Seed set in two sympatric banksias, Banksia attenuata and B. baxteri

Abstract

Two species of banksia, studied on the south coast of Western Australia, flowered simultaneously and had floral characteristics often associated with vertebrate pollination. The pollen of both was carried by honeyeater birds and small mammals (honey possums). Despite this, differential exclusion of vertebrates and invertebrates from inflorescences indicated that Banksia attenuata set substantial quantities of seed when visited only by invertebrates, although seed set increased with the addition of vertebrate visitors. Banksia baxteri set much seed in the absence of any animal visitors and seed set increased with invertebrate, but not vertebrate, visitation. We suggest that these differences in pollination strategies reflect regeneration by B. baxteri solely from canopy seeds released after fire, whereas B. attenuata also regenerates from seeds released between fires, as well as from lignotubers and epicormic buds.