Forests without primates: Primate/plant codependency

Abstract

Detailed studies of primates and fruiting trees have illustrated that these groups of organisms are involved in a very complex set of interactions, with primates relying on fruiting trees as important food resources and fruiting trees relying on frugivores for seed dispersal. Human activities that influence either primate seed dispersal or fruit production have the potential of having unanticipated effects on the other interactants. Here we evaluate what is known and what we still need to learn to evaluate the long-term consequences of disrupting the interactions between primates and tropical forest trees. We do this by first assessing the potential importance of primates at dispersing the seeds of tropical forest trees. Second, we consider possible consequences of hunting primates on recruitment in tropical tree communities. Third, we address the converse by considering the impacts of decreasing resource availability for primates through either logging or through the extraction of nontimber forest products. Finally, we provide a case study from Kibale National Park, Uganda, that contrasts seedling recruitment in 20 forest fragments in which primate seed dispersers have been dramatically reduced with seedling recruitment in areas that have an intact frugivore community. In comparison to the intact forest, the fragments had lower seedling density and fewer species of seedlings. Furthermore, a greater proportion of the seedlings were from small-seeded species that might not require primates for their dispersal, since they probably can be dispersed by small birds. All of these considerations suggest that disrupting the complex interactions between primates and fruiting trees can potentially have negative and possibly cascading effects on ecosystem processes.

The ecological implications of harvesting non‐timber forest products

“…Galetti & Aleixo (1998) illustrated that harvest of Euterpe edulis palm hearts negatively affected the abundance of two of 15 large frugivorous birds known to eat E. edulis fruits. Although primates are important seed dispersers and predators, and compete with human harvesters for food (Kinnaird 1992), the effect of fruit harvest on primates remains untested (Chapman & Onderdonk 1998).…”

Consequences of Seed Dispersal for Plant Recruitment in Tropical Forests: Interactions Within the Seedscape

“…In a recent meta-analysis, disperser loss from hunted or logged tropical forests reduced frugivore visits and seed removal for larger seeded species more than for smaller seed species (Markl et al 2012). Dispersal loss across the tropics has consistently led to declines in the abundance and diversity of seedling and sapling communities (Dirzo & Miranda 1991, Chapman & Onderdonk 1998, Nuñez-Iturri & Howe 2007, Vanthomme et al 2010, Stevenson 2011) unless the disperser decline was also associated with a decline in seed predators or destructive mammals, in which case seedling diversity did not change or increased (Roldan & Simonetti 2001, Wright et al 2007a. Disperser loss has led to compositional changes in the seedling and sapling community favoring species dispersed by non-preferred game species and abiotic means, such as wind (Nuñez-Iturri & Howe 2007, Wright et al 2007a, Terborgh et al 2008.…”

Re‐established mutualism in a seed‐dispersal system consisting of native and introduced birds and plants on the Bonin Islands, Japan

“…Plants with large seeds, such as Elaeocarpus photiniaefolius and Melia azedarach, likely suffered reduced dispersal opportunities due to the extinction of the crow from the islands. Large-seeded plants tend to have reduced numbers of dispersers due to the decrease or extinction of large vertebrates (Chapman and Onderdonk 1998;Meehan et al 2002). The bulbul has become more important as a large seed disperser under current conditions.…”