Composition of tropical agricultural landscape alters the structure of host-parasitoid food webs

Land-use change and habitat fragmentation are well-known to affect host-parasitoid interactions. However, the study of the effects of landscape composition, as a result of habitat fragmentation, on host-parasitoid food webs is still limited especially in a tropical agricultural landscape. This research was aimed to study the effect of agricultural landscape composition on the structure of host-parasitoid food webs. Field research was conducted in sixteen long-bean fields located in Bogor Regency, West Java, Indonesia. In each long-bean field, sampling of insect pests and their parasitoids was carried out using direct observation within a plot size of 25 m × 50 m. The collected insects were brought to the laboratory for rearing and observed for emerging parasitoids. Landscape composition of each long-bean field was measured by digitizing the whole patch within a radius of 500 m from the long-bean field as a center of landscape, and landscape parameters were then quantified by focusing on number of patches and class area of both semi-natural habitats and crop fields. In total, we found 51 morphospecies of insect pests and 110 morphospecies of associated parasitoids from all research locations. Lepidopteran pests are the most abundant and species-rich with 35 morphospecies and with 76 morphospecies of parasitoids. Based on the generalized linear models, landscape composition especially class area of natural habitat and crop field showed a positive relationship with host-parasitoid food-web structure especially on connectance and compartment diversity. In conclusion, landscape composition contributes to shaping the host-parasitoid food-webs in a tropical agricultural landscape.