Morphology and Phylogenetic Significance of Exine-less Pollen of Heliconia (Heliconiaceae)

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Abstract
Pollen morphology of 27 species of Heliconia (19 species with pendent inflorescences; eight species with erect inflorescences) was examined using brightfield and scanning electron microscopy. Pollen of species with erect inflorescences has many character states in common with pollen of pendent species. Among the species with pendent inflorescences four groups can be distinguished by pollen features. Within each group, however, species differences cannot always be resolved. A cladistic analysis of the 27 species based on pollen characters alone suggests that species with erect inflorescences have evolved independently several times from species possessing pendent inflorescences. This hypothesis is supported by a separate phylogenetic analysis in which additional reproductive and vegetative characters were used. Hence, inflorescence habit is of limited value in recognizing monophyletic groups (sensu Hennig) in Heliconia.