Rodent pollination in the African lily Massonia depressa (Hyacinthaceae)

Field studies in the semiarid Succulent Karoo region of South Africa showed that flowers of Massonia depressa (Hyacinthaceae) are visited at night by at least four rodent species. including two gerbil species. Live-trapped ro dents were found to carry Massonia pollen on their snouts: they also had la rge quantities of Massonia pollen in their feces as a result of grooming th eir fur. Visits by insects to the flowers were infrequent at one site and a pparently absent at another site. Plants enclosed in large-mesh wire cages, which excluded rodents but not insects, set very few seeds relative to ope n controls. Our initial hypothesis of rodent-pollination in M. depressa was based on the striking similarity of its flowers to those of unrelated. rod ent-pollinated Protea species. Convergent traits include dull-colored and v ery robust flowers situated at ground level, a strong yeasty odor, and secr etion of copious amounts of sucrose-dominant nectar during the evening when rodents are active. Despite having a low sugar concentration (similar to 2 0%), the nectar of M. depressa is almost 400 times as viscous as an equival ent sugar solution. The jelly-like constituent in the nectar may discourage robbing by insects, while also facilitating lapping by rodents. Our findin gs illustrate the utility of floral syndromes for generating testable predi ctions about pollination systems.