Broadway Arboretum

Species Information Page

Banksia elegans Elegant Banksia

   
 

Location in Arboretum: Northern Sandplains
No on Map: NS01

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  • Banksia elegans is a Priority 4 plant, which means it is a species that is considered to have been adequately surveyed and which, whilst being rare (in Australia), is not currently threatened by any identifiable factors. These species require monitoring every 5–10 years. 
  • Banksia elegans occurs only over a 65 square kilometre area north and west of Eneabba (1).
  • A study undertaken at a site near Lake Indoon found that Banksia elegans produces few fruits, and these only release their seeds in response to fire, depending on the temperatures reached by the follicles and subsequent number of wet-dry cycles. While 50% of intact seeds germinate in the laboratory, no seedlings were observed in the field. Despite the death of some old plants after a fire in a 15-year-old stand, population size increased by more than 300% over the following three years, entirely due to suckering from the parent lateral roots. Flowering of parent plants recommenced three years after the fire, with most of the new suckers remaining juvenile longer (2).
  • A study that aimed to quantify all possible constraints on seed and fruit availability in Banksia elegans found:
    (a) over 90% of post-fire resprouts and root suckers in the study population did not produce any seeds during the ensuing sixteen years.
    (b) All ramets (i.e. new plants produced by suckering which are genetically the same as the parent plant) flowered profusely in their sixteenth year. Damage to reproductive parts by insects' larvae and granivorous birds was negligible.
    (c) Banksia elegans appears to be essentially outbreeding (i.e. mating primarily between unrelated or distantly related individuals of a species).The efficiency of pollinators, mainly nectarivorous birds, was hampered by lack of anther dehiscence (i.e. the anthers did not explode and spray their pollen on the bird as occurs with most species) in the sterile plants.
    (d) Most flowers received no germinable pollen and almost all fertilized ovules did not develop further.
    (e) Shortage of mineral nutrients, especially nitrogen and phosphorus, appeared to account for the variations in follicle production and high level of seed abortion.
    (f) Viability of intact seed was very low. Only 0.0002% of ovules in the current crop contributed to the viable seed bank one year after fertilisation. Root suckering appears to function as a nutrient-conserving alternative to sexual reproduction in this species (3)
  • Low seed-set in Banksia elegans has been shown to be due to internal plant factors, suggesting that it's sterility is adaptive (Lamont & Barrett, 1988)
  • Banksia elegans possesses a malformed stigma which may prevent the normal reproductive process from taking place. Most populations of Banksia elegans are sterile (4).