Nocturnal scent in a 'bird-fig': a cue to attract bats as additional dispersers?

Abstract

The plant genus Ficus is a keystone resource in tropical ecoystems. One of the unique features of figs is the diversity of fruit traits, which in many cases match their various dispersers, the so-called fruit syndromes. The classic example of this is the strong phenotypic differences found between figs with bat and bird dispersers (color, size, and presentation). The bird-fig Ficus colubrinae represents an exception to this trend since it attracts the small frugivorous bat species Ectophylla alba at night, but during the day attracts bird visitors. Here we investigate the mechanism by which this bird-fig attracts bats despite its fruit traits, which should appeal solely to birds. We performed feeding experiments with Ectophylla alba to assess the role of fruit scent in the detection of ripe fruits. Ectophylla alba was capable of finding ripe figs by scent alone under exclusion of other sensory cues. This suggests that scent is the main foraging cue for Ectophylla alba. Analyses of odor bouquets from the bat- and bird-dispersal phases (i.e. day and night) differed significantly in their composition of volatiles. The combination of these two findings raises the question whether E. alba and F. colubrinae resemble a co-adaptation that enables a phenotypically classic bird-fig to attract bat dispersers by an olfactory signal at night thus maximizing dispersal.