Fruit removal in the forest herb Actaea spicata depends on local context of fruits sharing the same dispersers

Heterospecific effects from neighboring plants on fruit removal are rarely examined. In this study we recorded removal of fruits of four species from experimental plots. The main study species, the forest herb Actaea spicata, has berries attractive to rodents. We tested for effects from a larger-scale context (plant abundance) and a smaller scale (number of fruits aggregated including several species with fleshy as well as dry fruits). Fruit removal varied among sites. Fleshy-fruited species removal was correlated within sites. Fruit removal was higher within than outside Actaea populations but was unrelated to plant abundances among existing populations. The small-scale context treatment yielded clear results. Removal of Actaea fruits was higher from large aggregations of fruits, and it was the number of fruits rather than species identity that affected removal. Presence of both fleshy and dry fruits increased removal. This study provides experimental evidence of heterospecific effects on fruit removal, and we conclude that the species included in the study attract the same dispersers and that the small-scale biotic context is important. We suggest the existence of dispersal hot spots related to the fruit presence overlaid by an unexplained variation among sites.