Sexual Interference of the Floral Kind

Floral hermaphroditism results in conflicts and compromise in the parental roles of plants during pollination and mating. A potential cost of hermaphroditism is sexual interference between maternal and paternal functions resulting in gamete wastage and reduced fitness. Sexual interference may or may not be associated with self-pollination. In cases where self-pollination occurs, ovule or pollen discounting may reduce mating opportunities. Here I describe forms of sexual interference in flowering plants, distinguishing whether physical or biochemical interactions are involved and whether fitness costs associated with gamete wastage arise from intra-floral versus inter-floral processes. I review the limited experimental evidence for interference between sex functions and evaluate the hypothesis that some floral adaptations usually interpreted as anti-selfing mechanisms may serve an alternative function in reducing mating costs arising from this form of sexual conflict.