Reproductive biology of Erythrina crista-galli (Fabaceae)

Flowering phenology, floral morphology, nectar features (chemical compositi on, secretion pattern, standing crop, removal effects), breeding system, an d flower visitors were analyzed in seven populations of Erythrina crista-ga lli from Argentina and Uruguay. Its flowering phenology corresponds to the sub-annual frequency class of Newstrom et al., with a major burst in Novemb er. Flowers lasted for 3 to 4 days and produced abundant hexose-dominant ne ctar with its chemical composition and concentration (ca. 22%) constant acr oss all flowering stages. Most of the total nectar was secreted by buds. Wh en the flowers first opened, most (> 50%) of the total nectar was available to pollinators. As flowers faded, a resorption period began. The overall s ugar production was not affected by nectar removal. Hand crosses showed tha t this species is self-compatible. Crossed fruits showed significant differ ences from hand-selfed ones (autogamy and geitonogamy). Xenogamous fruits a nd seeds showed the highest values for many traits (fruit mass, total seeds per fruit mass, mean seed mass, and seed germination percentage). Approxim ately 6% of the flowers set seeds in natural populations. Hymenopterans (ca rpenter bees and honeybees) and hummingbirds (four species) assiduously vis ited the trees in all the areas sampled and can be assumed pollinators. Alm ost 93% of recorded flowers were visited by bees, with the rest visited by hummingbirds. Phylogenetically, this species was included in the basal clad e for the genus and characterized as passerine/hummingbird pollinated. Howe ver, we found that not only birds but bees functioned as major pollinators. This observation may indicate that this basal clade may represent an inter mediate step from entomophily (typical of tribe Phaseoleae) to ornithophily (typical of Erythrina).