monographs. The placement of B. petiolaris in George's 1999 arrangement may be summarised as follows: Banksia B. subg. Banksia B. sect. Banksia B. ser. Salicinae (11 species, 7 subspecies) B. ser. Grandes (2 species) B. ser. Banksia (8 species) B. ser. Crocinae (4 species) B. ser. Prostratae B. goodii B. gardneri B. gardneri var. gardneri B. gardneri var. brevidentata B. gardneri var. hiemalis B. chamaephyton B. repens B. blechnifolia B. petiolaris B. ser. Cyrtostylis (13 species) B. ser. Tetragonae (3 species) B. ser. Bauerinae (1 species) B. ser. Quercinae (2 species) B. sect. Coccinea (1 species) B. sect. Oncostylis (4 series, 22 species, 4 subspecies, 11 varieties) B. subg. Isostylis (3 species) 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. petiolaris, Mast's results have some semblance to George and Thiele's. It is somewhat basal in a group with the other prostrate species as well as species in series Tetragonae, and B. elderiana, B. baueri, and B. lullfitzii. However, B. repens, B. chamaephyton and B. blechnifolia form a closely knit group within this group, and the overall 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 cotyledons; 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. petiolaris is placed in subgenus Banksia. In a 2013 cladistics study, evolutionary scientists Marcell Cardillo and Renae Pratt found that its closest relative is B. brevidentata. Distribution and habitat Endemic to Western Australia, Banksia petiolaris is found near the state's south coast from the vicinity of Munglinup east to Israelite Bay, concentrated in two disjunct ranges—an eastern one around Cape Arid National Park, and western one east of Scaddan. It is found in white sandy soils in kwongan or mallee heathland, but sometimes occurs with the taller B. speciosa. It is often locally common, with many populations over 100 plants in size. Ecology Like many plants in Australia's Southwest, Banksia petiolaris is adapted to an environment in which bushfire events are relatively frequent. Most Banksia species can be placed in one of two broad groups