Removal and predation of aril-covered seeds: the case of Afzelia bipindensis (Fabaceae – Detarioidae)

Abstract

Background and aims – Most tree species with aril-covered seeds are assumed to be dispersed by frugivores. However, the number of studied African rainforest plant species remains low. This study focused on Afzelia bipindensis, an important timber species, which produces seeds partly covered by an aril. Specifically, this study aimed to: (1) identify the dispersers and the predators of A. bipindensis seeds, (2) characterize the role of those dispersers and predators in the regeneration process, and (3) understand the role of the aril in seed germination in relation to the feeding behaviour of the identified dispersers. Methods – The study took place in a Gabonese evergreen rainforest in 2015 and in a Cameroonian semi-deciduous rainforest in 2016 and 2017. We conducted more than 100 hours of direct observations, and used camera traps to monitor animal activities for 3000 hours within the canopy and 10 000 hours on the ground under fruiting trees. Key results – Three rodent taxa (Cricetomys emini, Funisciurus isabella and an undetermined species of Muridae) were mainly observed interacting with the seeds but neither birds nor monkeys were observed. Rodents removed more than 90% of the seeds, after detaching the aril, to probably cache them in burrows or superficial caches. Seeds from which we manually removed the aril (mimicking rodent behaviour) had a higher germination rate.Conclusions – Rodents may play a more important role than expected in the dynamics of tree species producing aril-covered seeds.