IMBIV   05474
INSTITUTO MULTIDISCIPLINARIO DE BIOLOGIA VEGETAL
Unidad Ejecutora - UE
artículos
Título:
Nectar secretion dynamic links pollinator behavior to consequences for plant reproductive success in the ornithophilous mistletoe Psittacanthus robustus
Autor/es:
GUERRA T.; GALETTO L.; SILVA W.
Revista:
PLANT BIOLOGY
Editorial:
WILEY-BLACKWELL PUBLISHING, INC
Referencias:
Lugar: Londres; Año: 2014 vol. 16 p. 956 - 966
ISSN:
1435-8603
Resumen:
The mistletoe Psittacanthus robustus was studied as a model to link flower phenology and nectar secretion strategy to pollinator behavior and the reproductive consequences for the plant. This species flowered throughout the rainy season and flowers typically presented  ornithophilous features, including a diurnal anthesis, bright-colored flowers and the production of copious diluted nectar. Most nectar was secreted just after flower opening with little sugar replenishment after experimental removals. During the second day of anthesis, flowers quickly reabsorbed the offered nectar in bagged flowers. Flower anthesis lasts three days and a single flower may receive over 30 visits during this period. Low values of nectar standing crop in open flowers can be linked with high visitation rates by pollinators.  Eight hummingbirds and two passerines were observed as flower visitors. Based on visitation rates, the main pollinators are Eupetomena macroura and Colibri serrirostris, the two largest hummingbird species that exhibited territorial behavior. The spatial separation between anthers, stigma and nectar chamber promotes pollen deposition on flapping wings of hovering hummingbirds that usually probe many flowers per visit. Seed set did not differ between hand self- and cross-pollinated flowers, but these treatments set significantly more seeds than flowers exposed to flower visitors. Although Psittacanthus robustus may be considered as a keystone nectar resource for birds, the excessive number of visits received by flowers seems to be detrimental for the plant. This conclusion is based on the lower female reproductive success reached by naturally pollinated flowers compared to values obtained from experimentally cross-pollinated flowers. We suggest that the limitation observed in the plant reproductive success is not related to pollinator scarcity but probably to its extreme frequency. The costs and benefits of plant reproduction depend on the strength of the interaction between flowers and pollinators, and nectar secretion dynamics allow the clarification of the complexity of such association.