A central problem in ecology is to understand how human impacts affect plant-animal interactions that lead to effective seed dispersal services for plant communities. Seed dispersal services are the outcome of plant-frugivore interactions that often form local networks of interacting species. Recent work has shown that some frugivorous bird species are more critical to network organization than others. Here, we explore how patch size and the potential local extinctions of obligate frugivorous birds affect the reorganization of seed dispersal networks. We examined the structure of 20 empirical seed dispersal networks documented across tropical avian assemblages occupying widely variable habitat patch sizes, a surrogate of the amount of remaining habitat. Networks within small forest patches consistently supported both lower plant and bird species richness. Forest patch size was positively associated with nestedness, indicating that reductions in patch size disrupted the nested organization of seed dispersal networks. Obligate frugivores, especially large-bodied species, were almost entirely absent from small forest patches. Analysis at the species level showed that obligate frugivores formed the core of interacting species, connecting species within a given seed dispersal network. Our combined results revealed that patch size reduction erodes frugivorous bird diversity, thereby affecting the integrity of seed dispersal networks. We highlight the importance of conserving large forest patches to maintain tropical forest functionality.

The intensification of agricultural activity can have profound impacts on biodiversity. We evaluated the influence of the landscape's percentage of forest cover and shaded cocoa plantations on the community of zoochorous bromeliads in southern Bahia, Brazil. We selected two contrasting landscapes, one dominated by Atlantic tropical rainforest and the other by traditional cocoa plantations. In each landscape we sampled three forest fragments and three areas of cocoa plantation, where we conducted a survey of epiphytic bromeliads of the genera Aechmea and Hohenbergia in eight plots of 400 m 2 in each area. The number of trees differed between landscapes and habitats, and was higher in forest fragments than in shade cocoa plantations, but the number of phorophytes was similar between landscapes and habitats. Highest richness of Aechmea and Hohenbergia species was found in forest fragments in landscapes where forests are predominant. Contrary to expectations, the richness in the other areas was relatively low, and extremely low in the landscape dominated by cocoa plantations, ranging from zero to four species per fragment. Bromeliad abundance was not different among landscapes and habitats, but the shade cocoa plantations located in predominant agroforest landscape showed the higher number of stands. Moreover, the species found in the cocoa plantations were more drought-tolerant species. These results suggest that the conservation of species of these genera depends on factors such as the conservation status of each forest fragment and the microclimatic alterations in the habitats, and not only on the percentage of forest in the landscape per se.

Abstract:To investigate the influence of forests and agroforestry systems on fruit consumption by birds, we studied two landscapes, one covered predominantly with forests and the other dominated by traditional shade cocoa plantations. In each landscape, we sampled three forest fragments and three shade cocoa plantations. We placed 15 artificial fruits in 25, 1–2-m-tall shrubs spaced every 50 m and evaluated the detection and consumption of fruits after 72 h. We used hemispherical photographs positioned above each fruit station to evaluate canopy openness. We found a statistically significant difference in fruit consumption between landscapes, which means that more fruits were detected and consumed in the forest-dominated landscape. However, forests and shade cocoa plantations within each landscape exhibited similar fruit consumption. Canopy openness was similar between the landscapes, however, the cocoa plantations exhibited greater canopy openness than forests. The results of this study reinforce the importance of the presence of forests in the agricultural landscape. Thus, to evaluate the capacity of agroforest to protect species and maintain ecological interactions it is also necessary to consider the landscape context.