Plant Systematics and Evolution

, Volume 275, Issue 3–4, pp 257–264 | Cite as

Floral traits, pollinators and breeding systems in Syncolostemon (Lamiaceae)

Original Article
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Abstract

Differentiation in floral traits among clusters of related species may reflect a process of pollinator-driven evolution. Pollination systems in the morphologically diverse southern African genus Syncolostemon (Lamiaceae) were investigated by means of field observations of floral visitors and analysis of their pollen loads. Among the five study species, those with short corolla tubes (S. parviflorus, S. ramulosus) were pollinated solely by bees, while those with long corolla tubes were pollinated by a broader array of visitors, primarily long-proboscid flies in S. rotundifolius and S. macranthus and sunbirds in S. densiflorus. The predominately insect-pollinated taxa have lax inflorescences, but S. densiflorus has a compact terminal inflorescence, which facilitates feeding by sunbirds from a single perching position. Experimental hand-pollinations involving three taxa (S. macranthus, S. densiflorus, and S. rotundifolius) showed that these possess a genetic self-incompatibility system. Production of fruits and seeds per fruit was pollen-limited in S. densiflorus and S. rotundifolius, but not in S. macranthus.

Keywords

Long-proboscid fly Nectar Pollen-limitation Pollination Pollination syndrome Pollinator effectiveness Specialization Sunbird 
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Notes

Acknowledgments

We wish to thank Mark Brown and Anna Hargreaves for their expert assistance with the mist netting of birds and Petra Wester and Christina Potgieter for comments on a draft version of the manuscript. This study was supported by the National Research Foundation, South Africa and the National Botanical Institute.

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Copyright information

© Springer-Verlag 2008

Authors and Affiliations

  1. 1.School of Biological and Conservation SciencesUniversity of KwaZulu-NatalPietermaritzburgSouth Africa

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