Pollination ecology and breeding systems of five Gesneria species from Puerto Rico.

BACKGROUND AND AIMS: The genus Gesneria diversified in the Greater Antilles giving rise to various floral designs corresponding to different pollination syndromes. The goal of this study was to characterize the pollination and breeding systems of five Puerto Rican Gesneria species.

METHODS: The study was conducted in Arecibo and El Yunke National Forest, Puerto Rico, between 2003 and 2007. Floral visitors were documented by human observers and video cameras. Floral longevity and nectar production were recorded for the five study species. Tests for self-compatibility and autonomous selfing were conducted through hand-pollination and bagging experiments.

KEY RESULTS: Floral phenology and nectar production schedules agree with nocturnal (in bell-shaped flowered G. pedunculosa and G. viridiflora subsp. sintenisii) or diurnal pollination syndromes (in tubular-flowered G. citrina, G. cuneifolia and G. reticulata). Nectar concentration is consistently low (8-13 %) across species. Gesneria citrina and G. cuneifolia are exclusively pollinated by hummingbirds, while Gesneria reticulata relies mostly on autonomous self-pollination, despite having classic ornithophilous flowers. A variety of floral visitors was recorded for the two species with bell-shaped flowers; however, not all visitors have the ability to transfer pollen. Bats are the primary pollinators of G. pedunculosa, with bananaquits probably acting as secondary pollinators. For G. viridiflora subsp. sintenisii, both bats and hummingbirds contact the flower's reproductive organs, thus, this species is considered to be a generalist despite its nocturnal floral syndrome. All species are self-compatible but only tubular-flowered Gesneria are capable of autonomous self-pollination.

CONCLUSIONS: The visitation patterns described in this study fit the predicted hummingbird and bat pollination syndromes and support both specialization and generalization of pollination systems in Puerto Rican Gesneria. Specialization is associated with low pollinator visitation, particularly by hummingbirds, which may explain the occurrence of autonomous selfing mechanisms in tubular-flowered species.