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- Title
Importance of birds versus insects as pollinators of the African shrub Syncolostemon densiflorus (Lamiaceae).
- Authors
WESTER, PETRA; JOHNSON, STEVEN D.
- Abstract
Flowers visited by a broad assemblage of animals may nevertheless be considered to have a specialized pollination system if pollen deposition is effected mainly by a subset of these visitors. The importance of a particular animal group for pollination derives mainly from the relative rate of floral visitation and per-visit effectiveness for pollen deposition. We assessed the relative importance of birds and insects for pollination of the African shrub Syncolostemon densiflorus (Lamiaceae). Flower visitors were observed to evaluate their visitation rates. Virgin flowers were exposed to single visits by nine animal visitor groups to evaluate their effectiveness at depositing pollen on stigmas. We selectively excluded birds and larger insects from flowers to assess the contribution of smaller visitors to pollen deposition and seed set. Sunbirds and insects visited flowers at a similar frequency, but on a per-visit basis, sunbirds deposited more pollen on stigmas than did any of the insect groups, including honeybees, long-proboscid flies, butterflies and day-flying hawkmoths. Selective exclusion of birds and larger insects resulted in a large decline in pollen deposition on stigmas and seed production. These results show that S. densiflorus is pollinated mainly by sunbirds, despite its attraction of a broad assemblage of insect flower visitors. These findings highlight the importance of per-visit pollination effectiveness and selective exclusion for understanding the ecological importance of different flower visitors.
- Subjects
LAMIACEAE; POLLINATORS; POLLINATION by birds; POLLINATION by insects; PLANT reproduction
- Publication
Botanical Journal of the Linnean Society, 2017, Vol 185, Issue 2, p225
- ISSN
0024-4074
- Publication type
Article
- DOI
10.1093/botlinnean/box054