Banksia Menziesii - Ecology

Ecology

Like many members of the family Proteaceae, Banksia menziesii is largely self-incompatible; that is, inflorescences require pollinators to be fertilised and produce seed. One mechanism by which the species promotes cross-pollination with other plants is protandry, whereby the male parts release pollen which becomes non-viable before the female parts become receptive on the same flower spike. The individual flowers are uniform, and it is unclear why so few go on to develop follicles. Published in 1988, a field study conducted in banksia woodland near Perth noted that anthesis occurred on an inflorescence at an average rate of 40 to 60 florets opening per day, although this varied widely between different flowerheads. Foraging by honeyeaters would cause the florets to open, but bees would not.

Banksia menziesii provides an important food source, as flowers and seeds, for the threatened Short-billed Black Cockatoo (Calyptorhynchus latirostris). Other bird species that have been observed feeding on B. menziesii include the Red-capped Parrot (Purpureicephalus spurius), Western Rosella (Platycercus icterotis), Red-tailed Black Cockatoo (Calyptorhynchus banksii), Australian Ringneck (Barnardius zonarius), Western Gerygone (Gerygone fusca) and several honeyeater species, the New Holland Honeyeater (Phylidonyris novaehollandiae), White-cheeked Honeyeater (P. nigra), Brown Honeyeater (Lichmera indistincta), Singing Honeyeater (Lichenostomus virescens), Western Spinebill (Acanthorhynchus superciliosus), Red Wattlebird (Anthochaera carunculata) and Western Wattlebird (A. lunulata). Insects recorded include ants and bees, as well as rove beetles (family Staphylinidae). A field study south of Perth noted that Banksia menziesii appeared particularly popular with the Brown Honeyeater and Western Spinebill, compared with other banksias.

Twenty-one species from several orders of slime molds (myxomycetes) have been isolated from the bark of Banksia menziesii. Over half (13) were from the order Stemonitales, and Echinosteliales and Liceales were also common. The abundance of the first two orders may be due to the acidity of the bark. Another order, the Physarales, was unusually rare—other studies have demonstrated that the order is typically abundant on the bark of various species of tree around the world.

Banksia menziesii regenerates after bushfire by resprouting from its woody lignotuber, or from epicormic buds on the trunk. It is generally only weakly serotinous in the southern part of its range, that is, it lacks a canopy seed bank as follicles on old flower spikes in the canopy release their seed after two years, but populations retain more seed as populations move north. Lower canopies and drier climates predispose to hotter fires which are more likely to kill plants and effect seed release, and thus facilitate seedling recruitment.

All banksias have developed proteoid or cluster roots in response to the nutrient poor conditions of Australian soils (particularly lacking in phosphorus). The plant develop masses of fine lateral roots which form a mat-like structure underneath the soil surface, and enable it to extract nutrients as efficiently possible out of the soil. A study of three co-occurring species in banksia woodland in southwestern Australia—Banksia menziesii, B. attenuata and B. ilicifolia—found that all three develop fresh roots in September after winter rainfall, and that the bacteria populations associated with the root systems of B. menziesii differ from the other two, and that they also change depending on the age of the roots.

Along with Banksia attenuata, Banksia menziesii is a facultative phreatophyte. The two species are less strictly tied to the water table and hence able to grow in a wider variety of places within banksia woodland habitat around Perth than the co-occurring Banksia ilicifolia and Banksia littoralis. Recent falls of the water table on the Swan Coastal Plain from use of the Gnangara Mound aquifer for Perth's water supply as well as years of below average rainfall have caused a drop in the population and vigour of Banksia menziesii since the mid-1960s. A 2009 Spanish study showed Banksia menziesii seedlings to be moderately sensitive to salinity. It is also sensitive to sulfur dioxide. A 1994 study by Byron Lamont and colleagues from Curtin University found that Banksia menziesii plants within 50 metres (150 ft) of road verges had crowns two and a half times bigger, and set three times as many seeds as plants further away from the road, and that this was likely due to increased availability of nutrients and water from runoff.