High conservation value of forest fragments for plant and frugivore communities in a fragmented forest landscape in South Africa.

摘要

Fragmentation is a major threat factor for plant-frugivore communities in tropical and subtropical forests. Resulting changes in the distribution of traits within these communities, e.g., a loss in large-bodied frugivores, may lead to strong changes in plant-frugivore interactions in fragmented forests. Yet, we still lack a thorough understanding of the interplay between forest fragmentation, the trait-composition of communities and resulting plant-frugivore interactions on a community-scale. In a fragmented South African landscape comprising different forest categories - i.e., continuous natural forest, forest fragments surrounded by natural grassland, and forest fragments surrounded by sugarcane - we investigated the relationship between communities of fruiting plants and their frugivore visitors in response to forest fragmentation, as well as the interactive effects of forest fragmentation and fruit size of the plants on the number of frugivore visitors and their body size. Neither the fruit size of plant nor the body mass of frugivore communities differed between natural forest sites and forest fragments. Moreover, in-depth analyses of frugivore assemblages visiting plant species revealed no effect of forest category on the number of frugivore visits or their mean body mass. The number of visits and body mass of frugivores were merely determined by the crop and fruit size of the focal plant species. Overall, our results suggest that frugivory of plant species with differently sized fruits was not reduced in forest fragments. Thus, fragments with high fruit availability may be key elements maintaining the functional connectivity of a heterogeneous forest landscape.