Floral scent chemistry and pollination ecology in phytelephantoid palms (Arecaceae)

The subfamily Phytelephantoideae comprises three genera (Ammandra, Aphandra, and Phytelephas) and seven species of dioecious palms. The floral scents of Ammandra dasyneura, A. decasperma, Aphandra natalia, Phytelephas aequatorialis, P. macrocarpa, and P. seemannii were analyzed by gas chromatography-mass spectrometry. We studied the pollination biology of A. natalia, P. aequatorialis, and P. macrocarpa, and tested how the synthetically produced main constituents of the floral scents of Aphandra and Phytelephas attracted insects in two natural populations of Phytelephas. The genera are distinct in terms of floral scents. Ammandra has sesquiterpenes, Aphandra (+)-2-methoxy-3-sec-butylpyrazine, and Phytelephas p-methyl anisol. These constituents dominated the scents quantitatively and qualitatively. The similarity between scents of male and female inflorescences was 76.5% in Ammandra, 84.2% in Aphandra, and >99% in Phytelephas. Different species of Aleocharinae (Staphylinidae) pollinate Aphandra natalia and Phytelephas species and reproduce in their male inflorescences. Derelomini (Curculinoidae) and Mystrops (Nitidulidae) only visit and pollinate Phytelephas in which male inflorescences they reproduce. A species of Baridinae (Curculionidae) only visits and pollinates Aphandra natalia, and reproduces in its female inflorescence. The apparent reliance on one or a few floral scent constituents as attractants and few and specific pollinators may indicate co-evolution. Sympatric species of Phytelephantoideae have different scents. We suggest that species with similar scents have allopatric distributions due to the absence of a pollinator isolation mechanism.