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Plant Systematics and Evolution

, Volume 298, Issue 1, pp 9–24 | Cite as

Pollen grain size variation in Caryophylloideae: a mixed strategy for pollen deposition along styles with long stigmatic areas?

  • Andreas JürgensEmail author
  • Taina Witt
  • Gerhard Gottsberger
Original Article

Abstract

The literature supports a positive correlation between pollen size and style length and that pollen size may be affected by a trade-off with pollen number. A correlation between pollen size and pollinator type has been hypothesized by some authors but not confirmed. To assess these associations, pollen grain number, pollen grain diameter and style length were measured in 53 species of Caryophylloideae that had been classified beforehand as being diurnal, nocturnal or self-pollinated. Surprisingly, many species showed two, and a few even three, distinct pollen grain size classes per individual anther. Therefore, further analyses were based on the different pollen size classes and respective pollen grain numbers. Firstly, we found no indication of a trade-off between pollen size and number. Secondly, a positive linear correlation between style length and pollen grain diameter was found using conventional analysis methods and phylogenetically independent contrasts. Thirdly, when using conventional analysis methods a strong relationship between style length and pollination mode was found, with nocturnal species having significantly longer styles and larger pollen grains than diurnal and selfing species. These results were not supported, however, when calculating comparisons of phylogenetically independent pairs. We discuss our findings in relation to intra-specific pollen polymorphism and pollen degeneration, both of which have been associated with different pollen grain sizes in Caryophylloideae. Furthermore, we discuss the possibility that pollen polymorphism might be a mixed strategy to optimise the success of pollen grains deposited at different pollen–ovule distances on long styles.

Keywords

Caryophyllaceae Silene Pollen size Pollen number Pollination mode Style length 

Notes

Acknowledgements

We wish to thank Hans Malchus for help in the field and laboratory. We thank the members of the Botanical Garden of Ulm for cultivating plants. Seeds were kindly provided by several botanical gardens. We thank two anonymous reviewers for helpful comments on the manuscript. Andreas Jürgens is supported by the National Research Foundation (South Africa).

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Copyright information

© Springer-Verlag 2011

Authors and Affiliations

  • Andreas Jürgens
    • 1
    Email author
  • Taina Witt
    • 1
  • Gerhard Gottsberger
    • 2
  1. 1.School of Biological and Conservation SciencesUniversity of KwaZulu-NatalPietermaritzburgSouth Africa
  2. 2.Botanical Garden and HerbariumUniversity of UlmUlmGermany

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