Does pollination by non-flying mammals contribute substantially to fruit set of Banksia (Proteaceae)? A test in four species with contrasting floral traits

Pollination by non-flying mammals (NFMs) is thought to be associated with cryptic, dull coloured, strongly scented flowers. In Western Australia, various Banksia species exhibit these traits, suggesting adaptation to primary pollination by NFMs, particularly the marsupial honey possum (Tarsipes rostratus). Here, we compare floral visitation rates and assess contribution to fruit set of NFMs and other pollinators in four species of Banksia with contrasting floral traits. Camera trap-based surveys revealed that honeyeater birds visited all species equally and were more frequent visitors than NFMs to the brightly coloured, unscented flowers of B. sessilis and B. splendida. By contrast, NFMs were more frequent visitors of the cryptic, strongly scented flowers of B. shuttleworthiana and B. subulata. Selective pollinator exclusion experiments showed that NFMs, birds, and insects contributed to pollination of all four species but indicated primary pollination by NFMs in B. subulata. Surprisingly, the most frequent visitors of this species were mice, not marsupials, providing the first compelling evidence of primary pollination by rodents in Australia. Notably, honey possums contributed substantially to fruit set of B. sessilis and B. splendida, despite infrequent visitation to these species. These findings challenge the assumption that in Banksia floral crypsis and strong scents are adaptations to primary pollination by honey possums. Instead, they suggest a spectrum of bird-NFM pollination systems, with rodents as key pollinators of some species.