Mating system instability in Schiedea menziesii (Caryophyllaceae)

Area of Science:

• Plant reproductive biology
• Evolutionary botany
• Population genetics

Background:

• Schiedea menziesii, a hermaphroditic species, exhibits a complex breeding system.
• Understanding inbreeding depression and selfing rates is crucial for assessing mating system stability.

Purpose of the Study:

• To investigate inbreeding depression and selfing rates in Schiedea menziesii.
• To assess the stability of its breeding system and potential evolutionary trajectories.

Main Methods:

• Population-level and family-level selfing rates were measured over three years.
• Inbreeding depression was quantified through greenhouse experiments across different life-history stages.
• Genotyping was used to determine cross status for field-collected seeds.

Main Results:

• Selfing rates varied significantly, with population-level rates ranging from 0.425 to 0.704.
• Strong inbreeding depression (0.608-0.870) was observed, with inbred plants not surviving to reproduction.
• Inbreeding depression varied by life-history stage and experimental conditions; no relation was found between inbreeding depression and selfing rate at the individual level.

Conclusions:

• The combination of high selfing and strong inbreeding depression suggests an unstable mating system in S. menziesii.
• Intrafloral selfing is unlikely, but the evolution of gynodioecy is a probable outcome.
• The establishment of female plants may be hindered by a lack of adaptations for wind pollination in the absence of biotic pollen vectors.