Adaptive function of duodichogamy: Why do chestnut trees have two pollen emission phases?

Area of Science:

• Plant reproductive biology
• Evolutionary ecology
• Floral mechanisms

Background:

• Intersexual mating facilitation in plants is poorly understood.
• Duodichogamy, a sequential male-female-male flowering pattern, is rare.
• Chestnuts (Castanea spp.) exhibit duodichogamy with distinct male and bisexual catkins.

Purpose of the Study:

• To investigate the adaptive advantages of duodichogamy in flowering plants.
• To test the hypothesis that duodichogamy increases female mating success.
• To understand how floral proximity influences pollen deposition and mating success.

Main Methods:

• Monitoring insect visits to 11 chestnut trees throughout the flowering period.
• Analyzing reproductive traits of all known duodichogamous species from published data.
• Observing insect visitation patterns in relation to different flowering phases.

Main Results:

• Insect visits were higher during the initial male phase but focused on female flowers during the second male phase.
• Duodichogamous species are predominantly mass-flowering woody plants prone to self-pollination.
• Female flower parts (gynoecia) are typically positioned near male flower parts (androecia) of the second phase.

Conclusions:

• Duodichogamy enhances female mating success by attracting pollinators via nearby male flowers.
• This flowering system effectively facilitates pollen deposition on stigmas.
• Duodichogamy serves as a mechanism to limit self-pollination in susceptible species.