Seed dispersal is a crucial component of plant population dynamics. Human landscape modifications, such as habitat destruction and fragmentation, can alter the abundance of fruiting plants and animal dispersers, foraging rates, vector movement, and the composition of the disperser community, all of which can singly or in concert affect seed dispersal. Here, we quantify and tease apart the effects of landscape configuration, namely, fragmentation of primary forest and the composition of the surrounding forest matrix, on individual components of seed dispersal of Heliconia acuminata, an Amazonian understory herb. First we identified the effects of landscape configuration on the abundance of fruiting plants and six bird disperser species. Although highly variable in space and time, densities of fruiting plants were similar in continuous forest and fragments. However, the two largest-bodied avian dispersers were less common or absent in small fragments. Second, we determined whether fragmentation affected foraging rates. Fruit removal rates were similar and very high across the landscape, suggesting that Heliconia fruits are a key resource for small frugivores in this landscape. Third, we used radiotelemetry and statistical models to quantify how landscape configuration influences vector movement patterns. Bird dispersers flew farther and faster, and perched longer in primary relative to secondary forests. One species also altered its movement direction in response to habitat boundaries between primary and secondary forests. Finally, we parameterized a simulation model linking data on fruit density and disperser abundance and behavior with empirical estimates of seed retention times to generate seed dispersal patterns in two hypothetical landscapes. Despite clear changes in bird movement in response to landscape configuration, our simulations demonstrate that these differences had negligible effects on dispersal distances. However, small fragments had reduced densities of Turdus albicollis, the largest-bodied disperser and the only one to both regurgitate and defecate seeds. This change in Turdus abundance acted together with lower numbers of fruiting plants in small fragments to decrease the probability of long-distance dispersal events from small patches. These findings emphasize the importance of foraging style for seed dispersal and highlight the primacy of habitat size relative to spatial configuration in preserving biotic interactions.

Summary1. Fluctuating asymmetry (FA) refers to the dierence between the right and left sides in characters that should otherwise be bilaterally symmetrical, but whose expression is aected by epigenetic stress during development. Forest fragmentation may promote an increase in FA in isolated populations, by either genetic or environmental stress. FA may function as a biomonitor index in conservation biology if increased levels were observed in populations from fragmented habitats. 2. We tested the hypothesis that FA is higher in birds from small tropical forest patches than in large forest tracts. We measured wing and tarsus FA on mist-netted birds from seven fragments and seven continuous areas from south-eastern Atlantic rain forest in Brazil. We performed FA comparisons between fragments and control groups for the whole community, for individual foraging guilds and for the six most abundant species. 3. Wing and tarsus FA were signi®cantly greater in fragments than continuous areas for the whole community and were both negatively correlated with forest fragment size. Dierences in FA varied among foraging guilds, being more evident for insectivorous species, especially those feeding in or near the understorey. 4. FA levels increased signi®cantly in forest fragments in at least one trait for ®ve of the six most abundant species. There was no correlation between tarsus and wing asymmetries for the individuals of any species nor any dierence between the degree of asymmetries of these characters. 5. We suggest that FA is a useful tool to assess the eects of fragmentation on forest birds, and may be applied in monitoring neotropical birds. FA indices might be pro®tably developed, particularly in species most threatened by fragmentation eects and when investigated in dierent morphological characters.