The consequences of monoecy and protogyny for mating in wind-pollinated Carex

New Phytol. 2009 Jan;181(2):489-497. doi: 10.1111/j.1469-8137.2008.02664.x.

Abstract

Monoecy and protogyny are widespread in wind-pollinated plants and have been interpreted as outcrossing mechanisms, though few studies have investigated their function. Carex, a large genus of anemophilous herbs, is predominantly monoecious and many species are protogynous. We investigated whether monoecy and protogyny limit self-pollination in seven Carex species. We conducted field experiments comparing stigmatic pollen loads and seed set between intact and emasculated stems. We tested for self-compatibility and evaluated pollen limitation of seed set by supplemental pollination. Finally, we measured outcrossing rates in open-pollinated and emasculated stems using allozyme markers. Emasculated stems captured significantly less pollen than open-pollinated stems and set less seed. Pollen deposition during the female-only phase for intact stems was only 12% of the total captured. Outcrossing rates for three species indicated high selfing (range t = 0.03-0.39). Allozyme loci in the remaining species were monomorphic also suggesting high selfing. These results demonstrate that neither monoecy nor protogyny is particularly effective at limiting self-fertilization. Selection for the avoidance of selfing is unlikely to maintain monoecy in many Carex species although protogyny may provide limited opportunities for outcrossing. We propose that geitonogamy in self-compatible wind-pollinated species with unisexual flowers may be widespread and provides reproductive assurance.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptation, Biological
  • Carex Plant / genetics
  • Carex Plant / physiology*
  • Flowers
  • Pollen
  • Pollination / physiology*
  • Reproduction / physiology*
  • Seeds / physiology*
  • Wind