title: Plant genetic variation mediates an indirect ecological effect between belowground earthworms and aboveground aphids.
abstract: BACKGROUND
  Interactions between aboveground and belowground terrestrial communities are often mediated by plants, with soil organisms interacting via the roots and aboveground organisms via the shoots and leaves. Many studies now show that plant genetics can drive changes in the structure of both above and belowground communities; however, the role of plant genetic variation in mediating aboveground-belowground interactions is still unclear. We used an earthworm-plant-aphid model system with two aphid species (Aphis fabae and Acyrthosiphon pisum) to test the effect of host-plant (Vicia faba) genetic variation on the indirect interaction between the belowground earthworms (Eisenia veneta) on the aboveground aphid populations.
  
  
  RESULTS
  Our data shows that host-plant variety mediated an indirect ecological effect of earthworms on generalist black bean aphids (A. fabae), with earthworms increasing aphid growth rate in three plant varieties but decreasing it in another variety. We found no effect of earthworms on the second aphid species, the pea aphid (A. pisum), and no effect of competition between the aphid species. Plant biomass was increased when earthworms were present, and decreased when A. pisum was feeding on the plant (mediated by plant variety). Although A. fabae aphids were influenced by the plants and worms, they did not, in turn, alter plant biomass.
  
  
  CONCLUSIONS
  Previous work has shown inconsistent effects of earthworms on aphids, but we suggest these differences could be explained by plant genetic variation and variation among aphid species. This study demonstrates that the outcome of belowground-aboveground interactions can be mediated by genetic variation in the host-plant, but depends on the identity of the species involved.
authors.affiliation: Terrestrial Ecology Research Group, Department for Ecology and Ecosystem Management, Centre for Food and Life Sciences Weihenstephan, Technische Universität München, Hans-Carl-von-Carlowitz-Platz 2, Freising, 85354, Germany. ga46jim@mytum.de.
authors.forename: Akanksha
authors.initials: A
authors.lastname: Singh
authors.affiliation: Terrestrial Ecology Research Group, Department for Ecology and Ecosystem Management, Centre for Food and Life Sciences Weihenstephan, Technische Universität München, Hans-Carl-von-Carlowitz-Platz 2, Freising, 85354, Germany. julia.amy@web.de.
authors.forename: Julia
authors.initials: J
authors.lastname: Braun
authors.affiliation: Terrestrial Ecology Research Group, Department for Ecology and Ecosystem Management, Centre for Food and Life Sciences Weihenstephan, Technische Universität München, Hans-Carl-von-Carlowitz-Platz 2, Freising, 85354, Germany. emilia.decker@mytum.de.
authors.forename: Emilia
authors.initials: E
authors.lastname: Decker
authors.affiliation: Terrestrial Ecology Research Group, Department for Ecology and Ecosystem Management, Centre for Food and Life Sciences Weihenstephan, Technische Universität München, Hans-Carl-von-Carlowitz-Platz 2, Freising, 85354, Germany. sarahhans@gmx.net.
authors.forename: Sarah
authors.initials: S
authors.lastname: Hans
authors.affiliation: Terrestrial Ecology Research Group, Department for Ecology and Ecosystem Management, Centre for Food and Life Sciences Weihenstephan, Technische Universität München, Hans-Carl-von-Carlowitz-Platz 2, Freising, 85354, Germany. sieb10a@aol.com.
authors.forename: Agnes
authors.initials: A
authors.lastname: Wagner
authors.affiliation: Terrestrial Ecology Research Group, Department for Ecology and Ecosystem Management, Centre for Food and Life Sciences Weihenstephan, Technische Universität München, Hans-Carl-von-Carlowitz-Platz 2, Freising, 85354, Germany. wolfgang.weisser@tum.de.
authors.forename: Wolfgang W
authors.initials: WW
authors.lastname: Weisser
authors.affiliation: Terrestrial Ecology Research Group, Department for Ecology and Ecosystem Management, Centre for Food and Life Sciences Weihenstephan, Technische Universität München, Hans-Carl-von-Carlowitz-Platz 2, Freising, 85354, Germany. sharon.zytynska@tum.de.
authors.forename: Sharon E
authors.initials: SE
authors.lastname: Zytynska
mesh_terms: D000818:Animals; D001042:Aphids / Q000502:physiology*; D018533:Biomass; D003163:Competitive Behavior; D020387:Food Chain; D014644:Genetic Variation; D058458:Nitrogen Cycle; D009835:Oligochaeta / Q000502:physiology*; D011157:Population Dynamics; D031307:Vicia faba / Q000235:genetics* / Q000254:growth & development