Dispersal and regeneration capacity of large-seeded tree species in a forest-savanna mosaic in Western DR Congo

It is widely recognized that the Congo Basin is affected by numerous anthropogenic pressures. A number of studies proved that hunting and forest fragmentation diminish the diversity and abundance of large vertebrates, more specifically, of large frugivores. The depletion of those animals can directly affect large-seeded tree species as large seeds closely depend on the community of large frugivorous vertebrates for their dispersal. Then, the disruption of animal mediated seed dispersal is thought to deeply impact the plant regeneration capacity. The forest-savanna mosaic situated in Western DR Congo is an ecotone characterized by naturally occurring forest fragments which are also subject to numerous anthropogenic pressures. Those are very likely to disrupt seed dispersal mechanisms and to alter forest regeneration processes. To date, few studies have considered the effect of such an ecosystem on plant-animal interaction dynamics such as seed dispersal, and none have been done in this region. This study will examine if the early stages of regeneration of the large-seeded tree species Anonidium mannii, namely the dispersal capacity and seedling establishment is affected by forest fragment size. We predict that the small fragment size will negatively affect the regeneration capacity of this species. To test this assumption, we will work along a gradient of forest fragment sizes to define the composition of the seed disperser communities. For each disperser assemblage, we will evaluate the quantitative capacity of seed dispersal by combining direct focal observations and camera trapping. A literature review on each disperser species seed retention time and habitat use will allow the computation of the seed dispersal kernels. We will also evaluate the effect of seed ingestion by a presumably important seed disperser, the bonobo, Pan paniscus, on its germination capacity. Seeds will be collected from dung to evaluate the effect of seed ingestion on the rate and velocity of germination. Finally, we will study the predation pressure exerted on dispersed and non-dispersed seeds and seedlings by setting up two sets of seeds below the canopy of parent trees and away from any conspecific trees. One set will be dispersed unprotected to seed predators; another one will be enclosed in a cage and permit seeds to germinate, allowing us to evaluate the herbivores pressure on seedlings.