Roles of seed dispersers in structuring plant communities through directed seed dispersal

Background/Question/Methods

Frugivorous vertebrates may influence plant community structure because they lay the initial template from which plant community patterns develop. The degree and scale of spatial distribution of seed deposition are critical for seed establishment success; and if the initial spatial pattern persists through recruitment, it can have long-term implications for the structure of plant communities. Here, we examined the spatial distribution of seeds dispersed by frugivorous lemurs in the tropical rainforest of Ranomafana National Park, Madagascar, to determine whether dispersers use trees with synchronous fruiting-time and those in their feeding network as dispersal foci. We conducted daily behavioral observations of feeding and defecation of three lemur species. We also examined fecal samples, and recorded the species of dispersed seeds and their closest neighbor adult-trees.

 Results/Conclusions

Results show that these seed-dispersing lemurs generate spatially contagious patterns of seed deposition under fruiting trees at which they feed, and under trees in their feeding network. The adult neighbors to which dispersed-seeds and seedlings are exposed may influence their recruitment patterns through competition, facilitation or shared natural enemies. Clustered recruitment of species sharing dispersers can also affect disperser attraction and probability of subsequent dispersal. If contagious patterns of dispersal are common in the tropics, it may have important implications for biodiversity maintenance in tropical forests.