Shaken vs scraped: floral presentation contributes to pollinator guild segregation in co-blooming Symphionema montanum and Isopogon anemonifolius (Proteaceae)

Sympatric populations of Symphionema montanum R.Br. and Isopogon anemonifolius (Salisb.) Knight showed overlapping flowering periods during November 2009 in the Blue Mountains (New South Wales, Australia). Symphionema montanum has porose anthers encircling the protruding style, and lacks a pollen presenter. In contrast, sessile, longitudinally dehiscent anthers of Isopogon anemonifolius deposit pollen grains on the subterminus of the style (pollen presenter). Neither species secretes nectar. The majority of foragers on Symphionema montanum were polylectic, female bees (Halictidae). Their pollen foraging resembled sonication and shaking. Polylectic, female bees (Colletidae) were dominant foragers on Isopogon anemonifolius grasping styles with their mandibles while scraping the pollen presenter. Exoneura species (Apidae) visited both shrubs. Only two specimens of Callomelitta antipodes on Isopogon anemonifolius carried pollen of both shrub species. Most bees, collected on either shrub, carried the grains of their host mixed with one to six pollen morphotypes of co-blooming, nectariferous taxa. We report a positive correlation between an increase in bee size and the number of morphotypes carried but colletids of Isopogon anemonifolius carried fewer morphotypes than halictids on Symphionema montanum.