Evidence for sunbird pollination in African blood lilies: Haemanthus (Amaryllidaceae)

Abstract

Flowers arranged in ‘paintbrush’ style inflorescences have evolved in several plant families. Their nectar is often accessible to both birds and insects, meaning that observations and experiments are required in order to establish which animal group pollinates these flowers most effectively. The southern African genus Haemanthus (Amaryllidaceae) includes more than 20 species, all with paintbrush style inflorescences and flower colour that ranges from white to red. Here we examine the contributions of birds versus insects to the pollination of four Haemanthus species varying in flower colour. Direct observations and camera trapping showed that flowers of these Haemanthus species are frequently visited by sunbirds as well as by insects. Bird exclusion experiments revealed that H. coccineus (red flowers) and H. deformis (white flowers) are strongly dependent on sunbirds for pollination, whereas H. humilis subsp. hirsutus (pink flowers) is co-pollinated by insects. All Haemanthus species tested were reliant on pollinators for seed production. Bird pollination appears to be frequent in Haemanthus and is correlated more strongly with large volumes of nectar in inflorescences than it is with a particular flower colour or floral and inflorescence morphology.