Seed dispersal strategies and the threat of defaunation in a Congo forest

Background

Seed dispersal is a crucial ecological process that shapes plant communities and maintains biodiversity in tropical forests. In the Congo Basin, most tree species rely on animals (zoochory) to disperse their seeds, with large vertebrates like forest elephants and bonobos playing a key role. However, hunting and poaching threaten these seed dispersers, which could have cascading effects on forest structure and plant regeneration. This study investigates the extent of animal-mediated seed dispersal in the LuiKotale forest, located in the Democratic Republic of the Congo (DRC), and assesses how hunting pressure on frugivores may impact tree community composition.

Goals and Methods

The study aimed to evaluate how defaunation affects seed dispersal and forest composition by analyzing dispersal strategies among plant species in the LuiKotale forest. Researchers conducted a decade-long plant inventory, identifying 735 species and categorizing their seed dispersal modes. They also assessed tree community structure in 12 one-hectare plots, measuring the proportion of zoochorous (animal-dispersed) species. Additionally, they identified frugivorous vertebrates in the ecosystem and determined which species were subject to hunting or poaching. The study examined how hunting pressure on seed dispersers compared to that on seed predators, with a particular focus on the role of large-bodied frugivores.

Conclusion

The findings revealed that 85% of the identified plant species in LuiKotale produce fleshy fruits and rely on animals for seed dispersal. Among tree species, this proportion was even higher, reaching 95% in terms of individual trees within the surveyed plots. This dominance of zoochory underscores the critical role of animal dispersers in maintaining forest dynamics. However, all observed seed-dispersing vertebrates—including bonobos, elephants, and hornbills—are either hunted or poached, whereas seed predators (such as rodents) face less human pressure. This imbalance suggests that defaunation could disrupt seed dispersal, potentially leading to shifts in tree species composition. The decline of large frugivores may favor wind-dispersed and autochorous species, altering forest structure and reducing biodiversity over time.