Rainforest conversion to cash crops reduces abundance, biomass and species richness of parasitoid wasps in Sumatra, Indonesia

Parasitoid wasps affect herbivory in natural and agricultural ecosystems, including cash crops. The impacts of rainforest transformation to rubber and oil palm on parasitoid wasp communities are poorly understood. We collected canopy arthropods, once each in dry season and rainy season, via canopy fogging in four land-use systems in Jambi, Sumatra, Indonesia: Rainforest, jungle rubber (extensive rubber cultivation) and plantations of rubber and oil palm. The combined abundance and richness of six parasitoid wasp families, and Braconidae individually, was twice as high in rainforest as in rubber and oil palm plantations, and intermediary in jungle rubber. There was a significant positive correlation between combined abundance of six parasitoid wasp families, and abundances of potential hosts from the orders Coleoptera, Diptera, Hemiptera and Lepidoptera. Braconid biomass tended to be highest in rainforest and lowest in oil palm plantations, and Braconid communities in oil palm differed from those in the other land uses. Both patterns were influenced by season. Our study details the effects of rainforest conversion to rubber and oil palm on parasitoid wasp communities, and provides first insights on the influence of rainfall seasonality on their abundance, biomass, species richness and community composition in Southeast Asian agricultural landscapes.

Automated summary

Parasitoid wasp communities in different land-use systems were studied in Jambi, Sumatra, Indonesia. The study found that the abundance and richness of parasitoid wasps were highest in rainforest, intermediate in jungle rubber, and lowest in rubber and oil palm plantations. The abundance of parasitoid wasps was positively correlated with the abundance of potential hosts from different insect orders. The biomass of one specific parasitoid wasp family, Braconidae, was highest in rainforest and lowest in oil palm plantations. Seasonality also influenced the abundance and composition of parasitoid wasp communities.