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.
Proc Biol Sci. 2013 Dec 4;281(1775):20132144. doi: 10.1098/rspb.2013.2144. Print 2014 Jan 22.
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.
由于复杂的直接和间接影响，较高营养级对植物的影响还不太清楚。在热带农业生态系统中，蚂蚁与作物共生和拮抗相互作用，但对于这种相互作用如何融入最终的生态系统服务——作物产量，人们知之甚少。我们在可可农业生态系统中结合了蚂蚁排除和入侵和本地优势种的引入，以测试是否：（i）蚂蚁排除会降低产量；（ii）优势种是否会最大化某些中间生态系统服务（例如特定害虫的控制）而不是产量，这取决于几个连锁的中间服务；（iii）即使是物种丰富的蚂蚁群落也会导致最高的产量。蚂蚁提供了包括减少叶片草食性和果实害虫损害以及间接授粉促进等服务，但也有一些不利影响，如增加粉蚧密度、传播植物病原体和间接增加害虫损害。未受干扰的、物种丰富的、均匀的蚂蚁群落产量最高，而蚂蚁排除使产量降低了 27%。引入入侵优势种会降低物种密度和均匀度，导致产量降低 34%，而引入非入侵优势种则会导致与未受干扰的对照相比，物种密度和产量相似。物种特征和蚂蚁群落结构以令人惊讶的复杂方式影响农业的服务和不利影响，物种丰富和均匀的群落促进了最高的产量。
