Reproductive Biology of Erythrina crista-galli (Fabaceae)

Flowering phenology, floral morphology, nectar features (chemical composition, secretion pattern, standing crop, removal effects), breeding system, and flower visitors were analyzed in seven populations of Erythrina crista-galli from Argentina and Uruguay. Its flowering phenology corresponds to the sub-annual frequency class of Newstrom et al., with a major burst in November. Flowers lasted for 3 to 4 days and produced abundant hexose-dominant nectar with its chemical composition and concentration (ca. 22%) constant across all flowering stages. Most of the total nectar was secreted by buds. When the flowers first opened, most (> 50%) of the total nectar was available to pollinators. As flowers faded, a resorption period began. The overall sugar production was not affected by nectar removal. Hand crosses showed that this species is self-compatible. Crossed fruits showed significant differences from hand-selfed ones (autogamy and geitonogamy). Xenogamous fruits and seeds showed the highest values for many traits (fruit mass, total seeds per fruit mass, mean seed mass, and seed germination percentage). Approximately 6% of the flowers set seeds in natural populations. Hymenopterans (carpenter bees and honeybees) and hummingbirds (four species) assiduously visited the trees in all the areas sampled and can be assumed pollinators. Almost 93% of recorded flowers were visited by bees, with the rest visited by hummingbirds. Phylogenetically, this species was included in the basal clade for the genus and characterized as passerine/hummingbird pollinated. However, we found that not only birds but bees functioned as major pollinators. This observation may indicate that this basal clade may represent an intermediate step from entomophily (typical of tribe Phaseoleae) to ornithophily (typical of Erythrina).