Pollination mode and life form strongly affect the relation between mating system and pollen to ovule ratios

Authors

  • Stefan G. Michalski,

    1. UFZ–Helmholtz Centre for Environmental Research, Department of Community Ecology (BZF), Theodor-Lieser-Strasse 4, D-06120 Halle, Germany
    Search for more papers by this author
  • Walter Durka

    1. UFZ–Helmholtz Centre for Environmental Research, Department of Community Ecology (BZF), Theodor-Lieser-Strasse 4, D-06120 Halle, Germany
    Search for more papers by this author

Author for correspondence:
Stefan G. Michalski
Tel: +49 345 558 5310
Email: Stefan.Michalski@ufz.de

Summary

  • • Pollen to ovule (P : O) ratios have been hypothesized to correlate with the degree of outcrossing and thus with the mating system of a plant. Also, P : O ratios are likely to vary with respect to pollination mode (i.e. wind pollination or animal pollination). Furthermore, constraints on the evolution of mating systems depending on life form may affect P : O ratios.
  • • We compiled P : O ratios and outcrossing rates for 107 angiosperm species and analyzed the relation between these traits considering pollination mode, life form and phylogenetic relatedness among species.
  • • In general, P : O ratios correlated significantly with outcrossing rates. However, when taking additional factors into account, the relation became ambiguous. The correlation was significantly positive in wind-pollinated species, but only marginally so in animal-pollinated species. Wind-pollinated species had higher P : O ratios than animal-pollinated taxa. In woody perennials, outcrossing was the predominant mating system and outcrossing rates did not correlate with P : O ratios. The results were not altered by accounting for phylogenetic relatedness among species.
  • • The results indicate that P : O ratios vary more strongly with pollination mode and life form than with the mating system.

Ancillary