Mobility of Impatiens capensis flowers: effect on pollen deposition and hummingbird foraging
- 122 Downloads
Flexible pedicels are characteristic of birdpollinated plants, yet have received little attention in studies of hummingbird-flower interactions. A major implication of flexible pedicels is that flowers may move during pollination. We examined whether such motion affected interactions between ruby-throated hummingbirds (Archilochus colubris) and jewelweed (Impatiens capensis) by increasing pollen deposition and by altering the effectiveness of nectar removal. For I. capensis, flower mobility enhanced pollen deposition: birds had significantly longer contact with anthers and more pollen deposited on their bills and crowns when foraging at mobile flowers than at flowers that had been experimentally immobilized. In contrast, flower mobility imposed a cost on hummingbirds by significantly increasing their handling times and reducing their extraction rates relative to their interactions with immobile flowers. Field observations indicated that the motion observed during hummingbird visits did not occur when bees (Bombus spp., Apis mellifera) visited I. capensis flowers, which suggests that the mobility of I. capensis flowers is an adaptation for hummingbird pollination.
Key wordsPollination Archilochus colubris Impatiens capensis Hummingbird Flower morphology
Unable to display preview. Download preview PDF.
- Baker HG (1961) The adaptation of flowering plants to nocturnal and crepuscular pollinators. Q Rev Biol 36: 64–73Google Scholar
- Bertin RI (1982) The ruby-throated hummingbird and its major food plants: ranges, flowering phenology, and migration. Can J Zool 60: 210–219Google Scholar
- Faegri K, Pijl L van der (1971) The principles of pollination ecology. Pergamon Press, OxfordGoogle Scholar
- Gass CL, Montgomerie RD (1981) Hummingbird foraging behavior: decision-making and energy regulation. In: Kamil AC, Sargent TD (eds) Foraging behavior: ecological, ethological and psychological approaches. Garland Press, New York, pp 159–194Google Scholar
- Gass CL, Sutherland GD (1985) Specialization by territorial hummingbirds on experimentally enriched patches of flowers: energetic profitability and learning. Can J Zool 63: 2125–2133Google Scholar
- Grant KA, Grant V (1968) Hummingbirds and their flowers. Columbia University Press, New YorkGoogle Scholar
- Laverty TM, Plowright RC (1985) Competition between hummingbirds and bumble bees for nectar in flowers of Impatiens biflora. Oecologia 66: 25–32Google Scholar
- Pulliam HR (1974) On the theory of optimal diets. Am Nat 108: 59–74Google Scholar
- Rust RW (1979) Pollination of Impatiens capensis: pollinators and nectar robbers. J Kans Entomol Soc 52: 297–308Google Scholar
- Snow DW, Snow BK (1980) Relationships between hummingbirds and flowers in the Andes of Columbia. Bull Br Mus Nat Hist (Zool) 38: 105–139Google Scholar
- Stebbins GL (1989) Adaptive shifts towards hummingbird pollination. In: Bock JH, Linhart YB (eds) The evolutionary ecology of plants. Westview Press, Boulder, pp 39–60Google Scholar