Dryandra

Dryandra nivea, from Wikimedia.

Belongs within: Banksia.

Dryandra has been recognised as a genus of shrubs and small trees found in south-western Western Australia. Recent revisions have suggested its synonymisation with the related genus Banksia, from which it was previously distinguished by having flat rather than conical inflorescences.

The Fall of Dryandra
Published 25 November 2010
Banksia nivea, previously Dryandra nivea, from here.

Adam Yates has requested that I do a post on the relationship between Banksia and Dryandra, two Australian genera (but read on) of the plant family Proteaceae. Banksia has a generally coastal distribution around Australia, but is conspicuously absent through the Nullarbor region and northern Western Australia (i.e. where the coast is driest). Dryandra is restricted to the south-west corner of Australia. A close relationship between the two genera has long been accepted, supported as it is by features including the bearing of flowers in compact inflorescences (cone-shaped in Banksia, capitate in Dryandra) and production of seeds with a hard bony endocarp. These seeds are contained in bivalved woody follicles, only a relatively small number of which develop to maturity in any given inflorescence. In most cases, the follicles do not open at maturity but remain closed until heated by the passage of a bushfire; only after the fire do they open to release their seeds. The appearance of remnant Banksia cones with the protruding follicles resembling eyes or gaping mouths has long affected Australian folklore, with the most familiar example being May Gibbs’ ‘bad banksia men’.

The banksia men, villainous characters from May Gibbs’ Snugglepot and Cuddlepie books, in their natural habitat.

However, recent years have seen the species of Banksia involved in a greater controversy than the mere kidnapping of gumnut babies: the kidnapping of an entire genus. Molecular studies have shown that Dryandra is phylogenetically nested within Banksia, rendering Banksia in its familiar sense paraphyletic (Mast & Givnish 2002; Mast et al. 2005). This has lead to the formal synonymisation of the two genera by Mast & Thiele (2007), an action that has incited its fair share of grumbling among Australian botanists and horticulturalists. However, the alternative—dividing Banksia into multiple genera—would have required establishment of a number of new genera as the type species, Banksia serrata, is among the closer relatives of Dryandra. Also, these new genera would probably not have been easily distinguishable morphologically.

Banksia gardneri, showing both new and persistent cones, photographed by Brian Walters.

Though initially incited by molecular studies, the paraphyly of Banksia excluding Dryandra is also supported by morphological factors. Mast & Givnish (2002) supported a division of Banksia into two clades which Mast & Thiele (2007) recognised as the subgenera Banksia (including Dryandra) and Spathulatae. Members of Banksia subgenus Banksia have beaked follicles while the follicles of Banksia subgenus Spathulatae are unbeaked. Also, most members of subgenus Banksia have the stomata on their leaves recessed into deep pits, though this feature has appeared apparently independently in one small subclade of subgenus Spathulatae (most of which have more superficial stomata). The sinking of the stomata into pits (an adaptation for living in arid environments) is also supported as a derived feature by the fossil record of Banksia sensu lato, the earliest known representatives of which in the Late Palaeocene lack such arid adaptations (arid-adapted banksiines are not known until the Late Eocene).

Images of Banksia ilicifolia, a short-coned potential relative of Dryandra from south-western Australia. Photos by T. J. Alford & C. Hortin.

Within Banksia subgenus Banksia, the clade now known as Banksia series Dryandra falls within a clade also containing other south-west Australian species of what have previously been regarded as ‘series Banksia‘ and ‘subgenus Isostylis‘. The latter are interesting in this regard as having particularly short cones, and had been compared to Dryandra even when the two were regarded as separate genera. But while the short-coned banksias are close to series Dryandra, they do not necessarily form an exclusive clade with them, so it is uncertain whether their short cones represent a transition between the normal Banksia cone and the capitate Dryandra inflorescence, or whether they have shortened convergently.

Systematics of Dryandra

Characters (from A. S. George): Shrubs or small trees, many prostrate. Leaves serrate to pinnatifid or pinnatipartite, sometimes almost pinnatisect, sometimes bipinnatifid, sometimes entire, hairy becoming glabrous adaxially, closely tomentose or woolly between nerves abaxially. Inflorescence terminal, axillary or on short lateral branchlet, commonly sessile, capitate; receptacle concave, flat or convex; involucre usually prominent, of many imbricate flat or subulate bracts, persistent; flowering usually centripetal; flowers 15–250 per head; floral bracts usually enlarged after flowering. Perianth straight or curved; tepals separating almost to base at anthesis. Pistil straight or curved, with style often exserted to one side before anthesis; pollen presenter usually erect, narrower, as wide as or wider than style. Follicles few per head, woody but not massively so, commonly striate, in 2 species cartilaginous. Seed usually with a terminal wing, rarely elliptic with an annular wing and then without a separator but with 2 supplementary outer wings.

<==Dryandra
    |--D. subg. DryandraMJH05
    |    |--D. sessilisMJH05
    |    |    |--D. s. var. sessilisMJH05
    |    |    `--D. s. var. cygnorumMJH05
    |    `--+--D. calophyllaMJH05
    |       |--D. serratuloidesMJH05
    |       |    |--D. s. ssp. serratuloidesMJH05
    |       |    `--D. s. ssp. perissaMJH05
    |       |--D. speciosaMJH05
    |       `--+--*D. formosaMJH05
    |          `--D. foliosissimaMJH05
    |--D. (subg. Diplophragma) bipinnatifidaMJH05
    `--D. (subg. Hemiclidia) falcataMJH05
Dryandra incertae sedis:
  D. arboreaG04a
  D. armataOS04
  D. carduaceaRL05
  D. cirsioidesC70
  D. erythrocephalaG04b
  D. ferrugineaG04b
    |--D. f. ssp. ferrugineaG04b
    `--D. f. ssp. flavescensG04b
  D. floribundaS35
  D. fraseriOS04
  D. lewardianaC70
  D. lindleyanaJK08
    |--D. l. ssp. lindleyanaOS04
    `--D. l. ssp. sylvestrisOS04
  D. niveaS35
  D. nobilisOS04
  D. pallidaG04b
  D. porrectaGK00
  D. praeformosa Ettingshausen 1886F71
  D. praemorsaJK08
  D. purdieanaG04b
  D. rufistylisOS04
  D. squarrosaJK08
  D. viscidaG04b

*Type species of generic name indicated

References

[C70] Common, I. F. B. 1970. Lepidoptera (moths and butterflies). In: CSIRO. The Insects of Australia: A textbook for students and research workers pp. 765–866. Melbourne University Press.

[F71] Fletcher, H. O. 1971. Catalogue of type specimens of fossils in the Australian Museum, Sydney. Australian Museum Memoir 13: 1–167.

[G04a] Gibson, N. 2004a. Flora and vegetation of the Eastern Goldfields Ranges: part 6. Mt Manning Range. Journal of the Royal Society of Western Australia 87 (2): 35–47.

[G04b] Gibson, N. 2004b. Flora and vegetation of the Eastern Goldfields Ranges: part 7. Middle and South Ironcap, Digger Rock and Hatter Hill. Journal of the Royal Society of Western Australia 87 (2): 49–62.

[GK00] Gibson, N., & G. J. Keighery. 2000. Flora and vegetation of the Byenup-Muir reserve system, south-west Western Australia. CALMScience 3 (3): 323–402.

[JK08] Johnstone, R. E., & T. Kirkby. 2008. Distribution, status, social organisation, movements and conservation of Baudin’s cockatoo (Calyptorhynchus baudinii) in south-west Western Australia. Records of the Western Australian Museum 25 (1): 107–118.

Mast, A. R., & T. J. Givnish. 2002. Historical biogeography and the origin of stomatal distributions in Banksia and Dryandra (Proteaceae) based on their cpDNA phylogeny. American Journal of Botany 89 (8): 1311–1323.

[MJH05] Mast, A. R., E. H. Jones & S. P. Havery. 2005. An assessment of old and new DNA sequence evidence for the paraphyly of Banksia with respect to Dryandra (Proteaceae). Australian Systematic Botany 18 (1): 75–88.

Mast, A. R., & K. Thiele. 2007. The transfer of Dryandra R.Br. to Banksia L.f. (Proteaceae). Australian Systematic Botany 20 (1): 63–71.

[OS04] Obbens, F. J., & L. W. Sage. 2004. Vegetation and flora of a diverse upland remnant of the Western Australian wheatbelt (Nature Reserve A21064). Journal of the Royal Society of Western Australia 87 (1): 19–28.

[RL05] Rafferty, C., & B. B. Lamont. 2005. Selective feeding by macropods on vegetation regenerating following fire. Journal of the Royal Society of Western Australia 88 (4): 155–165.

[S35] Solomon, M. E. 1935. On a new genus and two new species of Western Australian Aleyrodidae. Journal of the Royal Society of Western Australia 21: 75–91.

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