Why do stigmas move in a flexistylous plant?

Area of Science:

• Evolutionary biology
• Plant reproductive strategies
• Floral morphology

Background:

• Flexistyly is a floral polymorphism with spatial and temporal segregation of sexual functions.
• Understanding the evolutionary drivers of flexistyly is crucial for plant reproductive biology.

Purpose of the Study:

• To test if selection against interference between male and female functions drives stigma movement in flexistyly.
• To investigate the role of stigma movement in enhancing male fitness in Alpinia mutica.

Main Methods:

• Experimental manipulation of stigma movement in self-compatible Alpinia mutica flowers.
• Assessing pollen donor success using allozymes to determine seed paternity.
• Comparing reproductive success between intact and stigma-immobile flowers under varying pollen competition levels.

Main Results:

• Flowers with non-moving stigmas sired significantly fewer seeds, indicating reduced male fitness.
• The positive effect of stigma movement on male fitness was most pronounced under high pollen competition.
• This suggests stigma movement facilitates pollen export and reduces interference with pollen reception.

Conclusions:

• Stigma movement in flexistyly is likely maintained by selection for increased male fitness.
• Reducing interference between male and female functions is a key evolutionary factor driving stigma movement.
• Flexistyly plays a significant role in optimizing reproductive success in hermaphroditic plants.