title: Interaction complexity matters: disentangling services and disservices of ant communities driving yield in tropical agroecosystems.
abstract: Owing to complex direct and indirect effects, impacts of higher trophic levels on plants is poorly understood. In tropical agroecosystems, ants interact with crop mutualists and antagonists, but little is known about how this integrates into the final ecosystem service, crop yield. We combined ant exclusion and introduction of invasive and native-dominant species in cacao agroecosystems to test whether (i) ant exclusion reduces yield, (ii) dominant species maximize certain intermediate ecosystem services (e.g. control of specific pests) rather than yield, which depends on several, cascading intermediate services and (iii) even, species-rich ant communities result in highest yields. Ants provided services, including reduced leaf herbivory and fruit pest damage and indirect pollination facilitation, but also disservices, such as increased mealybug density, phytopathogen dissemination and indirect pest damage enhancement. Yields were highest with unmanipulated, species-rich, even communities, whereas ant exclusion decreased yield by 27%. Introduction of an invasive-dominant ant decreased species density and evenness and resulted in 34% lower yields, whereas introduction of a non-invasive-dominant species resulted in similar species density and yields as in the unmanipulated control. Species traits and ant community structure affect services and disservices for agriculture in surprisingly complex ways, with species-rich and even communities promoting highest yield.
authors.affiliation: Agroecology, Department of Crop Sciences, University of Göttingen, , Grisebachstrasse 6, Göttingen 37077, Germany, Department of Animal Ecology and Tropical Biology (Zoology III), Biocenter, University of Würzburg, , Am Hubland, Würzburg 97074, Germany, Department of Agriculture, Klabat University, , Airmadidi No. 1, Manado 95371, Indonesia, Faculty of Agriculture, University of Tadulako, , Palu 94118, Indonesia, Centre for Environmental and Climate Research, Lund University, , Sölvegatan 37, Lund 223 62, Sweden.
authors.forename: Arno
authors.initials: A
authors.lastname: Wielgoss
authors.forename: Teja
authors.initials: T
authors.lastname: Tscharntke
authors.forename: Alfianus
authors.initials: A
authors.lastname: Rumede
authors.forename: Brigitte
authors.initials: B
authors.lastname: Fiala
authors.forename: Hannes
authors.initials: H
authors.lastname: Seidel
authors.forename: Saleh
authors.initials: S
authors.lastname: Shahabuddin
authors.forename: Yann
authors.initials: Y
authors.lastname: Clough
mesh_terms: D000818:Animals; D001000:Ants / Q000502:physiology*; D001522:Behavior, Animal; D002099:Cacao / Q000502:physiology*; D018556:Crops, Agricultural / Q000502:physiology*; D017753:Ecosystem; D060434:Herbivory; D007303:Insect Vectors / Q000382:microbiology / Q000502:physiology; D058865:Introduced Species; D010935:Plant Diseases / Q000382:microbiology; D012919:Social Behavior; D014329:Tropical Climate
keywords: Indonesia; Sulawesi; Theobroma cacao; ant exclusion; indirect interactions; yield