The individual-based network structure of palm-seed dispersers is explained by a rainforest gradient

How species interactions change in space and time is a major question in ecology. In tropical forests, plant individuals share mutualistic partners (pollinators or seed dispersers), yet we have little understanding of the factors affecting these individual interaction patterns. We used a seed dispersal individual-based network describing interactions between individuals of a palm species with bird species to investigate how intrinsic and extrinsic characteristics of individual plants influence the network structure. In our work we evaluated if average canopy height, number of fruits, distance to forest gap, and habitat type influence the role of palm individuals in the network. From 102 palms, 62 individuals had their seeds dispersed at least once: 17 individual palms in the restinga, 15 in the lowland and 30 in the pre-montane habitat. Twelve bird species were recorded dispersing Euterpe edulis seeds in our study area.

Methods
Focal palm observations of birds consuming Euterpe edulis fruits were conducted for a total of 102 palm individuals across three different habitats in Cardoso Island, São Paulo (Brazil). Interactions between birds and palm individuals were considered a seed dispersal event only when the birds swallowed or carried the fruit away, thus ensuring seed deposition at a distance from the maternal plant.