Sunbird-pollination in the geoflorous species Hyobanche sanguinea (Orobanchaceae) and Lachenalia luteola (Hyacinthaceae)

Abstract

Sunbird-pollinated plants display a suite of floral adaptations, for example, red tubular flowers, significant volumes of dilute nectar, or a suitable perch from which to forage flowers. In this study we show that two sunbird species were important for seed-set in low-growing, perchless plants of Hyobanche sanguinea and Lachenalia luteola on Kommetjie Slangkop, southern Cape Peninsula, South Africa. Remote video camera footage and field observations showed that malachite sunbirds (Nectarinia famosa) and orange-breasted sunbirds (Anthobaphes violacea) perched on the ground while visiting flowers of both plant species. Open inflorescences of both species yielded significantly higher seed-set than excluded inflorescences, which showed zero to near zero seed-set. Inflorescences shown on video to have been visited by sunbirds showed significantly higher seed-set than those for which video footage was not obtained, suggesting sunbirds are effective pollinators. Besides being the first documented pollinator information on these two species, our results expand upon the known traits associated with sunbird-pollination systems and suggest that low-growing sunbird-pollinated plants need not evolve perching structures in order to achieve effective visitation.