FREQUENCY-DEPENDENT SEED PRODUCTION AND HYBRIDIZATION RATES: IMPLICATIONS FOR GENE FLOW BETWEEN LOCALLY ADAPTED PLANT...

Area of Science:

• Evolutionary Biology
• Plant Genetics
• Ecology

Background:

• Gene flow between distinct plant populations drives evolutionary change by increasing genetic diversity and transferring adaptations.
• The influence of immigrant frequency on gene exchange and introgression, particularly for rare migrants, remains underexplored.

Purpose of the Study:

• To investigate the roles of frequency-dependent selection and mating systems in mediating gene flow between two subspecies of Gilia capitata.
• To assess how immigrant frequency affects reproductive success and hybridization rates in different ecological contexts.

Main Methods:

• Field experiments with artificial plant arrays of varying subspecies mixtures in reciprocal habitats.
• Greenhouse hand crosses to control for pollinator effects and assess cross-fertilization success.
• Pollen supplementation experiments to validate field and greenhouse findings.

Main Results:

• Inland subspecies fitness (seed production, hybridization) was frequency-dependent, with rare immigrants exhibiting reduced success.
• Coastal subspecies reproductive function was frequency-independent, showing high seed production and no successful fertilization of inland subspecies.
• Greenhouse and field experiments confirmed unilateral incompatibility and a negative effect of coastal pollen on inland subspecies seed production.

Conclusions:

• Immigrant frequency, reproductive biology, and pollinator behavior interact to create asymmetric gene flow between Gilia capitata subspecies.
• Reproductive barriers are enhanced by ecological factors, restricting gene establishment and introgression in one direction while facilitating it in the other.