Banksia prionotes
Encyclopedia
Banksia prionotes, commonly known as Acorn Banksia or Orange Banksia, is a species of shrub
or tree
of the genus Banksia
in the family Proteaceae
. It is native to the southwest of Western Australia
and can reach up to 10 m (30 ft) in height. It can be much smaller in more exposed areas or in the north of its range. This species has serrated, dull green leaves and large, bright flower spikes, initially white before opening to a bright orange. Its common name arises from the partly opened inflorescence
, which is shaped like an acorn
. The tree is a popular garden plant and also of importance to the cut flower industry
.
Banksia prionotes was first described in 1840 by English botanist John Lindley
, probably from material collected by James Drummond
the previous year. There are no recognised varieties, although it has been known to hybridise with Banksia hookeriana
. Widely distributed in south-west Western Australia, B. prionotes is found from Shark Bay
(25° S
) in the north, south as far as Kojonup
(33°50′S). It grows exclusively in sandy soils, and is usually the dominant plant in scrubland or low woodland
. Pollinated
by birds, it provides food for a wide array of vertebrate
and invertebrate
animals in the autumn and winter months. It is an important source of food for honeyeater
s (Meliphagidae), 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.
young stems. The alternate dull green leaves are 15–27 cm (6–11 in) long, and 1–2 cm (⅓–⅔ in) wide, with toothed leaf margins made up of triangular lobes, and often a wavy surface.
Flowers occur in a typical Banksia flower spike, an inflorescence
made up of hundreds of small individual flowers, or florets, densely packed around a cylindrical axis. B. prionotes has cream-coloured flowers with a bright orange limb that is not revealed until the flower fully opens. Known as anthesis
, this process sweeps through the inflorescence from bottom to top over a period of days, creating the effect of a cream inflorescence that progressively turns bright orange. The old flower parts fall away after flowering finishes, revealing the axis, which may bear up to 60 embedded follicles
. Oval or oblong in shape and initially covered in fine hairs, these follicles are from 14 to 20 mm (0.55–0.8 in) long and 6–11 mm (0.25–0.4 in) wide, and protrude 3–6 mm (0.1–0.25 in) from the cone. Inside, they bear two seeds separated by a brownish woody seed separator
. The matte blackish seeds are wedge-shaped (cuneate) and measure 8–10 mm (0.3–0.4 in) long by 5–6 mm (0.2–0.25 in) wide with a membranous 'wing'.
The root system consists of a main sinker root, and up to ten lateral roots extending from a non-lignotuber
ous root crown
. The main sinker root grows straight down to the water table; it may be up to 15 m (50 ft) long if the water table is that deep. Typically from 3 to 5 cm (1.4–2 in) in diameter immediately below the root crown, roots become gradually finer with depth, and may be less than half a centimetre (0.2 in) wide just above the water table. Upon reaching the water table, the sinker branches out into a network of very fine roots. The laterals radiate out horizontally from the base of the plant, at a depth of 3–10 cm (2.4–4 in). They may extend over 5 m (15 ft) from the plant, and may bear secondary laterals; larger laterals often bear auxiliary sinker roots. Lateral roots seasonally form secondary rootlets from which grow dense surface mats of proteoid root
s, which function throughout the wetter months before dying off with the onset of summer.
in the January 1840 issue of his A Sketch of the Vegetation of the Swan River Colony
; hence the species' standard author citation is Banksia prionotes Lindl. He did not specify the type material
upon which he based the species, but A Sketch of the Vegetation of the Swan River Colony is based primarily upon the collections of early settler and botanist James Drummond
. A sheet of mounted specimens at the University of Cambridge
Herbarium (CGE), labelled "Swan River, Drummond, 1839" and annotated "Banksia prionotes m" in Lindley's hand, has since been designated the lectotype
. Lindley also made no mention of the etymology
of the specific epithet, "prionotes", but it is assumed to be derived from the Ancient Greek
prion ("saw") and -otes ("quality"), referring to the serrated leaf margins.
The most commonly reported common name
s of B. prionotes are Acorn Banksia, derived from the resemblance of partly opened inflorescences to acorn
s; and Orange Banksia. Other reported common names include Saw-toothed Banksia and Golden Banksia Bwongka is a generic Noongar
name for Banksia in the Avon River
catchment, where B. prionotes is one of several species occurring.
No further subspecies or varieties of B. prionotes have been described, 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. When Carl Meissner
published his infrageneric arrangement
of Banksia in 1856, he placed B. prionotes 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. This series was discarded in the 1870 arrangement
of George Bentham
; instead, B. prionotes was placed in section 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". In 1981, Alex George published a revised arrangement that placed B. prionotes 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 perianth
s and pistils.
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 series Banksia
, in subseries Cratistylis
. 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. prionotes in George's 1999 arrangement
may be summarised as follows:
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. 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 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 cotyledon
s; 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. prionotes is placed in subgenus Banksia.
(Hooker's Banksia) 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 hybrid
s 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 swarm
s. 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. hookeriana
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 not to be closely related. Mast's analyses, however, place them both in a clade
of eight species, though B. lindleyana remains less closely related to B. prionotes than B. hookeriana. Hybrids of B. prionotes with B. menziesii
(Firewood Banksia) have also been produced by artificial means, and presumed natural hybrids have been recorded.
Banksia prionotes occurs throughout much of the Southwest Botanical Province, occurring both along the west coast and well inland, and ranging from Shark Bay
(25°30′S) in the north, to Kojonup (33°50'S) and Jerramungup (34°24'S 118°55'E) in the south and south-east respectively. It grows among tall shrubland
or low woodland
, mostly in the swales and lower slopes of dune
s, and shows a very strong preference for deep white or yellow sand.
It is most common amongst the kwongan heath of the Geraldton Sandplains
north of Jurien; it has a fairly continuous distribution there, often as the dominant species, and extends inland to around the 350 mm isohyet. On the Swan Coastal Plain
to the south, its distribution is discontinuous, being largely confined to patches of suitable sand in the narrow transition zone where tuart forest
gives way to jarrah forest
. With the exception of a population at Point Walter (32°00′S), it does not occur on the sandplain south of the Swan River
.
The soils east of the Darling Scarp
are generally too heavy for this species, with the exception of some isolated pockets of deep alluvial or aeolian yellow sand. B. prionotes thus has a very patchy distribution east of the scarp. This area nonetheless accounts for around half of its geographic range, with the species extending well to the south and south-east of the scarp. In total, the species occurs over a north–south distance of about 815 km (500 mi), and an east–west distance of about 125 km (80 mi).
The species is almost totally restricted to the swales
and lower slopes of dunes. Various reasons for this have been proposed; on the one hand, it has been argued that its dependence on ground water necessitates that it grow only where ground water is relatively near the surface; on the other hand, it has been suggested that it cannot survive in higher parts of the landscape because fires are too frequent there. The latter hypothesis is supported by the recent expansion of B. prionotes along road verges of the Brand Highway
, where fires are relatively rare. Despite B. prionotes
in some areas that were previously flood-prone.
Annual growth increases exponentially for the first eight years or so, but then slows down as resources are diverted into reproduction and the greater density of foliage results in reduced photosynthetic
efficiency
.
ic concentrations of chloride
, sodium
, magnesium
, calcium
and potassium
that are adequate for the plant's nutritional needs.
The other common adaptation is the possession of cluster roots, which allow it to extract enough nutrients to survive in the oligotroph
ic soils in which it grows. With the onset of autumn rains, the lateral roots form dense surface mats of cluster roots in the top 20 cm (8 in) of soil, just below the leaf litter, where most minerals are concentrated. These roots exude chemicals that enhance mineral solubility
, greatly increasing the availability and uptake
of nutrient
s in impoverished soils such as the phosphorus
-deficient native soils of Australia. For as long as surface water
is available, they take in water and a range of minerals. In B. prionotes they are principally responsible for the uptake of malate
, phosphate, chloride, sodium and potassium. When soils are high in nitrate
s, they may also perform some nitrate reductase
activities, primarily the conversion of ammonium
into amino acids such as asparagine
and glutamine
.
The uptake of nutrient and water by the cluster roots peaks through winter and spring, but ceases when the upper layer of soil dries out in summer. The cluster roots are then allowed to die, but the laterals are protected from desiccation by a continuous supply of water from the sinker root. The water supplied to the laterals by the sinker root is continually lost to the soil; thus this plant facilitates the movement of ground water from the water table into surface soil, a process known as hydraulic redistribution
. Cluster roots have been estimated as comprising about 30% of total root biomass in this species; the seasonal production of so much biomass
, only for it to be lost at the end of the growing season, represents a substantial investment by the plant, but one that is critical in the competition for nutrients.
During winter, asparagine is metabolised
immediately, but other nutrients, especially phosphates and glutamine, are removed from the xylem sap
and stored in mature stem
, bark
and leaf
tissues
for release back into the xylem
just before shoot growth begins in mid summer. This is also the time when the oldest leaves senesce and die, returning nutrients to the plant at the time when they are needed most. When glutamine eventually reaches the leaves, it is broken down and used to synthesise protein
and non-amide
amino acids such as aspartate, threonine
, serine
, glutamate, glycine
, alanine
and cystine
. Together with sucrose
and other solutes
, these are then circulated in the phloem
. The phloem sap
of B. prionotes is unusual in having an extremely low ratio of potassium to sodium cations, and very low concentrations of phosphate and amino acids compared to chloride and sulfate anions. The low levels of potassium and phosphate reflect the extremely low availability of these minerals in the soil. The unusually high levels of sodium and chloride—at concentrations usually only seen under saline conditions—may be due to the necessity of maintaining turgor pressure
; that is, with so little potassium and phosphate available, and that needed in the building of new tissue, B. prionotes is forced to circulate whatever other ions are available in order to maintain turgor.
Flowering begins in February and is usually finished by the end of June. The species has an unusually low rate of flowering: even at the peak of its flowering season, it averages less than seven inflorescences per plant flowering at any one time. Individual flowers open sequentially from bottom to top within each inflorescence, the rate varying with the time of day: more flowers open during the day than at night, with a peak rate of around two to three florets per hour during the first few hours of daylight, when honeyeater foraging is also at its peak.
The flowers are fed at by a range of nectarivorous
birds: mainly honeyeaters, including the New Holland Honeyeater
(Phylidonyris novaehollandiae), White-cheeked Honeyeater
(P. nigra), Brown Honeyeater
(Lichmera indistincta), Singing Honeyeater
(Lichenostomus virescens), Tawny-crowned Honeyeater
(Gliciphila melanops) and Red Wattlebird
(Anthochaera carunculata). Lorikeets have also been observed feeding at the flowers, as have insects, including ants, bees, and aphid
s. Of these, evidence suggests that only birds are effective pollinators. Insects apparently play no role in pollination, since inflorescences do not form follicles when birds are excluded in pollinator exclusion experiment
s; and pollination by mammals has never been recorded in this species.
Honeyeaters prefer to forage at individual flowers which have only just opened, as these offer the most nectar. As they probe for nectar, honeyeaters end up with large quantities of pollen on their beaks, foreheads and throats, some of which they subsequently transfer to other flowers. This transfer is quite efficient: flowers typically lose nearly all their pollen within four hours of opening, and pollen is deposited on the majority of stigmata. Around 15% of these stigmata end up with pollen lodged in the stigmatic groove, a prerequisite to fertilisation.
The structure of the Banksia flower, with the style end functioning as a pollen presenter, suggests that autogamous self-fertilisation must be common. In many Banksia species, the risk of this occurring is reduced by protandry
: a delay in a flower's receptivity to pollen until after its own pollen has lost its viability. There is dispute, however, over whether this occurs in B. prionotes: one study claimed to have confirmed "protandrous development", yet recorded high levels of stigmatic receptivity immediately after anthesis
, and long pollen viability, observations that are not consistent with protandry.
If it does occur, protandry does nothing to prevent geitonogamous
self-pollination: that is, pollination with pollen from another flower on the same plant. In fact, when birds forage at B. prionotes, only about a quarter of all movements from inflorescence to inflorescence involve a change of plant. Geitonogamous self-pollination must therefore occur more often in this species than cross-pollination. This does not imply high rates of self-fertilisation, however, as the species appears highly self-incompatible: although pollen grains will germinate on flowers of the self plant, they apparently fail to produce pollen tubes that penetrate the style. Even where cross-pollination does occur, fertilisation rate is fairly low. It is speculated that this is related to "a variety of chemical reactions at the pollen-stigma interface".
Cone production varies a great deal from year to year, but, as a result of its low flowering rate, is generally very low. However there are typically a very high number of follicles per cone, leading to relatively high seed counts. There is some seed predation, primarily from the curculionid
weevil
Cechides amoenus
.
Like many plants in south-west Western Australia, B. prionotes is adapted to an environment in which bushfire events are relatively frequent. Most Banksia species can be placed in one of two broad groups according to their response to fire: reseeders are killed by fire, but fire also triggers the release of their canopy seed bank
, thus promoting recruitment of the next generation; resprouter
s survive fire, resprouting from a lignotuber
or, more rarely, epicormic buds
protected by thick bark. B. prionotes is unusual in that it does not fit neatly into either of these groups. It lacks a lignotuber or thick bark, and so cannot be considered a resprouter; yet it may survive or escape some fires because of its height, the sparseness of its foliage, and because it occurs in dune swales where fire are cooler and patchier. On the other hand, it is not a typical reseeder either, because of its relatively low fire mortality rates, and because it is only weakly serotinous
: although fire promotes seed release, seed release still occurs in the absence of fire.
The actual degree of serotiny and fire mortality in B. prionotes varies with latitude, or, more likely, climate. Observations suggest that it is always killed by fire in the north of its range, which is relatively hot and dry, and where individual plants are usually smaller, but may survive fire in the cooler, moister, south. Moreover, it is essentially non-serotinous in the south, since all seed is released by the end of the second year, but seed retention increases steadily to the north, and at the northern end of its range, it typically takes around four years for a plant to release half of its seed in the absence of bushfire, with some seed retained for up to 12 years.
A number of other characteristics of B. prionotes can be understood as secondary responses to weak serotiny. For example, winter flowering ensures that seed is ripe by the beginning of the bushfire season; this is very important for weakly serotinous species, which rely heavily upon the current year's seed crop. Another example is the deciduous florets of B. prionotes. In strongly serotinous species, the old florets are retained on the cones, where they function as fire fuel, helping to ensure that follicles reach temperatures sufficient to trigger seed release. In B. prionotes, however, seed release is triggered at relatively low temperatures: in one study, 50% of follicles opened at 265 °C (510 °F), and 90% opened at 330 °C (625 °F); in contrast, the closely related but strongly serotinous B. hookeriana required 340 °C (645 °F) and 500 °C (930 °F) respectively. Floret retention would therefore be to no advantage, and might even prevent seed from escaping spontaneously opened follicles.
Seed release in B. prionotes is promoted by repeated wetting of the cones. The seed separator
that holds the seeds in place is hygroscopic; its two wings pull together then wet, then spread and curl inwards as it dries out again. In doing so, it functions as a lever, gradually prying seeds out of a follicle over the course of a wet-dry cycle. This adaptation ensures that seed release following fire is delayed until the onset of rain, when germination and seedling survival rates are higher.
Because of its higher susceptibility and lower reliance on fire for reproduction, the optimal fire interval for B. prionotes is higher than for other Banksia species with which it occurs. One simulation suggested an interval of 18 years was optimal for B. prionotes, compared to 15 years for B. hookeriana and 11 years for B. attenuata. The same model suggested that B. prionotes is quite susceptible to reductions in fire intervals. On the other hand, it shows little susceptibility to increases in fire interval: although senescence and death are often observed in plants older than about 30 years, healthy stands have been observed that have escaped fire for 50 years. These stands have a multi-aged structure, demonstrating the occurrence of successful inter-fire recruitment.
Fire response may also furnish an explanation for the evolution
of this species. The differences in fire regime between dune crests and swales would have created different evolutionary pressures, with plants on crests adapting to frequent hot fires by becoming strongly serotinous, and plants in swales adapting to patchier, cooler fires with weaker serotiny. Speciation would be made possible by the much reduced genetic exchange between crest plants and swale plants, although evidence suggests that there was some introgression
at first. Eventually, however, the need for weakly serotinous plants to produce ripe seed by the bushfire season would have brought forward its flowering season until the flowering seasons no longer overlapped; thus a phenological barrier to exchange was erected, allowing the two populations to drift
independently of each other.
to a number of threatening processes. It is highly susceptible to Phytophthora cinnamomi
dieback; wild populations are harvested commercially by the cut flower industry
; and some of its range is subject to land clearing for urban or agricultural purposes. An assessment of the potential impact of climate change
on this species found that severe change is likely to lead to a reduction in its range of around 50% by 2080; and even mild change is projected to cause a reduction of 30%; but under mid-severity scenarios the distribution may actually grow, depending on how effectively it can migrate into newly habitable areas. However, this study does not address the potential of climate change to alter fire regime
s; these have already been impacted by the arrival of humans, and this change is thought to have led to a decline in the abundance and range of B. prionotes.
The species as a whole 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 does not consider it to be rare, and has not included it on their Declared Rare and Priority Flora List. It nonetheless has high conservation importance in at least one context: it is a keystone mutualist in the Avon Wheatbelt
, where it is the only source of nectar during a critical period of the year when no other nectar-producing plant is in flower. The loss of B. prionotes from the region would therefore mean the loss of all the honeyeaters as well, and this would affect the many other species of plants that rely on honeyeaters for pollination. The primary vegetation community in which Banksia prionotes occurs in the Avon Wheatbelt is considered a priority ecological community, and is proposed for formal gazetting as a threatened ecological community
under the name "Banksia prionotes and Xylomelum angustifolium
low woodlands on transported yellow sand". Although currently in near-pristine and static condition, it is considered at risk due to a large number of threatening processes, including land clearing, landscape fragmentation, rising soil salinity
, grazing pressure
, competition with weeds, changes to the fire regime, rubbish dumping, and P. cinnamomi dieback.
Described as "an outstanding ornamental species", its brightly coloured, conspicuous flower spikes make B. prionotes a popular garden plant. It is good for attracting honeyeaters to the garden, and sometimes flowers twice a year. A low growing dwarf form which reaches 1 m (3 ft) high is available in Western Australia, sold as "Little Kalbarri Candles".
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. Seeds do not require any treatment prior to sowing
, and take 21 to 35 days to germinate.
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. As such it is one of the most popular banksias for cut flower production, with commercial crops grown in Israel
, Victoria
, South Australia
and Hawaii
.
Shrub
A shrub or bush is distinguished from a tree by its multiple stems and shorter height, usually under 5–6 m tall. A large number of plants may become either shrubs or trees, depending on the growing conditions they experience...
or tree
Tree
A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to...
of the genus Banksia
Banksia
Banksia is a genus of around 170 species in the plant family Proteaceae. These Australian wildflowers and popular garden plants are easily recognised by their characteristic flower spikes and fruiting "cones" and heads. When it comes to size, banksias range from prostrate woody shrubs to trees up...
in the family Proteaceae
Proteaceae
Proteaceae is a family of flowering plants distributed in the Southern Hemisphere. The family comprises about 80 genera with about 1600 species. Together with the Platanaceae and Nelumbonaceae they make up the order Proteales. Well known genera include Protea, Banksia, Embothrium, Grevillea,...
. It is native to the southwest of Western Australia
Western Australia
Western Australia is a state of Australia, occupying the entire western third of the Australian continent. It is bounded by the Indian Ocean to the north and west, the Great Australian Bight and Indian Ocean to the south, the Northern Territory to the north-east and South Australia to the south-east...
and can reach up to 10 m (30 ft) in height. It can be much smaller in more exposed areas or in the north of its range. This species has serrated, dull green leaves and large, bright flower spikes, initially white before opening to a bright orange. Its common name arises from the partly opened inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
, which is shaped like an acorn
Acorn
The acorn, or oak nut, is the nut of the oaks and their close relatives . It usually contains a single seed , enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad...
. The tree is a popular garden plant and also of importance to the cut flower industry
Floriculture
Floriculture, or flower farming, is a discipline of horticulture concerned with the cultivation of flowering and ornamental plants for gardens and for floristry, comprising the floral industry...
.
Banksia prionotes was first described in 1840 by English botanist John Lindley
John Lindley
John Lindley FRS was an English botanist, gardener and orchidologist.-Early years:Born in Catton, near Norwich, England, John Lindley was one of four children of George and Mary Lindley. George Lindley was a nurseryman and pomologist and ran a commercial nursery garden...
, probably from material collected by James Drummond
James Drummond (botanist)
James Drummond was a botanist and naturalist who was an early settler in Western Australia.-Early life:...
the previous year. There are no recognised varieties, although it has been known to hybridise with Banksia hookeriana
Banksia hookeriana
The Hooker's Banksia is a species of shrub in the plant genus Banksia. It occurs on sandplain shrubland between Arrowsmith and Eneabba in Western Australia. Seeds do not require any treatment, and take 23 to 49 days to germinate....
. Widely distributed in south-west Western Australia, B. prionotes is found from Shark Bay
Shark Bay
Shark Bay is a World Heritage listed bay in Western Australia. The term may also refer to:* the locality of Shark Bay, now known as Denham* Shark Bay Marine Park* Shark Bay , a shark exhibit at Sea World, Gold Coast, Australia* Shire of Shark Bay...
(25° S
25th parallel south
The 25th parallel south is a circle of latitude that is 25 degrees south of the Earth's equatorial plane, just south of the Tropic of Capricorn...
) in the north, south as far as Kojonup
Kojonup, Western Australia
Kojonup is a town located 256 km south-east of Perth, Western Australia along Albany Highway.The name Kojonup is believed to refer to the "Kodja" or stone axe made by Indigenous Australians from the local stone....
(33°50′S). It grows exclusively in sandy soils, and is usually the dominant plant in scrubland or low woodland
Woodland
Ecologically, a woodland is a low-density forest forming open habitats with plenty of sunlight and limited shade. Woodlands may support an understory of shrubs and herbaceous plants including grasses. Woodland may form a transition to shrubland under drier conditions or during early stages of...
. Pollinated
Pollination
Pollination is the process by which pollen is transferred in plants, thereby enabling fertilisation and sexual reproduction. Pollen grains transport the male gametes to where the female gamete are contained within the carpel; in gymnosperms the pollen is directly applied to the ovule itself...
by birds, it provides food for a wide array of vertebrate
Vertebrate
Vertebrates are animals that are members of the subphylum Vertebrata . Vertebrates are the largest group of chordates, with currently about 58,000 species described. Vertebrates include the jawless fishes, bony fishes, sharks and rays, amphibians, reptiles, mammals, and birds...
and invertebrate
Invertebrate
An invertebrate is an animal without a backbone. The group includes 97% of all animal species – all animals except those in the chordate subphylum Vertebrata .Invertebrates form a paraphyletic group...
animals in the autumn and winter months. It is an important source of food for honeyeater
Honeyeater
The honeyeaters are a large and diverse family of small to medium sized birds most common in Australia and New Guinea, but also found in New Zealand, the Pacific islands as far east as Samoa and Tonga, and the islands to the north and west of New Guinea known as Wallacea...
s (Meliphagidae), and is critical to their survival in the Avon Wheatbelt
Avon Wheatbelt
Avon Wheatbelt is an Interim Biogeographic Regionalisation for Australia region in Western Australia and part of the larger Southwest Australia savanna ecoregion.-Further reading:...
region, where it is the only nectar-producing plant in flower at some times of the year.
Description
Banksia prionotes grows as a tree up to 10 m (30 ft) high in southern parts of its distribution, but in northern parts it is usually a shorter tree or spreading shrub, reaching about 4 m (13 ft) in height; it diminishes in size as the climate becomes warmer and dryer further north. It has thin, mottled grey, smooth or grooved bark, and tomentoseTomentose
Tomentose is a term used to describe plant hairs that are flattened and matted, forming a woolly coating known as tomentum. Often the hairs are silver or gray-colored...
young stems. The alternate dull green leaves are 15–27 cm (6–11 in) long, and 1–2 cm (⅓–⅔ in) wide, with toothed leaf margins made up of triangular lobes, and often a wavy surface.
Flowers occur in a typical Banksia flower spike, an inflorescence
Inflorescence
An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches. Strictly, it is the part of the shoot of seed plants where flowers are formed and which is accordingly modified...
made up of hundreds of small individual flowers, or florets, densely packed around a cylindrical axis. B. prionotes has cream-coloured flowers with a bright orange limb that is not revealed until the flower fully opens. Known as anthesis
Anthesis
Anthesis is the period during which a flower is fully open and functional. It may also refer to the onset of that period.The onset of anthesis is spectacular in some species. In Banksia species, for example, anthesis involves the extension of the style far beyond the upper perianth parts...
, this process sweeps through the inflorescence from bottom to top over a period of days, creating the effect of a cream inflorescence that progressively turns bright orange. The old flower parts fall away after flowering finishes, revealing the axis, which may bear up to 60 embedded follicles
Follicle (fruit)
In botany, a follicle is a dry unilocular many-seeded fruit formed from one carpel and dehiscing by the ventral suture in order to release seeds, such as in larkspur, magnolia, banksia, peony and milkweed....
. Oval or oblong in shape and initially covered in fine hairs, these follicles are from 14 to 20 mm (0.55–0.8 in) long and 6–11 mm (0.25–0.4 in) wide, and protrude 3–6 mm (0.1–0.25 in) from the cone. Inside, they bear two seeds separated by a brownish woody seed separator
Seed separator
A seed separator is a structure found in the follicles of some Proteaceae. These follicles typically contain two seeds, with a seed separator between them...
. The matte blackish seeds are wedge-shaped (cuneate) and measure 8–10 mm (0.3–0.4 in) long by 5–6 mm (0.2–0.25 in) wide with a membranous 'wing'.
The root system consists of a main sinker root, and up to ten lateral roots extending from a non-lignotuber
Lignotuber
A lignotuber is a starchy swelling of the root crown possessed by some plants as a protection against destruction of the plant stem by fire. The crown contains buds from which new stems may sprout, and a sufficient store of nutrients to support a period of growth in the absence of...
ous root crown
Root crown
A root crown is that part of a root system from which a stem arises. Since roots and stems have quite different vascular anatomies, major vascular changes take place at this point....
. The main sinker root grows straight down to the water table; it may be up to 15 m (50 ft) long if the water table is that deep. Typically from 3 to 5 cm (1.4–2 in) in diameter immediately below the root crown, roots become gradually finer with depth, and may be less than half a centimetre (0.2 in) wide just above the water table. Upon reaching the water table, the sinker branches out into a network of very fine roots. The laterals radiate out horizontally from the base of the plant, at a depth of 3–10 cm (2.4–4 in). They may extend over 5 m (15 ft) from the plant, and may bear secondary laterals; larger laterals often bear auxiliary sinker roots. Lateral roots seasonally form secondary rootlets from which grow dense surface mats of proteoid root
Proteoid root
Proteoid roots, also known as cluster roots, are plant roots that form clusters of closely spaced short lateral rootlets. They may form a two to five centimetre thick mat just beneath the leaf litter. They enhance nutrient uptake, possibly by chemically modifying the soil environment to improve...
s, which function throughout the wetter months before dying off with the onset of summer.
Taxonomy
Banksia prionotes was first published by English botanist John LindleyJohn Lindley
John Lindley FRS was an English botanist, gardener and orchidologist.-Early years:Born in Catton, near Norwich, England, John Lindley was one of four children of George and Mary Lindley. George Lindley was a nurseryman and pomologist and ran a commercial nursery garden...
in the January 1840 issue of his A Sketch of the Vegetation of the Swan River Colony
A Sketch of the Vegetation of the Swan River Colony
A Sketch of the Vegetation of the Swan River Colony, also known by its standard botanical abbreviation Sketch Veg. Swan R., is an 1839 article by John Lindley on the flora of the Swan River Colony...
; hence the species' standard author citation is Banksia prionotes Lindl. He did not specify the type material
Biological type
In biology, a type is one particular specimen of an organism to which the scientific name of that organism is formally attached...
upon which he based the species, but A Sketch of the Vegetation of the Swan River Colony is based primarily upon the collections of early settler and botanist James Drummond
James Drummond (botanist)
James Drummond was a botanist and naturalist who was an early settler in Western Australia.-Early life:...
. A sheet of mounted specimens at the University of Cambridge
University of Cambridge
The University of Cambridge is a public research university located in Cambridge, United Kingdom. It is the second-oldest university in both the United Kingdom and the English-speaking world , and the seventh-oldest globally...
Herbarium (CGE), labelled "Swan River, Drummond, 1839" and annotated "Banksia prionotes m" in Lindley's hand, has since been designated the lectotype
Lectotype
In botanical nomenclature and zoological nomenclature, a lectotype is a kind of name-bearing type. When a species was originally described on the basis of a name-bearing type consisting of multiple specimens, one of those may be designated as the lectotype...
. Lindley also made no mention of the etymology
Etymology
Etymology is the study of the history of words, their origins, and how their form and meaning have changed over time.For languages with a long written history, etymologists make use of texts in these languages and texts about the languages to gather knowledge about how words were used during...
of the specific epithet, "prionotes", but it is assumed to be derived from the Ancient Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
prion ("saw") and -otes ("quality"), referring to the serrated leaf margins.
Common name
A common name of a taxon or organism is a name in general use within a community; it is often contrasted with the scientific name for the same organism...
s of B. prionotes are Acorn Banksia, derived from the resemblance of partly opened inflorescences to acorn
Acorn
The acorn, or oak nut, is the nut of the oaks and their close relatives . It usually contains a single seed , enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad...
s; and Orange Banksia. Other reported common names include Saw-toothed Banksia and Golden Banksia Bwongka is a generic Noongar
Noongar
The Noongar are an indigenous Australian people who live in the south-west corner of Western Australia from Geraldton on the west coast to Esperance on the south coast...
name for Banksia in the Avon River
Avon River (Western Australia)
The Avon River is a river in Western Australia. It is a tributary of the Swan River totalling 280 kilometres in length, with a catchment area of 125,000 square kilometres.-Catchment area:...
catchment, where B. prionotes is one of several species occurring.
No further subspecies or varieties of B. prionotes have been described, and it has no taxonomic synonyms. Its only nomenclatural synonym is Sirmuellera prionotes (Lindl.) Kuntze, which arose from Otto Kuntze
Otto Kuntze
Otto Carl Ernst Kuntze was a German botanist.-Biography:Otto Kuntze was born in Leipzig.An apothecary in his early career, he published an essay entitled Pocket Fauna of Leipzig. Between 1863 and...
's unsuccessful 1891 attempt to transfer Banksia into the new name Sirmuellera. When Carl Meissner
Carl Meissner
Carl Daniel Friedrich Meissner was a Swiss botanist.Born in Bern, Switzerland on 1 November 1800, he was christened Meisner but later changed the spelling of his name to Meissner. For most of his 40 year career he was Professor of Botany at University of Basel...
published his infrageneric arrangement
Meissner's taxonomic arrangement of Banksia
Carl Meissner's taxonomic arrangement of Banksia was published in 1856, as part of his chapter on the Proteaceae in A. P. de Candolle's Prodromus systematis naturalis regni vegetabilis. It was the first attempt to provide an infrageneric classification for the genus, aside from Robert Brown's...
of Banksia in 1856, he placed B. prionotes in section Eubanksia
Banksia sect. Eubanksia
Banksia sect. Eubanksia is an obsolete section of Banksia. There have been two circumscriptions, one of which is synonymous with the recently abandoned B. subg. Banksia sensu Alex George, the other having no modern equivalent....
because its inflorescence is a spike rather than a domed head, and in series Salicinae
Banksia ser. Salicinae
Banksia ser. Salicinae is a valid botanic name for a series of Banksia. First published by Carl Meissner in 1856, the name has had three circumscriptions.-According to Meissner:...
, a large series that is now considered quite heterogeneous. This series was discarded in the 1870 arrangement
Bentham's taxonomic arrangement of Banksia
George Bentham's taxonomic arrangement of Banksia was published in 1870, in Volume 5 of Bentham's Flora Australiensis. A substantial improvement on the previous arrangement, it would stand for over a century. It was eventually replaced by Alex George's 1981 arrangement, published in his classic...
of George Bentham
George Bentham
George Bentham CMG FRS was an English botanist, characterized by Duane Isely as "the premier systematic botanist of the nineteenth century".- Formative years :...
; instead, B. prionotes was placed in section 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". In 1981, Alex George published a revised arrangement that placed B. prionotes in the subgenus Banksia
Banksia subg. Banksia
Banksia subg. Banksia is a valid botanic name for a subgenus of Banksia. As an autonym, it necessarily contains the type species of Banksia, B. serrata . Within this constraint, however, there have been various circumscriptions.-Banksia verae:B. subg...
because of its flower spike, section Banksia
Banksia sect. Banksia
Banksia sect. Banksia is one of four sections of Banksia subgenus Banksia. It contains those species of subgenus Banksia with straight or sometimes curved but not hooked styles. These species all have cylindrical inflorescences and usually exhibit a bottom-up sequence of flower anthesis...
because its styles are straight rather than hooked, and the series Crocinae
Banksia ser. Crocinae
Banksia ser. Crocinae is a taxonomic series in the genus Banksia. It consists of four closely related species, all of which are endemic to Western Australia; namely B. prionotes , B. burdettii , B. hookeriana and B. victoriae...
, a new series of four closely related species, all with bright orange perianth
Perianth
The term perianth has two similar but separate meanings in botany:* In flowering plants, the perianth are the outer, sterile whorls of a flower...
s and pistils.
George's arrangement remained current until 1996, when Kevin Thiele
Kevin Thiele
Kevin R. Thiele is curator of the Western Australian Herbarium. His research interests include the systematics of the plant families Proteaceae, Rhamnaceae and Violaceae, and the conservation ecology of grassy woodland ecosystems...
and Pauline Ladiges published an arrangement informed by a cladistic
Cladistics
Cladistics is a method of classifying species of organisms into groups called clades, which consist of an ancestor organism and all its descendants . For example, birds, dinosaurs, crocodiles, and all descendants of their most recent common ancestor form a clade...
analysis of morphological
Morphology (biology)
In biology, morphology is a branch of bioscience dealing with the study of the form and structure of organisms and their specific structural features....
characteristics. Their arrangement
Thiele and Ladiges' taxonomic arrangement of Banksia
Kevin Thiele and Pauline Ladiges' taxonomic arrangement of Banksia, published in 1996, was a novel taxonomic arrangement that was intended to align the taxonomy of Banksia more closely with the phylogeny that they had inferred from their cladistic analysis of the genus...
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 series Banksia
Banksia ser. Banksia
Banksia ser. Banksia is avalid botanic name for a series of Banksia. As an autonym, it necessarily contains the type species of Banksia, B. serrata . Within this constraint, however, there have been various circumscriptions.-According to Bentham:Banksia ser. Banksia originated in 1870 as...
, in subseries Cratistylis
Banksia subser. Cratistylis
Banksia subser. Cratistylis is a valid botanic name for a subseries of Banksia. It was first published by Kevin Thiele in 1996, but discarded by Alex George in 1999.-Cladistics:...
. 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
Flora of Australia (series)
The Flora of Australia is a 59 volume series describing the vascular plants, bryophytes and lichens present in Australia and its external territories...
series of monographs. To date, this remains the most recent comprehensive arrangement. The placement of B. prionotes in George's 1999 arrangement
George's taxonomic arrangement of Banksia
Alex George's taxonomic arrangement of Banksia was the first modern-day arrangement for that genus. First published in 1981 in the classic monograph The genus Banksia L.f. , it superseded the arrangement of George Bentham, which had stood for over a hundred years. It was overturned in 1996 by Kevin...
may be summarised as follows:
- BanksiaBanksiaBanksia is a genus of around 170 species in the plant family Proteaceae. These Australian wildflowers and popular garden plants are easily recognised by their characteristic flower spikes and fruiting "cones" and heads. When it comes to size, banksias range from prostrate woody shrubs to trees up...
- B. subg. BanksiaBanksia subg. BanksiaBanksia subg. Banksia is a valid botanic name for a subgenus of Banksia. As an autonym, it necessarily contains the type species of Banksia, B. serrata . Within this constraint, however, there have been various circumscriptions.-Banksia verae:B. subg...
- B. sect. BanksiaBanksia sect. BanksiaBanksia sect. Banksia is one of four sections of Banksia subgenus Banksia. It contains those species of subgenus Banksia with straight or sometimes curved but not hooked styles. These species all have cylindrical inflorescences and usually exhibit a bottom-up sequence of flower anthesis...
- B. ser. SalicinaeBanksia ser. SalicinaeBanksia ser. Salicinae is a valid botanic name for a series of Banksia. First published by Carl Meissner in 1856, the name has had three circumscriptions.-According to Meissner:...
(11 species, 7 subspecies) - B. ser. GrandesBanksia ser. GrandesBanksia ser. Grandes is a taxonomic series in the genus Banksia. It consists of two closely related species in section Banksia, both endemic to Western Australia. These are B. grandis and B. solandri ....
(2 species) - B. ser. BanksiaBanksia ser. BanksiaBanksia ser. Banksia is avalid botanic name for a series of Banksia. As an autonym, it necessarily contains the type species of Banksia, B. serrata . Within this constraint, however, there have been various circumscriptions.-According to Bentham:Banksia ser. Banksia originated in 1870 as...
(8 species) - B. ser. CrocinaeBanksia ser. CrocinaeBanksia ser. Crocinae is a taxonomic series in the genus Banksia. It consists of four closely related species, all of which are endemic to Western Australia; namely B. prionotes , B. burdettii , B. hookeriana and B. victoriae...
- B. prionotes
- B. burdettiiBanksia burdettiiBurdett's Banksia is a species of large shrub or small tree in the plant genus Banksia. It occurs on sandplain country north of Gingin, Western Australia....
- B. hookerianaBanksia hookerianaThe Hooker's Banksia is a species of shrub in the plant genus Banksia. It occurs on sandplain shrubland between Arrowsmith and Eneabba in Western Australia. Seeds do not require any treatment, and take 23 to 49 days to germinate....
- B. victoriaeBanksia victoriaeBanksia victoriae, commonly known as Woolly Orange Banksia, is a species of large shrub or small tree in the plant genus Banksia...
- B. ser. ProstrataeBanksia ser. ProstrataeBanksia ser. Prostratae is a taxonomic series in the genus Banksia. It consists of six closely related species in section Banksia, all endemic to Western Australia, with a prostrate habit.Banksia ser...
(6 species, 3 varieties) - B. ser. CyrtostylisBanksia ser. CyrtostylisBanksia ser. Cyrtostylis is a valid botanic name for a taxonomic series within the plant genus Banksia. First published at sectional rank by George Bentham in 1870, it was demoted to a series by Alex George in 1981. The name has had three circumscriptions.-According to Bentham:Bentham published B....
(13 species) - B. ser. TetragonaeBanksia ser. TetragonaeBanksia ser. Tetragonae is a taxonomic series in the genus Banksia. It consists of three closely related species of erect shrub with pendulous inflorescences in section Banksia. These are B. lemanniana , B. caleyi and B. aculeata ....
(3 species) - B. ser. Bauerinae (1 species)
- B. ser. QuercinaeBanksia ser. QuercinaeBanksia ser. Quercinae is avalid botanic name for a series of Banksia. First published by Carl Meissner in 1856, the name has had three circumscriptions.-According to Meissner:...
(2 species)
- B. ser. Salicinae
- B. sect. Coccinea (1 species)
- B. sect. OncostylisBanksia sect. OncostylisBanksia sect. Oncostylis is one of four sections of subgenus Banksia subg. Banksia. It contains those Banksia species with hooked pistils. All of the species in Oncostylis also exhibit a top-down sequence of flower anthesis, except for Banksia nutans which is bottom-up.Banksia sect...
(4 series, 22 species, 4 subspecies, 11 varieties)
- B. sect. Banksia
- B. subg. IsostylisBanksia subg. IsostylisBanksia subg. Isostylis is a subgenus of Banksia. It contains three closely related species, all of which occur only in Southwest Western Australia. Members of subgenus Isostylis have dome-shaped flower heads that are superficially similar to those of B. ser...
(3 species)
- B. subg. Banksia
Since 1998, American botanist Austin Mast
Austin Mast
Austin R. Mast is a research botanist. Born in 1972, he obtained a Ph.D. from the University of Wisconsin–Madison in 2000. He is currently an associate professor within the Department of Biological Science at Florida State University , and has been director of FSU's since August 2003.One of his...
has been publishing results of ongoing cladistic analyses of DNA sequence
DNA sequence
The sequence or primary structure of a nucleic acid is the composition of atoms that make up the nucleic acid and the chemical bonds that bond those atoms. Because nucleic acids, such as DNA and RNA, are unbranched polymers, this specification is equivalent to specifying the sequence of...
data for the subtribe Banksiinae, which includes Banksia. 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
Monophyly
In common cladistic usage, a monophyletic group is a taxon which forms a clade, meaning that it contains all the descendants of the possibly hypothetical closest common ancestor of the members of the group. The term is synonymous with the uncommon term holophyly...
, and B. hookeriana
Banksia hookeriana
The Hooker's Banksia is a species of shrub in the plant genus Banksia. It occurs on sandplain shrubland between Arrowsmith and Eneabba in Western Australia. Seeds do not require any treatment, and take 23 to 49 days to germinate....
is confirmed as B. prionotes' 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
Banksia subg. Spathulatae
Banksia subg. Spathulatae is a valid botanic name for a subgenus of Banksia. It was published in 2007 by Austin Mast and Kevin Thiele, and defined as containing all those Banksia species having spathulate cotyledons...
for the species of Banksia that have spoon-shaped cotyledon
Cotyledon
A cotyledon , is a significant part of the embryo within the seed of a plant. Upon germination, the cotyledon may become the embryonic first leaves of a seedling. The number of cotyledons present is one characteristic used by botanists to classify the flowering plants...
s; in this way they also redefined the autonym
Autonym (botany)
In botanical nomenclature, autonyms are automatically created names, as regulated by the International Code of Botanical Nomenclature . Autonyms are cited without an author. Relevant provisions are in articles 6.8, 22.1-3 and 26.1-3....
B. subgenus Banksia
Banksia subg. Banksia
Banksia subg. Banksia is a valid botanic name for a subgenus of Banksia. As an autonym, it necessarily contains the type species of Banksia, B. serrata . Within this constraint, however, there have been various circumscriptions.-Banksia verae:B. subg...
. They have not yet published a full arrangement, but if their nomenclatural changes are taken as an interim arrangement, then B. prionotes is placed in subgenus Banksia.
With Banksia hookeriana
Banksia prionotes readily hybridises with Banksia hookerianaBanksia hookeriana
The Hooker's Banksia is a species of shrub in the plant genus Banksia. It occurs on sandplain shrubland between Arrowsmith and Eneabba in Western Australia. Seeds do not require any treatment, and take 23 to 49 days to germinate....
(Hooker's Banksia) under experimental conditions, indicating that these species have highly compatible pollen. The cultivar
Cultivar
A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...
B. 'Waite Orange'
Banksia 'Waite Orange'
Banksia 'Waite Orange is a variety of Banksia. A hybrid between B. hookeriana and B. prionotes , it is generally intermediate in morphology between those two species.It was bred in 1988 from an open pollination seedling of B. hookeriana, during a breeding program conducted by Dr...
is believed to be such a hybrid, having arisen by open pollination
Open pollination
Open pollination is pollination by insects, birds, wind, or other natural mechanisms, and contrasts with cleistogamy, closed pollination, which is one of the many types of self pollination...
during a breeding experiment conducted at the Waite Agricultural Research Institute of the University of Adelaide
University of Adelaide
The University of Adelaide is a public university located in Adelaide, South Australia. Established in 1874, it is the third oldest university in Australia...
in 1988.
Honeyeater
The honeyeaters are a large and diverse family of small to medium sized birds most common in Australia and New Guinea, but also found in New Zealand, the Pacific islands as far east as Samoa and Tonga, and the islands to the north and west of New Guinea known as Wallacea...
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 hybrid
F1 hybrid
F1 hybrid is a term used in genetics and selective breeding. F1 stands for Filial 1, the first filial generation seeds/plants or animal offspring resulting from a cross mating of distinctly different parental types....
s 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 swarm
Hybrid swarm
A hybrid swarm is a population of hybrids that has survived beyond the initial hybrid generation, with interbreeding between hybrid individuals and backcrossing with its parent types. Such population are highly variable, with the genetic and phenetic characteristics of individuals ranging widely...
s. 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
Speciation
Speciation is the evolutionary process by which new biological species arise. The biologist Orator F. Cook seems to have been the first to coin the term 'speciation' for the splitting of lineages or 'cladogenesis,' as opposed to 'anagenesis' or 'phyletic evolution' occurring within lineages...
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. hookeriana
Other putative hybrids
During data collection for The Banksia AtlasThe Banksia Atlas
The Banksia Atlas is an atlas that documents the ranges, habitats and growth forms of various species and other subgeneric taxa of Banksia, an iconic Australian wildflower genus...
project, a single presumed natural hybrid between B. prionotes and B. lindleyana
Banksia lindleyana
Banksia lindleyana, commonly known as the Porcupine Banksia, is a species of woody shrub in the genus Banksia of the family Proteaceae. It generally grows as a small shrub to 1 m high with long narrow serrated leaves, and bright yellow oval or round inflorescences...
(Porcupine Banksia), with fruit like B. lindleyana but leaves intermediate between the two parents, was found north of Kalbarri National Park
Kalbarri National Park
Kalbarri National Park is located north of Perth. The major geographical features of the park include the Murchison River gorge which runs for nearly 80 kilometres on the lower reaches of the Murchison River...
. At the time this was considered an important discovery, as the parent species were thought not to be closely related. Mast's analyses, however, place them both in a clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...
of eight species, though B. lindleyana remains less closely related to B. prionotes than B. hookeriana. Hybrids of B. prionotes with B. menziesii
Banksia menziesii
Banksia menziesii, commonly known as firewood banksia, is a species of flowering plant in the genus Banksia. It is a gnarled tree up to 10 m tall, or a lower spreading 1–3 m shrub in the more northern parts of its range. The serrated leaves are dull green with new growth a paler grey...
(Firewood Banksia) have also been produced by artificial means, and presumed natural hybrids have been recorded.
Distribution and habitat
Shark Bay
Shark Bay is a World Heritage listed bay in Western Australia. The term may also refer to:* the locality of Shark Bay, now known as Denham* Shark Bay Marine Park* Shark Bay , a shark exhibit at Sea World, Gold Coast, Australia* Shire of Shark Bay...
(25°30′S) in the north, to Kojonup (33°50'S) and Jerramungup (34°24'S 118°55'E) in the south and south-east respectively. It grows among tall shrubland
Shrubland
Shrubland, scrubland, scrub or brush is a plant community characterized by vegetation dominated by shrubs, often also including grasses, herbs, and geophytes. Shrubland may either occur naturally or be the result of human activity...
or low woodland
Woodland
Ecologically, a woodland is a low-density forest forming open habitats with plenty of sunlight and limited shade. Woodlands may support an understory of shrubs and herbaceous plants including grasses. Woodland may form a transition to shrubland under drier conditions or during early stages of...
, mostly in the swales and lower slopes of dune
Dune
In physical geography, a dune is a hill of sand built by wind. Dunes occur in different forms and sizes, formed by interaction with the wind. Most kinds of dunes are longer on the windward side where the sand is pushed up the dune and have a shorter "slip face" in the lee of the wind...
s, and shows a very strong preference for deep white or yellow sand.
It is most common amongst the kwongan heath of the Geraldton Sandplains
Geraldton Sandplains
Geraldton Sandplains is an Interim Biogeographic Regionalisation for Australia region in Western Australia and part of the larger Southwest Australia savanna ecoregion.It has two sub regions: -* Geraldton Hills sub region* Lesuer sub region...
north of Jurien; it has a fairly continuous distribution there, often as the dominant species, and extends inland to around the 350 mm isohyet. On the Swan Coastal Plain
Swan Coastal Plain
The Swan Coastal Plain in Western Australia is the geographic feature which contains the Swan River as it travels west to the Indian Ocean. The coastal plain continues well beyond the boundaries of the Swan River and its tributaries, as a geological and biological zone, one of Western Australia's...
to the south, its distribution is discontinuous, being largely confined to patches of suitable sand in the narrow transition zone where tuart forest
Tuart forest
Tuart forest is open forest in which the dominant overstorey tree is Eucalyptus gomphocephala . This form of vegetation occurs only in the Southwest Botanical Province of Western Australia. Tuart being predominantly a coastal tree, tuart forest occurs only in a narrow belt along the coast...
gives way to jarrah forest
Jarrah forest
Jarrah forest is tall open forest in which the dominant overstory tree is Eucalyptus marginata . The ecosystem occurs only in the Southwest Botanical Province of Western Australia...
. With the exception of a population at Point Walter (32°00′S), it does not occur on the sandplain south of the Swan River
Swan River (Western Australia)
The Swan River estuary flows through the city of Perth, in the south west of Western Australia. Its lower reaches are relatively wide and deep, with few constrictions, while the upper reaches are usually quite narrow and shallow....
.
The soils east of the Darling Scarp
Darling Scarp
The Darling Scarp, also referred to as the Darling Range or Darling Ranges, is a low escarpment running north-south to the east of the Swan Coastal Plain and Perth, Western Australia...
are generally too heavy for this species, with the exception of some isolated pockets of deep alluvial or aeolian yellow sand. B. prionotes thus has a very patchy distribution east of the scarp. This area nonetheless accounts for around half of its geographic range, with the species extending well to the south and south-east of the scarp. In total, the species occurs over a north–south distance of about 815 km (500 mi), and an east–west distance of about 125 km (80 mi).
The species is almost totally restricted to the swales
Swale (geographical feature)
A swale is a low tract of land, especially one that is moist or marshy. The term can refer to a natural landscape feature or a human-created one...
and lower slopes of dunes. Various reasons for this have been proposed; on the one hand, it has been argued that its dependence on ground water necessitates that it grow only where ground water is relatively near the surface; on the other hand, it has been suggested that it cannot survive in higher parts of the landscape because fires are too frequent there. The latter hypothesis is supported by the recent expansion of B. prionotes along road verges of the Brand Highway
Brand Highway
Brand Highway is a 362 kilometre main highway linking the northern outskirts of Perth, the capital of Western Australia, to the port city of Geraldton in Western Australia's Mid West region. Together with North West Coastal Highway, it forms part of the Western Australian coastal link to the...
, where fires are relatively rare. Despite B. prionotes
Banksia littoralis
Banksia littoralis, commonly known as the Swamp Banksia, Swamp Oak, Pungura and the Western Swamp Banksia, is a tree in the plant genus Banksia. It is found in south west Western Australia from the south eastern metropolitan area of Perth to the Stirling Range and Albany...
in some areas that were previously flood-prone.
Growth
The structure of the root system, comprising a vertical tap root and multiple horizontal laterals, develops in the seedling's first year. Thereafter, the sinker and laterals continue to lengthen, and new laterals appear. There are only three to five laterals at first, but this number typically increases to eight to ten within ten years. During the first winter, there is a great deal of root system development, especially elongation of the sinker root, but almost no shoot growth. By summer, the sinker root has generally almost reached the water table, and shoot growth increases substantially. Around February, the shoot forms a resting bud, and growth then ceases until October. On resumption of shoot growth, the shoots grow rapidly for a short time, while the plant is under little water stress; then, with the onset of water stress, the plants settles into a long period of slower shoot growth. This pattern of summer-only shoot growth is maintained throughout the life of the plant, except that in mature plants, seasonal shoot growth may cease with the formation of a terminal inflorescence rather than a resting bud. Inflorescence development continues after shoot growth ceases, and flowering commences in February or March. March and April are the peak months for flowering, which ends in July or August.Annual growth increases exponentially for the first eight years or so, but then slows down as resources are diverted into reproduction and the greater density of foliage results in reduced photosynthetic
Photosynthesis
Photosynthesis is a chemical process that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight. Photosynthesis occurs in plants, algae, and many species of bacteria, but not in archaea. Photosynthetic organisms are called photoautotrophs, since they can...
efficiency
Photosynthetic efficiency
The photosynthetic efficiency is the fraction of light energy converted into chemical energy during photosynthesis in plants and algae. Photosynthesis can be described by the simplified chemical reactionwhere CH2O represents carbohydrates such as sugars, cellulose, and lignin.The value of the...
.
Nutrition and metabolism
The root structure of B. prionotes exhibits two common environmental adaptations. Firstly, this species is phreatophytic, that is, its long taproot extends down to the water table, securing it a continuous water supply through the dry summer months, when surface water is generally unavailable. This not only helps ensure survival over summer, but allows plants to grow then. Though the supply of water is the taproot's primary function, the ground water obtained typically contains ionIon
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
ic concentrations of chloride
Chloride
The chloride ion is formed when the element chlorine, a halogen, picks up one electron to form an anion Cl−. The salts of hydrochloric acid HCl contain chloride ions and can also be called chlorides. The chloride ion, and its salts such as sodium chloride, are very soluble in water...
, sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
, magnesium
Magnesium
Magnesium is a chemical element with the symbol Mg, atomic number 12, and common oxidation number +2. It is an alkaline earth metal and the eighth most abundant element in the Earth's crust and ninth in the known universe as a whole...
, calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
and potassium
Potassium
Potassium is the chemical element with the symbol K and atomic number 19. Elemental potassium is a soft silvery-white alkali metal that oxidizes rapidly in air and is very reactive with water, generating sufficient heat to ignite the hydrogen emitted in the reaction.Potassium and sodium are...
that are adequate for the plant's nutritional needs.
The other common adaptation is the possession of cluster roots, which allow it to extract enough nutrients to survive in the oligotroph
Oligotroph
An oligotroph is an organism that can live in an environment that offers very low levels of nutrients. They may be contrasted with copiotrophs, which prefer nutritionally rich environments...
ic soils in which it grows. With the onset of autumn rains, the lateral roots form dense surface mats of cluster roots in the top 20 cm (8 in) of soil, just below the leaf litter, where most minerals are concentrated. These roots exude chemicals that enhance mineral solubility
Solubility
Solubility is the property of a solid, liquid, or gaseous chemical substance called solute to dissolve in a solid, liquid, or gaseous solvent to form a homogeneous solution of the solute in the solvent. The solubility of a substance fundamentally depends on the used solvent as well as on...
, greatly increasing the availability and uptake
Mineral uptake
In plants, mineral uptake is the process in which minerals enter the cellular material, typically following the same pathway as water. The most normal entrance portal for mineral uptake is through plant roots. Some mineral ions diffuse in-between the cells...
of nutrient
Nutrient
A nutrient is a chemical that an organism needs to live and grow or a substance used in an organism's metabolism which must be taken in from its environment. They are used to build and repair tissues, regulate body processes and are converted to and used as energy...
s in impoverished soils such as the phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
-deficient native soils of Australia. For as long as surface water
Surface water
Surface water is water collecting on the ground or in a stream, river, lake, wetland, or ocean; it is related to water collecting as groundwater or atmospheric water....
is available, they take in water and a range of minerals. In B. prionotes they are principally responsible for the uptake of malate
Malic acid
Malic acid is an organic compound with the formula HO2CCH2CHOHCO2H. It is a dicarboxylic acid which is made by all living organisms, contributes to the pleasantly sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms , though only the L-isomer exists...
, phosphate, chloride, sodium and potassium. When soils are high in nitrate
Nitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...
s, they may also perform some nitrate reductase
Nitrate reductase
Nitrate reductases are molybdoenzymes that reduce nitrate to nitrite .* Eukaryotic nitrate reductases are part of the sulfite oxidase family of molybdoenzymes....
activities, primarily the conversion of ammonium
Ammonium
The ammonium cation is a positively charged polyatomic cation with the chemical formula NH. It is formed by the protonation of ammonia...
into amino acids such as asparagine
Asparagine
Asparagine is one of the 20 most common natural amino acids on Earth. It has carboxamide as the side-chain's functional group. It is not an essential amino acid...
and glutamine
Glutamine
Glutamine is one of the 20 amino acids encoded by the standard genetic code. It is not recognized as an essential amino acid but may become conditionally essential in certain situations, including intensive athletic training or certain gastrointestinal disorders...
.
The uptake of nutrient and water by the cluster roots peaks through winter and spring, but ceases when the upper layer of soil dries out in summer. The cluster roots are then allowed to die, but the laterals are protected from desiccation by a continuous supply of water from the sinker root. The water supplied to the laterals by the sinker root is continually lost to the soil; thus this plant facilitates the movement of ground water from the water table into surface soil, a process known as hydraulic redistribution
Hydraulic redistribution
Hydraulic redistribution refers to the mechanism by which some vascular plants redistribute soil water. It occurs in vascular plants that commonly have roots in both wet soil and extremely dry soil, especially plants with both taproots that grow vertically down to the water table, and lateral roots...
. Cluster roots have been estimated as comprising about 30% of total root biomass in this species; the seasonal production of so much biomass
Biomass
Biomass, as a renewable energy source, is biological material from living, or recently living organisms. As an energy source, biomass can either be used directly, or converted into other energy products such as biofuel....
, only for it to be lost at the end of the growing season, represents a substantial investment by the plant, but one that is critical in the competition for nutrients.
During winter, asparagine is metabolised
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
immediately, but other nutrients, especially phosphates and glutamine, are removed from the xylem sap
Plant sap
Sap is a fluid transported in xylem cells or phloem sieve tube elements of a plant. It transports water and nutrients throughout the plant....
and stored in mature stem
Plant stem
A stem is one of two main structural axes of a vascular plant. The stem is normally divided into nodes and internodes, the nodes hold buds which grow into one or more leaves, inflorescence , conifer cones, roots, other stems etc. The internodes distance one node from another...
, bark
Bark
Bark is the outermost layers of stems and roots of woody plants. Plants with bark include trees, woody vines and shrubs. Bark refers to all the tissues outside of the vascular cambium and is a nontechnical term. It overlays the wood and consists of the inner bark and the outer bark. The inner...
and leaf
Leaf
A leaf is an organ of a vascular plant, as defined in botanical terms, and in particular in plant morphology. Foliage is a mass noun that refers to leaves as a feature of plants....
tissues
Tissue (biology)
Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...
for release back into the xylem
Xylem
Xylem is one of the two types of transport tissue in vascular plants. . The word xylem is derived from the Classical Greek word ξυλον , meaning "wood"; the best-known xylem tissue is wood, though it is found throughout the plant...
just before shoot growth begins in mid summer. This is also the time when the oldest leaves senesce and die, returning nutrients to the plant at the time when they are needed most. When glutamine eventually reaches the leaves, it is broken down and used to synthesise protein
Protein
Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...
and non-amide
Amide
In chemistry, an amide is an organic compound that contains the functional group consisting of a carbonyl group linked to a nitrogen atom . The term refers both to a class of compounds and a functional group within those compounds. The term amide also refers to deprotonated form of ammonia or an...
amino acids such as aspartate, threonine
Threonine
Threonine is an α-amino acid with the chemical formula HO2CCHCHCH3. Its codons are ACU, ACA, ACC, and ACG. This essential amino acid is classified as polar...
, serine
Serine
Serine is an amino acid with the formula HO2CCHCH2OH. It is one of the proteinogenic amino acids. By virtue of the hydroxyl group, serine is classified as a polar amino acid.-Occurrence and biosynthesis:...
, glutamate, glycine
Glycine
Glycine is an organic compound with the formula NH2CH2COOH. Having a hydrogen substituent as its 'side chain', glycine is the smallest of the 20 amino acids commonly found in proteins. Its codons are GGU, GGC, GGA, GGG cf. the genetic code.Glycine is a colourless, sweet-tasting crystalline solid...
, alanine
Alanine
Alanine is an α-amino acid with the chemical formula CH3CHCOOH. The L-isomer is one of the 20 amino acids encoded by the genetic code. Its codons are GCU, GCC, GCA, and GCG. It is classified as a nonpolar amino acid...
and cystine
Cystine
Cystine is a dimeric amino acid formed by the oxidation of two cysteine residues that covalently link to make a disulfide bond. This organosulfur compound has the formula 2. It is a white solid, and melts at 247-249 °C...
. Together with sucrose
Sucrose
Sucrose is the organic compound commonly known as table sugar and sometimes called saccharose. A white, odorless, crystalline powder with a sweet taste, it is best known for its role in human nutrition. The molecule is a disaccharide composed of glucose and fructose with the molecular formula...
and other solutes
Solution
In chemistry, a solution is a homogeneous mixture composed of only one phase. In such a mixture, a solute is dissolved in another substance, known as a solvent. The solvent does the dissolving.- Types of solutions :...
, these are then circulated in the phloem
Phloem
In vascular plants, phloem is the living tissue that carries organic nutrients , in particular, glucose, a sugar, to all parts of the plant where needed. In trees, the phloem is the innermost layer of the bark, hence the name, derived from the Greek word "bark"...
. The phloem sap
Plant sap
Sap is a fluid transported in xylem cells or phloem sieve tube elements of a plant. It transports water and nutrients throughout the plant....
of B. prionotes is unusual in having an extremely low ratio of potassium to sodium cations, and very low concentrations of phosphate and amino acids compared to chloride and sulfate anions. The low levels of potassium and phosphate reflect the extremely low availability of these minerals in the soil. The unusually high levels of sodium and chloride—at concentrations usually only seen under saline conditions—may be due to the necessity of maintaining turgor pressure
Turgor pressure
Turgor Pressure or turgidity is the main pressure of the cell contents against the cell wall in plant cells and bacteria cells, determined by the water content of the vacuole, resulting from osmotic pressure, i.e...
; that is, with so little potassium and phosphate available, and that needed in the building of new tissue, B. prionotes is forced to circulate whatever other ions are available in order to maintain turgor.
Breeding system
The flowers are fed at by a range of nectarivorous
Nectarivore
In zoology, nectarivore is an animal which eats the sugar-rich nectar produced by flowering plants. Most nectarivores are insects or birds, but there are also nectarivorous mammals, notably several species of bats in the Southwestern United States and Mexico, as well as the Australian Honey Possum...
birds: mainly honeyeaters, including the New Holland Honeyeater
New Holland Honeyeater
The New Holland Honeyeater is a honeyeater species found throughout southern Australia. It was among the first birds to be scientifically described in Australia, and was initially named Certhia novaehollandiae...
(Phylidonyris novaehollandiae), White-cheeked Honeyeater
White-cheeked Honeyeater
The White-cheeked Honeyeater inhabits the east coast and the south-west corner of Australia. It has a large white patch on its cheek, a brown eye, and a yellow panel on its wing.- Description :...
(P. nigra), Brown Honeyeater
Brown Honeyeater
The Brown Honeyeater is a honeyeater, a group of birds found mainly in Australia and New Guinea which have highly developed brush-tipped tongues adapted for nectar feeding...
(Lichmera indistincta), Singing Honeyeater
Singing Honeyeater
The Singing Honeyeater, Lichenostomus virescens is a small bird found in Australia, and is part of the honeyeater family. Although it is common there, it is not very well known in other places....
(Lichenostomus virescens), Tawny-crowned Honeyeater
Tawny-crowned Honeyeater
The Tawny-crowned Honeyeater is a passerine bird native to eastern Australia.The Tawny-crowned Honeyeater was originally described by ornithologist John Latham in 1802 as Certhia melanops...
(Gliciphila melanops) and Red Wattlebird
Red Wattlebird
The Red Wattlebird , also known as Barkingbird or Gillbird, is a honeyeater; a group of birds found mainly in Australia and New Guinea which have highly developed brush-tipped tongues adapted for nectar feeding...
(Anthochaera carunculata). Lorikeets have also been observed feeding at the flowers, as have insects, including ants, bees, and aphid
Aphid
Aphids, also known as plant lice and in Britain and the Commonwealth as greenflies, blackflies or whiteflies, are small sap sucking insects, and members of the superfamily Aphidoidea. Aphids are among the most destructive insect pests on cultivated plants in temperate regions...
s. Of these, evidence suggests that only birds are effective pollinators. Insects apparently play no role in pollination, since inflorescences do not form follicles when birds are excluded in pollinator exclusion experiment
Pollinator exclusion experiment
Pollinator exclusion experiments are experiments used by ecologists to determine the effectiveness of putative plant pollination vectors. Essentially, certain pollinators are prevented from visiting certain flowers, and observations are then made on the which flowers develop seeds...
s; and pollination by mammals has never been recorded in this species.
Honeyeaters prefer to forage at individual flowers which have only just opened, as these offer the most nectar. As they probe for nectar, honeyeaters end up with large quantities of pollen on their beaks, foreheads and throats, some of which they subsequently transfer to other flowers. This transfer is quite efficient: flowers typically lose nearly all their pollen within four hours of opening, and pollen is deposited on the majority of stigmata. Around 15% of these stigmata end up with pollen lodged in the stigmatic groove, a prerequisite to fertilisation.
The structure of the Banksia flower, with the style end functioning as a pollen presenter, suggests that autogamous self-fertilisation must be common. In many Banksia species, the risk of this occurring is reduced by protandry
Dichogamy
Sequential hermaphroditism is a type of hermaphroditism that occurs in many fish, gastropods and plants. Here, the individual is born one sex and changes sex at some point in their life. They can change from a male to female , or from female to male...
: a delay in a flower's receptivity to pollen until after its own pollen has lost its viability. There is dispute, however, over whether this occurs in B. prionotes: one study claimed to have confirmed "protandrous development", yet recorded high levels of stigmatic receptivity immediately after anthesis
Anthesis
Anthesis is the period during which a flower is fully open and functional. It may also refer to the onset of that period.The onset of anthesis is spectacular in some species. In Banksia species, for example, anthesis involves the extension of the style far beyond the upper perianth parts...
, and long pollen viability, observations that are not consistent with protandry.
If it does occur, protandry does nothing to prevent geitonogamous
Geitonogamy
Geitonogamy is the pollination of a flower with the pollen from another flower on the same flowering plant. In animal pollinated systems this is accomplished by a pollinator visiting multiple flowers on the same plant...
self-pollination: that is, pollination with pollen from another flower on the same plant. In fact, when birds forage at B. prionotes, only about a quarter of all movements from inflorescence to inflorescence involve a change of plant. Geitonogamous self-pollination must therefore occur more often in this species than cross-pollination. This does not imply high rates of self-fertilisation, however, as the species appears highly self-incompatible: although pollen grains will germinate on flowers of the self plant, they apparently fail to produce pollen tubes that penetrate the style. Even where cross-pollination does occur, fertilisation rate is fairly low. It is speculated that this is related to "a variety of chemical reactions at the pollen-stigma interface".
Cone production varies a great deal from year to year, but, as a result of its low flowering rate, is generally very low. However there are typically a very high number of follicles per cone, leading to relatively high seed counts. There is some seed predation, primarily from the curculionid
Curculionidae
Curculionidae is the family of the "true" weevils . It was formerly recognized in 1998 as the largest of any animal family, with over 40,000 species described worldwide at that time...
weevil
Weevil
A weevil is any beetle from the Curculionoidea superfamily. They are usually small, less than , and herbivorous. There are over 60,000 species in several families, mostly in the family Curculionidae...
Cechides amoenus
Cechides amoenus
Cechides amoenus is a species of curculionid weevil, native to Western Australia.It is the main seed predator of Banksia prionotes....
.
Response to fire
Canopy seed bank
A canopy seed bank or aerial seed bank is the aggregate of viable seed stored by a plant in its canopy. Canopy seed banks occur in plants that postpone seed release for some reason....
, thus promoting recruitment of the next generation; resprouter
Resprouter
Resprouters are plant species that are able to survive fire by the activation of dormant vegetative buds to produce regrowth.Plants may resprout by means of lignotubers at the base or epicormic buds on the trunk or major branches....
s survive fire, resprouting from a lignotuber
Lignotuber
A lignotuber is a starchy swelling of the root crown possessed by some plants as a protection against destruction of the plant stem by fire. The crown contains buds from which new stems may sprout, and a sufficient store of nutrients to support a period of growth in the absence of...
or, more rarely, epicormic buds
Epicormic shoot
An epicormic shoot is a shoot growing from an epicormic bud which lies underneath the bark of a trunk, stem, or branch of a plant.-Epicormic buds:...
protected by thick bark. B. prionotes is unusual in that it does not fit neatly into either of these groups. It lacks a lignotuber or thick bark, and so cannot be considered a resprouter; yet it may survive or escape some fires because of its height, the sparseness of its foliage, and because it occurs in dune swales where fire are cooler and patchier. On the other hand, it is not a typical reseeder either, because of its relatively low fire mortality rates, and because it is only weakly serotinous
Serotiny
Serotiny is an ecological adaptation exhibited by some seed plants, in which seed release occurs in response to an environmental trigger, rather than spontaneously at seed maturation. The most common and best studied trigger is fire, and the term serotiny is often used to refer to this specific case...
: although fire promotes seed release, seed release still occurs in the absence of fire.
The actual degree of serotiny and fire mortality in B. prionotes varies with latitude, or, more likely, climate. Observations suggest that it is always killed by fire in the north of its range, which is relatively hot and dry, and where individual plants are usually smaller, but may survive fire in the cooler, moister, south. Moreover, it is essentially non-serotinous in the south, since all seed is released by the end of the second year, but seed retention increases steadily to the north, and at the northern end of its range, it typically takes around four years for a plant to release half of its seed in the absence of bushfire, with some seed retained for up to 12 years.
A number of other characteristics of B. prionotes can be understood as secondary responses to weak serotiny. For example, winter flowering ensures that seed is ripe by the beginning of the bushfire season; this is very important for weakly serotinous species, which rely heavily upon the current year's seed crop. Another example is the deciduous florets of B. prionotes. In strongly serotinous species, the old florets are retained on the cones, where they function as fire fuel, helping to ensure that follicles reach temperatures sufficient to trigger seed release. In B. prionotes, however, seed release is triggered at relatively low temperatures: in one study, 50% of follicles opened at 265 °C (510 °F), and 90% opened at 330 °C (625 °F); in contrast, the closely related but strongly serotinous B. hookeriana required 340 °C (645 °F) and 500 °C (930 °F) respectively. Floret retention would therefore be to no advantage, and might even prevent seed from escaping spontaneously opened follicles.
Seed release in B. prionotes is promoted by repeated wetting of the cones. The seed separator
Seed separator
A seed separator is a structure found in the follicles of some Proteaceae. These follicles typically contain two seeds, with a seed separator between them...
that holds the seeds in place is hygroscopic; its two wings pull together then wet, then spread and curl inwards as it dries out again. In doing so, it functions as a lever, gradually prying seeds out of a follicle over the course of a wet-dry cycle. This adaptation ensures that seed release following fire is delayed until the onset of rain, when germination and seedling survival rates are higher.
Because of its higher susceptibility and lower reliance on fire for reproduction, the optimal fire interval for B. prionotes is higher than for other Banksia species with which it occurs. One simulation suggested an interval of 18 years was optimal for B. prionotes, compared to 15 years for B. hookeriana and 11 years for B. attenuata. The same model suggested that B. prionotes is quite susceptible to reductions in fire intervals. On the other hand, it shows little susceptibility to increases in fire interval: although senescence and death are often observed in plants older than about 30 years, healthy stands have been observed that have escaped fire for 50 years. These stands have a multi-aged structure, demonstrating the occurrence of successful inter-fire recruitment.
Fire response may also furnish an explanation for the evolution
Evolution
Evolution is any change across successive generations in the heritable characteristics of biological populations. Evolutionary processes give rise to diversity at every level of biological organisation, including species, individual organisms and molecules such as DNA and proteins.Life on Earth...
of this species. The differences in fire regime between dune crests and swales would have created different evolutionary pressures, with plants on crests adapting to frequent hot fires by becoming strongly serotinous, and plants in swales adapting to patchier, cooler fires with weaker serotiny. Speciation would be made possible by the much reduced genetic exchange between crest plants and swale plants, although evidence suggests that there was some introgression
Introgression
Introgression, also known as introgressive hybridization, in genetics is the movement of a gene from one species into the gene pool of another by the repeated backcrossing of an interspecific hybrid with one of its parent species...
at first. Eventually, however, the need for weakly serotinous plants to produce ripe seed by the bushfire season would have brought forward its flowering season until the flowering seasons no longer overlapped; thus a phenological barrier to exchange was erected, allowing the two populations to drift
Genetic drift
Genetic drift or allelic drift is the change in the frequency of a gene variant in a population due to random sampling.The alleles in the offspring are a sample of those in the parents, and chance has a role in determining whether a given individual survives and reproduces...
independently of each other.
Conservation
Banksia prionotes is susceptibleVulnerability and susceptibility in conservation biology
In conservation biology, susceptibility is the extent to which an organism or ecological community would suffer from a threatening process or factor if exposed, without regard to the likelihood of exposure...
to a number of threatening processes. It is highly susceptible to Phytophthora cinnamomi
Phytophthora cinnamomi
Phytophthora cinnamomi is a soil-borne water mould that produces an infection which causes a condition in plants called root rot or dieback. The plant pathogen is one of the world's most invasive species and is present in over 70 countries from around the world.- Life cycle and effects on plants :P...
dieback; wild populations are harvested commercially by the cut flower industry
Floriculture
Floriculture, or flower farming, is a discipline of horticulture concerned with the cultivation of flowering and ornamental plants for gardens and for floristry, comprising the floral industry...
; and some of its range is subject to land clearing for urban or agricultural purposes. An assessment of the potential impact of climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...
on this species found that severe change is likely to lead to a reduction in its range of around 50% by 2080; and even mild change is projected to cause a reduction of 30%; but under mid-severity scenarios the distribution may actually grow, depending on how effectively it can migrate into newly habitable areas. However, this study does not address the potential of climate change to alter fire regime
Fire regime
A fire regime is the pattern, frequency and intensity of the bushfires and wildfires that prevails in an area. It is an integral part of fire ecology, and renewal for certain types of ecosystems. If fires are too frequent, plants may be killed before they have matured, or before they have set...
s; these have already been impacted by the arrival of humans, and this change is thought to have led to a decline in the abundance and range of B. prionotes.
The species as a whole is not considered particularly vulnerable
Vulnerability and susceptibility in conservation biology
In conservation biology, susceptibility is the extent to which an organism or ecological community would suffer from a threatening process or factor if exposed, without regard to the likelihood of exposure...
to these factors, however, as it is so widely distributed and common. Western Australia's Department of Environment and Conservation does not consider it to be rare, and has not included it on their Declared Rare and Priority Flora List. It nonetheless has high conservation importance in at least one context: it is a keystone mutualist in the Avon Wheatbelt
Avon Wheatbelt
Avon Wheatbelt is an Interim Biogeographic Regionalisation for Australia region in Western Australia and part of the larger Southwest Australia savanna ecoregion.-Further reading:...
, where it is the only source of nectar during a critical period of the year when no other nectar-producing plant is in flower. The loss of B. prionotes from the region would therefore mean the loss of all the honeyeaters as well, and this would affect the many other species of plants that rely on honeyeaters for pollination. The primary vegetation community in which Banksia prionotes occurs in the Avon Wheatbelt is considered a priority ecological community, and is proposed for formal gazetting as a threatened ecological community
Threatened ecological community
Threatened ecological community is a term used in Australia for ecosystems that are in danger of being lost due to some threatening process. Federally, threatened ecological communities are identified and protected under the Environment Protection and Biodiversity Conservation Act 1999. Some states...
under the name "Banksia prionotes and Xylomelum angustifolium
Xylomelum angustifolium
Xylomelum angustifolium is a tree species in the family Proteaceae, endemic to Western Australia. A mature Xylomelum angustifolium grows from 2 to 7 metres though trees up to 10m have been observed. Produces cream flowers between December and February though flowering can commence as early as...
low woodlands on transported yellow sand". Although currently in near-pristine and static condition, it is considered at risk due to a large number of threatening processes, including land clearing, landscape fragmentation, rising soil salinity
Salinity in Australia
Soil salinity and dryland salinity are two problems degrading the environment of Australia. Salinity is a concern in most states, but especially in the south-west of Western Australia....
, grazing pressure
Grazing pressure
Grazing pressure is the stress on plant populations due to the grazing of animals. Plants may be lost either directly as a result of animals grazing upon them, or indirectly as a result of damage to the vegetation or ecosystem by animals moving through the area...
, competition with weeds, changes to the fire regime, rubbish dumping, and P. cinnamomi dieback.
Cultivation
It is fairly easy to grow in areas with a Mediterranean climate
Mediterranean climate
A Mediterranean climate is the climate typical of most of the lands in the Mediterranean Basin, and is a particular variety of subtropical 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. Seeds do not require any treatment prior to sowing
Sowing
Sowing is the process of planting seeds.-Plants which are usually sown:Among the major field crops, oats, wheat, and rye are sowed, grasses and legumes are seeded, and maize and soybeans are planted...
, and take 21 to 35 days to germinate.
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. As such it is one of the most popular banksias for cut flower production, with commercial crops grown in Israel
Israel
The State of Israel is a parliamentary republic located in the Middle East, along the eastern shore of the Mediterranean Sea...
, Victoria
Victoria (Australia)
Victoria is the second most populous state in Australia. Geographically the smallest mainland state, Victoria is bordered by New South Wales, South Australia, and Tasmania on Boundary Islet to the north, west and south respectively....
, South Australia
South Australia
South Australia is a state of Australia in the southern central part of the country. It covers some of the most arid parts of the continent; with a total land area of , it is the fourth largest of Australia's six states and two territories.South Australia shares borders with all of the mainland...
and Hawaii
Hawaii
Hawaii is the newest of the 50 U.S. states , and is the only U.S. state made up entirely of islands. It is the northernmost island group in Polynesia, occupying most of an archipelago in the central Pacific Ocean, southwest of the continental United States, southeast of Japan, and northeast of...
.