Leaf-fungal incidence and herbivory on tree seedlings in tropical rainforest fragments: An experimental study

Abstract

We tested the effects of forest fragmentation on the incidence of leaf-fungal infection and its interaction with herbivores in central Amazonia. An experiment was initiated in 1992 on seedlings of three co-occurring tree species that were transplanted into continuous forest and forest fragments of 1, 10, and 100 ha in area. Nearly 6 years later, for each site and species, we calculated the proportion of leaves within five damage categories (herbivory alone; fungal infection surrounding herbivory injuries; fungal infection and herbivory in the same leaf but fungi not surrounding herbivory injuries; fungal infection alone; undamaged leaves). We also estimated the percentage of leaf area damaged by herbivory and by each type of fungal infection. Leaves of Pouteria caimito and Chrysophyllum pomiferum were most frequently damaged by herbivory, whereas most Micropholis venulosa leaves were undamaged. Herbivore damage varied among study areas but was not consistently related to fragment area. While fungal infection was rare, two species (P. caimito and C. pomiferum) had significantly lower rates of fungal infection associated with herbivory damage in fragments than in continuous forest. Overall, our results suggest that herbivory is the main type of seedling damage among these three species, that fungal infection is so rare that it is unlikely to affect seedling performance, and that the interactions among seedlings, herbivores, and fungi may be influenced by forest fragmentation.