Effect of neighboring seeds associated with habitats on the seed removal of two coexisting myrmecochorous plants in central China

Although neighboring plants can influence animal-seed dispersal interactions, little is known about the effect of neighboring seeds and the influence of habitat on seed dispersal by ants. Here we investigated the influence of neighboring seeds on seed removal in two coexisting myrmecochorous species (Epimedium pubescens and Helleborus thibetanus) from temperate deciduous forests of Qinling Mountains, central China, by examining (1) the potential role of ants and rodents and (2) whether the neighboring seed effect differed between forest edge and interior. We found that, presence of the higher-ESMR (elaiosome: seed mass ratio) E. pubescens did not significantly affect seed removal of the lower-ESMR H. thibetanus. By contrast, the presence of H. thibetanus decreased the seed removal rates of E. pubescens, with only a significant effect in rodent exclusion (ant alone) rather than in both ant exclusion (rodent alone) and full access (rodent + ant). Moreover, we found that those effects were not significantly different between the forest edge and the interior, which may be attributed to a similar pattern of overall seed-dispersing ant abundance in the two habitats. This suggested that neighboring seeds could influence seed removal of the focal plant depending on the absence of rodents; when rodents were present, the interaction of rodents and ants rendered no influence of neighboring seeds on seed removal. Our results show that the neighborhood effect was regulated by both dispersers and predators, and this effect was not context-dependent at a small spatial scale. This study highlights the importance to understand the effect of shared seed-removing animals and habitat context to assess the neighboring seed effect on plant-animal interactions.