An evaluation of the Janzen-Connell hypothesis for a dry tropical forest in Guinea-Bissau

Abstract: The Janzen–Connell hypothesis states that seedling survival increases with distance from the parent tree, which promotes regular spacing of species within a forest and thus biodiversity. Very few studies have tested this hypothesis in tropical Africa. This paper evaluates the occurrence of Janzen-Connell effects for seedlings and adult trees of the species Cola cordifolia in a dry tropical forest in Guinea-Bissau, West Africa. This was done by field observations of naturally occurring seedlings and adult trees. Seedlings further away from the parent tree were found to be significantly larger in size, but less numerous, which is in accordance with the Janzen-Connell hypothesis. For the evaluation of the adult trees, a comparison was made with two other species that are commonly found in the area. All adult trees showed strongly clustered patterns, which is not in accordance with the Janzen-Connell hypothesis. The mixed results show a need to further study the drivers of biodiversity in tropical Africa.