title: Bottom-up effects of host-plant species diversity and top-down effects of ants interactively increase plant performance.
abstract: While plant diversity is well known to increase primary productivity, whether these bottom-up effects are enhanced by reciprocal top-down effects from the third trophic level is unknown. We studied whether pine tree species diversity, aphid-tending ants and their interaction determined plant performance and arthropod community structure. Plant diversity had a positive effect on aphids, but only in the presence of mutualistic ants, leading to a threefold greater number of both groups in the tri-specific cultures than in monocultures. Plant diversity increased ant abundance not only by increasing aphid number, but also by increasing ant recruitment per aphid. The positive effect of diversity on ants in turn cascaded down to increase plant performance; diversity increased plant growth (but not biomass), and this effect was stronger in the presence of ants. Consequently, bottom-up effects of diversity within the same genus and guild of plants, and top-down effects from the third trophic level (predatory ants), interactively increased plant performance.
authors.affiliation: Department of Ecology and Evolutionary Biology, University of California, Irvine, CA 92697, USA. xmoreira@mbg.csic.es
authors.forename: Xoaquín
authors.initials: X
authors.lastname: Moreira
authors.forename: Kailen A
authors.initials: KA
authors.lastname: Mooney
authors.forename: Rafael
authors.initials: R
authors.lastname: Zas
authors.forename: Luis
authors.initials: L
authors.lastname: Sampedro
mesh_terms: D000818:Animals; D001000:Ants / Q000502:physiology*; D044822:Biodiversity; D018533:Biomass; D020387:Food Chain; D007313:Insecta / Q000502:physiology*; D028223:Pinus / Q000033:anatomy & histology / Q000254:growth & development / Q000502:physiology*; D011157:Population Dynamics; D013030:Spain; D013112:Spiders / Q000502:physiology; D013559:Symbiosis