Post-dispersal seed removal in an agricultural landscape of semi-arid West Africa

Abstract

Post-dispersal seed removal is crucial for maintaining plant diversity by influencing secondary dispersal, recruitment, and mortality of seeds. In this study, we examined the effect of three habitat types (conventional farmland, agroforestry parkland, and woodland) and two seed species (Leucaena leucocephala and Faidherbia albida) on post-dispersal seed removal by invertebrates and vertebrates in an agricultural landscape using selective exclosure treatments. The exclosure treatments, closed and open, were designed to respectively impose restrictions that allow only invertebrates as well as both invertebrates and vertebrates access to seeds. The results showed that habitat type (χ2=65.06, p = <0.0001) and seed species (χ2=6.207, p = 0.013) influenced the rate of seed removal: i.e., the woodland habitat and F. albida seeds recorded the highest removal rates while the parkland habitat recorded the least. However, while not always statistically significant for most habitat pairwise comparisons for the different seed species investigated, our findings suggest that invertebrates likely dominated seed removal events compared to vertebrates. The diversity of fauna often associated with natural or woodland habitats coupled with their differential seed selection habits may have accounted for the observed findings. We further suspect that the presence of bushes and fallow lands near conventional farmlands resulted in its high seed removal rate compared to the parkland habitat. Thus, post-dispersal seed removal benefits from fauna diversity in bushes or fallows near conventional farmlands. Overall, our study has demonstrated that woodland and agricultural habitats can potentially contribute to maintaining plant population dynamics through predation and dispersal events.