Chimpanzees as ecosystem service providers: Seed dispersal of an economically important plant resource

Vertebrate-mediated seed dispersal is vital to the maintenance of diversity in tropical ecosystems, and seed-dispersing animals are increasingly thought to provide ecosystem services by dispersing the seeds of plant species utilized by people. However, few studies have demonstrated a link between vertebrate frugivores and plants used by people, thus limiting the generalizability of the seed-disperser-as-ecosystem-service-provider concept. We examined the effectiveness of western chimpanzees (Pan troglodytes verus) as seed dispersers (i.e., their influence on seedling recruitment) of an economically important fruit resource, Saba senegalensis, at the site of Fongoli, a savanna-woodland environment in southeastern Senegal. The fruit from the Saba vine is commonly harvested from the wild by local people and is also an important food item for chimpanzees. We conducted germination experiments on gut-passed seeds alongside non-gut-passed seeds and analyzed the germination success of chimpanzee-dispersed seeds in situ. We also analyzed the effect of habitat type and canopy cover at each seed dispersal site to determine which sites are most suitable for Saba germination. Germination trials showed that chimpanzee gut passage and manual pulp removal increased the likelihood of germination over seeds left intact. Nearly a quarter of chimpanzee-dispersed seeds germinated in situ and Saba seeds were distributed non-randomly throughout Fongoli, with more dispersed seeds found in habitats most suitable for Saba germination. These results suggest that chimpanzees aid in the early stages of Saba recruitment and thus provide an ecosystem service via seed dispersal that may contribute to the well-being of local people.