Effects of connectivity on seed dispersal patterns in hedgerows

Question Habitat isolation is a major driver of biodiversity because it affects dispersal among local communities, especially for plants. Corridors are supposed to facilitate the movement of organisms and hence their effective dispersal, thereby increasing biodiversity. Hedgerows provide favorable habitats for forest plant establishment, but their role in dispersal among forest patches is still unknown. In addition, seeds can be more predated within hedgerows because animal movement is also encouraged by these corridors. We aimed to answer the question: Are plant dispersal and seed removal by animals in connected hedgerows compared with unconnected hedgerows promoted for forest plant species? Location Long-term ecological site "Zone Atelier Armorique", western France (ca. 150 km(2)). Methods We analyzed seed dispersal along two pathways in 16 woodlots: connected (least-cost pathways, i.e., optimal corridors); and unconnected high cost pathways (absence of corridor). Using a trap study, we first quantified seed rain and analyzed seed composition after trapped seeds were germinated in the greenhouse. At the same sampling points, we then analyzed the rate at which two different sized seeds were removed from seed baits by animals. Results Our results revealed no difference in the number of trapped seeds in connected and unconnected pathways, but did reveal a difference in the number and richness of viable seeds, with corridors having a positive impact. In the predation experiment, the rate of removal of small seeds was higher in connected pathways than in unconnected pathways. Conclusion Connectivity enhanced the dispersal of viable forest plant species but also the predation of small seeds, which possibly played a role in their subsequent dispersal. This work highlighted the effect of connectivity on seed dynamics within hedgerows and improves our understanding of the role of hedgerows as stepping-stones for seed dispersal among forest patches.