Pollination syndromes in African Marantaceae.
OBJECTIVE
The Marantaceae (550 spp.) is the most derived family in the order Zingiberales and exhibits a complex explosive pollination mechanism. To understand the evolutionary significance of this unique process of pollen transfer, comparative morphological and ecological studies were conducted in Gabon.


METHODS
During a total stay of 11 months, 31 species of Marantaceae were investigated at different sites in Gabon. The study included analyses of floral diversity, observations on the pollinator spectrum as well as ecological measurements (e.g. nectar sugar concentration and volume).


RESULTS
Analyses reveal five flower types based on flower size and pigmentation, spatial arrangement of the floral tube and presence/absence of nectar guides and conspicuous outer staminodes. Each type is associated with a specific functional pollinator group leading to the description of distinct pollination syndromes. The 'small (horizontal)' flowers are predominantly pollinated by small bees (Thrinchostoma spp., Allodapula ornaticeps), the 'large (horizontal)' and 'medium-sized (horizontal)' flowers by medium-sized bees (Amegilla vivida, Thrinchostoma bicometes), the 'locked (horizontal)' flowers by large bees (Xylocopa nigrita, X. varipes) and the '(large) vertical' flowers by sunbirds.


CONCLUSIONS
The longevity of Marantaceae individuals and the omnipresence of their pollinators allowed the specialization to a given functional pollinator group. Intermediate ecological values, however, make occasional pollinator overlaps possible, indicating potential pathways of pollinator shifts. Similar radiation tendencies observed on other continents hint at similar selective pressures and evolutionary constraints.
Ley
Alexandra C
AC
Institut für Spezielle Botanik und Botanischer Garten, Johannes Gutenberg-Universität Mainz, Germany. aley@uni-mainz.de
Classen-Bockhoff
Regine
R
D000818:Animals; D001516:Bees / Q000502:physiology; D035264:Flowers / Q000033:anatomy & histology* / Q000378:metabolism / Q000502:physiology*; D032426:Marantaceae / Q000033:anatomy & histology* / Q000378:metabolism / Q000502:physiology*; D054817:Pollination / Q000502:physiology*