Avon Wheatbelt biogeographic region; while B. oligantha occurs slightly further south, in the vicinity of Wagin. Ecology Ecologically, B. subg. Isostylis is similar to other Banksias. As with other Banksia taxa, all three species have proteoid roots, roots with dense clusters of short lateral rootlets that form a mat in the soil just below the leaf litter. These roots are particularly efficient at absorbing nutrients from nutrient-poor soils, such as the phosphorus-deficient native soils of Australia. They lack a lignotuber, so shrubs are killed by bushfire; mature trees of B. ilicifolia have a limited ability to resprout from epicormic buds on the trunk. But like all Banksias they release their aerial seed bank following a bushfire. This adaptation, known as serotiny, ensures the rapid regeneration of populations killed by fire. B. cuneata and B. oligantha have been declared rare under both Western Australia's Wildlife Conservation Act 1950, and the federal Environment Protection and Biodiversity Conservation Act 1999. Threats include loss of habitat, Phytophthora cinnamomi dieback, and grazing on seedlings by feral rabbits. Cultivation None of the B. subg. Isostylis species are popular in cultivation. The two rare species are virtually unknown in cultivation. B. ilicifolia is better known, but its usefulness as an amenity plant is limited by the fact that it has very prickly leaves. References External links subg. Isostylis Eudicots of Western Australia Plant subgenera Taxa named by Robert Brown (botanist, born 1773)