POLLEN PERFORMANCE AND SEX-RATIO EVOLUTION IN A DIOECIOUS PLANT

Area of Science:

• Evolutionary genetics
• Plant reproductive biology
• Population genetics

Background:

• Sex-linked or cytoplasmic genes can distort sex ratios to increase their own transmission.
• The effectiveness of sex-ratio distortion depends on the transmission advantage, which can be reduced by male gamete limitation or intense pollen competition.
• Understanding these dynamics is crucial for predicting the spread and impact of such genes.

Purpose of the Study:

• To analyze pollen competition outcomes in Silene alba with varying sex ratios.
• To estimate how sex-ratio bias influences sex chromosome transmission properties.
• To evaluate the role of multiple paternity in the transmission advantage of sex-ratio distorting genes.

Main Methods:

• Controlled pollen competition experiments in Silene alba by varying pollen quantity.
• Utilized single-male pollinations and pollen mixtures to assess multiple paternity effects.
• Employed allozymes to estimate paternity in pollen mixtures.

Main Results:

• Sex-ratio bias was influenced by pollen quantity, though the effect was minor.
• Pollen performance varied significantly, particularly under multiple paternity.
• Males with biased sex ratios sired fewer offspring in pollen mixtures but not in single-male crosses.

Conclusions:

• X-linked genes can enhance transmission via sex-ratio distortion in Silene.
• The magnitude of this transmission advantage is contingent on ecological factors promoting multiple paternity.
• Ecological context significantly modulates the evolutionary dynamics of sex-ratio distorting elements.