Tillandsia multicaulis is an epiphytic bromeliad found in montane forests from Panama to Mexico. In Veracruz, Mexico, T. multicaulis is self-incompatible. However, in Monteverde, Costa Rica, large amounts of self-pollen are transferred autonomously to the stigma before and during floral opening. I hypothesized that T. multicaulis is self-compatible and capable of autonomous self-pollination in Costa Rica, and I examined the breeding system of one popUlation in Monteverde. Fruit and seed set were high in open-, self-, and cross-pollinated treatments, and in caged, unmanipulated flowers. Flowers emasculated two days before opening did not set fruit. Therefore, T. multicaulis is self-compatible and autogamous, but not agamospermous in Monteverde. Prior selting occurs during the day before anthesis. Fruit set ranged from 22-32% in emasculation treatments performed the day before anthesis to 78% among flowers emasculated within one hour after floral opening. Although plants in Monteverde offer pollen and nectar rewards and are visited by pollen-collecting bees and hummingbirds, past pollen limitation has likely driven the evolution of self-compatibility. The current potential for fruit set via autonomous self-pollination is high, thus populations may be predominantly inbred. However, mixed mating could be maintained if outcrossed pollen is prepotent or if post-fertilization mortality is higher among inbred offspring.
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License.