Seeds go up and down: The role of dung beetles in soil seed movement in the Southern Atlantic Forest of Argentina

Abstract

1. The vertical movement of seeds performed by dung beetles from the soil bank andin animal faeces influences seed germination and the temporal dynamic of forestregeneration. While this process has been explored at the community level, theindividual role of species is less understood. Here, we investigated the role of dungbeetle size and seed size in this vertical movement under experimental conditions.2. We performed experiments using a gradient of dung beetle sizes and three sizes ofartificial seeds (plastic beads) in two situations: inside faeces (secondary dispersal)and buried in the ground (soil bank). Through regression analysis, we related dungbeetle size, seed size, and the initial position of seeds on the soil bank to the finalposition of seeds and their potential germination.3. For seeds in the soil bank, upward movement and exhumation were mainly ofmedium and large seeds, initially located at shallower depths, with larger beetlesbeing primarily responsible for this movement. The downward movement was similarfor all seed sizes. In dung seeds, the percentage of small seeds buried graduallyincreased with beetle size, while larger beetles made the main contribution formedium and large seeds. Besides, all seed sizes were buried at an average maximumbury depth of nearly 4 cm (the limit of the germination zone).4. The relative contribution of species depended on the interaction between dungbeetles and seed sizes. Moreover, large dung beetles were essential for buryinglarge seeds in the Southern Atlantic Forest.