Does inbreeding avoidance maintain gender dimorphism in Wurmbea dioica (Colchicaceae)?

Area of Science:

• Evolutionary Biology
• Plant Reproductive Strategies
• Population Genetics

Background:

• Gender dimorphism in plant populations necessitates a fitness advantage for females to offset reproductive limitations.
• The subdioecious species Wurmbea dioica presents a model for studying the maintenance of females in dimorphic systems.

Purpose of the Study:

• To investigate if inbreeding avoidance confers a fitness advantage to females in Wurmbea dioica.
• To estimate seed production, outcrossing rates, and inbreeding depression in two populations.

Main Methods:

• Estimation of seed production and outcrossing rates in natural populations.
• Calculation of inbreeding coefficients and inbreeding depression.
• Glasshouse experiments to assess female fitness advantage under varying outcrossing rates.

Main Results:

• Fruiting males produced significantly fewer seeds than females due to low outcrossing and inbreeding depression.
• Inbreeding depression estimates exceeded 0.85, indicating reduced survival of selfed progeny.
• Females showed a fitness advantage of 3.7, which decreased to 1.4 when male outcrossing rates increased.

Conclusions:

• Inbreeding avoidance can contribute to maintaining females in populations, but the advantage may be insufficient if sex is genetically controlled.
• Environmental plasticity in gender determination could influence the frequency of fruiting males and thus female maintenance.