Banksia Brownii

Location & distribution maps

Phylogeny & links to associated information:

Wikipedia links:       Angiosperms > Eudicots >  Proteales > Proteaceae > Banksia  

Other links:     

Plant  information

Common name:                Feather-leaved Banksia or Brown's Banksia  

• Conservation status:  Critically endangered

• All major populations care threatened by Phytophthora cinnamomi dieback, a disease to which the species is highly susceptible

• Other threats include loss of habitat, commercial exploitation and changes to the fire regime

• Ten populations are now presumed extinct and the total number of plants is estimated at around 1000

Etymology:   

• x

Flowers:                  

• Flowers occur in typical Banksia "flower spikes", inflorescences made up of hundreds of pairs of flowers densely packed in a spiral around a woody axis

• Flower spikes are held erect and are typically terminal on a branch; often other branchlets grow up and around a spike from below

• Flower spike is a metallic red-brown colour, roughly cylindrical, 6 to 19 cm high and 8-10 cm wide

• Each flower consists of a tubular perianth made up of four united tepals, and one long wiry style. Perianths are cream at the base and grey-brown at the end

• Styles are rusty red-brown with a cream tip, and downwardly hooked rather than straight

• The style end is initially trapped inside the upper perianth parts, but breaks free at anthesis

Fruit:                         

• The fruiting structure is a stout woody "cone", around 5 cm in diameter, with a hairy appearance caused by the persistence of old withered flower parts

• A "cone" may be embedded with up to 60 follicles, although usually there are very few or even none at all 

• Unusually for Banksia, each follicle contains just one seed

• This is shiny black, oval in shape, about 20 mm long, with a brown papery wing

Leaves:         

• The leaves are long and thin, from 3-10 cm long, and 5-10 cm wide

• Dark green and hairless above but with a hairy white underside

• They are easily recognised by their feather-like appearance, caused by the fact that they are finely divided almost back to the midrib, into as many as 70 thin tapered lobes

Stem & branches: 

• The bark is a grey-brown colour, smooth and thin, with lenticels

Roots:         

• x

Habit:        

• A plant with fine feathery leaves and large red-brown flower spikes, it usually grows as an upright bush around two m high, but can also occur as a small tree or a low spreading shrub

• It usually grows as an upright bush between one and 1-3m high

• It can also grow as an openly branched small tree to 6 m in sheltered gullies, or as a low, spreading shrub in exposed locations such as the peaks of the Stirling Range

Habitat:   

• In the Stirling Range it occurs among heath on rocky mountain slopes; further south it occurs among jarrah woodland in shallow nutrient-poor sand. 

• The species occurs there in two distinct population clusters: southern populations occur among low woodland of Eucalyptus marginata (jarrah) in shallow, nutrient-poor white or grey sand over laterite

• Stirling Range populations occur at altitudes of between 500 and 1100 m, among heath on rocky mountain slopes and tops, and in shale in gullies

• There are 27 known populations within this region, but only nine of these populations contain more than 10 individual plants, and only five populations have more than 100

Distribution:                  

• Grows in southwest Western Australia

• It occurs between Albany (35°S) and the Stirling Range (34°24'S) in the southwest of Western Australia, at the juncture of the Esperance Plains, Warren and Jarrah Forest biogeographic regions

• This is the taxonomically richest area for Banksia, with 19 species, of which six are endemic, including B. brownii itself

• It is cool and wet, with temperatures between four and 30 °C and rainfall of ~ 800 mm 

Additional notes:     

• Taxonomy

  • First collected in 1829 and published the following year, it is placed in Banksia subgenus Banksia, section Oncostylis, series Spicigerae

  • There are two genetically distinct forms

  • See also: Taxonomy of Banksia

  • Banksia brownii was first collected near King George Sound in 1829 by William Baxter, who named it in honour of botanist Robert Brown. A formal description was published by Brown in his 1830 Supplementum Primum Prodromi Florae Novae Hollandiae; thus the full botanic name of the species is Banksia brownii Baxter ex R.Br.[9] Under Brown's taxonomic arrangement, B. brownii was placed in subgenus Banksia verae, the "true banksias", because its inflorescence is a typical Banksia flower spike. Banksia verae was renamed Eubanksia by Stephan Endlicher in 1847

  • Carl Meissner demoted Eubanksia to sectional rank in his 1856 classification, and divided it into four series, with B. brownii placed in series Dryandroideae.[10] When George Bentham published his 1870 arrangement in Flora Australiensis, he discarded Meissner's series, placing all the species with hooked styles together in a section that he named Oncostylis. This arrangement would stand for over a century

  • 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 brownii. 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

  • Alex George published a new taxonomic arrangement of Banksia in his landmark 1981 monograph The genus Banksia L.f. (Proteaceae). Endlicher's Eubanksia became B. subg. Banksia, and was divided into three sections, one of which was Oncostylis. Oncostylis was further divided into four series, with B. brownii placed in series Spicigerae because its inflorescences are cylindrical

  • In 1996, Kevin Thiele and Pauline Ladiges published a new arrangement for the genus, after cladistic analyses yielded a cladogram significantly different from George's arrangement. Thiele and Ladiges' arrangement retained B. brownii in series Spicigerae, placing it in B. subser. Occidentales along with B. occidentalis (red swamp banksia), B. seminuda (river banksia), B. verticillata (granite banksia) and B. littoralis (swamp banksia). This arrangement stood until 1999, when George effectively reverted to his 1981 arrangement in his monograph for the Flora of Australia series

  • Under George's taxonomic arrangement of Banksia, B. brownii's taxonomic placement may be summarised as follows:

    • • Genus Banksia

        • Subgenus Banksia

          • Section Banksia

          • Section Coccinea

          • Section Oncostylis

            • Series Spicigerae

              • B. spinulosa - B. ericifolia - B. verticillata - B. seminuda - B. littoralis - B. occidentalis - B. brownii

            • Series Tricuspidae

            • Series Dryandroidae

          • Series Abietinae

        • Subgenus Isostylis

  • The closest relative to B. brownii is held to be B. occidentalis, which differs in having smaller, deep red flowers and narrow, sparsely serrate leaves.

  • Since 1998, Austin Mast has been publishing results of ongoing cladistic analyses of DNA sequence data for the subtribe Banksiinae, which comprises Banksia and Dryandra. With respect to B. brownii, Mast's results are somewhat at odds with those of both George and Thiele and Ladiges, finding it to be more closely related to B. nutans (nodding banksia) and B. quercifolia (oak-leaved banksia) than to many of the Spicigerae. Overall, the inferred phylogeny is very greatly different from George's arrangement, and provides compelling evidence for the paraphyly of Banksia with respect to Dryandra.[17][18][19] 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. 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. brownii is placed in B. subg. Spathulatae

  • Three genetically distinct forms of B. brownii are recognised: the better known forms are a "mountain form" with a shrubby habit, short thin hard leaves, and a squat inflorescence; and a "Millbrook Road form", with a tree habit and longer, wider, soft leaves.[3][21] Some horticulturists also recognise an intermediate form. Recent genetic testing has confirmed the existence of three distinct forms, but as of 2005 these have no taxonomic status

• Ecology

  • See also: Ecology of Banksia

  • Coastal plants begin to flower at around five years from seed, but plants in the Stirling Range take much longer to mature

  • In one Stirling Range population, only 15% of plants had flowered after eight years

  • Flowering time is highly variable, but in general it occurs between March and August, with a peak around June. More flowers open during the day than at night

  • As with other Banksia species, it is a heavy producer of nectar, and serves as a food source for a range of nectariferous birds, mammals and insects

  • Honeyeaters such as Phylidonyris novaehollandiae (New Holland honeyeater), Acanthorhynchus superciliosus (western spinebill) and Anthochaera carunculata (red wattlebird) are frequent visitors that often carry heavy pollen loads, making them important pollinators

  • Nocturnal mammals such as Rattus fuscipes (bush rat) and Tarsipes rostratus (honey possum) also carry heavy pollen loads, but the foraging behaviour of bush rats suggests that these may transfer pollen only over very short distances

  • Invertebrate visitors include the introduced Apis mellifera (western honeybee), native bees, flies and ants; bees appear to be effective pollinators, but ants and flies forage only at the base of flowers and do not come in contact with plant pollen

  • The species is partly self-compatible, as some seed is set when pollinators are excluded. Selection against self-pollinated seed has been observed, but the species has nonetheless been shown to have one of the lowest outcrossing rates of any Banksia 

  • This is probably caused by the small population sizes, which increase the probability of self-fertilisation, and may discourage visits by pollinators

  • It has a low rate of fruiting, with less than 1% of flowers developing into follicles, and more than half of the inflorescences failing to form any follicles at all

  • Seed survival rates are similarly low

  • More than half of a plant's seed crop may be lost to the larvae of moths and weevils, which burrow into the cobs to eat the seeds and pupate in the follicles; and further seed losses are caused by granivorous birds such as cockatoos, which break off the cobs to eat both the seeds and the insect larvae

  • A small proportion of follicles open and release their seed spontaneously, but most remain closed until stimulated to open by bushfire

  • Bushfire kills the maternal plant, which has neither thick bark nor lignotubers, but the subsequent shedding of seed allows the population to regenerate

  • Seed predation continues after its release: in one study, B. brownii seeds were placed on the ground in both burnt and unburnt sides; almost all were eaten by parrots within four weeks

• Conservation

  • Threats to B. brownii include loss of habitat due to land clearing, commercial exploitation, disease, and changes to the fire regime

  • The fragmentation of populations is also of concern, as it causes the genetic diversity of the species to decline, potentially reducing vigour

  • Climate change is also of concern: depending on the severity of change, the range of this species is predicted to contract by 30% to 50% by 2080

  • Microsatellite markers for assessing population genetic structure were developed for B. brownii in 2009

  • A subsequent study by these authors, published in 2015, estimated that B. brownii has lost between 35–40% of its historical genetic diversity due to P. cinnamomi dieback

  • It has been assessed as having a high risk of extinction, and that this would be "not only a tragedy in itself but may have unforeseen, and potentially disastrous, consequences for the functioning of the vegetation communities of which feather-leaved banksia is an integral part"

  • The species has been formally assessed for the IUCN Red List as "Critically Endangered (CR)"; populations are projected to decline by more than 80% within the next three generations

  • It is listed as "Endangered" under Australia's Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), and "Rare" under Western Australia's Wildlife Conservation Act 1950

  • These acts provide legislative protection against a range of potential threats, including commercial harvesting of flowers and land clearing

  • Further statutory protection is afforded by the fact that populations occur within the Eastern Stirling Range Montane Heath and Thicket threatened ecological community, which is listed as "Endangered" under the EPBC Act, and the Montane Mallee Thicket of the Stirling Range threatened ecology community, which has been assessed as "Endangered" by the Western Australian government; and by the presence of northern population within the Stirling Range National Park

  • A five-year interim management plan was put in place by the Western Australia's Department of Environment and Conservation in October 2005

  • Actions under that plan include regular monitoring of populations, management of the threats of fire and P. cinnamomi, and the cold storage of seed

  • This was followed by a national recovery plan and a translocation project was begun in 2008 

  • This has met with some success as one of three original sites established appears to have a viable reproducing population

• Disease

  • The main threat to B. brownii is dieback caused by the introduced plant pathogen P. cinnamomi, a soil-borne water mould that causes root rot

  • Studies of the effect of P. cinnamomi on B. brownii have found it to be "highly susceptible" to dieback, with specimens "frequently and consistently killed in the wild"

  • As of 2007, all major populations of B. brownii, and all but one minor population, are suffering from dieback

  • Moreover, all populations are in an area vulnerable to dieback, so even the uninfected population is considered under threat

  • According to Western Australian botanist Byron Lamont, "the demise of this species in the wild appears imminent"

  • A number of protective measures have been implemented, including site access restrictions, the collection and cold-storage of seed, and the treatment of plants with phosphite

  • Phosphite boosts the resistance of both infected and uninfected plants, and also acts as a direct fungicide

  • Aerial spraying of phosphite boosts plant survival and slows the spread of infection, but must be carefully managed as studies have shown that foliar spraying of phosphite adversely affects root and shoot growth

  • Direct injection of phosphite into the stem of each tree appears to lack this disadvantage, but is costly to administer and restricted to known plants.

  • Other diseases to which B. brownii is vulnerable include the parasitic fungus Armillaria luteobubalina[46] and the aerial canker fungus Zythiostroma

• Fire regime

  • Because it releases its seed in response to bushfire, it is important that fires occur at intervals that allow the plants to generate plenty of viable seed

  • The optimum fire interval is around 18 years 

  • If fire occurs too frequently, plants are burned before reaching maturity or before they have produced sufficient seed to ensure regeneration of the population

  • This may cause populations to decline, or even local extinction

  • Too-infrequent fire also causes population decline, as more plants die of natural attrition without releasing their seed, resulting in seed wastage

• Ex situ conservation measures

  • Because of the difficulty of conserving it in its present disease-exposed locations, it is an especially suitable candidate for ex situ conservation measures, such as the cold-storage of seed, and the translocation of plants to disease-free locations

  • Seed has been collected by Western Australia's Threatened Flora Seed Centre, and placed in cold-storage both in Perth and at Kew's Millennium Seed Bank

  • This includes seed collected from populations that have since become extinct

  • In 2008, some of this seed was germinated, and seedlings were planted at a location near Albany

  •  Genetic analysis of the seedlings revealed some genetic diversity that was not present in any extant population

  • The conservation of these seeds had thus preserved some of the species' genetic diversity that would otherwise have been lost through population extinction, providing a powerful example of the importance of seed banking to conservation efforts 

  • A seed orchard was planted in 2007, and by 2010 this had yielded over 400 disease-free, healthy plants, some of which had grown more than three times the rate of those in the wild

  • A 2007 seedling flowered for the first time at Wakehurst Place in February 2011

• Cultivation

  • Highly valued by Australia's horticultural and cut flower industries, it is widely cultivated in areas not exposed to dieback

  • With large metallic red inflorescences and attractive feathery leaves that are perhaps the softest of all Banksia species, B. brownii is highly valued by Australia's horticultural and cut flower industries

  • Seeds and plants are readily available in Australian nurseries, and it is widely cultivated in areas not exposed to dieback

  • Seeds do not require any treatment, and take 20 to 50 days to germinate

  • The plant prefers a sheltered position in soil with good drainage, and must be provided with moisture over summer

  • It grows quickly, but takes several years to flower

  • Once established, it is frost-tolerant and tolerates light pruning not below the green foliage

  • The flowers are attractive in late bud, but lose their colour as soon as they open

  • Because they are usually surrounded by branchlets, they may be partly hidden by foliage

  • The main obstacle to cultivation is the species' extreme sensitivity to dieback, which is widespread in suburban gardens

  • However, the species has been successfully grafted onto a rootstock of B. integrifolia (coast banksia), which renders it hardy on a range of soils

Taxonomy of Banksia

As with other flowering plants, the taxonomy of Banksia has traditionally been 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. Increasingly, molecular evidence from DNA is providing important new insights into relationships within the genus and between this and other genera in the Proteaceae.

The genus is placed in family Proteaceae, subfamily Grevilleoideae, tribe Banksieae and subtribe Banksiinae. The most recent complete revision is that published in Alex George's 1999 monograph for the Flora of Australia book series; this recognises two subgenera, three sections, 13 series, 77 species, 6 subspecies and 18 varieties, and treats the traditionally related genus Dryandra as separate but closely related. Recent molecular cladistic analyses have provided an alternative view in which Dryandra is shown to be nested inside, and hence should be included within, Banksia. This interpretation has been controversial in some circles, and is not universally accepted.

Banksia (in the traditional sense, not including Dryandra), 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 possums, and they are of economic importance to the nursery and cut flower industries. However they are threatened by a number of processes, including land clearing, frequent burning, and disease; and a number of species are rare and endangered.

Taxonomic history

See also: Timeline of Banksia

Banksia was first described in Carolus Linnaeus the Younger's April 1782 publication Supplementum Plantarum.

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 genus Banksia 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 of his father's classification,[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 Pimelea, a name previously chosen for the genus by Banks and Solander.

Banksia L.f. has since been challenged a number of times. The later near-homonym 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.

In 1810, Robert Brown published descriptions and a taxonomic arrangement of the 31 known species of Banksia in his Prodromus Florae Novae Hollandiae et Insulae 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] Banksia verae was renamed Eubanksia by Stephan Endlicher in 1847.

By the time Carl Meissner published his 1856 classification of the Proteaceae, there were 58 described Banksia species. Meissner's arrangement gave Isostylis and Eubanksia sectional rank, and divided the latter into four series based on leaf properties; these series were all highly heterogeneous.

George Bentham published his arrangement 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, taking the number of sections to five. Three of these 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.

Classification and relationships within Proteaceae

The former genus Dryandra was mereged into the Banksia in 2007. (Banksia ser. dryandra sessilis pictured).

The framework for classification of genera within Proteaceae was laid by L. A. S. Johnson and Barbara Briggs in their influential 1975 monograph "On the Proteaceae: the evolution and classification of a southern family".[8] Their arrangement has been refined somewhat over the ensuing three decades, most notably by Peter H. Weston and Nigel Barker in 2006. Proteaceae is divided into five 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 is placed 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:[10]

Family Proteaceae

Subfamily Bellendenoideae

Subfamily Persoonioideae

Subfamily Symphionematoideae

Subfamily Proteoideae

Subfamily Grevilleoideae

Tribe Roupalae

Tribe Banksieae

Subtribe Musgraveinae

Subtribe Banksiinae

Genus Banksia

Tribe Embothrieae

Tribe Macadamieae

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.[11] 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 respect to Dryandra (that is, Dryandra is a sub-group of Banksia. Mast suggested that the least disruptive approach to restore monophyly would be to sink Dryandra into Banksia.[12][13] This has been put into effect in a 2007 paper by Mast & Thiele, in which all existing species of Dryandra were transferred into Banksia.

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 taxon was considered a distinct species only if it exhibited a "significant and consistent difference in the morphology of flowers and/or fruit".[11] 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,[15] which remains the standard text on the genus, and the treatment of Banksia in the Flora of Australia series.

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.[11] 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.

This conventional taxonomic arrangement of Banksia, as provided by George and published in the Flora of Australia series, may be summarised as follows:

Genus Banksia

Subgenus Banksia

Section Banksia

Series Salicinae

Subseries Acclives

B. dentata – B. plagiocarpa – B. oblongifolia – B. robur

Subseries Integrifoliae

B. aquilonia – B. integrifolia – B. conferta – B. paludosa – B. marginata – B. canei – B. saxicola

Series Grandes

B. grandis – B. solandri

Series Banksia

Subseries Banksia

B. serrata – B. aemula – B. ornata

Subseries Cratistylis

B. baxteri – B. speciosa – B. menziesii – B. candolleana – B. sceptrum

Series Crocinae

B. prionotes – B. burdettii – B. hookeriana – B. victoriae

Series Prostratae

B. goodii – B. gardneri – B. chamaephyton – B. blechnifolia – B. repens – B. petiolaris

Series Cyrtostylis

B. media – B. praemorsa – B. epica – B. pilostylis – B. attenuata – B. ashbyi – B. benthamiana – B. audax – B. lullfitzii – B. elderiana – B. laevigata – B. elegans – B. lindleyana

Series Tetragonae

B. lemanniana – B. caleyi – B. aculeata

Series Bauerinae

B. baueri

Series Quercinae

B. quercifolia – B. oreophila

Section Coccinea

B. coccinea

Section Oncostylis

Series Spicigerae

Subseries Spinulosae

B. spinulosa

Subseries Ericifoliae

B. ericifolia

Subseries Occidentales

B. verticillata – B. seminuda – B. littoralis – B. occidentalis – B. brownii

Series Tricuspidae

B. tricuspis

Series Dryandroidae

B. dryandroides

Series Abietinae

Subseries Nutantes

B. nutans

Subseries Sphaerocarpae

B. sphaerocarpa – B. micrantha – B. grossa

Subseries Leptophyllae

B. telmatiaea – B. leptophylla – B. lanata – B. scabrella

Subseries Longistyles

B. violacea – B. incana – B. laricina – B. pulchella – B. meisneri

Subgenus Isostylis

B. ilicifolia – B. oligantha – B. cuneata

Cladistic analyses

Thiele and Ladiges

Main article: Thiele and Ladiges' taxonomic arrangement of Banksia

In 1996, Kevin Thiele and Pauline Ladiges published a cladistic analysis of the genus Banksia in the journal Australian Systematic Botany.[6] As their cladogram differed substantially from the current taxonomic arrangement, they published a revised arrangement that accorded better with their results. Four varieties were promoted to species rank: B. conferta var. penicillata to B. penicillata (now B. conferta subsp. penicillata); B. gardneri var. brevidentata to B. brevidentata; B. gardneri var. hiemalis to B. hiemalis; and B. sphaerocarpa var. dolichostyla to B. dolichostyla. Two new series and eleven subseries were introduced; Banksia sect. Oncostylis and Banksia ser. Crocinae were discarded; and Banksia ser. Cyrtostylis was largely redefined. Six species were left incertae sedis.

Most aspects of Thiele and Ladiges' arrangement were not accepted by George in his 1999 revision. He stated that "the infrageneric classification and systematic sequence presented here are modified from that of George (1981) and take into account new data revealed in the work of Thiele & Ladiges (1996)", but none of the four promotions to species rank was accepted, and none of the thirteen infrageneric taxa introduced by Thiele and Ladiges was retained.[9] 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.

DNA analysis

Following on from an earlier molecular study,[16] 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, in 2002 and 2005. 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 paraphyletic with respect to Dryandra. Although they did not propose a new taxonomic arrangement, they did consider various options for adjusting the current accepted arrangement to remove the paraphyly. They conclude that the simplest and least disruptive solution would be to merge Dryandra into Banksia.[12][13] This solution was put into effect in a subsequent paper by Mast & Thiele.

The change has been adopted by a number of Australian herbaria including the Western Australian Herbarium, now headed by Thiele (this has the largest holdings of specimens), and by the Australian Plant Census, a project of the Council of Heads of Australasian Herbaria. This is in accordance with majority current taxonomic practice, in which only holophyletic groups are named as taxa, and groups found to be paraphyletic (e.g. Banksia not including Dryandra) are adjusted to achieve a holophyletic naming system. Alex George maintains a firm position against the change, arguing variously that the phylogenetic analyses are flawed and that paraphyly does not necessitate taxonomic changes