Tóm tắt
Banksia includes 38 fire-killed (seeders) and 20 resprouting species, and two species with contrasting
ecotypes, in south-western Australia. There may be up to 12 seeders per 50 × 50 km grid cell in the
southern sandplains and 12 resprouters in the northern sandplains. The patterns of distribution of
species across soil type and eight climatic attributes is similar for both life forms, except that greater
numbers of resprouting species occur at higher rainfalls and where there is greater seasonal spread of
rainfall. Most seeders occur on white sands and rocky substrates, and resprouters occur on yellow sands
and the more fertile lateritic soils. Nutrient requirements for both life forms appear to be similar.
Resprouters are more widespread than seeders which suggests that resprouters show greater
environmental tolerances. The distribution of grid cells containing each life form across soil types and
eight climatic attributes is similar and any differences in climatic profile for all species in each category
are considered biologically insignificant. Both life forms in section Abietinae are well represented in
the climatically distinct southern and northern sandplains indicating no climatic preferences within the
lineage. There are no consistent trends in environmental attributes from fire-killed to resprouting
ecotypes of B. ashbyi E.G.Baker and B. violacea C.A. Gardner. Multiple-partitioning classification of
the floristic data produced 10 groups varying greatly in geography, species richness, and proportion and
endemism of each life form. The Lesueur (northern) district has four endemic seeders, six endemic
resprouters and a mean of 10 resprouters per cell. The East Eyre (southern) district has five endemic
seeders, no endemic resprouters and one resprouter per cell. Both groups have a mean growing season
of 5 months. The relative aridities and fluctuations of present and past (Quaternary and late Tertiary)
climates are invoked to explain the much higher proportion of resprouters in the northern than southern
sandplains and the absence of seeders in the most marginal cells. The absence of endemic species yet
high proportion of resprouters (73%) in the extreme south-western corner of the region might be
explained by elimination of seeders through frequent burning by Aborigines in the late Quaternary. The
increase in the proportion of fire-killed species along the south coast from 23% to 100% at the edge of
the Nullarbor Plain also requires an explanation.