Search tips
Search criteria 


Logo of procbhomepageaboutsubmitalertseditorial board
Proc Biol Sci. Mar 22, 2004; 271(1539): 603–608.
PMCID: PMC1691633
Floral symmetry affects speciation rates in angiosperms.
Risa D. Sargent
Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, British Columbia V6T 1Z4, Canada.
Risa D. Sargent: sargent/at/
Despite much recent activity in the field of pollination biology, the extent to which animal pollinators drive the formation of new angiosperm species remains unresolved. One problem has been identifying floral adaptations that promote reproductive isolation. The evolution of a bilaterally symmetrical corolla restricts the direction of approach and movement of pollinators on and between flowers. Restricting pollinators to approaching a flower from a single direction facilitates specific placement of pollen on the pollinator. When coupled with pollinator constancy, precise pollen placement can increase the probability that pollen grains reach a compatible stigma. This has the potential to generate reproductive isolation between species, because mutations that cause changes in the placement of pollen on the pollinator may decrease gene flow between incipient species. I predict that animal-pollinated lineages that possess bilaterally symmetrical flowers should have higher speciation rates than lineages possessing radially symmetrical flowers. Using sister-group comparisons I demonstrate that bilaterally symmetric lineages tend to be more species rich than their radially symmetrical sister lineages. This study supports an important role for pollinator-mediated speciation and demonstrates that floral morphology plays a key role in angiosperm speciation.
Full Text
The Full Text of this article is available as a PDF (96K).
Selected References
These references are in PubMed. This may not be the complete list of references from this article.
  • Barraclough TG. Revealing the factors that promote speciation. Philos Trans R Soc Lond B Biol Sci. 1998 Feb 28;353(1366):241–249. [PMC free article]
  • Owens IPF, Bennett PM, Harvey PH. Species richness among birds: body size, life history, sexual selection or ecology? Proc Biol Sci. 1999 May 7;266(1422):933–933. [PMC free article]
Articles from Proceedings of the Royal Society B: Biological Sciences are provided here courtesy of
The Royal Society