Effects of nectar theft by flower mites on hummingbird behavior and the reproductive success of their host plant,Moussonia deppeana(Gesneriaceae)

Abstract

Hummingbird flower mites are transported in the nares of hummingbirds and may compete with them by “robbing” nectar secreted by the host plants. We have shown thatTropicoseiussp. flower mites consume almost half the nectar secreted by the long‐lived, protandrous flowers ofMoussonia deppeana(Gesneriaceae) pollinated byLampornis amethystinus(Trochilidae). In this paper, we ask whether mimicking nectar consumption of flower mites alters some aspects of hummingbird foraging patterns, and, if so, how this affects host plant seed production. We observed hummingbirds foraging on (a) plants in which nectar was removed from the flowers and then filled with a sugar solution to half the volume of nectar simulating nectar consumption by flower mites, and (b) plants where nectar was removed and then filled with the sugar solution up to normal nectar volumes. Flower mites were excluded from both groups of plants to control for mite activity. Hummingbirds made fewer but longer visits to plants and revisited more the flowers with nectar removal than those without the treatment. We then conducted a pollination experiment on pistillate flowers using a stuffedL. amethystinushummingbird to evaluate the effect of pollination intensity (number of bill insertions into one flower) on seed production. Flowers with more insertions produced significantly more seeds than those flowers that received fewer insertions. We conclude that the simulation of nectar consumption by hummingbird flower mites can influence the behavior of the pollinator, and this may positively affect seed production.