Sugar composition of nectars and fruits consumed by birds and bats in the tropics and subtropics

Several characteristics of flowers and fruits have been suggested as compri sing syndromes of characters that indicate particular classes of pollinator s and fruit dispersers. Common phylogenetic history among species, however, may also significantly influence these characters and obscure or enhance p erceived patterns of plant syndromes. We analyzed the proportions of glucos e, fructose, and sucrose by paper chromatography in the nectar and fruit ju ice of 525 tropical and subtropical plant species to test whether sugar che mistry was correlated with volant vertebrate pollinator or fruit disperser classes. Samples were taken from Old World and New World species and the ca lculations kept separate. Kruskal-Wallis tests of family means showed signi ficant deviations in the percent sucrose content among pollinator/disperser classes. Mann-Whitney U-tests showed significant differences among nectars of all pollinator classes but fruit juices differed only due to the high s ucrose content of megachiropteran dispersed fruits. In addition, sign tests of samples occurring within families showed significant correlations betwe en percentage sucrose content and pollinator/disperser classes. Passerine n ectars had low sucrose content. In striking contrast, the nectar of humming bird flowers had very high sucrose content. The Microchiroptera nectars sho wed hexose richness with a sucrose content somewhat greater than that of pa sserine flowers. Megachiroptera flowers showed sucrose-rich nectars. The re sults for fruits were comparable to those for nectars. Passerine fruits wer e hexose dominated, microchiropteran fruits had a sucrose content similar t o passerine fruits, and megachiropteran Fruits were sucrose-rich. We specul ate on the evolutionary sequence of changes in nectar and fruit juice sugar composition and suggest that future investigations consider the chemistry of other food sources such as pollen and leaves. Only with these additions and other ecological studies can the full interplay of such plane-animal in teractions be anticipated.