Role of long nectar spurs in pollination systems

Figure – The hoverfly Rhingia mecyana with its long proboscis in the exposed nectar spur of Impatiens burtonii.

Anna Vlašánková and Eliška Padyšáková from our Department of Biodiversity and Conservation Biology and Department of Ecology, respectively, collaborated on a study of pollination system the long-spurred jewelweed Impatiens burtonii in Cameroon, West Africa. The study specifically focused on how level of nectar in its long flower spur influences spectrum and behaviour of its insect pollinators. Despite our expectations that only long-tongued pollinators could visit and efficiently pollinate the long-spurred flowers, we revealed three different pollinators with a range of tongue lengths that foraged for nectar and pollinated the plant. The visitation patterns closely correspond to the nectar availability. As nectar levels drop from full spur in morning to nearly empty in late afternoon, the main visitors swap from short-tongued hoverflies to medium-tongued honeybees and finally to long-tongued hoverflies which are all able to reach the nectar in different parts of a day. Although the most adapted long-proboscid syrphid fly is an efficient pollinator of the plant, it is fully comparable with an intermediate-proboscid honey bee which brings even slightly more pollen grains per single visit. We thus argue that in this case the long spur length serves rather for the temporal food resource partitioning to maintain a diversified pollinator assemblage. For more information on our pollination biology projects, visit webpage of the Laboratory of Community Ecology: www.insect-communities.cz.

Vlašánková A., Padyšáková E., Bartoš M., Mengual X., Janečková P., Janeček Š. (2017) The nectar spur is not only a simple specialization for long-proboscid pollinators. New Phytologist 215: 1574-1581. DOI: 10.1111/nph.14677