Arthropods on plants in a fragmented Neotropical dry forest: a functional analysis of habitat loss and edge effects

Abstract

Loss and fragmentation of natural ecosystems are widely recognized as the most important threats to biodiversity conservation, with Neotropical dry forests among the most endangered ecosystems. Area and edge effects are major factors in fragmented landscapes. Here, we examine area and edge effects and their interaction, on ensembles of insects associated to native vegetation in a fragmented Chaco Serrano forest. We analyzed family richness and community composition of herbivores, predators and parasitoids on three native plant species in 12 fragments of varying size and at edge/interior positions. We also looked for indicator families by using Indicator Species Analysis. Loss of richness with the loss of forest area was observed for the three functional groups, with similar magnitude. Herbivores were richer at the edges without interaction between edge and area effects, whereas predators were not affected by edge/interior position and parasitoid richness showed an interaction between area and position, with a steeper area slope at the edges. Composition of herbivore, predator and parasitoid assemblages was also affected by forest area and/or edge/interior situation. We found three indicator families for large remnants and five for edges. Our results support the key role of forest area for conservation of insect taxonomic and functional diversity in a highly threatened region, and emphasize the need to understand the interactions between area and edge effects on such diversity.