Tropical keystone guild interactions: Fruit removal by a frugivore foraging guild and disperser attraction by a Ficus fruiting guild in Ankarana, Madagascar

Throughout the tropics, the vast majority of tree species rely for their reproduction on seed dispersal by vertebrate frugivores, and Ficus (fig) species provide frugivores with essential resources during periods of fruit scarcity. However, despite the importance of these interactions for the regeneration and maintenance of tropical forests, the structure of frugivore and Ficus guilds remains poorly understood. We studied the 5 lemur, 5 bird, and 3 fruit bat species that comprise the frugivore foraging guild and 4 species of the Ficus fruiting guild in Ankarana Special Reserve in northern Madagascar. Between late 2005 and early 2007, we used a suite of diurnal and nocturnal direct and indirect observations of frugivore foraging to measure frugivore activity and fruit removal rates by each frugivore species visiting each of 40 fruiting Ficus trees. Ficus fruits were generally sought after by frugivores and quickly consumed upon ripening. However, Ficus species varied in attractiveness to subsets of the frugivore guild, and frugivore species differed in fruit removal from each species of Ficus. In addition, Ficus attractiveness and frugivore-specific fruit removal varied by stage of the trees’ fruiting periods. These findings indicate that large variation exists within the two guilds, and that the two guilds interact through a dynamic set of loosely specialized mutualisms. These results provide insight into community ecology theory, and suggest new strategies for the conservation of threatened frugivores and restoration of tropical forests.