. robur (Swamp Banksia). In June the ship was careened at Endeavour River, where specimens of B. dentata (Tropical Banksia) were collected.
Every specimen collected during the Endeavour voyage was sketched by Banks' botanical illustrator Sydney Parkinson. On the Endeavour's return to England in July 1771, Banks' specimens became part of his London herbarium, and artists were employed to paint watercolours from Parkinson's sketches. Banks had plans to publish his entire collection as "Banks' Florilegium", but for various reasons the project was never completed, and it would be ten years before any of the Banksia species were formally published.[2] By this time, a sixth species had been collected; in 1776, during Cook's third voyage, David Nelson collected specimens of B. marginata (Silver Banksia) from South Bruny Island, Tasmania.
The Banksia genus was finally described and named by Carolus Linnaeus the Younger in his April 1782 publication Supplementum Plantarum; hence the full name for the genus is "Banksia L.f.". Linnaeus placed the genus in class "Tetrandra", order "Monogynia",[3] and named it in honour of Banks. The name Banksia had in fact already been published in 1775 as "Banksia J.R.Forst & G.Forst", referring to some New Zealand species that the Forsters had collected during Cook's second voyage. However Linnaeus incorrectly attributed the Forsters' specimens to the genus Passerina, and therefore considered the name Banksia available for use. By the time Joseph Gaertner corrected Banks' error in 1788, Banksia L.f. was widely known and accepted, so Gaertner renamed Banksia J.R.Forst & G.Forst to Pimelia, a name previously chosen for the genus by Banks and Solander.[2]
Banksia L.f. has since been challenged a number of times. "Banksea Koenig" was published in 1783, but subsequently determined to be a synonym of Costus L. In 1790 James Bruce published "Bankesia Bruce", later corrected to "Banksia Bruce", but the name was rejected in favour of Johann Friedrich Gmelin's name Hagenia. In 1820 the name "Banksia Dombey ex DC. was published, but this was later determined by be a nomen nudum that referred to the genus Cuphea, In 1891, Otto Kuntze proposed to enforce the right of precedent of Banksia J.R.Forst & G.Forst, renaming Pimelea to Banksia, and proposing the name Sirmuellera Kuntze in place of Banksia L.f. This challenge failed, as did James Britten's 1905 challenge.[4] In 1940, Banksia L.f. was formally conserved against Banksia J.R.Forst. & G.Forst by Thomas Sprague.[5]
In 1810, Robert Brown described 31 known species of Banksia in his Prodromus Florae Novae Hollandiae et Insularae Van-Diemen. He placed B. ilicifolia alone in subgenus Isostylis, in recognition of its unusual dome-shaped inflorescence. All other species were placed in subgenus Banksia verae, the "True Banksias". Brown made no attempt to classify the species below the subgenus level. He described another eleven Banksia species in his 1830 supplement, placing them all in Banksia verae in accordance with his 1810 classification.[6].
By the time Carl Meissner published his 1856 classification of the Proteaceae, there were 58 described Banksia species. Meissner gave Isostylis sectional rank, renamed Brown's Banksia verae to section Eubanksia, and divided it into four series based on leaf properties. These series were all highly heterogeneous.[6]
George Bentham published a new classification of the Banksia in his landmark 1870 publication Flora Australiensis.[7] The number of recognised Banksia species was reduced to 46, and Meissner's four heterogeneous series were replaced by four sections based on leaf, style and pollen-presenter characters. Two of the sections were fairly well-defined and homogeneous, while another, Orthostylis, was somewhat heterogeneous. The fourth, Cyrtostylis, was erected to contain the species that did not belong in the other sections, and was therefore highly heterogeneous.[6] Despite these shortcomings, this arrangement would stand for over 100 years.
[edit] Classification and relationships within Proteaceae
The framework for classification of genera within Proteaceae was laid in 1975 by L. A. S. Johnson and Barbara Briggs.[8] Their classification has been refined somewhat over the ensuing three decades, resulting in a fairly stable and widely accepted arrangement. Proteaceae is divided into seven subfamilies, with Banksia placed in subfamily Grevilleoideae because the individual flowers in its inflorescence occur in pairs. On the basis of certain characters of the leaf venation, hairs and pollen, it is grouped with three other genera in the tribe Banksieae. Two small genera, Austromuellera and Musgravea, both of which occur only in the rainforests of Queensland, are placed in subtribe Musgraveinae. Banksia and Dryandra are placed in subtribe Banksiinae on a number of grounds of which the most obvious and easily recognised is the occurrence of flowers in condensed heads.[9] The placement of Banksia in Proteaceae can be summarised as follows:
- Family Proteaceae
- Subfamily Persoonioideae
- Subfamily Bellendenoideae
- Subfamily Eidotheoideae
- Subfamily Proteoideae
- Subfamily Sphalmioideae
- Subfamily Carnarvonioideae
- Subfamily Grevilleoideae
- Tribe Oriteae
- Tribe Knightieae
- Tribe Embothrieae
- Tribe Helicieae
- Tribe Macadamieae
- Tribe Grevilleeae
- Tribe Banksieae
- Subtribe Musgraveinae
- Genus Austromuellera
- Genus Musgravea
- Subtribe Banksiinae
- Subtribe Musgraveinae
Although the taxonomic legitimacy of tribe Banksiinae is universally recognised, there has been some debate about the legitimacy of the tribe's resolution into genera Banksia and Dryandra. For a number of years this debate centred on similarities between the inflorescences of Banksia subg. Isostylis species and those of Dryandra. These similarities led to calls for the genera to be merged, or for Isostylis to be moved across to Dryandra. However, Alex George and other supporters of the status quo argued that the similarities between Isostylis and Dryandra were matters of superficial appearance, whereas similarities between Isostylis and other Banksia species were far more important diagnostically.[10] Recent DNA analyses led by Austin Mast have confirmed George's position that Dryandra and Isostylis are not especially closely related, but have also provided powerful evidence that Banksia is paraphyletic with Dryandra. Mast has advised that the least disruptive approach to restore monophyly would be to sink Dryandra into Banksia.[11][12]
[edit] Classical taxonomic treatment
In 1981, Alex George published his classic 1981 monograph The Genus Banksia L.f. (Proteaceae). George's arrangement was based on a variety of properties including leaf, style, pollen-presenter, follicle and seed characters, with the criterion that a taxa was considered a distinct species only if it exhibited a "significant and consistent difference in the morphology of flowers and/or fruit".[10] It was the first thorough revision of the taxonomy of Banksia for over a century, and formed the basis for George's 1984 The Banksia Book,[13] which remains the standard text on the genus, and the treatment of Banksia in the Flora of Australia series.[9]
George followed Brown in dividing Banksia into two subgenera, Banksia and Isostylis. He then divided subgenus Banksia into two sections: Banksia for species with straight or slightly curved styles, and Oncostylis for species with hooked styles.[10] These two sections were then divided into nine and three series respectively. The arrangement into series largely followed Bentham, with series Orthostylis remaining somewhat heterogeneous, and Cyrtostylis remaining highly heterogeneous.[6]
The standard taxonomic arrangement of Banksia, as determined by George and published in the Flora of Australia series, may be summarised as follows:
- Genus Banksia
- Subgenus Banksia
- Section Banksia
- Series Salicinae
- Series Grandes
- Series Banksia
- Series Crocinae
- Series Prostratae
- Series Cyrtostylis
- Series Tetragonae
- Series Bauerinae
- Series Quercinae
- Section Coccinea
- Section Oncostylis
- Series Spicigerae
- Series Tricuspidae
- Series Dryandroidae
- Series Abietinae
- Section Banksia
- Subgenus Isostylis
- Subgenus Banksia
[edit] Cladistic analyses
[edit] Analysis of morphological characters
In 1996 Kevin Thiele and Pauline Ladiges published a cladistic analysis of Banksia based upon traditional morphological and anatomical characters, and included a proposed taxonomic arrangement based on their phylogenetic findings. This arrangement was similar to George's classical arrangement, but promoted four taxa to species rank and discarded a number of taxa that were shown to be paraphyletic or polyphyletic.[6] When Alex George published his 1999 arrangement for the Flora of Australia series, he did not incorporate most of Thiele and Ladiges' findings. However a number of Australian herbaria have continued to follow Thiele and Ladiges on some points, for example by recognising the four species that they promoted.[5]
Thiele and Ladiges 1996 arrangement was as follows:
- Genus Banksia
- Subgenus Isostylis
- Banksia elegans (incertae sedis)
- Subgenus Banksia
- Series Tetragonae
- Series Lindleyanae
- Series Banksia
- Subseries Banksia
- Subseries Cratistylis
- Banksia baueri (incertae sedis)
- Banksia lullfitzii (incertae sedis)
- Banksia attenuata (incertae sedis)
- Banksia ashbyi (incertae sedis)
- Banksia coccinea (incertae sedis)
- Series Prostratae
-
- Banksia petiolaris - Banksia repens - Banksia chamaephyton - Banksia blechnifolia - Banksia hiemalis - Banksia gardneri - Banksia brevidentata - Banksia goodii
-
- Series Cyrtostylis
- Series Ochraceae
-
- Banksia benthamiana - Banksia audax - Banksia laevigata subsp. laevigata - Banksia laevigata subsp. fuscolutea
-
- Series Grandes
- Series Salicinae
- Subseries Acclives
- Subseries Integrifoliae
- Banksia marginata - Banksia conferta - Banksia penicillata - Banksia paludosa - Banksia canei - Banksia saxicola - Banksia integrifolia subsp. integrifolia - Banksia integrifolia subsp. monticola - Banksia integrifolia subsp. compar - Banksia integrifolia subsp. aquilonia
- Series Spicigerae
- Subseries Spinulosae
- Banksia spinulosa var. spinulosa - Banksia spinulosa var. collina - Banksia spinulosa var. cunninghamii - Banksia spinulosa var. neoanglica
- Subseries Ericifoliae
- Banksia ericifolia var. ericifolia - Banksia ericifolia var. macrantha
- Subseries Occidentales
- Subseries Spinulosae
- Series Quercinae
- Series Dryandroideae
- Series Abietinae
- Subseries Nutantes
- Banksia nutans var. nutans - Banksia nutans var. cernuella
- Subseries Sphaerocarpae
- Banksia grossa - Banksia dolichostyla - Banksia micrantha - Banksia sphaerocarpa var. sphaerocarpa - Banksia sphaerocarpa var. caesia
- Subseries Leptophyllae
- Banksia telmateaea - Banksia scabrella - Banksia leptophylla var. melletica - Banksia leptophylla var. leptophylla - Banksia lanata
- Subseries Longistyles
- Banksia violacea - Banksia laricina - Banksia incana - Banksia tricuspis - Banksia pulchella - Banksia meisneri var. meisneri - Banksia meisneri var. ascendens
- Subseries Nutantes
- Series Prostratae
[edit] DNA Analysis
In 2002 and 2005, Austin Mast and co-authors published cladistic analyses of genetic data from DNA samples of almost all species of Banksia, along with five Dryandra species. Their results indicated the presence of two large clades of Banksia, which they named "/Cryptostomata" ("hidden stomates") and "/Phanerostomata" ("visible stomates").
The /Phanerostomata were defined as those taxa in which the leaf stomata occur superficially or in shallow pits. These taxa are typically tall shrubs and trees that occur in moist areas; they have unbeaked follicles and soft, short-lived leaves that are in many cases needle-like. The clade includes all eastern taxa of the series Salicinae and Spicigerae (that is, all taxa except B. serrata, B. aemula and B. ornata) and also the western Spicigerae, Quercinae, Grandes, Abietinae and Dryandroideae.
The /Cryptostomata were defined as those taxa in which the leaf stomata occur in crypts with constricted entrances. These are usually small shrubs that occur on dry, infertile sandplains. They have beaked follicles and thick, tough, long-lived serrated leaves. It includes all other western taxa, plus the eastern species B. serrata, B. aemula and B. ornata, and also appears to include Dryandra. It is worth noting that Dryandra does not appear especially closely related to the Isostylis group, which is instead most closely related to B. elegans and then B. attenuata.
Thus, the results presented by Mast et. al. strongly suggest that Banksia is polyphyletic with Dryandra. Although they did not propose a new taxonomic arrangement, they did consider various options for adjusting the current accepted arrangement to remove the polyphyly. They conclude that the simplest and least disruptive solution would be to merge Dryandra into Banksia.[11][12]
[edit] References
- ^ Cook, James (1893). William J. L. Wharton (ed.): Captain Cook's Journal during his First Voyage Round the World made in H. M. Bark "Endeavour" 1768-71: A Literal Transcription of the Original MSS. London: E. Stock.
- ^ a b Salkin, A. I. (1981). "A Short History of the Discovery and Naming of Banksias in Eastern Australia: Part I, Banks & Solander". Victorian Naturalist 98 (2).
- ^ {{cite book | author = Carolus Linnaeus the Younger | year = 1782 | title = [[Supplementum Plantarum|Supplementum Plantarum Systema Vegetabilium Editionis Decima Tertia, Generum Plantarum Editionis Fexta, Et Specierum Plantarum Editionis Secunda | location = Brunsvigae | publisher = Orphanotrophei}}
- ^ George, A. S. (1981). "The genus Banksia L.f. — a case history in Australian botany". History in the Service of Systematics: 53-59.
- ^ a b c Olde, Peter, Neil R. Marriott (2002). "One new Banksia and two new Grevillea species (Proteaceae: Grevilleoideae) from Western Australia". Nuytsia 15 (1): 85–99. ISSN 0085-4417.
- ^ a b c d e f Thiele, Kevin, Pauline Y. Ladiges (1996). "A Cladistic Analysis of Banksia (Proteaceae)". Australian Systematic Botany 9 (5): 661-733.
- ^ Bentham, George. (1870). "Banksia". Flora Australiensis: A Description of the Plants of the Australian Territory Volume 5: Myoporineae to Proteaceae: 541–562. London: L. Reeve & Co..
- ^ Johnson, L. A. S., Barbara Briggs (1975). "On the Proteaceae: The evolution and classification of a southern family". Journal of the Linnean Society of London. Botany 70: 83–182. ISSN 0368-2927.
- ^ a b c George, Alex. (1999). "Banksia". Flora of Australia Volume 17B: Proteaceae 3: Hakea to Dryandra: 175–251. Ed. Wilson, Annette. Collingwood, Victoria: CSIRO Publishing / Australian Biological Resources Study. ISBN 0-643-06454-0.
- ^ a b c George, Alex (1981). "The Genus Banksia L.f. (Proteaceae)". Nuytsia 3 (3): 239–473. ISSN 0085-4417.
- ^ a b Mast, Austin R., Thomas J. Givnish (August 2002). "Historical Biogeography and the Origin of Stomatal Distributions in Banksia & Dryandra (Proteaceae) Based on Their cpDNA Phylogeny". American Journal of Botany 89 (8): 1311–1323. ISSN 0002-9122. Retrieved on 2006-07-02.
- ^ a b c 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. ISSN 1030-1887.
- ^ George, Alex (1996). The Banksia Book. Kangaroo Press and The Society for Growing Australian Plants (NSW Region). ISBN 0-86417-818-2.
