title: A below-ground herbivore shapes root defensive chemistry in natural plant populations.
abstract: Plants display extensive intraspecific variation in secondary metabolites. However, the selective forces shaping this diversity remain often unknown, especially below ground. Using Taraxacum officinale and its major native insect root herbivore Melolontha melolontha, we tested whether below-ground herbivores drive intraspecific variation in root secondary metabolites. We found that high M. melolontha infestation levels over recent decades are associated with high concentrations of major root latex secondary metabolites across 21 central European T. officinale field populations. By cultivating offspring of these populations, we show that both heritable variation and phenotypic plasticity contribute to the observed differences. Furthermore, we demonstrate that the production of the sesquiterpene lactone taraxinic acid β-D-glucopyranosyl ester (TA-G) is costly in the absence, but beneficial in the presence of M. melolontha, resulting in divergent selection of TA-G. Our results highlight the role of soil-dwelling insects for the evolution of plant defences in nature.
authors.affiliation: Root Herbivore Interactions Group, Department of Biochemistry, Max Planck Institute for Chemical Ecology, Jena, Germany mhuber@ice.mpg.de.
authors.forename: Meret
authors.initials: M
authors.lastname: Huber
authors.affiliation: Institute of Plant Sciences, University of Bern, Bern, Switzerland.
authors.forename: Zoe
authors.initials: Z
authors.lastname: Bont
authors.affiliation: Institute of Plant Sciences, University of Bern, Bern, Switzerland.
authors.forename: Julia
authors.initials: J
authors.lastname: Fricke
authors.affiliation: Root Herbivore Interactions Group, Department of Biochemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Théo
authors.initials: T
authors.lastname: Brillatz
authors.affiliation: Root Herbivore Interactions Group, Department of Biochemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Zohra
authors.initials: Z
authors.lastname: Aziz
authors.affiliation: Department of Biochemistry, Max Planck Institute for Chemical Ecology, Jena, Germany.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Gershenzon
authors.affiliation: Root Herbivore Interactions Group, Department of Biochemistry, Max Planck Institute for Chemical Ecology, Jena, Germany Institute of Plant Sciences, University of Bern, Bern, Switzerland matthias.erb@ips.unibe.ch.
authors.forename: Matthias
authors.initials: M
authors.lastname: Erb
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001517:Coleoptera / Q000502:physiology*; D005960:Glucosides / Q000378:metabolism*; D060434:Herbivory; D007783:Lactones / Q000378:metabolism*; D007840:Latex / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism*; D012717:Sesquiterpenes / Q000378:metabolism*; D031205:Taraxacum / Q000502:physiology*
chemical_list: D005960:Glucosides; D007783:Lactones; D007840:Latex; D012717:Sesquiterpenes; C000608106:taraxinic acid glucopyranosyl ester
keywords: defence; fitness costs; latex; plant secondary metabolites; root herbivory; selection